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h ' '' f MASGC-B-78-001 c. 3 A MARINE MALADIES? , Germs, and Other Symbionts From the Northern Gulf of CRCDU7M COPY Sea Grant Depositor

NATIONAL SEA GRANT DEPOSITORY \ PELL LIBRARY BUILDING URI NA8RAGANSETT BAY CAMPUS % NARRAGANSETT. Rl 02882

Robin M. Overstreet r ii

MISSISSIPPI—ALABAMA SEA GRANT CONSORTIUM

MASGP—78—021 MARINE MALADIES? Worms, Germs, and Other Symbionts From the Northern

by

Robin M. Overstreet Gulf Coast Research Laboratory Ocean Springs, Mississippi 39564

This study was conducted in cooperation with the U.S. Department of Commerce, NOAA, Office of Sea Grant, under Grant No. 04-7-158-44017 and National Marine Service, under PL 88-309, Project No. 2-262-R. TheMississippi-AlabamaSea Grant Consortium furnish ed all of the publication costs. The U.S. Government is authorized to produceand distribute reprints for governmental purposes notwithstanding any copyright notation that may appear hereon. Copyright© 1978by Mississippi-Alabama Sea Gram Consortium and R.M. Overstrect

All rights reserved. No pari of this book may be reproduced in any manner without permission from the author.

Primed by Blossman Printing, Inc.. Ocean Springs, Mississippi CONTENTS

PREFACE 1 INTRODUCTION TO 2 AS HOSTS 5 THE AMERICAN 5 Public Health Aspects 6 Dcrmo 7 Other Symbionts and Diseases 8 Shell-Burrowing Symbionts II Fouling and Predators 13 THE BLUE 15 Protozoans and Microbes 15 Mclazoans and their I lypeiparasites 18 Misiellaneous Microbes and Protozoans 25 PENAEID 28 Microbial Diseases 28 Protozoan Infections 32 Helminths 34 Miscellaneous Diseases and Attached Organisms 38 GRASS 10 Protozoans 41 Metazoans 42 AS HOSTS 46 16 Microbes 47 Protozoans in General 50 50 5- Sporozoans 52 Microsporidans 53 Myxosporidans 54 55 Tapeworms Jl Monogenean Flukes <" Digenean Flukes &/ Roundworms ,- Thorny-headetl Worms 79 80 MISCELLANEOUS HOSTS 85 The American Alligator 85 86 Marine 88 MISCELLANEOUS SYMBIONTS 89 -KILLS AND MISCELLANEOUS DISEASES 92 TECHNICAL ASPECTS 96 SYMBIOSIS 96 THE AMERICAN OYSTER 98 THE BLUE CRAB 101 PENAEID SHRIMPS 104 GRASS SHRIMP 107 FISHES 107 Microbes 108 Protozoans 108 Cestodes Ill Monogeneans 112 Digeneans 113 114 Acanthocephalans 114 Crustaceans 115 MISCELLANEOUS HOSTS 116 The American Alligator 116 Birds 116 Marine Mammals 118 MISCELLANEOUS SYMBIONTS 118 FISH-KILLS AND MISCELLANEOUS DISEASES 119 ACKNOWLEDGMENTS 121 LITERATURE CITED 122 GLOSSARY 137 Preface 1 PREFACE sideration. An effort has been made to define scientific terminology either in the textor in This guidebook will inform thosecurious a glossary at the end of the guide.Terms pre about parasites and other symbionts as sented in the glossary are indicated by an sociated with marine and estuarine hosts in asterisk (*) the first and occasionally other the northern Gulf of Mexico. Designed as a times they are used. Diagrams, illustrations, teaching aid for students, fishermen, sea photographs, and legends provide further food consumers, beachcombers, and even assistance. parasitologists, it should allow for better understanding and appreciation of several Latin names have been included as well of the numerous shellfish and finfish sym as common names for three reasons. First, bionts. (A symbiotic is one that some organisms have no common name. Second, a specific common name may refer interacts with the in or on which it .) Even though most selected examples to more than one or one animal may are from Mississippi and other regions a- have several common names. When most long the northern Gulf, the same or related people talk about the blue crab, they pro also occur along the Atlantic sea bably talk about sapidus, but board and elsewhere; present information they might also knowingly orunknowingly should apply similarly for several butnotall be referring to , Callin of those cases. Some symbiontssignificantly ectes omatus, or a variety of other related affect the size and production of a . On the other hand, residents of and consumption of the product, whereas Mississippi call the spotted seatrout (Cyno- scion nebulosus) a speck or speckled others mostly stimulate environmental or whereas people elsewhere may call it or a academic interests. In the natural environ related species by the name weakfish, ment, parasitic relationships seldom result squeteague, or any of several others. Third, in harm to the host. Harm, however, often knowing a Latin name often allows one to becomes apparent when are con more easily find other literature about the centrated and confined as they are during organism. culture or when they are otherwise stressed. This guide will discuss some of those cases. A binomial name, that is the two-compo This guidebook is divided into sections nent Latinized name of an organism, con discussing the various hosts of parasites. sists of the capitalized generic name and the Primary headings refer to basic host-types. noncapitalized specific name. Oneor several The reader, however, must keep in mind species may occur in a , and different that groups of both symbionts and hosts taxonomists, scientists who deal with the overlap. The same parasite may have a nomenclatural problems, may not all agree different stage of its history infecting a to which genus a given species belongs. shrimp, a fish, and a . Consequently, Nevertheless, names allow people to refer to perusal of several sections may help the specific organisms. Some names reflect the reader understand more about the sym animal's characteristics, its locality, or its bionts of any particular host. finder, whereas others are merely fabricated. The guidebook has been written with Readers interested in the hygienic aspects both the student withouta strong biological of eating infected finfishes and shellfishes background and the layman in mind, but it may be comforted by the fact that cooking presents additional separate notes for more destroys all potentially harmful agents in serious readers interested in technical as products from the northern Gulf of pects. That technical section, in the latter Mexico. Perhaps this statement needs some half, directs the reader to referenced scienti qualification. A person could acquire gas fic literature which either presents support tric distress from eating cooked seafood if ing data or reviews the topics under con- staphylococci toxin was present, if contam- 2 Marine Maladies? inalion occurred after cooking, if the pro "symbiosis," "," and "mu duct was spoiled before cooking, or if tualism." condiments contained salmonellae, shi- "Symbiosis," which means "living to gellae, or some other infectious . gether," accounts for a variety of long and Also, heavy metals and some other non short term relationships that benefit one or parasitic toxins are not destroyed by both parties. For purposes of simplicity, I cooking. Products infected with parasites consider symbiotic relations to be those spe should not dismay a consumer. Seldom does cialized associations ranging from com one get the opportunity to see some of these mensalism, where neither party is harmed puzzling little invadersl If infected products and both could live without the other, to are cooked, all becomeedible, a few have less , where both parlies benefit each appeal and flavor, andseveral taste better be other and neither could live without the cause of the added rich, juicy nestled other. A true parasite lies in between. Para among the . I am willing to admit, sitism defines a one-way relationship in however, that most people preferring in which one partner, the parasite, depends fected products do not realize that the upon and benefits from the other partner, "flavor bud" is a parasite. the host. The host is usually the larger of any two associates and can be harmed by the parasite. Actually, much overlap in types of relationships exists, and, for most readers, INTRODUCTION TO what happens in a given relationship far SYMBIOSIS surpasses in importance the term someone may want to tag on it. As is the case with many scientific en "Commensalism" means "eating at the deavors, the same concept or item may be same table." A sea anemone attached to the referred to by different terms, and, converse mollusc an shell of a hermit crab derives ly, different concepts or items can be called mobility and scraps of food from the crab the same name. Seldom does one realize that without being metabolically dependent on confusion exists until he progresses into a it. The relationship, however, might not be discussion. What is a parasite? Does it have one sided and may be truly mutual. In some to harm its host? If so, does it have to harm cases, the anemone, by virtue of its stinging all the different hosts in all stages of its life? tentacles, contributes by warding off octo Does it have to be smaller than its host? Can puses or other predators from the crab. The it be the same speciesas the host?Depending degree of benefit to each party depends on on how one prefers to answer the above the species of anemone and crab involved as questions, even a human baby can qualify well as the environmental conditions and as a parasite. Before the nourishes the additional organisms which make up itself at the expense of its host (mother) and the *. In the northern Gulf of releases toxic wastes into that host; occas Mexico, a specific anemone (Calliactis tri ionally at birth, it even causes the host's color) usually attaches to a shell, often of the death. After normal birth, it continues to moon snail, inhabited by a hermit crab suck vital nutrients from the host. From (e.g., Pagurus longicarpus), as illustrated in another viewpoint, even after maturing, Figure 1. that offspring may obtain its well being Some inhabited shells harbor hydroids from its parents or friends at their ex rather than anemones. Two species of hy pense. By defining terms now, we should droids (Podocoryne selena and Hydractinia have a clearer understanding of some of the echinata) commonly use this movable sub different types of relationships among ani stratum* in the northern Gulf of Mexico mals. Three terms that must be understood (Figure 2). They probably benefit the crab to aid in understanding parasites are because colonies of each possess protective Symbiosis 3

Figure 3. A commensal hydroid (Clytia sp.) attached to a coquina clam ( roemerl protracta). The hydroid benefits by having a substratum along a sandy beach on which to attach, but neither clam nor hydroid harms the other.

the clam shell as something hard on which to attach in the turbulent beach . If, however, the clam benefits by being protect ed from infection by a parasite that destroys its reproductive tissue, that hydroid is some what mutualisticeven though both theclam and hydroid can live without the other. Already the reader probably realizes that we do not always know what constitutes a parasite. When a symbiont depends entirely on a host, occasionally harming it in the Figures 1 and 2. Hermit crabswith symbionts process, it is unequivocally a parasite. Harm on theU molluscan shells. Top, two can result from boring into tissues, digest individuals of an anemone (Calllactls ing tissues, displacing vital tissues, releas tricolor) on the moon snail Inhabited by Pagurus longlcarpus. Bottom, a hydroid ing toxic metabolic products, or competing covering the shell housing Pagurus for nutrients. Some parasites even live apart pollicarls. from their hosts for a portion of their lives, whereas others always remain with their stinging zooids* in addition to the nutri hosts, but act as commensal until confront tive, generative, and sensory ones found in ed with a particular stress. Tapeworms and colonies of related nonsymbiotic hydroids. spiny-headed worms are obvious parasites Commensalism can be expanded to in since they have no gut and necessarily de clude "phoresis" meaning "traveling to pend on their hosts to provide all their gether." The two parties in this relation nutrients in a state that can pass through ship do not eat at the same table. A possible their body surfaces. Whether many other example of a phoront is a hydroid (Clytia symbionts are parasites requires a subjective sp.) that attaches to the posterior edge of a decision. live coquina's shell (Figure 3). These The difference between a parasiteand pre clams in Texas with the hydroid attached dator can also be confusing. Some animals contained no internal parasitic flukes. This kill their prey outright rather than depend finding suggests the hydroid prevented the on a living source of food, and these consti parasitic infection*. If true, we could inter tute predators. When animals feed on a pret the clam-hydroid relationship as mu- variety of prey much smaller than them tualistic, a relationship to be discussed selves, they act as predators. However, some later, because both parties benefit. If Clytia micropredators and even large predators sp. is a phoront, it benefits only by utilizing periodically eat away part of specific species 4 Marine Maladies? of prey without killing them, and these enzyme cellulase which digests the ingested could be considered parasites. I will let the wood so that the termite can utilize it. reader term such a relationship anything he Neitheranimal can survive for long by itself, desires, but the more biochemically and and the two together do much to benefit an physiologically dependent a "predator" be ecological community* (assuming a house comes on a given "prey," the more parasitic is not the food source!). In the ocean, num the relationship becomes. erous cases of mutualism occur. Many of In a well-adapted host-parasite relation these include specific associated with ship, the host is not significantly harmed. particular invertebrates. This may sound like a contradiction, but as Symbiotic algae inhabit various tissues a parasite becomes moredependenton a spe or cells of invertebrates belonging to numer cific host species, it becomes more vulner ous genera in at least ten phyla*. Reef- able to extinction if it or anything else building corals provide often-mentioned seriously harms that host. It must be able to examples. An assumption dictates that all obtain its well being from the host without the hosts would die without harming it because the parasite needs a their algae, but experimental studies have healthy host to survive. Strangely, however, shown that these otherwise greenish or a well-adapted parasite often benefits when brownish (from chlorophyll*) corals and one of its larval stages affects the inter other cnidarians may survive when bleached mediate host in such a manner that the final in darkness from shedding their symbionts. hostcan preyon thatintermediate host more Nevertheless, the well-adapted relationships easily and thereby insure completion of the benefit both parties, even though some ani parasite's life cycle. mals may appear to exploit their algal mu- Usually for a parasite to harm its host, the tualist excessively. In each association, the host is either stressed or weakened or the in benefits probably vary, and most have not fection is either "accidental" or heavy. An been thoroughly investigated. The inverte accidental, or incidental, parasite afflicts brate host provides nutrients and shelter for a host other than its normal one. Excessive the alga. The alga provides the host oxygen numbers of an otherwise harmless parasite and organic nutrients (by photosynthesis*); in the normal host can cause disease*. removes carbon dioxide, nitrogenous wastes Twenty or so in an individual's and other metabolic products from host intestine would have noestheticappeal if he cells; provides protective coloration for knew about them, but such an infection the host; and in the case of corals, aids in would not constitute disease. When the deposition of a calcified skeleton. Few of number of worms increases, especially in a these algae have been cultured and properly malnourished patient, a disease becomes identified. Consequently, for most associa manifest. The actual number of worms tions, an alga's possible relationships with needed to cause bloody stools, anemia, loss different invertebrates, its metabolic de of appetite, a desire to eat soil, and other mands on a host, and its ability to live symptoms of disease depends on both the without a host have not been firmly esta species of and the individual blished. person (host) involved. Most conspicuous examples of inverte "Mutualism" requires that both mutuals brate-alga mutualism occur in tropical depend on each other. In the strict sense, this waters, but some less conspicuous ones must be a metabolic* dependency in which occur in the northern Gulf. Perhaps some neither party survives without the other. readers will search for the typicallygreenish The combination of a termite with its inter or brownish invertebrate hosts. One is the nal protozoans provides an exampleclose to sun jellyfish (Cassiopea xamachana) which home. Intestinal flagellates produce the occasionally can be found near Horn Island American Oyster 5 where, when not swimming, it rests on the bottom with its underside facing up, expos ing the algal symbionts. Hosts from Florida which appear to utilize multiple symbionts are colonial zoanthid anthozoans (two species of Zoanthus, see Figure 4 for one of them). Theirgreenish-brown polyps with extruded tentacles give the impression of a flower; the color is derived mostly from the internal golden-brown zooxanthella. Rather than having one symbiont like corals and other Figure 4. A colonial zoanthid anemone commonly called a green sea mat. The investigated hosts, these cnidarians have a animal normally utilizes internal and variety of symbionts. One form migrates animal symbionts for its well-being. extensively, perhaps depending on the amount of light present. Since the Floridian bill, or flared end, above the mud. On the zoanthids readily feed when presented small other hand, on a firm uncrowded bottom, crustaceans or pieces of fish, the symbionts the oyster forms a broad cupped shell. It appear to have a function other than a sole grows best in estuarine* water with nutritive source. Some other animals reasonably constant salinity* between culture their food. Algae are grown in 15 and 30 ppt. amphipod tubes by some amphipod Figure 5 illustrates a partially shucked inhabitants, and fungi grow on the (opened) oyster. In a closed oyster, the two pieces of leaves provided by leaf- valves join anteriorly immediately internal cutting ants. The identification and to the umbo, or beak, by a continually interrelationships among the zoanthids and replaced elastic hinge ligament. The large symbionts other than the zooxanthella adductor muscle, referred to as the "eye" by (alga) which is similar in appearance to that shuckers, holds the valves togetherand must in most other cnidarian-algal associations be cut to open the oyster. have not been established. Special cells in the mantle secrete three primary layers of the shell. Externally, a thin horny organic layer (periostracum) covers a middle prismatic layer of mineral INVERTEBRATES AS which develops most substantially on the HOSTS right flat valve. The inner shiny layer (calcific ostracum) usually constitutes the THE AMERICAN OYSTER thickest stratum. The American oyster (Crassostrea Features of the soft body are mostly self- virginica) supports an important fishery explanatory. Dark bands ofsensory tentacles in most regions where it occurs along the border mantle flaps. Ciliary rows of the gills Atlantic and Gulf of Mexico coasts from direct up to 28 liters (about 30 quarts) of Canada to Mexico. The benthic* animal water per hour. The gills remove oxygen grows rapidly in the warm water of the from and excrete wastes into that water. northern Gulf, reaching 8 centimeters (cm) They also accumulate food which, when (about 3 inches, see glossary for examples acceptable to the oyster, continues to be of measurements) in as short a period as 4 conveyed to the mouth by action of cilia months, but typically taking a year or so. (these structures will be described in a later When on soft mud, it sinks and conse section on protozoans of fishes) on the gills quently grows thin and long to keep its and palps. 6 Marine Maladies? vmho of shell

dlomach iigestiye diverticala

adductor mu$cle

iticnvtle

shell Figure 5. Selected anatomical features of the American oyster. One valve has been removed and portions of the oyster's soft tissues cut out to reveal structures.

Most young function as males, but typically heavy, especially in summer. Be may change sex one or more times in cause of this , a greater number of subsequent years. During warm weather young oysters from the fall set typically between April and October an individual's survives to the following year compared spawning often stimulates others to spawn. with the relatively larger spring set of spat. Each oyster releases millions of eggs every spawn and can spawn several times per Public Health Aspects season. After a develops, it settles People may be concerned about the in about a week andsearches for a hardclean possibility of a parasitic infection from con surface on which to cement itself. The suming raw oysters. No such parasite from greatest and subsequent the Americanoyster has been implicated in "setting" of young oyster larvae occurs in health problems. On the other hand, oysters May or June, depending on the water tem from polluted water do concentrate patho perature. The small oysters, called spat, of genic human viruses and bacteria. These ten set on largeroyster shells, but will utilize human pathogens, however, are killed by almostanything. All stages are vulnerable to proper cooking and usually are not present some kind of symbiont. Predation is also in oysters harvested from nonconlaminated American Oyster 7 mortalities in Louisiana had been blamed on oil pollution until the oil industry con tracted Texas A&M to investigate the problem in the 1950's. Findings of that study revealed many things about the dermo organism, including how to detect it easily. When infected oyster

•f *; yi^i j.* ja&^e'isv. tissue is placed for a week or more in a Figure 6. The middle gaping oyster cannot thioglycollate culture medium with anti close its valves tightly. Several disease- biotics, the organisms enlarge and become agents and environmental stresses can readily distinguishable. These enlarged cause gaping, but this condition is a common sign during the hot summer cells develop a wall which turns a bluish- indicating that the oysters may have heavy black color when stained with an iodine infections of dermo. These dying oysters solution (Lugol's) (Figure 7). Clusters of become easy prey for a numberof predators, including organisms previously acting as these spores* can be detected without a commensals. microscope. Most tissues of infected individuals harbor the parasite, but the waters. Certain inorganic contaminants, gills, rectum, mantle, or adductor muscle such as lead or mercury, and some algal provide the best results. toxins are sometimes found in polluted Infections* by dermo have important waters, and these may be concentrated economic implications. The prevalence* in oysters growing there. These potential (percentage) of infected oysters and the toxins are not removed by cooking. number of organisms per infected indi Even though not harmful to man, several vidual typically remain low during winter parasites do injure the oyster. Mostof these and increase considerably during summer. cause significant disease* in oysters only Periodically, the majority of adult oysters when antagonized by additional stresses. on a reef succumb to this pathogen during Environmental stresses — such as high hot summer months, producing massive temperature, low salinity, excessive kills, or epizootics. In order to avoid the siltation, or pollutants —probablyall affect loss of these oysters to consumers several some symbiotic relationships. When threat years ago, William Demoran of the ened, the soft-bodied oyster closes together Mississippi Marine Conservation its two thick shells, or valves. After be Commission would sample oysters from coming overpowered by predators or intolerable conditions, the oyster gapes (Figure 6) and soon after dies or is eaten.

Dermo Many oysters in the northern Gulf of Mexico gape because of "dermo" a colloquial name for a disease caused by Dermocystidium marinum (presently known as marinus). This micro organism, once thought to be a protozoan, Figure 7. Enlarged spores of dermo then a , and now a protozoan again, (Dermocystidium marinum) that have been cannot be seen without a microscope; cultured in a special fluid (thioglycollate medium) and stained with iodine. The however, oysters dying in late summer with method allows easy detection of this a shrunken appearance and a yellowish cast organism which kills many stressed oysters probably have dermo. For a long time such during the hot summer. 8 Marine Maladies? Lower Square Handkerchief Reef during and their defenses against the parasite. the winter. If the sample revealed a high Heavy oyster mortalities — an estimated prevalence of dermo, the Commission 50% of the crop — occur annually on the allowed most of the oysters from that vul average from the disease in Florida. For nerable region to be harvested then, tunately, spat and juveniles quickly rather than wait for the expected summer reestablish reefs, even after extensive die- mortalities. offs. Salinity has often been considered the Dermocystidium marinum is considered critical factor regulating the disease since rather specific for the American oyster. infections rarely occur in water less than However, a few other invertebrates harbor 15 ppt. Such is not always the case. In fact, similar and, in some cases, identical spores, biologists from Mississippi and Florida but apparently do not undergo mass have found over half of many samples from mortalities. Actually, several related, water less than 15 ppt to be infected. Often poorly-understood species infect oysters and oysters have infections in water that is fresh other invertebrates, and some of these can or quite low in salt content. cause mortalities in stressed hosts. Apparently temperature acts as the primary controlling factor. Acquisition of Other Symbionts and Diseases most infections probably occurs during Several other organisms in addition to a period of high salinity, butdevelopment is dermo-like agents cause disease in oysters. most pronounced when temperature is Most necessitate a microscope to see. An relatively high. High temperature may de unidentified "mycelial" (suspected fungus, crease the host's ability to defend itself seehypha in glossary) disease infects oysters against the organism, justas indiscriminant from at least Texas and Louisiana use of steroids can cure one condition in a primarily in spring; infections result in person but allow another previously some mortalities, but show no obvious controlled condition to become expressed. relationships with salinity. Juvenile oysters do not seem to develop Other diseases of bacterial and fungal dermo as readily or severely as older ones. origin also occur. One discussed here is Although host-mediated resistance* (also "foot disease." That name is a misnomer see humoral and cellular mechanisms in because the oyster's foot, an organ which glossary) in juveniles has been suggested, aids crawling of the larva before it attaches, thephenomenon is probably because young becomes rapidly resorbedby the young spat oysters are in comparatively better health aftersetting.Apparentlycausedbya fungus, than older ones and therefore better able small rough greenish spots speckle the in to fight off or control any challenging side of the shell under the attachment of the infective agents. Active defense mechanisms adductor muscle. In severe cases, part of the used to fight the parasiteare well known and muscle separates from the shell and a horny chemical defenses may exist as well. Also, elastic cyst forms. As it extends beyond the young oysters commonly grow so fast that site of attachment, the cyst acquires a hard they can reach adult size as fast as an in calcareous encasement. The site of fection can occur. This is especiallytrue of attachment necessarily changes continually the numerous latesummer-spawned oysters to accommodate growth of the oyster and that grow through the winter when the shell. Thought bysome to bemore prevalent parasite is limited by lower temperature. in warm muddy waters, foot disease makes Oysters seem most susceptible to infection an oyster vulnerable to predation because and disease immediately after spawning. the valves no longer close efficiently. The extreme stress associated with spawn The cyst illustrated in Figure 8 may be ing apparently greatly weakens the oysters foot disease, a rare condition in Mississippi American Oyster 9 since the spores do not undergo repro duction like spores of Dermocystidium marinum, they are not numerous, and they cause little pathological change in the oyster, the likelihood is greater for other factors being involved in the mortalities. A bucephalid digenean () also infects oysters in the northern Gulf of Mexico. Some infected individuals gape, suggesting harm caused by the fluke or an Figure 8. A hard horny growth secreted by associated stress. Most infected oysters, the oyster. This may exemplify "foot however, become castrated, and their full disease," a reaction by the oyster against a ness and tastiness often improves like thatof fungus underthe attachmentoftheadductor muscle. Low quality pearls form when the a gelded domestic animal. The oyster secretes a protective coating around improvement becomes noteworthy during an irritant. the summer when the condition of uninfected oysters diminishes because of Sound, or some other similar condition. A spawning activity. Even though eating variety of hard growths can develop in an oysters harboring the larval stages of this oyster. Pearls form when the oyster secretes fluke may be esthetically displeasing, the a protective calcareous coating around an consumer cannot be harmed. The larvae irritant such as a sand grain ora larval para only infect specific fishes which in turn site, but these rarely have the quality must be consumed by otherfishes to mature. essential for good jewelry. "Mud pearls" Man digests both larval and adult stages. may also be caused by penetration of Life cycles of other digenetic flukes, or mud worms at the site where the adductor trematodes as they are often called, will be muscle attaches. discussed in detail later. Consumers occasionally worry about Any oyster in the Gulf can occasionally eating pink oysters. This condition typi harbor a tapeworm larva, one or two larval cally develops in oysters refrigerated for a roundworms, or a variety of amoeboid, few days. A yeast can cause this, and it is de ciliated, or flagellated protozoans. When stroyed with even minimal cooking. Other the oyster undergoes stress, some of the discolorations occur in live oysters. The ad protozoans reproduce extensively and ductor muscle of an oyster that has fed on a become implicated in disease. Quantifica specific (a very small alga) "bleeds" tion of the role of those protozoans in a reddish pigment when cut. Certain oyster disease and mortality must await (other small algal forms) further investigation. and heavy metals also cause discoloration A few larger symbionts, visible to the in various tissues. naked eye, inhabit the oyster, but seldom A microscope allows detection of spores* harm it by themselves. Those most likely of a gregarine protozoan. Two similar to arouse curiosity are a small snail, species, one infecting mostly mantle tissue crabs, and turbellarian . and the other infecting gill tissue, occur A 5 millimeter (mm) long (see glossary commonly in Mississippi. Within thespores under measurements), whitish snail are worm-like protozoans, and if eaten by (commonly known as the impressed certain small crabs, the life cycle is odostome) congregates in numbers some completed. Some inconclusive experi times greater than 100 at the edge of an mental evidence suggests that the gregarine oyster shell. Reaching over the edge, a snail spores cause mortality in oysters. However, intermittently protrudes its proboscis into 10 Marine Maladies? the oyster's mantle to feed on mucus and tissues. Not specific to the oyster, but apparently preferring it, the little gastro pod also feeds on other molluscs and on worms. It is part of the high salinity oyster reef community*. Younger snails replace the older ones in late summer, more often inhabiting older oysters. Pea crabs associate with a variety of invertebrates. One species, popularly referred to as the , commonly invades oysters in New England and on occasion inhabits individuals along the northern Gulf, especially from high salinity reefs such as those off Pass Christian, Mississippi. Small crabs less than 1 mm wide enter an oyster, usually settling on the gill surface. Spat and year-old oysters appear to attract more crabs, even though the crab survives best in year-old and older oysters. The pinkish female crab grows Figures 9-11. A polyclad flatworm along with the oyster until it reaches over (Stylochus ellipiicus) commonly known as 1 cm wide. In contrast, the male remains an "oyster leech." Top, the flatworm gliding across a 105 mm long oyster valve. Note the small and even has a hard stage which deeply-pigmented adductor muscle scar on allows it to leave one oyster to mate with the shell. The degree of pigmentation varies females in others. Usually one or two fe widely among individuals, and its presence differentiates the American oyster from the males occupy an oyster, but many can be smaller Gulf oyster. The small dark areas tolerated. surrounded by lighter areas result from the Not feeding directly on the oyster, the burrowing clam. Bottom left, close-up of same flatworm. Bottom right, a preserved crab nevertheless irritates and erodes the and stained specimen of the same species. host's gills. To feed, it traps mucusand food The worm feeds on oysters and , masses in its walking legs, or it picks strings but seldom severely harms any oystersother than young or stressed ones. of food directly off the host's gills with its pinchers. Young crabs probably filter food entering worm by rapid closure, it will from the water. secrete a horny partition along the margin From a gourmet's standpoint, any to keep the worm out. When oysters possess diminishment caused in an oyster's several such concentric partitions, oyster condition is compensated for by the fishermen recognize that "leeches" have addition of a tasty morsel. In New England, been present. According to some people, the pea crabs get eaten both raw and cooked. If flatworm has an easier time getting into spat cooked, the bite-sized morsels can be than adults and periodically causes sauteed or deep-fat fried along with hermit mortalities. Those infested adult oysters crabs and small fish. typically also harbor an infection of The oyster "leech," actually not a leech Dermocystidium marinum. but a polyclad flatworm (Figures 9 to Another related polyclad commonly 11), lives among oysters and feeds on them occurs in the oyster drill, and it can even or on associated animals such as barnacles. enter an oyster. If one wanted to collect any Occasionally, if an oyster cannot eject an of the different polyclads, there is a trick to American Oyster 11 it. An easy way is to place oysters or crushed drills in a bucketofwaterfrom the mollusc's habitat and leave them for a day or so. Once the water fouls and loses its oxygen to de composing hosts, the flatworms will crawl about on the side of the bucket and can be readily seen. Without a concertedcollecting effort, many worms may be overlooked. Indeed, most fall off or dry up and are never seen by those who relish oysters-on-the-half- shell. An organic solvent such as xylene will cause these and many other hidden symbionts to leave their host, but use of such methods will kill the organisms. With a dish of specimens plus some healthy hosts, some enterprising student should be able to design an experiment to study feeding and pathological effects on the hosts, to investigate survival or reproductive capabilities of the worms under different conditions, and to win a prize in a science fair. All species usually inhabit the mantle cavity of their hosts, but I have observed specimens inside a drill's shell near the top of the spire. Whatare they doing there? One species in a hermit crab's shell eats the crab's eggs, but, during other seasons, helps maintain the inner surface of the shell by feeding on fouling organisms.

Shell-Burrowing Symbionts A few associations between oyster and Figures 12-14. The burrowing clam symbiont involve species that burrow into (Diplothyra smlthli) in the oyster. Top, oysters show the diagnostic small round the shell. Even though confusion exists holes of the clam as well as the raised siphon- concerning definitions, here I consider a chimneys that protect the burrow from silt. burrowing animal one that excavates a Specimens of the hooked occur on space for the purpose of living all or a part both margins of the middle oyster; the outer central portion of that oyster's valve became of its life. In contrast, a borer is one which weakened and broke off because of clam forms a hole in order to obtain food or burrows. Middle, valve has been purpose inject a substance. fully broken to expose clam. The small irregular holes are burrows. The One burrower on high salinity reefs in conspicuous network of pits at the margin is Mississippi (Diplothyra smithii) actually an encrusting bryozoan. Bottom, commonly goes by the name burrowing (or adult burrowing clams removed from their final excavation site. boring) clam (Figures 12 to 14). The foot of a young individual secretes an etching or finitely, only excavating as a juvenile. softening substance, allowing the serrated During summer months, spawning occurs margin of the clam's shell to raspand scrape and the larval stage with its developed foot a tunnel. The clam does not burrow inde- finds and penetrates into an oyster or, less 12 Marine Maladies?

Figures 15-16. Radiographs of oyster valves. Left, the large opaque specimens of the burrowing clam are surrounded by the marginal U-shaped burrows of the mud worm. Right, the burrowing clam is surrounded by the network of cavities formed by a burrowing sponge. These photos are printed from negatives made by the same apparatus that X-rays teeth. often, into the shells ofa few othermolluscs. season was opened early for the lower reefs After about3 monthsof slow burrowing, the off Pass Christian because shells possessed clam's incomplete shell begins to reach its numerous clams. full size and encloses the foot. That foot Two other culprits in Mississippi degenerates as the clam matures. At about commonly burrow in shells, and these are 1 cm in length, the separate males and depicted in radiographs (often called females remain stationary in the cavities. X-rays). Figure 15 shows both the clam and Externally, this pest can be recognized U-shaped burrows of mud worms, whereas by its characteristic small hole in the Figure 16 reveals the numerous smaller host's shell through which the clam receives excavations made by the burrowing sponge food andoxygen andremoves excreted waste as well as the clams. products (Figure 12).Sometimes raised well The mud worm, a polydorid polychaete above the shell, relatively high siphon- (Polydora websteri), forms mud blisters. chimneys (note where oysters join in Figure Larval individuals, after developing first in 12) protect the clam from excess silt. When egg capsules lining the adult's tube, become a burrow approaches or extends into the planktonic and then settle onto the outside inner part of the shell, the oyster pro of the shell or on the lip's margin to begin duces layers of a hard proteinaceous burrowing. What starts as small horseshoe- material (conchiolin) to reinforce the shaped depressions ultimately develop into region. Nevertheless, burrows materially large U-shaped encasements of mucus- weaken the shell, making the oyster vulner cemented mud along the inner shell-surface able to predation and less desirable to covered by a host-secreted semitransparent consumers because the shells crumbleapart. material. Following stressful periods of As recently as 1975, Mississippi's oyster high temperatures, often about November, American Oyster 13 black blotches may speckle the mantle, visceral mass, and shell. The extensive network of burrows creates rather brittle shells. Each species of yellowish-to-orange sponge seems to thrive best in different salinity conditions. Some species turn brownish when they die.

Fouling Organisms and Predators A variety of animals grow on oysters. These fouling organisms do not parasitize them, but they may compete with them for food, smother them, or prohibit spat settling. Some of these are slipper shells, the hooked mussel, , bryzoans, hydroids, , and barnacles. A polychaete (Nereis [=Neanthes] succinea), much longer and greener than the reddish polydorid, commonly crawls among these fouling inhabitants and even feeds on gaping oysters, acquiring spores of Figures 17 and 18. Oyster valvedepicting the presence of the mud worm. Top, blisters Dermocystidium marinum. Occasionally resulting from the oyster's protective one accidentally drops in with a shucked secretions. These signs also favor use of the oyster to the disgust of a consumer. name"blister worm." Bottom, reverse sideof the same valve with typical external pits as Comments on predators should be made sociated with the blisters. for a few reasons: one, to exemplify the difference between a parasite, which mud worms commonly lack the oyster's seldom harms a non-stressed host, and a thick, protective, nacreouscovering. Figure predator, which eats and usually kills its 17depicts diagnostic blisters, and Figure 18 "host"-prcy; two, to relate that some preda of the other side of the shell shows the ex tors, just like some disease-agents, can ternal pits associated with those same decimate large populations; and three, to blisters. Whereas probably not killing an emphasize that completion of some life oyster, the presence of several of these cycles of parasites depends upon a predator. often signifies that the oyster is in A variety of oyster predators exists in the poor condition. Gulf. The most devastating is the southern Young (alpha-stage) burrowing sponges oyster drill, or conch, which will be treated affect the shells of both living and dead in detail- later. Another carnivorous oysters. In fact, they continue growing after gastropod, the lightning whelk, also the death of an oyster until large masses are consumes many oysters. It opens the oyster formed. The size and shape of the small shells by chipping away at the valves until cavities (Figures 13 and 16) and the size and it can insert its proboscis. In some Atlantic shape of the siliceous (glass) spicules, ob coast regions starfish eat many oysters, but servable by dissolving away surrounding in Mississippi, blue crabs, mud crabs, and tissue with laundry bleach, characterize the stone crabs rank as more important several species of Cliona. Unless the oyster predators. A blue crab can consume many has grown very old or undergone excessive spat each day (Figure 19). It prefers 3 to4 cm stress, it does not allow direct contact be long individuals and seldom feeds on a large tween its tissue and the sponge. It if does, oyster unless it is damaged or unhealthy. 14 Marine Maladies?

Figure 19. The valve of an oyster spat Figure 20.Anoysterdrill(conch) pulled back showing a hole made by a blue crab in order from a bored spat on an old oyster valve. All to eat the oyster. drills do not bore holes in their prey like the one shown here. When a drill does bore into Both mud and stone crabs help complete its prey, the hole is often near the margin. life cycles of parasites by feeding on oyster tissue. They are definitive hosts for gregarines and facilitate development and dispersion of Democystidium marinum spores. Other examples of life cycles will be presented in other sections. Fish such as the cow-nosed ray eat many oysters as does the black drum, which has well-developed pharyngeal teeth to crush the oyster's shell. Above all, man with his numerous devised means to collect and prepare oysters is the primary predator. Figure 21. Snail (gastropod) egg-capsules As indicated earlier, the southern oyster on the beach. The lightning whelk produced the long string of capsules, the true tulip drill (Thais haemastoma) is generally the deposited the triangularonesattached to the most devastating predator in the northern string near the center, and the oyster drill Gulf. It does not always bore into the shell attached the narrowonesvisible above those of the tulip. If the within thecapsule of its prey (Figure 20). Aided by secretions, of the drill die, a purple color stains it. A hole boring involves movement of the radula, a at the top indicates the young escaped. ribbonlike organ with rows of teeth, which rasps back and forth etching away shell their large populations. They undergo material. Young moderately-sized drills communal spawning, attaching egg cases usually bore oysters, especially large ones, to a hard substratum*. With up to 10 or near the edge of the shell, whereas older more drills in a group, many young are drills seldom bore at all. The drill produced. Each drill typically produces apparently emits a paralytic agent, a yel about 8, but sometimes up to 17, egg cap lowish secretion from the anal gland, that sules an hour, and each of these encloses up turns purple in sunlight. Oysters preyed to 900 embryos. A mass (Figure 21) often on by drills often have purple stained contains over 1000 of these 6 mm by 2 mm tissue. A drill can devour a large oyster capsules. Following a storm, a beachcomber every few days and can kill nearly 100 can observe masses of capsules washed up on week-old spat per day. Increased tempera the beach. The purple color discloses that ture usually increases feeding rates and the embryos died, whereas an open hole weakens oysters which in turn can be on the flattened top surface shows that the disastrous to a reef. larvae escaped. The drill is dispersed over Drills have a catastrophic effect because of large areas because its larva is planktonic. Blue Crab 15 THE BLUE CRAB As the most economically important crab from the Gulf and Atlantic states, the blue crab () is caught pri marily in chicken wire "crab pots" and trawls by professional crabbers (Figure 22) and in drop nets or on a piece of twine by sports fishermen. Rather than being attracted to poultry parts, pork scraps, or fish using the above means, the soft-shelled stage of the crab does not feed and can be collected with a dip net or in an artificial shelter. This special gourmet's delight re Figure 22. Commercial crabber and his son mains in the soft stage for several hours emptying catch from crab pot into sorting following molting. Molting will be tray. described later, but of importance here to those who have never eaten soft-shelled on by winter northerly winds, usually signals females to leave the . Atypical crabs is that the entire crab minus gills, "apron*," and a narrow anterior portion conditions like the extended high salinities provides a rich broiled, fried, or barbequed in Lake Borgne, Louisiana, during late 1976 and early 1977 inhibited the migration, delicacy. thereby causing a decline in the winter's In most of the northern Gulf of Mexico, crab catch in Mississippi Sound. the adult crab may spawn once or twice I presented the above features of thecrab's during the 9 months from spring through life history because they dictate the kinds fall as opposed to once in Chesapeake Bay and amounts of symbionts that affect a crab. where the crab concentrates spawning to Molting represents an example. When a about a 2 month period. Spawning occurs in crab sheds its molt, it sheds many high salinity regions, often near barrier ectosvmbionts. Discussion of some islands in the Gulf. If not in high salinity symbionts follows, not all of which are water, the first larval stage (nauplius) held shed by molting. by the female and the next larval stage (zoea) die or do not develop properly. After de Protozoans and Microbes veloping in a highly saline habitat, the larva As true parasites, microsporidan proto metamorphoses (into a megalops), migrates zoans infect a variety of host cells. Of at into , and metamorphosesagain (to least five different species infecting the an early crab stage). Juveniles thrive in the blue crab, one (/Imhabitats from Chesapeake Bay some cases for as long as 5 years. The advent through Louisiana. Heavy infections can be of dropping temperatures, usually in recognized easily because muscle tissue conjunction with lowered salinities brought acquires a chalky appearance in joints of 16 Marine Maladies?

Figure 23. Life cycle of a microsporidan (Ameson michaelis) in the bluecrab.The cycleofthis pro tozoan is direct; there is no true intermediate host. When a blue crab feeds on infected crab meat or spores from another source, the long internal tubular filament of the spore turns inside out as it protrudes, allowing the Infective nucleus and associated material to pass through it and infect a host blood . Divisions of the microsporidan within the blood cell produce a continuous supply of the parasite that reaches muscle tissue where there forms a string of developing spores. As a spore approaches maturity, there are first two Joined cells and then a single mature spore. Crab meat infected with spores turns opaque and chalky. The muscle tissue surrounding the masses of spores breaks down, and the crab becomes weakened and vulnerable to stress.

the appendages and the abdomen often who would recognize infections. Naturally turns grayish. Even though virtually absent infected crabs often fail to undergo migra from Mississippi Sound until spring of tions with noninfected counterparts, and 1978, sick crabs typically inhabit nearby they tend to die more readily when stressed. Lake Pontchartrain and Lake Borgne in Before learning about the life history of Louisiana. Generally less than 1% of the the infectious agent, fishermen would crabs there show infections, but occasion smash infected crabs and return them to the ally more than this number linger in warm water, allowing noninfected blue crabs to and close to shore. Perhaps this feed on the tissue and acquire the disease. disease has a great impact on young crabs. In Education therefore helped the fishermen in our studies, we have experimentally infected a way similar to the situation when oyster both young and old individuals without fishermen from Chesapeake Bay and from difficulty. Naturally-infected crabs as Puget Sound, Washington, learned that for narrow as 2 cm across their carapace* have each starfish arm ripped off with a central been seen, but small crabs avoid most portion, another predator starfish re routine collecting procedures by people generated to feed on their crop. Blue Crab 17

Figure 24. Highly magnified view of micro sporidan spores (Ameson michaelis) among Figure 25. Claw of blue crab with shell- muscle fibers of blue crab. disease. This brownish lesion with degenerated internal regions apparently A diagram (Figure 23) reveals an results from a bacterium (Benekla type I) extremely magnified representation of which digests the from the exo- skeleton. An infection is rarely fatal and is stages in the cycle. A mature spore (Figure lost during molting of the host. 24) measures about one-fourth that of a human red blood cell (1.9 microns[;i] versus thin external lipid (fat) layer of the shell 7.6 pi). Under appropriate conditions, an (epicuticle) has been disrupted, the exposed ingested spore everts its long internal chitin* becomes digested by specific tube (polar filament), an action roughly bacteria and possibly also fungi. Probably analogous to blowing out the inverted fewer crabs than lobsters die from the finger of a rubber glove. The nucleus and disease, especially if lobsters are cultured cytoplasm of this single celled animal in warm water. Death probably results from squeezes through the extruded pliable secondary infections. Nevertheless, crabs filament and invades a host crab's blood look esthetically displeasing, and confine cell. Once there, the organism undergoes ment fosters disease. Hence, some crabbers vegetative growth, producing cells which in know the disease as "box burnt" because turn produce strings of eight individual they maintain crabs in floating cypress-box spores along muscle tissue. Ultimately, cages waiting for their catch to molt. enormous numbers of these resistant spores Certain other bacteria harm both crabs and their products destroy adjacent tissue and people, when given the proper and replace the crab's normal musculature. conditions. One such organism This parasite can be considered highly host- (Vibrio parahaemolyticus) readily kills specific* because the muscle tissue of only crabs and causes food poisoning in people. Callinectes sapidus exhibits infections. In crabs, species including Vibrio Many symbionts, like the bacteria parahaemolyticus cause large jelly-like mentioned in the next paragraph, have a blood clots in addition to whitish-colored wide, or loose, host-specificity* because they nodules to develop in thegillsand elsewhere associate with a wide range of hosts. from masses of aggregated blood cells and Shell disease ("box burnt" crabs) repre bacteria. Crabs from Mississippi waters sents a typically non-fatal microbial occasionally die from these infections. In condition usually initiated by a wound. In people, numerous cases of intestinal upset any event, infected crabs usually have not associated with eating seafood probably molted for a long period and have under also result from this organism. Even gone stress. Starting as brownish areas with minimal heating, however, eliminates this reddish brown depressed centers forming on threat. To avoid food poisoning in crab- the exoskelton, these lesions develop into preparing operations, continued care deep necrotic* pits (Figure 25) that typically should be taken not to permit fluid from do not penetrate through the shell. Once the fresh crabs to contaminate previously- 18 Marine Maladies? boiled crabs. Additonal difficult-to- microphallid known. Most other species diagnose microbial diseases of crabs will average less than 1 mm, appearing some appear following the section on metazoans what similar to a comma in diis booklet in and their hyperparasites*. Metazoa, not a both size and shape. Also very unusual. natural group of organisms, designates that Levinseniella capitanea has no gut or an included organism is multicellular with muscular pharynx, principal features for two or more tissue layers. most larval microphallids and used by almost all adult digeneans for feeding. The Metazoans and their Hyperparasites gut does not develop even after the larva in Larval flukes (digeneans), unlike larval its spherical, yellowish cyst has been eaten tapeworms (cestodes) (Figures 26 and 27), by and matures in a raccoon. infect many freshwater, estuarine, and ma The second species (Microphallus rine crabs. Microphallids form a family of basodactylophallus) can barely be seen in digeneans that utilize three hosts: l) a snail crabmeat (striated muscle tissue) without a as a first intermediate host*, 2) a microscope, unless a urosporidan protozoan as a second intermediate host, and 3) a bird, has hyperparasitized it. It measures about , or rarely a cold blooded 0.45 mm (450 microns) long after removal as a definitive host. At least six species infect from the spherical 0.35 mm cyst (about the the blue crab. We will mention two, the first size of the following period). (Levinseniella capitanea) because it can be seen easily among the gonads or the Figure 28 illustrates the life history of diverticula of the digestive gland if the this digenean. Any of four species of snails crab's carapace* is removed. Nearly 4 mm from the shallow low salinityestuaries* may long, the excysted worm ranks as the largest release the infective free swimming larva (cercaria). That free-living larva was pro duced in quantity within another asexual stage (sporocyst) which was itself produced by a similar larva that in turn had developed from a germ ball within the initial ciliated larva (miracidium). The initial larva occupied the egg which was fed on by the snail. In other words, from one egg develops an enormous number of larvae infective to the blue crab and at least two of the several species of fiddler crabs. Also, eac h resulting adult worm produces an enormous number of eggs. Because of de pendency on environmental parameters and on need for specific hosts, these large numbers of eggs and larvae are necessary to assure completion of the cycle for one or more individuals and continued survival of the species. Each individual possesses both male and female organs, making it hermaphroditic. Figures 26 and 27. Two views of same larval It can successfully fertilize itself, even tapeworm moving through muscle of lesser though all tested species of digeneans blue crab (Callinectes slmllls). Although prefer to utilize partners, if given the apparently common in this crab, it has not been observed in the common blue crab opportunity. These worms mature when an (Callinectes sapidus). appropriate final host eats the infected crab, Blue Crab 19

Figure 28. Life cycle of the microphaiiid fluke (Microphallus basodactylophallus). The blue crab harbors the infective larva, sometimes hyperparasitized by a haplosporidan protozoan (Urospor- Idlum crescens) which allowsthe infected fluke to impartthe names"buckshot"or "pepper spot" to involved crabs. When eaten by an appropriate host such as a raccoon, the healthy larva develops into an adult and produces eggs infective to a few different estuarine snails. Asexual reproduction of the fluke occurs in a snail, as it generally does for all digeneans, and ultimately results In a tailed, swimming larva that penetrates the crab, loses its tail, encysts, and develops into a stage Infective for the vertebrate. assuming the larva has developed for at least internal parasites. I assume they did not see a month in the crab. In Mississippi, the the flukes because when such digenean raccoon and serve this need, cysts have a protozoan hyperparasite*. but some birds and other mammals also people often exhibit apprehension. fulfill the role. If a person ate a heavily- The minute, brownish, hyperparasitic infected raw crab, he would probably haplosporidan (Urosporidium crescens) acquire an infection and possibly develop infects tissues of the encysted worm. This minor gastric distress. Even though an in protozoan undergoes extensive multiplica fected person's health probably would not tion until the cyst increases in size by many be seriously affected, a related species has times and the worm's tissue has been been known to cause extensive gastric and replaced by spores (Figure 28). The vast neurological disorders. I recommend number of spores in a cyst distinguishes cooking crabs! each cyst as a visible black speck. Some Local coastal residents have never dis fishermen term these cysts "buckshot" or closed to me any concern abouteatingcrabs, infected crabs as "pepper crabs." Although presumably because they did not see any severely debilitating the worm, the spores 20 Marine Maladies?

Figure 29. Buckshot, or pepper spot, in blue crab meat. Dark, almost spherical objects near the pointer and at the top of the meat are fluke larvae (Microphallus basodactylo phallus) infected with a protozoan (Urosporldlum crescens). The immense number of spores enlarges the fluke cyst many times. The piece of crab has been cooked; the for the swimming leg occurs in the lower left of the photo. harm neither the crab nor man. A piece of cooked crab (Figure 29) reveals a couple of clusters of buckshot. Other encysted digenean larvae also harbor this or related species. Some also possess other kinds of protozoan hyperparasites including micro- sporidans, myxosporidans, flagellates, and opalinids. The blue crab, a crustacean, has its own crustacean symbionts. Thosediscussed here, however, appear much different from the crab except for the early larval stage. Figures 30-32. External bamacle symbionts They are barnacles and range between being on the blue crab. Top, the acorn fouling organisms and true parasites. (Chelonibia patula) on the carapace. One common barnacle ( venustus Middle, a goose-neck barnacle (Octolasmis muelleri) on a gill filament propped up by a niveus) found on a varietyofhardsubstrata* dissecting pin. Bottom, underside of gills in the Gulf also establishes itself on the showing many medium-sized and small carapace and legs of the blue crab. Another, Octolasmis muelleri. Note how few can be the acorn barnacle (Chelonibia patula), seen without lifting the gills. exhibits more host-specificity*. It restricts including the blue crab (Figure 31). It needs itself to the external surfaces of a small a living crab for survival. Special cleaning group of crabs. Figure 30 shows it on the appendages sweep gill surfaces freeof debris blue crab. Whether lacking or expressing and presumably of settlingorganisms. Once specificity towards the crab, both encrusted an individual does become established, the barnacles cause their host hardship by crab's cleaners apparently become less producing excess weight which sometimes efficient. Consequently, increasing constitutes a considerable burden. amounts of debris and numbers of larvae A gooseneck, or pedunculate, barnacle can settle on the gills. In fact, a crab can (Octolasmis muelleri) confines its presence acquire over 1000such barnacles on the gills to the gill region of a few decapod species. and elsewhere in the gill chamber. When Blue Crab 21

small-and medium-sized barnacles infest a host, over 700 can coat the under side of the gills without hardly being apparent on the top surface of the gills (Figure 32). The combination of these heavy infesta tions* and debris can make respiration difficult for the crab because barnacles compete for oxygen and decrease the amount of gill surface available for respira tion. Healthy crabs are hardy; they live for long periods out of the water when their gills are moist, but die quickly immersed in stale water. Infested crabs act sluggish most of the time and probably attract pre dators. The last barnacle to be discussed truly parasitizes its host (Figures 33 to 35). If not for being able to recognize its larval stages, biologists would not have been able to classify it as a barnacle. An external portion of this rhizocephalan (Loxothyla- custexanus) protrudes from under thecrab's abdomen (Figure 33). This bulge, called the externa, contains a brood- pouch for larvae and both male and female gonads. A crab can have as many aseight externae, and three are fairly common (Figure 35). The remainder of the barnacle consists of root like structures penetrating through most host tissues(interna). Crabs becomeinfected Figures 33-35. Sacculinid barnacle when young by a swimming larva (cypris). (Loxothytocus texanus) of the blue crab. After a period of internal development, the Top, the protruding pouch (externa) under the crab's abdomen contains larvae and interna of the organism penetrates through gonads ( and testes). Long, narrow a crab's soft abdominal joint when the crab extensions invade most other tissue. Middle, molts. Infection retards a host's gro\vth, top crabhas dark externa indicatinganolder infection than thatof the yellowish externa of leaving most externae-bearing individuals the middle.crab. The larger lower crab between 3 and 8 cm wide. Additionally, reveals the small size of infected crabs. It is secondary sexual characteristics of infected an immature female, wheras the aprons on the infected crabs reveal the apron of a males transform into those of females. mature crab. Infections also modify the Therefore, most infected crabs appear as shape of the male's abdomen into that of a miniature adult females, either with or female. Bottom, crab with three developing without externae. The size-difference externae. Usually only one externa occurs per crab, but occasionally over five may be between an egg-bearing (sponge or berry) present. female and an infected crab is usually great. Figure34shows the size-difference between rounded apron normal for mature females. an uninfected immature female with her Castration of the crab may result from acutely pointed abdominal apron and a involvement with a structure called an smaller infected crab with the transformed androgenic gland. Male crabs have this 22 Marine Maladies? gland, and, if it is removed from a young individual, female characteristics, in cluding ovarian tissue in the testes, develop. Perhaps destruction of this gland or some action on its secretions, possibly additionally involving hormones produced by the barnacle's ovary, causes feminization of the infected crab. Crabs with externae can molt and lose that part of the parasite, but whether that process is typical is unknown. Most bio logists assume crabs with this and other mature rhizocephalans do not molt. Infections, although prevalent in some Figure 36. Sacculinid barnacle parasite high salinity bays and bayous in Louisiana, (Loxothylacus panopael) in the mud crab have been negligible until 1977 in (Eurypanopeus depressus) from Chincoteague Bay, . Note difference Mississippi Sound since an epizootic between this species and the one in the blue outbreak in 1965. While aboard a shrimp crab. boat in July 1977,1 noted over half the crabs and early summer in Mississippi result from we trawled in the Sound exhibited a distinctive genetic stock, from infections. The apparent magnitude of environmental influence, or from a infection in the population could be ex parasitic infection? It seems quite possible aggerated because the small crabs would be that these crabs possess prepatent* continually thrown back by shrimpers for sacculinid infections, and, indeed, that others to recapture, whereas large ones problem needs attention. would be saved for eating. Nevertheless, Mud crabs, much smaller crabs than the infections occurred commonly for several blue crab, also possess a related rhizocepha weeks, and epizootics will undoubtedly lan barnacle, and the externa of that species occur again. (Loxothylacuspanopaei)differs(Figure 36). As with other cited barnacles, infections An understanding of molting aids relate directly with salinity and probably interpretation of barnacle-crab associations with temperature. In inshore regions with and othersymbiotic relationships for crusta moderately high salinity water, crabs have ceans. Like most crustaceans, the blue crab a greater potential for infection. Infections has a hard external skeleton also known usually coincide with breedingand matura as a cuticle* or shell. In order to increase tion peaksof the bluecrab, beingmostpre in size, the crab must shed the old shell. valent about May and Octoberin Louisiana. When initiating this molting process Unlike the other barnacles attached to the (ecdysis), a new soft shell forms beneath crab, the adult rhizocephalan cannot the hard one of this "peeler" stage. tolerate low salinity. Maturing externae Enzymes begin to dissolve the shell, allow apparently do not protrude, and ones al ing the products to be resorbed into the readyprotruding takeon waterand rupture. body-proper. Thus, amino acids, calcium, Low salinity habitats characteristic of and other products can be salvaged for Mississippi estuaries certainly do not incorporation in the new cuticle. The favor barnacle infections. posterior part of the old shell then cracks, The presence of "dwarf" or "button" allowing the "buster" stage crab to wiggle crabs concerns some fishermen. Do these out backwards. This amazing process is small apparently sexually mature indivi controlled by a balance of separately- duals that show up mostly during spring produced molt-inhibiting and molt- Blue Crab 23

Figure 39. Long orange ribbonworm (Carclnonemertes carclnophlla) pulled out from between gill lamellae. Other light colored regions on gills are additional specimens. The orange color indicates that the worm fed on the crab-host's eggs; thus, the crab had spawned. Also, note the barnacles on the gills. Both the ribbonworm and the barnacle indicate that the crab had inhabited high salinity water.

A ribbonworm (nemertean) (Carcinone- Figures 37 and 38. Blue crab molting. Top, mertes carcinophila) approximately 1.5 cm molt, or ecdysis, including covering of gills in length often inhabits the space between and lining of fore- and hindgut. Crabs that back out of shells like this remain extremely gill lamellae in crabs from high salinity soft and pliable for about 4 or 5 hours. water (Figure 39). Since, in the northern Bottom, soft-shelled crab. Note pliable Gulf, most males do not accompany females nature of the twisted claw and depressed migrating to salty regions in order to spawn, carapace. fewer male than female crabs have stimulating hormones. The results are the nemertean * (see infection in discarded molt (Figure 37) and the helpless glossary). This higher prevalence for soft-shelled crab enlarged by 20 to 60%of its females also acts in the best interest of the previous size (Figure 38). The crab imbibes nemertean because in order for the worm to and otherwise incorporates water while still achieve sexual maturity and reproduce, it soft in order to achieve the expanded size. must migrate from the gills to the egg mass After about 5 hours, unless retarded or of the host. While there, it builds a mucus halted in a refrigerator, the new shell tube for inhabitation. Crab eggs provide hardens because the protein becomes tanned nourishment for the worm, transforming and calcium chloride is redeposited. Even the worm's color from creamy to orange. though not as soft, this "paper-shell," or Because of the large quantity of mat "buckram" crab will remain vulnerable to erial, crab eggs appear orange during the predators for another day or so. first 5 days of the larva's 14-daydevelopmen As mentioned earlier, following mating, a tal period. Since a crab can produce over 2 female rarely molts again. Consequently, million eggs and may generate those twice the shell of a mature female offers a prime in a year, even a heavy by the substratum* on which barnacles and other nemertean has little effect on crab pro fouling and symbiotic organisms can duction. attach. In addition to being able to shed Some time after mating, the female worm some symbionts by molting, the mature leaves her collapsed tube with its attached male usually inhabits low salinity habitats eggs. The resulting ciliated larva hatches not conducive for barnacles. and stays in the tube, swims among the crab 24 Marine Maladies? eggs, or leaves the host and undergoes metamorphosis into a creeping stage that infests another crab. The blue crab is the common host, but other portunids (swimming crabs) and occasionally nonrelated crabs harbor the worm. Because of an attraction by both the nemertean larva and the crab toward light, the two often come into contact and infestation occurs readily. As indicated above, worms change color •••:i;;^\!0?"5:' after feeding on crab eggs. Consequently, since adults return to the host's gills, the presence of orange worms encased between lamellae reveals that such a host crab has spawned at least once. The worm is a bio logical indicator! Strangely though, these tags lose some of their adult characteristics and may not feed at all during the winter. A leech (Myzobdella lugubris), unlike the nemertean and barnacles, conspicuously inhabits crabs in low salinity regions (Figures 40 and 41). Even though a case of numerous leeches associated with a few dying crabs implicates them in harming the crab, I doubt the leech causes lesions in mm nfl*B '-.vat: iiii. ''fe-^;Wiiw the crab. The leech often occurs onconsider Figures 40-43. Leech (Myzobdella lugubris) able numbers of crabs in Mississippi and on blue crab. Top, several specimens of the adjacent areas, but I have seen no evidence leech on the crab's anterior. Middle, several specimens on crab's posterior; most suggesting a harmful relationship. individuals deposit cocoons near the rear After seeing Humphrey Bogart covered margin. Bottom left, cocoons on carapace. Bottom right, enlarged cocoon. A single with leeches in the African Queen and young leech emerges from each cocoon; it hearing tales of people having their blood develops in low salinity water and searches sucked while walking through tropical rain for a fish in order to obtain a blood meal. forests or wading through swamps, people blood, the crab leech does. Soon after hatch have a tendency to be disgusted by the ing, it obtains its first blood meal from a intriguing jawless leeches that thrive in our fish. In Mississippi, a specimen of the local fresh-to-. Perhaps the southern flounder, striped mullet, or Gulf thought of losing blood intensifies when killifish may have several individuals at people realize that in 1863, doctors used 7 tached to its gills, opercles, nostrils, fins, million medicinal leeches (Hirudo or body surface. Other estuarine fish may medicinalis) on their patients in London also possess this or other species of leeches, hospitals and almost that same number in but usually in lesser numbers. The white Paris. The practice of bloodletting in catfish acts as a good host in regions where Europe declined soon after, but occasionally it enters brackish habitats. After receivingan someone will still pull one of these from a adequate amount of blood, the engorged culturing jar to remove blood from a bruise leech transforms from a skinny reddish and alleviate swelling. worm about I cm long to a robust greenish- Even though many leeches do not suck brown worm which can stretch a distance Blue Crab 25 greater than 4 cm. At least four different viruses infect the The engorged crab leech typically crab. Figures 44 and 45 provide an ultra- associates with vegetation and throughout structural view of one of these. Until its life shows some ability to swim. Since recently, few viruses had been reported from the blue crabalso associates with vegetation, any invertebrate. Of the four in the crab, the two come in contact. The leech then de three cause fatalities when the hosts are kept positsadhesivecocoons near the rearmargin captive. They occur in crabs along the east of the crab's carapace (Figures 42 and 43). ern U.S. coast, and, if examined for in the Often many leeches infestonecrab. Based on Gulf, some would probably be found. Little observations of leeches attaching cocoons to has been learned about any of them or their finger bowls, some individuals probably at relationships with the crab host. tach their cocoons on other hard surfaces, A severely pathogenic also. In addition to providinga substratum* ( pernicosa) causes mortalities for cocoons, the crab offers a means of in the blue crab from high salinity habitats dispersing the leeches. along the eastern U.S. coast. It is treated A single young leech develops within here because of the potential for it to be each cocoon. It can swim after emerging, introduced or to be present already, but and, like its parent, prefers water with unrecognized, in the Gulf. The causative little or no salt; neither stage tolerates much amoeba occurs in connective tissues and more salt than 15 ppt. Theyoung leech must blood (hemal) spaces throughout the infect infest a fish to continue its cycle. ed crab's body during all times of the year, A leechlike organism also infests the blue but enters the blood and kills the host crab in low salinity and freshwater habitats primarily during summer. When amoebae of Alabama, Mississippi, and Louisiana. enter the blood, the ventral portion of This branchiobdellid (Cambrincola the crab, especially a male, becomes gray mesochoreus) shows phylogenetic* affini ish in color, and, if the disease advances to ties to both leeches and oligochaetes (the this state, the crab always dies. Crabs with latter being best known for earthworms and this "gray crab disease" may have all their aquatic worms used to feed tropical fishes). blood cells destroyed and replaced by the About 2 to 3 mm long, this pink colored amoeba. The nonclotting hemolymph* ac worm infests both the gill chamber and the quires the grayish tint from the organisms. external shell-surfaces without causing its By this stage of the disease, the host's host apparent harm. It feeds on small proto stored nutrients have been depleted, making zoans, algae, and detritus, and its presence recovery unlikely. Some crabs of all sizes, suggests that the host crab has been in fresh sexes, and stages, however, can overcome or nearly fresh water for some time. light infections and survive. Hemocytes* engulf or encapsulate the protozoan, and Miscellaneous Microbes and Protozoans other individuals are destroyed by humoral* The crab harbors many more organisms mechanisms. than those already discussed. Most nec The presence of even low grade amoebic essitate a microscope to observe indivi infections has not been discovered in the dually, but a few can be seen when present in Gulf. If thatabsence results from geographi large numbers or when the crab shows signs cal barriers and not from insufficient indicative of specific infections. An electron examinations or from some biological or microscope is needed to confirm the pre environmental reasons, it becomes sence of some organisms. I will briefly imperative not to introduce eastern crabs comment on some of these microscopically- into the Gulf. Crabs are already transported sized organisms, none of which has been in the opposite direction. Seafood com implicated in human disease. panies routinely ship live Gulf crabs to the 26 Marine Maladies?

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Figures 44and 45. Electron micrographs of herpeslike virus fromblue crab. Top, note dark-staining virus particles in crab's blood cell. Bottom, close-upof virus particles. (Photos magnified4,550 and 67,000 times, respectively).

east coast where they attract great profit as Within this small, about 55 micron diameter a food item. (about nine would touch end to end across A few protozoans infest the crab. the narrowest width of the letter i) trans One (Lagenophrys callinectes) produces its parent dome, the common animal inhabits own "house" or lorica* (Figures 46 and 47). lamellae of the gills of crabs from both the Blue Crab 27 are old, and perhaps the ability of heavily- infested crabs to respire becomes diminished under stressful situations. Internally, a "holotrich" ciliate moves about with the hemolymph. Even though present in large numbers in somedying con fined crabs, this protozoan also occurs in healthy crabs from Mississippi. Pre sumably, the potential for these and other protozoans to become hazardous to crab health increases considerably when crabsare reared or kept captive in water of poor quality. Crabs from North Carolina to the Gulf harbor a parasitic ( sp.) in the hemolymph. The organism, about the size of a crab blood cell, infected 30% of a sample of crabs in Florida. It causes tissues to appear milky and the blood to clot (like with infections of gram negative bacteria); the dino may be responsible for numerous mortalities, especially those occurring during autumn in habitats with salinity greater than 11 ppt. A haplosporidan (MincAtnia-like) related to the organism in the oyster has been en countered in moribund crabs from Virginia and North Carolina. It causes hemolymph to become milky and not clot. No spores have been observed. Critical examination will uncover additional protozoans on or in the gills, appendages, hemolymph, and muscles of Figures 46 and 47. Different preparations ofa the blue crab. Some of these have never been loricate ciliate (Lagenophrys callinectes) from the gills of the blue crab. Note the reported. aperture in the transparent lorica. Large numbers of dead crabs occasionally line some of the high salinity beaches in Atlantic and Gulf coasts. It can control the Mississippi and Louisiana. I have never lips at the opening near one margin, and it seen these crabs, and biologists have as feeds on nonhost matter. Another loricate sumed that the old crabs, mostly spawned- ciliate, an undescribed suctorian (Acineta out females heavily infested with barnacles sp.*, see sp. in glossary) occurs among in on their gills and shells, died of old age. dividuals of Lagenophrys callinectes in Perhaps some of these also had complicat Mississippi. In contrast, a stalked ciliate ing protozoan or viral infections! (Epistylis sp.) usually attaches to the In addition to infesting crabs, disease margins and stems of the gill lamellae organisms also involve crab eggs in the Gulf rather than the flat portion. None of these and elsewhere. I already discussed a nemer ciliates seem to harm the crab. Most hosts tean larva feeding on eggs. A fungus 28 Marine Maladies? (Lagenidium callinectes) invades them. In arriving about March and most white salinities of 5 to 30 ppt, up to 25%of an egg shrimp during the summer. As both become mass may be infected. Infected eggs are juveniles, the white shrimp can be found smaller and moreopaque than healthy ones. further up bayous and rivers than brown The diseased portion of the sponge, which shrimp; the white shrimp remains longer in is always at the periphery, appears brown inshore regions. ish rather than yellowish-orange or grayish The number of these young shrimp that when the crab's larvae have developed will enter the commercial fishery depends enough to give the healthy part of the not on the number of spawning adults, but sponge a brown or blackish appearance. on the temperature, amount of freshwater, Infections become a real concern for and other environmental conditions that people rearing crustaceans, especially since affect survival and growth. These factors larvae can become infected. On the other also have a bearing on the parasites and hand, infections can aid natural popula diseases of shrimp hosts. tions; the fungus also infects the ova of the Adults usually live 1 to 2 years, spawning symbiotic barnacle (Chelonibia patula). two or more times. Some individuals, how ever, survive a few additional years and these shrimp usually possess quite an assortment PENAEID SHRIMPS of symbionts. Shrimp of all ages and stages The valuable shrimp fishery in the harbor parasites, and the parasites occur in northern Gulf of Mexico includes primarily many sites. Figure 48 of a brown shrimp in three species: the brown shrimp (Penaeus dicates many of these sites occurring in all aztecus), the white shrimp (Penaeus species. setiferus), and the pink shrimp (Penaeus The majority of parasites and disease duorarum), the latter being much more conditions affecting shrimp, unlike those important in southern Florida than in the affecting most marine organisms, have been northern Gulf. investigated in some detail. Still, a week All species spawn in high salinity regions; end or even a commercial their larvae develop in the offshore plank shrimper seldom recognizes many of the ton* before metamorphosing into post- conditions. In fact, those people rearing larvae and invading the estuarine* nursery shrimp and encountering heavy mortalities regions. Of all the shrimp, the pink shrimp rarely know the causes. Although blamed requires the highest salinity water; it also for many shrimp-kills, low oxygen prefers a sandy-shell habitat. Brown and concentration levels may not always be the white shrimp thrive in muddy-sand or silty sole culprit. The shrimpmay have to harbor habitats, where, in about 30 to 50 meters a symbiont in addition to being exposed to of water, the brown shrimp can be caught in low oxygen levels in order to succumb. large numbers during night hours between Because shrimp diseases are well docu June and August. It remains commercially mented, I will discuss several of the abundant down to 110 meters. On the other conspicuous ones as well as some parasites hand, the white shrimp moves aboutduring that could be encountered from a high the day and occurs more commonly in water percentage of shrimp if a curious individual less than 18 meters deep with salinity less decided to dissect his specimens and use a than full strength seawater. Consequently, microscope. the white shrimp is available for small in shore trawlers, usually between August and Microbial Diseases November. Unlike most viral diseases known from Postlarval shrimps invade the estuary at crustaceans, one (Baculovirus penaei) different periods, with most brown shrimp involves the digestive gland of shrimp, and Penaeid Shrimps 29

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(pereiopolsj Figure 48. Selected anatomical features of brown shrimp with part of the carapace cut away from the lower specimen to show internal structures. indications of its presence can be seen with a do not have to be present in infected shrimp. regular microscope. These signs include a Perhaps these obvious bodies act as a means relatively large refractile polyhedral-shaped to protect and disperse the virons when the inclusion body* and swollen nuclei and host is eaten or otherwise dies. other cellular alterations of the hepatopan- Shrimp, either crowded in a tank or ex creas (Figures 49 and 50). Inclusion bodies posed to polluting polychlorinated 30 Marine Maladies? mz r?» •

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v ms.M^jm&ft* Figures 49 and 50. Inclusion bodies for virus (Baculoviruspenael) in digestive gland of shrimp. Top, note mostinclusion bodiesare tetrahedrons. They encasevirus particles. Bottom, a phase-contrast close-up showing the refractive inclusion bodies within the nucleus of the digestive gland cells as well as others that are free.

biphenyls or Mirex have a tendency to bodies. For mortalities to be caused by the exhibit an increased number of inclusion virus in nature, some pollutant or antagon- bodies. Such individuals also tend to die ist may have to be present. The virus affects more readily than shrimp without these pink, brown, and white shrimps at least in Penaeid Shrimps 31

Figure 53. A white shrimp with some white- colored gills probably caused by a bacterial infection. Many host blood cells crowded together in the affected gills.

infection. A massive hemocytic response involved the area, producing the opaque condition. Black gills or "black gill disease" can result from a bacterial infection, but more often this multicaused disease results from Figures 51 and 52. Brown shrimp with shell- disease. Bottom, disease-condition other agents, and a few of these will be occurring in site of wound. Lesions in both discussed later. shrimp possessed a bacterium (Beneckea Externally, a filamentous bacterium type I) which digests chitin in the exo- (probably Leucothrix mucor) entangles skeleton and probably caused the disease. larval shrimp, and it, along with consider Florida and Mississippi and probably in able trapped debris, probably inhibits fects many penaeids wherever they occur. respiration and otherwise burdens the host. Chitinoclastic organisms including As with most diseases, reared shrimp usually bacteria cause shell disease, or black spot constitute the primary victims. The same or disease, in shrimps (Figures 51 and 52) as a similar bacterium also occurs on a variety well as in the blue crab and other crusta of crustaceans, fishes, and . ceans. The lesion in Figure 52 illustrates Shrimp, as well as a variety of other a wound inflicted by a predator. Such in marine animals, can harbor Mycobacterium fections are usually lost with a molt, and marinum. This bacterium, related to the rarely does an affected shrimp die from this agent of man, can cause a skin alone. When specific bacteria (e.g., a rash (dermatitis) on those susceptible chitinoclastic variety of Vibrio people who handle shrimp or other seafood anguillarum) involve pond-reared shrimps, products. Reactions differ among people: death can occur. Indeed, low grade mortali some have hard pustules on their hands ties, apparently not resulting from whereas others have blisters. secondary* infections, have plagued reared- A variety of fungi infects shrimps, but shrimp production in Mexico. most have not been cultured or investigated. Shrimps, just as the blue crab, host a One that has been investigated (Fusarium variety of internal bacteria, some of which solani) shows variation in its virulence to cause extensive mortalities in pond-reared different penaeid shrimps. A response by the hosts and others that do not affect the host. host hemocytes to spores and hyphae* in the The white opaque gill filaments of a white gills can result in a deposition of dark shrimp from Mississippi Sound shown in pigment (melanin) producing "black gill Figure 53 probably exemplify a bacterial disease." 32 Marine Maladies?

Figures 54-57. Fungal black gill disease. Top left, brown shrimp with disease compared with un infected individual. Top right, spores (macroconldia) ofcausativeagent (Fusarlum solani). Bottom left, host response by shrimp blood cells after 24 hours. Bottom right, increased pigmentation (melanization) apparent by 28 hours. The text discusses several otheragents that cause black gill disease.

Deposition of brown-to blackish melanin pigment occurs in shrimp that have been wounded, have been exposed to foreign materials, and have fungal (see Figures 54 to 57), protozoan, or helminth infections. In somecases, the tissue underlying the cara pace* and not the actual gills is darkened. Perhaps waste products (nitrates or ammonia) discharged through the gills or even precipitation of materials (metallic sulfides) produces the condition.

Figure 58. Tails of the brown shrimp; the top Protozoan Infections shrimp exhibits cotton shrimp disease. What's a cotton shrimp? Four species of Three different species of microsporidans cause this milky or chalky appearance of microsporidan protozoans infect commer tails of penaeids in the northern Gulf of cial shrimps in the northern Gulf. Three of Mexico. In this case, tiny spores of Ameson those infect and replace nearly all the nelsonl surround and eventually replace the muscle bundles. abdominal muscle tissue of their hosts, resulting in an extremely opaque condition shrimp." The name "cotton shrimp" also somewhat similar in appearance to a cooked reflects the texture of the cooked product. shrimp (Figure 58). Shrimpers refer to these The fourth microsporidan species hosts as "cotton shrimp" or "milky (Agmosoma penaei, Figure 59) is more Penaeid Shrimps 33 ships with penaeids. Also, all species of shrimp in the northern Gulf harbora cepha- line gregarine (Nematopsispenaeusor some other indistinguishable species). The motile stage (trophozoite) can be seen attached to or gliding about in the intestine, sometimes with as many as seven individuals joined end to end in a chain or branched so as to exhibit a forked posterior end (Figures 60 and 61). Two attached individuals develop Figure 59. Chalky appearance under cuticle into a spherical cyst that embeds in the reflects microsporidan (Agmasoma penaei) shrimp rectum (Figure 62); the cyst in turn that invaded blood vessels under the cara pace of the white shrimp. Usually, tissue produces a stage infective for some yet un along the middle portion of the top of the tail known mollusc. exhibits infections by this protozoan. An ****?" insert shows some spores in the typical ». packet of eight. Others have broken loose from the membrane, and one spore (macro- spore) is typically much larger than the others. <•; *- host-specific than the others and does not infect the tail. Involving primarily the white shrimp, an infection appears most distinctly along the dorsal midline of the tail and under the carapace in the cephalo- thorax. Many people think that infected gonads and intestinal tissue are ripe ova ready to be released. Consequently, some prefer the taste of these "ripe" shrimp over noninfected shrimp. More than one species of microsporidan "J can infect an individual shrimp. In fact, three species in a single shrimp can be visually differentiated by their color and location if the tail is cut crossways. Infected shrimp react poorly to stress conditions. Usually, when compared with their noninfected counterparts, they die more readily when handled, are more vul nerable to predators, and do not normally partake in migrations. Often many shrimp caught inshore exhibit microsporidan infections. In these cases the bulk of the Figures 60-62. A cephaline gregarine from shrimp stock may have previously departed the white shrimp. Top, an association of to other waters; however, a few cotton three Individuals in a chain gliding about in the intestine. Middle, a forked association. shrimp do occur in offshore catches, Bottom, cysts (gamontocysts) embedded in suggesting that some infected individuals rectum. These result from encystment of migrate and survive. associations and can barely be seen as a Several protozoans other than chalky-colored dot with unaided naked eyes. Stages in the rectum infect appropriate microsporidans have symbiotic relation- molluscan hosts. 34 Marine Maladies?

For another similar appearing species often survive the stress whereas those with ( duorari) restricted to pink many die. shrimp, the shrimp acquires infections by- A related species (Epistylis sp.) differs feeding on mucus trails of several common from Zoothamnium sp. primarily by lack bivalves including the Atlantic bay scallop, ing a central contractile fibril within the broad ribbed cardita, cross-barred venus, stalk. Thus, it cannot contract its stalk. The and sunray venus. fibrils (myonemes) of Zoothamnium sp. These and at least two more gregarine connect where the stalks branch, allowing species that attach to feeding appendages simultaneous contraction or expansion of probably cause no more than minor disease an entire and a wonderful show in either the shrimp or the corresponding when seen under the microscope! molluscan hosts. Unlike Zoothamnium sp., Epistylis sp. Ciliated protozoans occur in as much usually infests the appendages and exo- variety as do gregarines. On the gills, skeleton-proper rather than the gills. Both colonies of a stalked peritrich (Zootham- species infest larval shrimp and present nium sp.) give a brownish cast to the gills treatable threats to cultured shrimp. The when enough of these organisms attach. effect on natural populations has not been The attachment of the stalk to a gill ex established. amined with an electron microscope reveals Another unnamed ciliate encysts on or in no pathological alterations. The simple gills. Common where distal gill filaments attachment of a small colony can be seen in branch, this nonstalked apostome also Figure 63. However, when a large numberof causes black gills (Figures 64 to 67). Specks the ciliate infests the gills, as it can when of melanin surround the ciliate. The life hosts are crowded or placed under specific cycle of this foettingeriid has not been es environmental conditions, shrimp often tablished, and several technical papers die. Death usually coincides with periods of confuse it or a similar species with loricate low concentration of the water's oxygen, a forms like the one on the bluecrab. External common condition following several warm loricae*. however, have apertures surround overcast days or followingdecomposition of ed by lip-like structures and thereby provide a large algal bloom. The ciliate apparently an easy means of differentiation. competes for the available oxygen because Other protozoans can be seen by carefully shrimp with few colonies of the organisms examining shrimps from a variety of habitats. Relationships among some of these with the host remain obscure. An un identified suctorian species of Ephelota on the exoskeleton looks entirelydifferent from the one on crab gills. An internal ciliate (Parauronema sp.) which can fill the entire hemocoel and a flagellate (TLeptomonas sp.) which also occurs internally have been implicated in larval mortalities, possibly in conjunction with the virus Baculovirus penaei. Figure 63. A colonial ciliate (Zoothamnlum sp.) on the gills of a commercial shrimp. The dark fiber extending along the stalk's center Helminths permits the entire colony to contract Shrimps act as second intermediate hosts simultaneously. Note the cilia at the top of for a few digeneans. For those species with the bell which direct food particles into the organism. The protozoan harms shrimp only spherical cysts enclosing the larval worms, when certain environmental stresses arise. infections are localized primarily in the tail, Penaeid Shrimps 35

Figures 64-67. A brown shrimp with "black gills" caused by an apostome ciliate. Top left, part of carapace removed to show dark specks on gills. Top right, close-up showing apostomes and melanin pigmentation. Bottom left, close-up showing individual ciliate under the cuticle with the associated melanin. Bottom right, close-up of ciliated stage. whereas the elongated cyst of one species occupies the cephalothorax. The spherical cysts all harbor micro phallids which develop to maturity pri marily in mammals and birds. Figure 68 shows an experimentally infected white shrimp with one of the several species that infect it. Most shrimp microphallids infect their hosts in inshore low salinity regions and probably follow a life cycle similar for Figure 68. A penaeid shrimp experimentally that shown for a species in the blue crab infected with a microphaiiid fluke larva (metacercaria). (Figure 28). On the other hand, the species with larger family ) that eats the infected elongated thin cysts found in the hemocoel shrimp. adjacent to the alimentary tract typically Larval tapeworms (cestodes) occur in two infects shrimps from high salinity water in principal sites: in the digestive gland and in Mississippi. The worm (Opecoeloides the intestine. Almost all cestode species in fimbrialus), about 2 mm long when ex- shrimp from the northern Gulf utilize elas- cysted, has a pedunculated ventral mobranchs as final hosts: one encysted one with small papillae on the surrounding may use a bird, and a small single suckered lobes. The same frilled appearance of the mobile species in the intestine has not yet sucker exists for the mature worm in thegut been correlated to its adult form. An indivi of a fish (usually a drum or croaker of the dual shrimp often harbors more than 1000 36 Marine Maladies? specimens of this larval intestinal cestode (Figure 69), and large numbers may harm the shrimp. Becausemost prevalent, most studied, and most conspicuous in all penaeids from the Gulf, one larval trypanorhynch, or tetra- rhynch as it is also called (Prochristianella hispida), will be treated in detail. Crustacean-feeding stingrays (Dasyatis sabina and Dasyatis sayi) harbor mature Prochristianella hispida in theirspiral valve (an adaptation of the intestine to increase its surface area). Figure 70 diagrams the life Figure 69. Larval (plerocercoid) tapeworm cycle. Segments (proglottids) with partially from intestine of commercial shrimp. Over developed eggs break free from the tape 1000 individuals of this small unidentified worm and pass out with a ray's feces.Once in larva can attach by their single sucker to the gut of a single shrimp. seawater the proglottids split open, liberat ing many eggs, each with two thin, sticky

Figure 70. Life cycle of a trypanorhynch tapeworm (Prochristianella hispida) in commercial shrimps. Stingraysharbortheadultworm in theirspiral valve.Terminal segmentsdrop offtheworm and release eggs that develop larvae when in seawater. The enclosed larva develops In cope- pods. Whether shrimp obtain their infections from eggs or from has not been estab lished, but rays probably acquire infections from various shrimps. Penaeid Shrimps 37 penaeid shrimps, may be the ray's most utilized crustacean host. In order for the cycle to be complete, the ray eats an infected crustacean. The blastocyst, but not the actual plerocercoid, can be seen in a shrimp without disturbing it if the cyst protrudes through the host's membrane covering the digestivegland (Figure 72). Some individual blastocysts occur entirely within the gland and elsewhere within the hemocoel. The adult trypanorhynch attaches to the .-• ' ray's gut by means of four eversible hooked i"" in. tentacles. A tentacle turns itself inside out. alll* /ililflllill By the size, shape, and arrangement of the hooks, one characterizes the several species -?*r ££**"'''•• w that infect penaeids as well as other species that parasitize a wide variety of crustaceans,

dr " molluscs, fishes, and occasionally other hosts. These attachment structures remain unchanged from the late larval to adult Figures 71 and 72. Larval stages of a stage. trypanorhynch cestode (Prochristianella Larval roundworms (nematodes) also hispida). Top, filamented eggs with larvae infect penaeids and several other hosts. clumped together. Bottom, blastocysts,each with enclosed larva (plerocercoid) in the Most common in a variety of fishes and digestive gland of a penaeid shrimp. A invertebrates including shrimp is an ascari- portion of the pigmented membrane doid (Thynnascaris type MA). Several in covering the digestive gland has been dividuals of this worm and a smaller removed on one half to expose digestive caeca. Three whitish cysts are apparent on number of a smaller member in the the pigmented membrane. same genus (Thynnascaris type MB) occur filaments (Figure 71). A single hooked larva commonly either coiled and encysted or free (oncosphere with six anchor-like hooks) in the digestive gland, among other tissues within the egg develops to an infective of the cepahlothorax, or occasionally in the stage in about 4 days. Whether shrimp get tail portion of the shrimp. The smaller infected by eating food with entangled eggs species (type MB) may be a health hazard. or by eating infected copepods has not been Within an hour after being eaten by a established. A larval form (procercoid to mouse, it can penetrate into or through the plerocercoid) develops in the hemocoel of wall of the mouse's alimentary tract and some copepods and may progress similarly cause a host-response. Some individuals in a variety of shrimp, or possibly a shrimp live for a considerable time in the mammal, may have to eat the infected . A hard whereas the host reacts against and quickly capsular cyst surrounds the early plerocer kills others. In anyevent, the potential exists coid within the fleshy procercoid-like stage for a person to develop a severe inflamma (blastocyst) when in the copepod. This en- tory response after eating raw seafood cystment has never been seen nor reported harboring the worm or to express a hyper from shrimp and might be a transitory de sensitivity reaction from worms eaten velopmental structure present only under subsequent to the initial infection. Such certain conditions. On the other hand, other conditions, with symptoms similar to those crustaceans such as the ghostshrimp, which for an ulcer, appendicitis, or cancer, have possesses blastocysts larger than those in affected people in Japan, the Netherlands, 38 Marine Maladies? and other places where people consume raw the only other fairlycommon that seafood harboring related nematodes. Either I have seen in Gulf shrimp is what appears cooking or subzero freezing prevents human to be a free-living* nematode (Leptolaimus infections! sp.). Leptolaimus sp. in shrimps from Life histories and identifications of the Louisiana to Alabama appear able to live larval nematodes have not been established. in and on shrimp without being digested. Just as with the trypanorhynch, I do not The tolerance by the shrimp and relation know if shrimp acquire infections by eating ship between worm and shrimp require larvae directly, by eating copepods with further investigation; all related nematode infective larvae, or by other means. The species thrive without hosts in muddy-sandy final host must be a fish and several species habitats, and this one probably also lives of these nematodes exist in the Gulf of in such a habitat. Many strictly free-living Mexico and elsewhere. nematodes exist in water and soil, and One reason why so many individual hosts notably few of these possess any strong may harbor the same species of larva is that family ties to any of the symbiotic species an individual worm may penetrate through from aquatic hosts. the alimentary tract of a predator after being eaten along with a previous host and Miscellaneous Diseases and Attached rcencyst in the mesentery or elsewhere, re Organisms maining infective for another predator that One amazing disease can be characterized in turn eats and retains it. Not until ac by the opaque musculature in the tail of quired by a proper definitive host will the affected shrimp. Going by the technical worm molt and develop to maturity. name "spontaneous necrosis," this pro Parasitologists call these hosts in which gressive disease begins as a whitish area no development of a worm occurs "para- usually near the end or middle of the tail. tenic" hosts. These hosts allow completion Caused by an adverse stress such as low of a cycle in cases where the definitive host oxygen concentration or rapid change of rarely feeds on the true intermediate host. the water's temperature or salinity, the The worm may increase in size, but it does condition progressively worsens, leading to not develop additional features. A similar death unless the harsh conditions improve. pattern of life cycle probably occurs for The disease may occur frequently in shrimp most related ascaridoid nematodesand these held in bait holding tanks and could be con will be diagrammed and discussed more fused with cotton shrimp unless shrimp later. with each of the two conditions could be Even though quite rare in penaeid compared. shrimp, another larval nematode (Spiro- The above necrosis* is reversible. Shrimp camallanus cricotus) completes its cycle in a provided water of adequate quality will lose wide variety of fishes. Whether shrimps ac the opaque appearance unless the condition tually constitute a necessary link in the has developed beyond a certain threshold cycle has not been established, but they point. Once the tip of the tail acquires a probably do not because other invertebrates totally chalky white appearance, the shrimp also host the larva of this dramatic worm. It usually dies. The really amazing pheno will be figured and discussed in more detail menon that biologists should pursue is how in the section on fish nematodes because it shrimp with a partially necrotic condition is in fish where the large reddish adult can, within a day or so, recover and appear worm is most easily visible and most normal. Microscopic examination of affect commonly found. ed opaque tissue reveals nearly totally Even though other larval nematodes in dissociated material, but a few days later, fect penaeids from other parts of the world. the tissue appears to regain its normal Penaeid Shrimps 39 character. Investigation of this regenerating ing devices and a glutinous material. Since tissue aided by the electron microscoj>e the brown shrimp has a closed thelycum, should go a long way to explain the process copulation apparently occurs between a of muscle regeneration, a transformation recently molted, soft-shelled female and a that takes considerable time in man and hard-shelled male in contrast with the pro other vertebrates. cess in white shrimp which takes place Another condition called "cramped between hard-shelled individuals because shrimp" develops in individuals held in the thelycum is open. In spite of the plates, bait tanks and ponds. The tail can be bristles, spines, glue, and other devices, the completely or partially flexed. It becomes capsule easily dislodges. Nevertheless, so rigid that it cannot be straightened fertilization of ova in these individuals out. Partially-cramped individuals swim seems to take place. about in a humped fashion and may survive The female white shrimp with the the ordeal. Those laying on their sides sel attached spermatophore in Figures 73 and dom improve and usually die. An imbalance 74 shows a typical condition in offshore of ions appears to cause cramping. shrimp. A fisherman, however, collected Occasionally a shrimp portrays a golden this particular shrimp from inshore water appearance throughout all its tissue. The where attachment is rare and, for that yellowish-gold shrimp may appear either matter, unproductive if eggs are released opaque or transparent, and the rarity of unless the salinity concentration is higher affected individuals reared in ponds than normal. The strange attached object suggests that the condition may represent could be misinterpreted as an external an hereditary phenomenon rather than one parasite. resulting from dietary deficiency or some Some noninfectious diseases result from other unnatural process. The crab leech may also occur on pena eids, but not nearly as frequently as it utilizes the crab or grass shrimp. A variety of symbionts and fouling or ganisms often attach to older shrimp. Usually those shrimp not molting for long periods reveal the most spectacular cases because large sessile barnacles grow on the carapace or elsewhere. Algae, hydroids. and occasionally other organisms attach to and sometimes invade gills, eyes, or less vul nerable regions. Presumably these interfere with the best possible life style for a shrimp. Confusion may also exist when separat ing parasites from normal anatomical structures. One of these structures, the pod like sperm capsule, or spermatophore, is rarely seen in inshore shrimp. Most indivi duals spawn offshore. During mating, the male transfers his sperm capsule to the fe male where it becomes attached to the female's external genital organ (thelycum), Figures 73 and 74. A male's spermatophore (encapsulated sperm) attached to a 173 mm located between her fourth and fifth pair of long female white shrimp. Top, side view. walking legs, by means of various anchor- Bottom, underside view. 40 Marine Maladies? environmental contaminants. Usually de Even though many thousand shrimps were finite proof for such relationships is examined from a variety of habitats, only lackingand that is the case for a growth that postlarval individuals from near a small appears to result from some unidentified boat harbor receiving the city's treated pollutant in Ocean Springs, Mississippi. sewage, the presumed most polluted habi An overgrowth of muscle protruded tat, exhibited the anomaly. Apparently through the ventral portion of the last something interrupted the normal growth abdominal segment in both post-larval process. When postlarval shrimpgrow from brown and white shrimps (Figures 75 to 77). 6 to 25 mm in length, the relative length of the sixth abdominal segment gradually decreases. In affected shrimp, the muscle "%$& apparently continued to grow at the pre Ml-; vious rate while the relative length of exoskeleton decreased as expected for normal shrimp. As a result, the muscle folded and protruded through a weak joint, usually pushing the with it. Since the nerve is stretched and vulner able to being frayed by mud and sand, the affectedshrimp probably cannotavoid pred ators before reaching adulthood because shrimp avoid predators by darting backwards using quick flexions of the tail.

GRASS SHRIMP

Even though not commercial species, grass shrimps (especially Palaemonetes pugio) deserve inclusion in the treatment on shrimp diseases because they are usually easier than penaeids to obtain with a dip net, they are better hosts for a few of the same or related symbionts that associate with penaeids, and one of their isopod parasites often attracts a variety of queries. Also, they act as a very important source of food for fishes, birds, and other animals. Near banks of bayous and among marsh grass, thousands of specimens of Palae monetes pugio can often be seined or dip Figures 75-77. Abnormality in postlarval netted in a few minutes. An adult cannot brown shrimp. Top, fourth through sixth tail grow as long as a regular house-key and can segments of a normal shrimp. Middle, quickly be separated from young penaeids moderate overgrowth of muscle tissue extruding through joint of sixth segment. because the female broods her eggs under Bottom, slightly larger shrimp (13 mm) with her abdomen. A few grass shrimp symbionts frayed overgrowth. The likelihood exists that will be discussed; the cover-illustration the growth (hamartoma) resulted from an reproduced as Figure 78 shows several of unidentified pollutant interfering with the normal growth process of the shrimp. these. Grass Shrimp 41

Figure 78. A grass shrimp (Palaemonetes pugio) with a variety of its symbionts. On the tail fan and legs, a ciliate (Lagenophrys lunatus) lives within a transparent encasement opened to the external environment. Another ciliate attached by its stalks to the anterior claw. In the tail muscle, the encysted spherical fluke larva (Microphallus choanophallus) looks conspicuous in the illustration and also in the living shrimp if a host is held up to the light. The three larger dark spheres consti tute the same fluke cysts, but hyperparasitized by a haplosporidan protozoan (Urosporldlum crescens). When Infecting a related fluke in the blue crab, the association has been termed "buckshot" or "pepper spot." A bopyrld isopod (Probopyrus pandallcola) occludes the anterior side of the shrimp, and the common leech (Myzobdella lugubris) darts about on the top of the shrimp. The text covers these and several other symbionts from the grass shrimp.

Protozoans the lorica, a gapexists that allowsa swarmer The loricate ciliate (Lagenophrys (its telotroch larva) to emerge. The adult lunatus) encased on the tail fan, walking organism can also contract, sealing off that legs, and swimming legs in the illustrated aperture formed by the lorica's flexible col shrimp provides an easier model to study lar extension. Microscopic examination than the related ciliate species infesting the clearly shows the horseshoe-shaped gills of the blue crab. It can be observed and small without harming the host and its develop diagnostic of many ciliates. ment on a molting host can be followed. Preceding the host's molting, the or This protozoan species appears specific to ganism, most prevalent on sites with the shrimps of the family Palaemonidae (grass greatest water flow, undergoes a special type and river shrimp) in fresh and brackish of asexual division producing twoswarmers water. (free swimming larvae). Loricas on fresh Within the transparent lorica*, the molts contain these swarmers, as well as peritrich projects its oral cilia through dividing (asexually reproducing), trophic the aperture for feeding on scraps from the (feeding), and conjugating (sexually re host's food and on phytoplankton. Even producing) individuals. In other words, though its body isattached to the openingof when the host molts, stages have already 42 Marine Maladies? been produced to reinfest the same host or feces probably aid in tangling the spore to additional hosts and thereby perpetuate the vegetation or trapping tidbits that might species. ultimately induce another grass shrimp to Other ciliates also infest grass shrimp. ingest it. While developing, the tails may One (Terebrospira chattoni) can be seen al channelize nutrients and ions to and from most anywhere except on or adjacent to the the forming spore. Eight of these tailed 'c/ gills. Small (50 to 100 u) elliptical cysts spores occur within a pansporoblast. usually divided into compartmentalized Electron micrographs (Figures 80 and 81) sectors maycontain individuals orbe empty. show the organelles that these tiny (3 u long Related apostomes feed on molting by 2 u wide) spores possess. The polar fila (exuvial) fluid, but this species has become ment has its base (end of the diagonal nar adapted to feeding on the endocuticle. The row structure) attached to the apical end. tiny flattened ciliate can be found digesting Alterations in the plug at this juncture the cuticle* at the end of a tunnel leading allow the tube to turn inside outandextrude away from one of the empty compartments. a considerable distance (about 40 u). The Is this a transition between an external and process is aided by the lamellar (layered) internal symbiont? structure (polarplast) at the apical end. The In addition to ciliates, a variety of micro small, round, peripheral structures are sporidan protozoans also infect grass cross-sections of the uneverted coiled por shrimp. One (Pleistophora linloni) differs tion of the filament. The external tails do little from related species in penaeids, crabs, not extrude; they develop simultaneously and even fishes. Large numbers of spores fill with the spores. The second micrograph the pansporoblast's chamber (Figure 79), shows several early developing stages separ and a heavy infection produces an opaque ated from mature ones by some unharmed tail characteristic of "cotton shrimp." host muscle tissue. Each of the early stages Another species (Inodosporus spraguei) will divide, producing eight spores. The produces the same gross appearance, but tunnel-like arrangements adjacent to the the spores are unusual. Each undischarged maturing spores constitute various sections spore (with polar filament intact) contains through the tails. Luck allowed a few spores three or four long extensions ("tails") on its in this very thin section to reveal the place basal portion and a divided short one on the where the tails join the spores. apical end. After an infected shrimp iseaten, Whereas microphaiiid larval cysts tails on a spore voided with the predator's (metacercariae) are hard to see in the penae ids because of a shrimp's large size and the paucity of infections, cysts of Micro phallus choanophallus are seldom absent in most stocks of Palaemonetes pugio. By- holding a grass shrimp up to a light or to the sky, many opaque specks, each representing a cyst, stand out conspicuously. Often, Vrosporidium crescens hyperparasitizes* one or more of the cysts (Figure 78), making the cyst even more recognizable.

Metazoans A bopyrid isopod (related to terrestrial Figure 79. A microsporidan (Pleistophora llntonl) from the tall of the grass shrimp. organisms called sowbugs, roly-poly bugs, Members of this genus have several to many or potato bugs) stands as a good example of hundred spores per chamber. a parasite on grass shrimp that is not found Grass Shrimp 43

Figures 80 and 81. Electron micrographs of a microsporidan (Inodosporus spraguel) from the grass shrimp. Top, close-up of spore that causes cotton shrimp. Large light-colored round objects near periphery and straight object diagonal through spore all portray different views of the filament that protrudes and discharges infective material. Bottom, mature spores on top and developing ones on bottom are separated by functional muscle tissue In between. The common species in the blue crab (Ameson michaelis) and some other microsporidans destroy adjacent muscle tissue. Eight spores occur within a membrane for the figured species. Members of the genus are unusual because they have long external tails attached to the spores. The tubular material among the spores are these tails. Inspection of either photo will reveal where some of the tails attach. They probably act as a means to provide nutrients todeveloping sporesand attach free sporestovegeta tion or debris so that the spores can be eaten. 44 Marine Maladies?

Figure 82. Life cycle of a bopyrid isopod (Probopyrus pandallcola) under the carapace of the grass shrimp. The tiny male clinging to the illustrated female separated from the host fertilizes the ova, and several individuals of the resulting larva remain with the female until that larva develops and the host molts. Once freed, the larva attaches to a copepod host and develops further into the stage infective for grass shrimp. on local penaeids. The coloration and large host molts, many individuals of the first swelling on the side of the carapace makean stage larva (epicaridean) are liberated and infested individual obvious. Different swim toward light. After attaching to the species of bopyrids infest various crusta copepod intermediate host (Acartia tonsa), ceans; the one on the grass shrimp the larva metamorphoses intoanother larval (Probopyrus pandalicola) associates only stage (microniscus) larva which grows with specific grass and river shrimps. As rapidly at the expense of the copepod, and, suggested by Figure 82, it undergoes a life when several are present, may even surpass cycle requiring an intermediate host*. the host-copepod's mass. That larva molts The large, distorted female isopod nearly to form the larva (cryptoniscus) infective for usurps the host's entire gill (branchial) either a larval or young grass shrimp. The chamber (Figure 83). The ventral (under first individual reaching a host's gill cham side) view of the female shows the dwarf ber develops into a female, whereas all later mature male near the posterior end among ones become males. If the ability for sex the female's pleopods. She broods many transformation is the same as for a related larvae within her marsupium (middle bopyrid, a male taken from onegrass shrimp portion of illustrated female). When the and introduced to an uninfested shrimp Grass Shrimp 45 :^V;,"V^f.--' -?£*-. •••:'-$*'. j'i ' •" ii r ** •••"•%, /^

•*•: **''!*» 4&f&, j\\ ! ••••J& •0 #"'•• ;"v^* •• '" •rrl^lS? %- ••-' *' *

Figure 83. Adult female bopyrid isopod (Probopyrus pandallcola) under carapace of Figure 84. Three Individuals of a common grass shrimp. leech (Myzobdella lugubris) swaying about on their grass shrimp host. would turn into a female! If several larvae invade an uninfected shrimp simultaneous ly, all become females, but only one would eventually mature. Think of the experi ments that could be conducted using this host-symbiont system. The ability for symbionts and hosts to sense their surroundings provides a continual source of problems to investigate. The grass shrimpacts as a good host to study for harboring the "crab leech" (Myzobdella lugubris). Occasionally one finds an in dividual with two or more leeches attached (Figure 84). However, if a person putsan in fested and many noniniested shrimp in a bowl and starts adding leeches to the bowl, he will observe that most will even tually attach to one or a few shrimp. As many as 20 can reside on a single shrimp. The leech probably does not utilize the shrimp as much as the blue crab for deposi tion of cocoons. It will use the shrimp, Figure 85. The oriental fluke (Para- gonlmus westermani) which is related toone though, and after it does, the shrimp often that encysts In pairs in the of local eats the leech. Perhaps this results from that feed on crayfish. lethargy on the part of the spent* leech. I have seen the anterior third ofan eaten leech mitted by a few crabs in the Far East. Unlike remain alive in a grass shrimp for an entire many intestinal flukes that infect local day, sucking on the digestive gland and estuarine and terrestrial mammals, the local moving. The shrimp stayed alive! lung fluke can grow over 1 cm in length. It A few freshwater crustaceans rate highly has provocative mate-finding behavior that with consumers or fishermen, and they har needs to be critically investigated. Never bor a variety of parasites. One of these theless, if two or occasionally more parasites from a crayfish will serve as an individual migrating larvae occur in the example. cat, they quickly join together and become Cats and other mammals that feed on encapsulated by the host in the lung without crayfish (pronounced "crawfish" in causing much harm. On the other hand, if a Louisiana) from ditches may acquire a lung single worm infects a cat, it migrates about fluke ( kellicotti). Figure 85 for an extended period in the lung or lung shows the closely related oriental lung fluke cavity, presumably needing to come in con of man () trans- tact with a mate and occasionally causing 46 Marine Maladies? continuous damage to the host. Thus, a remain in the flesh or under the skin may be host appears better off with several worms either easily visible or loo small to see with than with one. Like most investigated unaided eyes. In either case, most do not digeneans, appears infect man, but those that can die readily to cross-fertilize rather than fertilize itself. when cooked, even for short periods. According to veterinarians along the The following treatments should en Gulf Coast, this freshwater lung fluke is rare courage an appreciation of some of these in pets except for outbreaks in Mobile, variously-adapted piscine symbionts. Most Alabama. Still, presence of the fluke should will be grouped by category of symbiont. be recognized. Pets that eat either dead or The reader, however, should remember that living fish from the estuaries stand the many parasites utilize more than just a fish chance of acquiring several different to complete their life histories, and some of helminths. those hosts have already been discussed. In order to help readers locate the site of a para site, Figure 86 reveals many anatomical fea tures of a bony fish in general and of the Atlantic croaker specifically. Because many VERTEBRATES AS HOSTS symbionts from elasmobranchs do not in volve bony fishes () and because FISHES Hollywood has spurred recent interest in Because of the large number of fishes* sharks, elasmobranchs deserve some special present in the northern Gulf, I make no comments. attempt to treat each species as thoroughly About 800 species of elasmobranchs as I covered symbionts of selected inverte (sharks, skates, and rays) exist worldwide. brates. I picked only a few of the many Of these, at least 38 may occur during a part invertebrates from the Gulf, but they are all of the year in the northern Gulf of Mexico commercially important. A much larger and 26 are sharks. Many sharks can be number of commercially important fin- caught near shore until the water tempera fishes than shellfishes inhabits that region. ture drops. Perhaps their prey moves The number of fishes one is likely to offshore or becomes otherwise unavailable encounter commonly while shrimping and during winter. The , a common probably would be about 100, but species, exemplifies this by not turning up exerted effort should probably turn up over in nets or on fishermen's long lines* in 400 species. These fishes exhibit a wide Pensacola, Florida, from November to mid- variety of living and eating habits. Such April. Sharks often aggravate both ecological differences plus additional bio commercial and recreational fishermen by chemical and physiological ones guarantee damaging fishing gear and removing bait a variety of parasites. intended for other fishes. However, because In our Parasitology Section at the Gulf sharks are usually available, because of the Coast Research Laboratory, one of our in thrill of catching a shark, and because vestigations deals specifically with sharks taste good, many are caught and various aspects of parasites from the brought ashore. Atlantic croaker. From this single species Different elasmobranchs feed on a variety in Mississippi, we have encountered about of fishes and invertebrates, including many 90 different species of parasites, about one- commercial species. This variation among third of which occurcommonly. Wide over species is reflected by the variety of internal lap of different hosts occurs for somespecies parasites they host. Large sharks tend to infectingcroaker, whereas others infectonly have more individual specimens than sting the croaker or just a few host species. rays, but the large rays, probably because Possibly a remark should be added for they feed on a wider range of dietary items those squeamish about parasites from fish than sharks, including crustaceans and in general. When one cleans a fish, he re molluscans in addition to fish, usually host moves most of the parasites. Those that a larger number of species. Fishes 47 dorsal fins alll rackyrs bum bladder caudal fin

$en$cry barbels I heart ITr^^f ff^<^«w/fci urinary bladder directed operculum t&eta ° (axil cover) Figure 86. Selected anatomical features of a bony fish (Atlantic croaker). Most fishes have similar, but modified, features. organs of worms and thereforeon the species of parasites present. Rather than possessing a simple tube for an intestine like most teleosts, elasmobranchs have developed a spiral valve which increases the absorptive area. This structure exists in a few different forms. The concentric spiral valve in charcharhinid sharks (Figure 87) reminds me of a jelly roll whereas that in skates, rays, and other sharks looks more like a cork Figure 87. Opening up the spiral valve of a small blacktlp shark. This modified intestine screw. increases the amount of absorptive area and provides an ideal habitat for tapeworms.

Many species of parasites, especially tape Microbes worms, occur in one or a few species of Lymphocystis exemplifies a viral disease elasmobranchs. This specificity may relate of fishes which has external signs* that can primarily to the kind of prey preferred by the be readily observed (Figure 88). A specific different hosts. Structures of the jaw and type of host cell (fibroblast*) becomes in teeth usually govern the type of prey an fected by the viral particles and may enlarge elasmobranch can easily capture. Sharks (hypertrophy) to a few hundred times its with sharp, pointed, or serrated teeth original size. Enlarged cells acquire a thick (charcharhinids) probably eat many fish, hyaline* capsule, and critical examination whereas sharks with flattened or small teeth of an affected fish will reveal these indivi (mustelids and squalids) eat more crusta dual cells among crusty masses, or ceans and molluscs. Modificationsof the gut "tumorous growths." The disease cannot be also have some bearing on the attachment associated with cancer* (see tumor in 48 Marine Maladies?

Figure 88. Atlantic croaker with lympho cystis. White encrusting masses consist of numerous greatly-enlarged connective tissue cells infected with a virus.

glossary) in the true sense because the giant- sized cells do not divide nor metastasize. In fact, the disease rarely kills its host outright, but probably does make it vulnerable to predation. In Mississippi Sound, two strains of the lymphocystis-virus cause disease in estuarine fishes. Several other strains infect other fishes in adjacent and distant waters, but for purposes of showing that strains differ, I will limit my discussion to a strain which affects the Atlantic croaker and sand Figure 89. Electron micrograph of lympho seatrout and another which affects the silver cystis virus particles (dark hexagon-shaped perch. One or two fishes other than those structures) in an enlarged connective tissue cell from an Atlantic croaker. The granular- mentioned can be experimentally infected like structure atthe bottom Is a characteristic with each strain, but the croaker strain will nonrefractile inclusion body (compare with not infect the perch and vice versa. Develop refractile inclusion bodies associated with a ment of infections in croaker progresses virus in penaeid shrimp). more slowly at low temperatures, but infec tions occur in local water most prevalently duces a lesion on the gill, allowing it to during cold months. Granular masses can spread through the blood stream (Figure cover portions or nearly all of the skin and 91). The isopod commonly occurs on perch fins and can slough off in older infec with lymphocystis in the gills as well as on tions. Once the encrusting masses slough, several other fishes, none of which exhibits the host appears resistant to a challenge lymphocystis. infection. Lymphocystis in croaker from As indicated above, the strain in silver Mississippi may be related to increased perch does not infect the croaker, and the pollution or other stresses. Long-time viral particle measures larger than the one sports fishermen who have fished croaker from croaker. Figure 89 shows an electron from Mississippi Sound for decades have micrograph of the virus particles. Even witnessed their first cases of lymphocystis though the perch's body surface exhibits during the past few years. Additionally, I crusty masses (Figure 90), infections also have seen a considerable increase in pre occur commonly in the gills (Figure 91) and valence* since 1969 in Mississippi waters. in various internal organs. Figures92 and93 In fact, occasionally over one half of a reveal an infection involving the eye! hundred croaker in a trawl haul will have Perhaps the virus invades internally because recognizable hypertrophied cells. The a symbiotic isopod (Lironeca ovalis) pro- disease in perch also can infect over half a Fishes 49

Figures 90 and 91. Silver perch with lymphocystis. Left, infection similarin appearance to that from Atlantic croaker. Right, raised operculum showing infected gills and isopod (LIroneca oralis) that may allow dispersal of the infective agent to the internal organs. Croakerhave no apparent internal (visceral) infections. on both viral and bacterial diseases. Even though bacteria can be more easily studied than most viruses, relatively few species from marine fishes have been care fully investigated. A chronic fish-kill, one that occurred over a long period of time in Alabama and northwestern Florida, appear ed to be caused by the combined effects of bacterial involvement and environmental stress. Without stress-factors in addition to bacteria, the bacteria by themselves seldom cause fish mortalities. " syndrome," a condition for which the rays of fins exhibit erosion, disintegration, fusion, or abrasion, usually with associated bleeding (hemorrhaging), can be associated with bacteria and can result in death. In some regions heavily contaminated with industrial and agricul tural pollutants, however, bacteria are not always involved in cases of this syndrome. As with the term "cancer," the name "fin rot syndrome" also applies to more than one specific disease. In Mississippi, lesions on Figures 92 and 93. Pop-eye caused by many fish probably result predominantly lymphocystis Infection belowand behind the eye. Top, side view showing enlarged from predators and trawl damage in con individual cells massed together with rich junction with trauma caused by blood supply. Bottom, top view of same fish contaminants and other environmental

showing extent of bulging eye. stresses. Similar to situations with most disease- sample, but the prevalence of infections causing agents, a relatively small number of fluctuates differently than that for the strain bacteria may occur without harming the from croaker. Possibly fluctuations relate host. After undergoing stress, however, the to the amount of rainfall, increasing with host's defense mechanisms allow the abundant rains. bacterium or combination of contagions to Several otherviral organisms probably in multiply rapidly and thereby harm it. An fect Gulf fishes, but few have been reported. example of a secondary bacterial infection Considerable research needs to be conducted associated with a protozoan (Epistylis sp.) 50 Marine Maladies?

Protozoans in General Many different groups of protozoans infect fishes. The * by definition contains all single-celled ani mals, both parasitic and entirely free-living. Actually, many biologists presently working with different nonrelated proto zoans have decided that they should split up the phylum into several phyla, thereby further emphasizing the differences among nonrelated groups. Not until various stages of selected species can be critically investi gated with an electron microscope and modern biochemical analyses, can many scientists feel confident about the classifi cation schemes. Many relationships still need clarification. Even though single-celled, protozoans possess a variety of specialized structures that aid in food gathering, locomotion, attachment, and protection. Some of these structures will become apparent in the Figures 94 and 95. Tidewater silverside with gas bubble disease. Top, side view. Bottom, following sections. The sections also pre top view emphasizing bulging nature of eye sent a few of the numerous possible and clearer view of a bubble. A variety of examples which portray a wide range in factors cause pop-eye and some are fish-symbiont relationships. They include discussed in the text. flagellates, amoebas, sporozoans, micro sporidans, myxosporidans, and ciliates. will be discussed in the section on proto zoans. Flagellates In most bacterial diseases, the presence A dinoflagellate acts as the most harmful of bacteria has to be determined byculturing flagellate to captive marine fishes. Most in order to diagnosea disease. The nonspeci dinoflagellates occur in the *, fic "pop-eye" disease (technically called possess chlorophyll*, and do not parasitize "exophthalmos") provides a good example. hosts; they possess two flagella (read later A variety of bacteria can cause this disease comments on cilia) which permit the liny recognizable by a bulging eye. We, organism to spiral through the water. One however, have already learned that wraps around a subequatorial depression of lymphocystis can cause eyes to bulge in the subspherical organism and the other silver perch, and many other factors also trails a long distance posteriorly. Actually, cause a protrusion. Helminths cause it and the parasitic species also produce a stage so can mechanical injury or gas bubbles. A that looks like a typical planktonic case of "gas bubble" disease in a tidewater dinoflagellate mentioned above, and it is silverside is illustrated by both top (dorsal) that stage that allows proper classification and side (lateral) views (Figures 94 and 95). of the parasite. That stage, however, turns The presence of gas does not rule out into opaque chalky blobs (Figures 96 and bacteria, but gas can be produced by over- 97) on the gills and skin of fishes. aeration, malfunctioning organs, and other A few different species of parasitic causes. Because bacteria in finfishes that dinoflagellates occur in the Gulf of Mexico, could influence human health are the same but one () as those in shellfishes, fish from contamina happens to be especially pathogenic to ted waters should also be cooked to insure a captive fish. Careful examination reveals a safe product. large nucleus, several food vacuoles, an Fishes 51

Figures 96-99. A parasitic dinoflagellate (Amyloodlnlum ocellatum) from the gills ofa fish. Top left, a moderately-heavy infestation of feeding Individuals (trophonts) on the gills. Top right, close-up showing food vacuoles, nucleus, attachment structure, and pigment stigma (above attachment). Bottom left, encysted individual undergoing early divisions. Bottom right, later division stages. From one trophont develops 128 cells that each form two swimming dinoflagellate-swarmers. Each swarmer can infect a fish, repeat the cycle, and kill the fish if enough individuals Infest it. attachment plate with numerous pro intoa trophont. In the natural environment, jections (rhyzoids) that penetrate the host- contact between swarmer and fish seldom tissue, an elongated flexible process occurs, but in an aquarium or pond, the (stomapode tube) that apparently aids in probability of contact is high. When digesting host-tissue, and a reddish sensory thousands of these individuals infest one organelle near the attachment (Figure 97). fish (Figure 96 shows a moderate infestation Other features require an ultrastruciural on the gills), the host can die within half a examination to distinguish them. day, and nearly all marine fishes are sus Rapid and extensive multiplication ceptible. allows the parasite to harm confined hosts. Freshwater baths given aquarium-fishes Once the attached feeding stage (trophont) will cause the parasites to drop off the gills, on thegills reaches a large size (barely visible but a few of thesecan getcaught in mucusor with an unaided eye) or the host becomes be swallowed to remain dormant in a host's severely stressed, the parasite withdraws its intestine. They can reproduce in water with penetrating processes, drops to the sub from 3 to 45 ppt salt, andjustone individual stratum, and covers itself with a cellulose can start new infestations. Infestations secretion. Cellular division (Figures 98 and represent an enormous loss to marine aqua- 99) continues until I28 resulting cells culture and the aquarium trade. A fresh develop into the greenish chloroplast*- water species that more readily infests the abundant, free-swimming, swarming cells skin rather than the gills also kills many (dinospores). The dinospores then divide fish. once to form a total of 256 swarmers all Other types of flagellates also infect the originating from the single attached gills, skin, and gut of estuarine and marine trophont; each can infest a host and develop fishes. Those that infect fishes possess from 52 Marine Maladies? vivida). In addition to being an invertebrate host, a leech can also be a passive vector* for trypanosomes.

Amoebas > Commensal amoebas probably occur in intestines of Gulf fishes, but fishes have not been adequately examined for them. At least one species has invaded pond-reared fresh water fish in the southeastern U.S. and Figure 100. Trypanosome (Trypanoplasma caused serious disease. Implicated bullocki) in blood of the southern flounder. mortalities may have required additional Note the anteriorand posterior flagella. Also, involvement with bacteria or other note that fish red blood cells, unlike human ones, have nuclei. protozoans. one to eight flagella. Most occur in low numbers in fish from natural waters, butcan rapidly intensify in stressed or cultivated Sporozoans hosts. For most of those flagellates, the A group of entirely parasitic protozoans identification and life histories are poorly called Sporozoa have members that typically understood, but reproduction typically have a spore* stage. Life cycles usually takes place on the host. include alternation between one host in The blood of several fishes harbors a which gametes* and asexually-produced different type of flagellate. The most individuals are formed, and another host in common blood flagellate in Mississippi which gametes unite and spores with infec estuaries (Trypanoplasma bullocki, Figure tive stages develop. Malaria-causing organ 100) has two flagella, whereas some others isms belong to this group; fertilization and have one. Both flagella extending from this "spore" (nonresistant) formation occurs in elongated organism originate at its anterior mosquitoes, and the asexual phase takes end. One borders a protruding undulating place in reptiles, birds, man, and other membrane and trails beyond it. This mammals. parasite, the body of which is longer than Coccidians constitute the most studied the host's blood cells, can best be organisms with "resistant" spores (those appreciated when viewed alive. A drop of that can withstand the elements when blood from an infected southern flounder passing from one host to another) because of placed under a coverslip reveals intense their devastating effects on poultry and undulating activity through a microscope. livestock. Some species have intermediate If a fish has trypanosomes, individuals can hosts, whereas others bypass such hosts be observed easily by allowing several drops completely and are transmitted by feeding of blood to clot. The parasitesswim about in on the spores. Figure 101 shows four spores the clear serum*. in a cyst (oocyst) taken from a lesion on the Unlike their mammalian counterparts tail fin of a Gulf killifish in a Louisiana which cause African sleeping-sickness, marsh in Cameron Parish. Each spore piscine trypanosomes rarely cause disease. contains two organisms (sporozoites) One species has harmed hatchery-reared presumably infective for other killifish. in . The number of spores and sporozoites per Transmission of trypanosomes into fish cyst determines to what genus a species occurs when leeches obtain their blood belongs. The genus of the figured species meal. In the case of Trypanoplasma ( sp.) also includes many species bullocki in the southern flounder, sexual that infect most farm-animals; however, its reproduction of the flagellate probably takes cyst wall is thinner because the host's place in a specific small leech (Calliobdella aquatic environment is seldom threatened Fishes 53

Figure 101. Coccidian (Eimeria sp.) from Figure 102. Hemogregarine (Haemogre- lesion on tail fin of the Gulf killifish. Each garina platessae) in blood cells of southern thin-walled cyst contains four spores, and flounder. Note that the parasite (a gamete each spore contains two infective organisms stage) is inside the red blood cell rather than (sporozoites). Related members of this same external to it. A pairofgametes fuse to form a genus cause serious economic losses to , presumably in a leech. untreated, infected, farm animals. by desiccation. Unlike species in most warm-blooded vertebrates, all or most of those infecting fishes produce infective stages while still in fish tissues and do not utilize an intermediate host. Different piscine coccidians involve different host tissues such as the testes of menhaden and swim (air) bladder of cod. Medical doctors have misdiagnosed as human coccidian infections cases where cysts were recovered in stools of people having eaten sardines and other fishes Figure 103. Spot with tumorous growths uncooked. These fish parasites do not harm caused by a microsporidan protozoan (Pleistophora sp.). Insert showsmicroscopic man. view of spores. Related sporozoans (hemogregarines) infect peripheral red blood corpuscles of feeders other than leeches may also transmit elasmobranchs and bony fishes. Most some hemogregarines. species presumably also infect blood cells in marrow, liver, or elsewhere in the same host, but these stages have not been Microsporidans properly described for a piscine hemo Another group of Protozoa, the Micro- gregarine; they have been for a turtlespecies. sporida, has been treated in some detail For some other species, however, asexual earlier when discussing the life cycle of multiplication occurs in peripheral blood. Ameson michaelis in the blue crab and the More prevalent in Mississippi fishes than spores of Inodosporus spraguei in grass trypanosomes, hemogregarines may l>e shrimp. Several microsporidans infect more difficult to find in a cursory exam fishes, but more appear to infect species in ination because thin blood smears must be regions more temperate than the northern stained to observe the subspherical to Gulf. In the Northeast, winter flounder and greatly-elongated parasites (gametes*) shad are conspicuous hosts. In the Gulf, which occupy a peripheral blcx>d cell sciaenids (the croaker, spot, drums, and (Figure 102). An individual southern seatrouts) and a few other fishes host micro flounder may have both a hemogregarine sporidans, but cysts are usually small and ( platessae) and a flagellate infections are much more prevalent in (Trypanoplasma bullocki). The same leech crustaceans and other invertebrates, probably transmits both parasites. Blood- including flukes. The conspicuous growth 54 Marine Maladies?

• ••,•*• .••'' • '••••. *••- •. , "".. • • • :.'<:•.*%'-. •. .. • J ,. • • • *••••.• ^vV-i-Sffj*:'!-"'.''JM >.:••

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. ;•• ,r :, lit'.:, ••.•.••.•:.•'••.•,. •;•: ••:••(• EM*.:- .•:•::.'.'. ;i • ., Figure 104. Myxosporidan from cyst in liver i- •• '•.•:•:• ..;•;»-...-...... *-:,.•.. .. of striped mullet showing discharged polar filaments. Figure 105. Sheepshead minnow with tumorous growths caused by myxosporidan on the spot in Figure 103 results from large ( lintoni). As in the microsporidan infection from spot, the cysts contain masses of a microsporidan (Pleistophora millions of infective spores. sp.). Some growths are hard, whereas others are soft; all are infrequently seen. affects the sheepshead minnow at least from Mississippi to Texas, may be related to pollution or other stresses. It has other Myxosporidans similarities to cancer in addition to possibly Myxosporidans occur much more being induced by a pollutant. Vegetative commonly than microsporidans in Gulf growths invade and replace healthy muscle fishes, and they comprise a quite unusual tissue and new growths spread to other protozoan group for several reasons. From regions of the body. A related species an evolutionary point of view, () invades and erodes Myxosporida does not fit in with other supporting the central nervous protozoan groups because members have system of salmonid fishes. Hatchery-reared more than a single cell. Depending on the rainbow and seem most sus species under consideration, the actual ceptible to "whirling disease." the result number of cells per spore differs, but a of heavy infections. Infected fish can be spore of most piscine species develops from spotted quickly because their tail region five cells. turns black; neurological control of From an anatomical point of view, chromatophores* becomes impaired. myxosporidans possess internal polar Several histozoic species infect muscle, capsules which evert an elongated filament gill, liver, skin, cartilage, and other tissue in (Figure 104) similarly to the various struc Gulf fishes. One worth mentioning because tures (stinging, adhesive, anchoring, and it can be readily seen in commercially im entangling) everted from capsules found in portant fishes without a microscope forms jellyfishcs and other cnidarians. cysts between fin rays of some seatrouts From a host-symbiont point of view, and related species. Figure 106 shows myxosporidans can be divided into two several cysts of this species (Henneguya primary types: those that infect lumens sp.) in a spot. As with most species, millions of hollow organs such as the gall bladder of spores fill each cyst. In members of this (coelozoic) and those that infect tissues genus, the two joined spore-valves have such as muscles (histozoic). Rather than long posterior extensions (tails) (see insert occurring in spaces between muscle cells of Henneguya sp. in Figure 106). like a histozoic form in the strict sense, some Coelozoic or cavity forms comprise a species develop within muscle fibers larger group of parasites, but fish must be (cytozoic). dissected in order to detect them. Some large, Tumorous* growths caused by a histozoic flat, elliptical forms (trophozoites) can be myxosporidan (Myxobolus lintoni) pro seen through a gall bladder's wall, whereas vide a dramatic example (Figure 105). Not smears of bile or other fluid must be micro prevalent in the Gulf, the disease, which scopically examined to detect others. Gall Fishes 55

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Figure 106. Spot with myxosporidan (Henneguya sp.) cysts between rays in dorsal and caudal fins. An insert shows the tail-like extensions of the two valves.

bladders, urinary bladders, and ureters comprise common sites. Myxosporidans generally parasitize cold blooded vertebrates. As one of three excep tions to this, a species (Fabespora vermicola) infects a fluke that inhabits the intestine of the sheepshead (a porgy) (Figures I07 lo 109). Vegetative growth stages surround both primary and secondary reproductive organs, leaving the fluke unable to produce Figures 107-109. The only reported myxo eggs. Sporesdevelop in pairs (Figure 108);as sporidan (Fabespora vermicola) from a flatworm and one of three from an inverte they mature, they occupy the tegument brate. Top, spores showing polarcapsules at (skin) (Figure 109). Most unusual for any opposite ends of the spore. Middle, two myxosporidan, however, is that after the spores develop together within a membrane. spores either actively penetrate through the Bottom, developing stages occur primarily tegument or passively slough with external around reproductive organs of the digenean host, and mature spores pass through the tegument, single spores move by themselves. tegument (darkly-stained outer layer of Possibly this unique characteristic allows tissue). other flukes to acquire infections because composed of nine peripheral and two usually either several worms or no worms central filaments enclosed in a sheath and per host have infections. Neither sheeps elaborately connected both to the body- head with the fluke norothers examined had proper of the animal and to the internal any myxosporidan infections. Still, the most bases of other cilia in their row. The well- similar described relative to this parasite in coordinated and controlled system allows fects a fish in Russia. progressive beats to form waves that aid locomotion and food gathering. Ciliates also possess two types of nuclei: a small one Ciliates (micronucleus) important in sexual re The ciliates comprise another large im production and a large one (macronucleus) portant groupof Protozoa that infests fishes. produced from the small one and involved Many commensal species become parasitic with nonsexual functions; the macro- when environmental or host conditions nucleus of some ciliates appears like a dictate. Ciliates possess cilia in one or more horseshoe excessively twisted by an over- stages of their life cycle. A , like a enthusiastic blacksmith. , is an elongated structure usually Ciliates are often classified according to 56 Marine Maladies? their feeding apparatus. Peritrichs have a long tubular buccal cavity lined with spiral ling cilia leading toward the mouth, as well as some stouter cilia in rows encircling the top of the cavity. Many peritrichs attach permanently to their host or other sub stratum by a stalk, disk, or lorica (discussed earlier with crustacean ciliates), whereas other motile ones may attach only tem poral ily. All living peritrichs provide impressive spectacles under a microscope. Most coastal fishes in Mississippi harbor at least one motile species of peritrich !J ••**.>;,>? (members of Trichodina or a related genus). l . * •" .< ^ • «... '.'••W!: The ciliates occur primarily on the gills, but i' •; •mm also infest the skin. In contrast, most of those that infest freshwater fishes, and there are many, preferentially infest the skin. Normally few individuals infest a fish, but some fishes typically host both more indivi duals and more species than others. The Figures 110 and 111. Trichodlnid ciliate Florida pompano and striped mullet each parasites from estuarine fishes. Top, live commonly hostat least two species. Juvenile specimen. Bottom, stained (impregnation pompano placed in a garbagecan filled with with silver nitrate) specimen of another aerated seawater and examined daily for gill species to accentuate the ring of "teeth" and skin protozoans will acquire increas (denticles) on the ventral surface. These ciliates can cause mortalities in reared fish. ingly dense populations of trichodinids. Apparently reproducing extensively when because of the detailed study necessary to their hosts become crowded and stressed, delineate the patterns of cilia for the differ they may be undergoing a "normal survival ent stages. procedure" in order to assure a few Attached peritrichs have also been individuals an opportunity to infest implicated in fish mortalities. One species additional hosts should theirs die. (Epistylis sp.) has, within the last few years, Trichodinids may attract curiosity be infested an increasingly large number of cause of the ring of interlocking teeth bluegill, bream, bass, and marine fishes (denticles) on the ventral surface. Figures that invade fresh ornearly freshwater coastal 110 and 111 show these denticles for two Mississippi bayous. The disease derives its different species. One photograph displays name, "red sore," from the bloody lesions a live ciliate and the other shows a preserved associated with this long-stalked, colonial one stained to accentuate the denticles. ciliate. Devastating as these denticles mightappear, Red sore disease portrays a good example they do not harm the host; they support the of both a disease associated with pollution disk like a flexible skeleton. Ciliary move and a disease resulting from interactions ments permit an individual to glide over or between two organisms. Fish with extensive hover close to its host. On the other hand, red sores have a systemic* bacterial infection the peripheral border of the basal disk (Aeromonas hydrophila) that can kill the membrane can pinch and even dislodge host host. I believe the ciliate which is invading tissue. In this manner, the ciliate can harm host tissue acts as the primary invader, al its host, especially if the fish is young or has lowing secondary entrance by the bacterium dense populations on its gills. Pathological into the blood where it can proliferate conditions usually involve hosts in rearing extensively. The bacterium can also enter facilities. Many estuarine and marine by other routes, even in fish without the ciliates have not been named, possibly ciliate. Fishes 57 Some pollutants seem to enhance re Free-living ciliates in other groups can productive capabilities of Epistylis sp. also turn parasitic. A hypotrich (a species Hundreds of colonies of this organism of or closely-related genus) produce a fuzzy growth which appears like damaged gills and skin of several specimens cotton or fungi. Fish farmers find that an of the sheepshead minnow collected from increase in organic materials in their ponds Horn Island and maintained for a month in promotes an increase in red sores. In some an aquarium. The opercula and snout of low salinity and freshwater bayous that infested fish developed bloody lesions, their have, over the past few years, increased their normal swimming behavior modified into concentration of pollutants or decreased jerky and gasping motions, and they died, dieir flow of water, the prevalence of red either from secondary infections or directly sore disease has increased dramatically. In from the ciliate. fact, fishing in poorly-flushed regions can. during certain seasons, produce a prepon Tapeworms derance of bluegill with red sores. Such Tapeworms (cestodes) form a group of catches have kept some fishermen from worms which exhibits two striking features. returning to particular favorite holes where The worms have no alimentary canal, and they have fished for decades. Infections have they have an elongated "segmented" body, kept some from fishing at all. thereby giving an impression of a measur Holotrichous ciliates do not form a ing tape, hence their common name natural (phylogenetically* related) group; "tapeworm." As adults they inhabit tubular most have simple uniform body cilia and no regions like an intestine with its high specialized cilia around the mouth. The best nutritional level, attaching to their host known marine "holotrich," at least to with a holdfast organ (scolex). This organ aquarists, is the marine counterpart may be simple or ornamented with a variety ( irritans) of the ireshwater of hooks, suckers, and other structures, and species that causes "ich," a shortened term it represents the major feature used for used by tropical fish fanciers to designate classification. Each segment of the "tape" Ichthyophthirius multifiliis. Both the salt usually possesses one set of reproductive water and freshwater species cause eleva organs (a proglottid), and in most species a tions on the gills and skin consistingof nests few segments are continuously being of these ciliates eating away at tissues formed. just under the outer layer of skin. They In general, few marine bony fishes (tele irritate the host and promote secondary osts) in the northern Gulf host adult bacterial infections. As in the life cycle of the tapeworms. Examples are a worm dinoflagellate Amyloodinium ocellatum, (Anantrum tortum) from the inshore the release of one feeding individual lizardfish and those (ptychobothriids) from ultimately gives rise to numerous infective needlefishes and related species. The organisms, each adding to disorder in an aquarium or pond. Most aquarium- remedies affect the short-lived swarming stage; therefore, treatment should continue until all feeding individuals (trophonts) leave the fish. Cryptocaryon irritans affects a variety of hosts, but is rare in nature. Most other holotrichs do not share its parasitic mode of life; however, under appropriate conditions, some free-living species invade Figure 112. An inshore lizardfish portraying fish and cause damage. Reported cases have its viscera and the adult tapeworms involved freshwater species primarily, but (Anantrum tortum) from the intestine of a confined marine hosts possess the same similar-sized fish. Worms also occur in vulnerability. Illustrated fish. 58 Marine Maladies?

Figure 113. Life cycle of the tapeworm (Poecllanclstrlum caryophyllum) that causes "wormy trout." The adult develops in the bull shark (or other related sharks). Released segments from the adult disperse eggs,each with a larvathat infectsa crustacean which in turn is eaten by a fish. When eaten by seatrout and related fishes, the larva develops further in flesh and becomes infective for sharks. lizardfish worm looks more like a twisted freshwater (theone-fourth seawater solution Christmas ribbon than a measuring tape. approximates the host's body fluidsand will The normally twisted body possesses a maintain most helminths for several hours). series of reproductive organs, but they are Even though marine teleosts have few not compartmentalized into segments. adult cestodes, they harbor a rich variety of Without any specialized holdfast organ, this larval ones. They act as intermediate hosts worm (Figure 112) often maintains its for the stage (plerocercoid) that infects the position by winding in clumps of several final host. With a few exceptions, these individuals at bends in the intestine or by larvae mature in specific elasmobranchs. sticking an expanded or folded-over The perfect example of this causes "wormy "scolex" into a pyloric caecum. The posi trout." Indeed, when coastal residents, tion in the gut appears related to external especially those who catch and fillet marine water temperature. As the temperature in and estuarine fishes, are asked if they know creases, an increased percentage of worms about any parasites in fishes, most respond locates near the anus. If a fresh lizardfish first and some respond exclusively about comes into possession, see whether a rela this trout-worm (Poecilancistrium tively large creamy-colored worm occupies caryophyllum). To regress a bit, fish harbor the intestine. Watch it writhe in a corkscrew many parasites, but even the most patho fashion within a mixture of one or more genic is rendered harmless by cooking. The parts full strength seawater and three parts common one in the trout does not even need Fishes 59

Figures 114-117. Larval stages of tapeworm (Poecllanclstrlum caryophyllum) that causes "wormy trout." Top left, egg with enclosed coracidium showing cilia and booklets.Top right, earlydevelop ment (procercoid) in copepod (Tlgriopus callfomlcus). Bottom left, a more-developed larval stage. Note two individuals are present. Bottom right, subsequent larval stage (plerocercoid in blasto cyst) in flesh of spotted seatrout. These organisms have been lifted some from the flesh to make them more obvious, but most fillets will have 80% of the worms obvious. Usually about two worms infect a fish, but cutting the caudal extension of a cyst gives the impression of many worms being present. heating to become harmless to people. 116). This host in turn must be eaten by an Unfortunately, too many people feel dis appropriate fish, usually a seatrout (see gust at these infections. Figures 117and 118).The worm apparently "Wormy trout" refers to the presence can live in the trout for a few years. Most of the entwined fleshy stage (blastocyst) that infected sharks measure longer than 135 cm harbors an encased infective larva (plero (45$ feet) long, presumably because larger cercoid) at its swollen end. As seen in the sharks eat more seatrout. diagram (Figure 113), sharks (the bull Even though some fishermen think their shark and related species) acquire infections catch had 20 or so worms per fish, few by eating seatrout (or less often a few other individual fish have more than 3 or 4. The related fishes includingredfish, croaker, and elongated, twisted, fleshy extension may be drum). Within the intestineand spiral valve, cut into several pieces, giving the illusion the worm matures, reaching about 20 cm of many worms. Apparently, once a fish long and producing eggs in attached pro becomes infected, it acquires resistance* to glottids. When the worm or a batch of future infections. Examination of a large segments passes into seawater, a ventral number of spotted seatrout suggests that the cleft in a segment splits, allowing eggs worms do not harm adult fish. However, no (Figure 114) to disperse. After about a week, fish less than 14 cm and few less than 25 cm a tiny swimming larva (coracidium) pops long had infections, suggesting either that out of the capped egg. If eaten within 2 days young fish do notget infected or that the fish by an appropriatecrustacean, another larval get killed. Larvae in small fish occasionally stage (procercoid) develops (Figures 115and encroach on vital organs, giving some sup- 60 Marine Maladies?

Figure 118. Plerocercoid of Poecllanclstrlum caryophyllum removed from fleshy blastocyst. Note the four hooked tentacles Figure 119. Close-up of tentacles of Poecllan and the sheaths that contain the tentacles clstrlum caryophyllum from "wormy when they are not protruded. Constriction of seatrout." Note the different shapes and the bulbs at the posterior of the attachment sizes of hooks, the muscle in the sheath that organ (scolex) protrudes them. retracts the tentacle, and the darkened ciliated pits at the anterior margin. The port to the latter possibility. Perhaps the sensory pits protruded and actively moved worm is detrimental to good fishing. It is about when the fixed worm was alive. not detrimental to good eating! Another "fish tale" needs rectifying. The above cestode plerocercoidbelongs to Wormy trout occur year around because the trypanorhynch group and is diagnosed once a host becomes infected, the\vormscan primarily by the presence of four eversible remain for a few years. When average sal hooked tentacles (proboscises) (Figure 119). inity levels are high, usually during Contraction of muscles around the fluid- summer, the percentage of fish infected is filled proboscis bulb protrudes the tentacle also high. However, the percentage of (Figure 118). The hooks then allow these infected fish during other seasons may far tentacles to attach in the host gut. Another surpass that percentageencountered during related trypanorhynch (Dasyrhynchus sp.) a summer for which the average salinity was in the crevalle jack (Figure 120) can be ob low. More spotted seatrout have heavier served commonly infecting the head and less infections in the clean high saline water of often occurring elsewhere in the flesh. The Apalachee Bay, Florida, (an average of 4.4 plerocercoid of many species infects crusta worms in 98% of fish over 25 cm and a maxi ceans and an earlier example (Prochris mum of 16 worms in a fish) than in any tianella hispida, Figures 70 and 72) repre other region sampled. High saline water sents an extremely abundant one. probably supports more potential interme Tentacle-hooks come in all sizes and diate hosts. An average of two worms infects shapes, sometimes with considerablevariety about 40% of the eating-sized fish in Texas, on a single tentacle. Long spikes with small Louisiana, and Mississippi. In polluted distal barbs (Figure 121) characterize a Tampa Bay, Florida, only 1.3 worms per species (Pterobothrium heteracanthum) fish infected 10% of the trout. from the muscles and body cavity ofAtlantic Fishes 61 croaker, and a variety of hooks (Figure 122), mullet. Hooks shaped like rose-thorns are including a stout recurved one, occurs on the most common type on trypanorhynchs. another species from the kidney of a striped Another cestode group (Tetraphyllidea) infecting local elasmobranchs has members with four similar muscular holdfast organs without tentacles on the scolex. Each may have hooks, spines, suckers, or folds to attach to the gut. In order to appreciate the variety of these holdfasts, some photo graphs are presented. Note the folded margins (Figure 123) on one from the (Phyllobothrium foliatum). In lihinebothrium corymbum (Figure 124) from the southern stingray there are 27 grooves (loculi) on each pe dunculated bothridium. Rhinebothrium maccallumi, also from the southern sting Figure 120. Individuals of a cestode larva ray, has fewer (Figure 125). Members of the (plerocercoid of Dasyrhynchus sp.) being genus Acanthobothrium have triloculate cut out from tissue of the crevalle jack. The bothridia, each with two forked hooks blastocyst has a long thin tail (caudal anteriorly. Compare the scolex (orAcantho extension) and contains the plerocercoid. bothrium paulum (Figure 126) from the

Figures 121 and 122. Variation intypesofhookson thetentaclesoftrypanorhynch tapeworms. Left shows small barbs on thin spikes (Pterobothrlum heteracanthum from flesh of Atlantic croaker). Right shows morethan onetype. Inaddition to numerousthin hooks, some robust ones shaped like a latch-hook provide the most conspicuous form (ICaltltetrarhynchus sp. from kidney of striped mullet). 62 Marine Maladies?

Figures 123-125. Variety in scotices of nonhooked tetraphyllideans. Left, Phyllobothrlum sp. from spiral valve of Atlantic stingray. Middle, Rhlnebothrium corymbum from a southern stingray has more "loculi" on each of the four bothridia than Rhlnebothrium maccalluml (right) from the same host.

Figures 126-128. Two related species of the hooked tetraphyllidean tapeworm Acanthobothrlum. Left, scolex (attachment organ) of Acanthobothrlum paulum from spiral valve of southern sting ray. Middle and right, mature proglottid (the reproductive segment) and scolex of Acanthoboth rlum brevlsslme from the . Note the divided bothridia of both species and the bend (abnormal) in the hooks of the latter species occurring in both sets of hooks. The hooks also bend on two unseen opposing bothridia. Fishes 63 southern stingray with that of Acantho- bothrium brevissime (Figure 128) from the Atlantic and bluntnose stingrays. The latter does have hooks with an abnormal bend, but they are always thinner than those in the other species. A mature proglottid of Acanthobothrium brevissime shows the large stained internal testes, the lateral yolk glands, and the tubular genitalia (including the large male sac) leading to the margin (Figure 127). These proglottids drop off the worm and then develop eggs while still in the gut of the stingray. Detached, the en larged proglottids of both tetraphyllideans and trypanorhynchs move about in the gut and present an appearance similar to that of a fluke. Some even develop suckers or spines. The typical life cycle of tetraphyllideans probably follows that of the trypano rhynchs, but the underdeveloped scolex of Figure 130. An unusual tapeworm (Catheto- the plerocercoid larva does not allow identi cephalus thatcherl) from the spiral valve of a fication like that of trypanorhynchs. In fact, bull shark. Up to 14 bodies can extend from plerocercoids of many species are collective the perpendicular scolex of a single worm. ly called "Scolex polymorphus" (Figure 129). Possibly this plerocercoid stage for Tapeworms in general have a single long some species can be attained in a single body. A few specimens of a species crustacean host. Vertebrates, molluscs, (Cathetocephalus thatcheri) from the bull and other invertebrates alsoact as intermedi shark caught from a variety of regions had ate and paratenic hosts. up to 14 bodies (strobila) attached to one transversely elongated scolex. Possibly entirely separate worms could be formed a- sexually if each body detached and formed a new scolex. A single body is shown in Figure 130.

Monogenean Flukes All groups of flukes show similarities to and are classified with tapeworms as flat- worms. Even though exceptions exist, these similar features include being more or less flattened, not having a body cavity, being hermaphroditic (male and female sexual or gans occurring in the same individual), and having flame cells (cells with a tuft of cilia extending into tubules) to aid in elimin Figure 129. Larval (plerocercoid) tetra ating metabolic wastes and regulating water phyllidean tapeworm (Scolex polymorphus) balance. Flukes can be easily distinguished from Intestine of small striped mullet. Larvae from tapeworms since they possess a gut representing a number of different species, but similar in appearance and also called rather than depending entirely on nutrients Scolex polymorphus, infect a variety of passing through their tegument (skin). fishes and invertebrates. Also, larvae of flukes develop differently 64 Marine Maladies?

Figure 131. Sawfish with heavy infestation of monogenean (Dermophthlrius sp.). White blobs all over head (and rest of body) are the fluke, and they are especially conspicuous because the fish had been frozen and thawed.

than those of cestodes. Biologists separate flukes, or trematodes as they are frequently called, into those forms which typically infest their hosts externally and do not require an inter mediate host from those that infect their hosts internally and undergo asexual reproduction requiring intermediate hosts. The external types (monogeneans) seem to be more closely related to tapeworms than to internal ones (digeneans). Monogeneans primarily infest the gills or skin of fishes; however, a few occur in the gut of fishes and others infect the urinary bladders of frogs and turtles and other sites. A few even occur on or in squid and crus taceans. They usually lay a small number of eggs each day. Within each egg, an encapsulated ciliated larva ultimately hatches and develops into an adult without undergoing asexual reproduction. Worms deposit these eggs, some of which have Figures 132 and 133. A capsalid mono shells with long filaments or other tangling genean (Benedenlella posterocolpa) from or anchoring devices, in such a manner that the belly skin of a cownose ray. Top, entire helps assure completion of the cycle. Some stained worm. Bottom, close-up of anchors attach eggs to sand grains on which their and accessory structures used for forming suction cup effect for attachment. benthic* hosts usually rest, and others deposit them on their schooling host's gills, latter can be seen on the tough skin of some gambling on ultimate contact with school local sharks and other elasmobranchs. The mates just as children pass head-lice to their large conspicuous objects on the sawfish in friends. A variety of methods aid trans Figure 131 are specimens of a monogenean mission. (Dermophthirius sp.) that were implicated Some adult monogeneans are so small in the death of the host in a public marine that a high-powered microscope must be aquarium. The related species (Benedeni- used to identify or even see them, whereas ella posterocolpa) shown in Figure 132came others grow larger than a thumb-nail. The from a cownose ray. The beauty of this Fishes 65 common worm has been accentuated by pigfish. Often when a pigfish is not infested staining. In life, the transparent milky- by the cymothoid isopod, it still has colored worm on the belly of the ray can be immature specimens of the monogenean on easily overlooked without critical exam the gills. Primarily large adult flukes favor ination. It attaches to its host using the large the isopod, and they deposit clumps of eggs central anchors and small marginal hooks on it. The combined worms and eggs on the on the large posterior organ (haptor, Figure isopod present a flowery appearance. The 133). It feeds with its anteriorly-located mouth. Smaller monogeneans, but those still large enough to observe with naked eyes, occur commonly on gills of fishes in the Gulf. Jacks, drums, seatrouts, sharks, and many other fishes often have them. These exhibit a reddish or blackish appearance caused in part by ingested host blood or its breakdown products. Asa general rule, these (polyopisthocotylids) feed on blood instead of tissue and mucus like the others (mono- pisthocotylids). Rather than havinganchors and hooks like those monopisthocotylids discussed above from elasmobranchs, most of these polyopisthocotylids have members characterized by having clamps or suckers. Members of one family () from sharks have large curved hooks associated with suckers (Figure 134). At the risk of leading the reader into thinking monogeneans are not primarily parasites of fishes, an example of those with clamps also exemplifies a hyperparasite that does not always infest fish. Large specimens of this species with stalked clamps (Choricotyle aspinachorda, Figure 135) typically attach near the bases of the legs of a symbiotic isopod (Cymothoa excisa) lodged in the throat cavity (fre quently on the or gill rakers) of a

Figures 135 and 136. Monogeneans from symbiotic isopods on fish. Top, entire worm (Choricotyle aspinachorda) from isopod (Cymothoa excisa) In throat of pigfish. Note Figure 134. Holdfast (haptor) of a mono posterior holdfast organ with eight genean (Heteronchocotyle leucas) from the pedunculated clamps. Bottom, close-up of a gills of a bull shark. Note the large curved clamp from a related worm (Choricotyle hooks (sclerites) associated with the loulslanensls) on isopod in southern suckers. kingfish. 66 Marine Maladies? close-up of a clamp (Figure 136) actually belongs to a closely related worm (Choricotyle louisianensis) which has a similar relationship with a cymothoid isopod on the southern kingfish (also commonly called ground mullet). Next time one of these fiesty bottom feeders is caught, a reader should look for the isopod and its symbionts. Relatives of the isopod monogeneans that infest gills of fish occasionally cause mortalities, but usually only when infesting confined fish. Fishes such as the com mercially valuable Florida pompano acquire infestations heavy enough to succumb. Most relatives of the first men tioned type (monopisthocotylids) on bony fish, and there are many, never reach a size visible to the naked eye. These tiny tissue- feeding species comprise a much bigger threat than polyopisthocotylids to confined hosts, including freshwater fishes. If present in an aquarium or small pond, however, infestations can usually be controlled with a Figure 138. Filamented eggs from a variety of chemical treatments. Figure 137 monogenean fluke (Udonella caligorum) on shows a couple of individuals in conjunc a copepod (Caligus praetextus) on the sea tion with a parasitic dinoflagellate stressing catfish. The segmented appearing structure their ailing host. at the lower right is the copepod's egg sac. In a manner similar to that of the observed on caligids from the gills and skin monogeneans on the isopod from the fish of local sea catfish (hardhead catfish), throat, another species (Udonella seatrout, and striped mullet (popeye caligorum) often associates with copepods mullet). Apparently cosmopolitan, it infects (usually species of Caligus) on which it a wide range of hosts. attaches its eggs by filaments (Figure 138). Monogeneans make good biological in Unusual because it lacks hooks or anchors, dicators (tags) because a singlemonogenean this monogenean can be commonly species usually limits its infestations to a single host species (see host-specificity in glossary). Many fish can be identified on the basis of their parasites! Evolutionary relationships among fishes can also be suggested on the basis of these parasites. Even though not accepted by all ichthyolo gists, diskfishes (remoras and shark suckers which have their spinous dorsal fin modified into a laminated disk-mechanism allowing attachment of the fish to turtles, sharks, rays, and large fish) seem to be close ly related to thecobia (also called lemonfish, Figure 137. Two small monogenean flukes ling, and a variety of other names). As moving about near the attached parasitic parasitic evidence for this relationship, dinoflagellate (Amyloodlnlum ocellatum) on the gills of a sheepshead. Eitherof these two species of one family of monogeneans parasites could kill a captive fish If enough (Dionchidae) infest exclusively the cobia individuals occur at one time. and diskfishes. Since dionchids infest no Fishes 67 other noncaptive hosts and since members of the two fish families host no other monogeneans, a long period of isolation is suggested. Several other groups of mono geneans infest primarily members of certain families, indicating strong evolutionary trends.

Dlgenean Flukes Digenean flukes exhibit considerably more variety in their adaptations than monogeneans and quite possibly more than any other helminth group. Many different groups of animals serve as intermediate hosts for the larvae. In addition to fishes, adultdigeneans infect amphibians, reptiles, birds, mammals, and occasionally crusta ceans and molluscs. In fishes, most species infect the alimentary tract, but a few encyst in flesh, lodge in blood vessels, or occupy other sites. More species in birds and Figures 139 and 140. The giant stomach mammals than in fishes occupyspacesother worm (Hlrudlnella ventricosa) from "blue- than the alimentary tract. Some of these arc water" fishes. Top, contracted, preserved the kidneys, air spaces, and the bile ducts. specimens from . Bottom, more elongated preserved specimens from little Almost all digeneans utilize a snail or tunny; living worms can extend further than bivalve mollusc as a first intermediate host. an opened hand. Note the two suckers. The An earlier diagram (Figure 28) already dark color represents breakdown products portrayed a complete cycle of a snail to crab of blood obtained from feeding on the host's to raccoon pattern, and more cycles will be stomach. discussed in this section. In general, asexual layers added by the host. The metacercariaof reproduction takes place in the mollusc. a few species develops without cysts This reproduction involves a few different (unencysted metacercaria), but examples of kinds of larvae. The larva from the egg in this type represent exceptions. After fects the mollusc and produces a stage that developing for an adequate period, the larva either yields additional individuals of the can infect its final host. Occasionally, it can identical type which then produce free- debilitate or alter its intermediate host in living* larvae (cercariae) or another stage such a manner that the final host has easier which also produces the same kind of access to individuals that are infected: some free-living larvae. The route of infection and infected amphipods turn reddish or pale, kind of larvae depend on the species con making them more visible to final hosts, sidered. Cercariae of some species crawl or some snails do not burrow as deeply as un encyst in the host mollusc without leaving infected ones, and some fish cannot swim as it. Most, however, have long tails allowing fast or as long as those without cysts. Those them to swim or to attract predators. Some species without special means to alter the penetrate their hosts, some encyst external intermediate host's behavior may have to ly, and some are ingested directly. Often, the produce many more larvae in order to assure time of day, amount of light, temperature, that enough larvae will mature to complete tidal phase, or water pressure controls the cycle. release of these larvae. Once in or on their One trematode that fishermen who fish proper host (or vegetation or some other for billfish and other pelagic fish should be object), the tail, if present, sheds and the aware of is the giant stomach worm minute larva (metacercaria) forms a (). Fishermen may capsular cyst, with or without more cyst know it because of its large size. Figure 139 68 Marine Maladies? shows some preserved contracted ones suckers, one species (Crassicutis archosargi) ("walnut worms") from the stomach of a from a sheepshead can modify its tegument wahoo, whereas those in Figure 140 from into an adhesive surface (Figures 141 and ("bonita") exhibit less con 142). traction. When alive, the fluke can elongate The line drawings of three species much farther than shown. What appears to (Figures 143 to 145) portray examples of be the same or at least similar species infects several features. The one on the left a variety of "bluewater" fishes. When in the (Lecithaster leiostomi) comes from the wahoo, usually only two individuals are intestine of spot and a few other fishes. Un present. This common occurrence of two like the related Hirudinella ventricosa worms in fish shorter than 160 cm has from billfish stomachs, it does not need a allowed many a wagering fisherman to win thick skin (tegument) for protection from a six-pack of beer. One should use caution, stomach acid and from churning food however, because tunas and other fishes do particles. Also, Lecithaster leiostomiseldom not usually possess two per fish. reaches 1 mm in length. Most members of its Most flukes have two suckers. A central family (Hemiuridae) inhabit the stomach's one primarily holds on, whereas an anterior lumen, but other exceptions exist. In fact, one operates in feeding, holding, and another small species(Satumiusmaurepasi) moving. These suckers can be seen in the even dwells in the tissue under the lining of photos and in most of the digenean illustra the striped mullet's "gizzard" (pyloric tions in this guide. In addition to the stomach). The middle worm (Glaucivermis spinosus) is a littleshorterand has a thinner tegument than Lecithaster leiostomi, but also infects the intestine (of the southern kingfish). The worm on the right (Neochasmus sogandaresi) is about twice the size and infects the striped bass. It has several relatives that infect a wide range of freshwater and marine fishes. One relative without the spines about the mouth (Metadena spectanda) ranks among the most common, but seldom seen, animals in the estuaries. For example, during February of 1971 an average of 54.3 individuals in fected each of 53% of the Atlantic croaker examined near Ocean Springs that had the worm (90% of the fish larger than 7 cm were infected). Because croaker during that period comprised the most common fish besides the bay anchovy and many speci mens of the fluke infected most of them, that fluke should be recognized as a common constitutent of the animal community. In fact, other fishes also host Figures 141 and 142. A sectioned digenean the worm! During the past couple of years, (Crasslcutls archosargl) expressing its however, the population density of both the ability to modify its tegument adjacent to the croaker and digenean have decreased. host's (sheepshead) Intestinal tissue so that it expands, fills all available space, and The three illustrated digeneans represent adheres firmly. Top, cross-section through different families, but all have small eggs level of the fluke's testis. Bottom, especially (about 30 u, or 0.030 mm, long). Several stained (periodic acid Schlff with diastase) other digenean groups have members with worm-tegument showing positive reaction. Most digeneans attach to their host by their eggs several times larger. As a general rule, ventral sucker. large eggs produce larvae (miracidia) that Fishes 69

Figures 143-145. Line drawings of three digeneans from fishes. Left, a hemiurid (Lecithaster leiostomi) from a spot. Middle, a zoogonid (Glauclvermls splnosus) from a southern kingfish. Right, a cryptogonimid (Neochasmus sogandaresl) from a striped bass. These do not begin to exhibit the variety in characteristics of digeneans. Note the ventral suckers, the lobation of the ovary (dark organ), lobation and follicles of yolk gland (lightly stippled organ), and male terminal organ (exists marginally in center worm). leave the egg to search out and penetrate the mollusc, whereas small eggs usually have to be ingested by a mollusc in order for the enclosed larva to parasitize the mollusc and complete the cycle. Consequently, many- more small eggs have to be produced to re sult in final populationsequivalent to those producing large eggs. The normal golden- tanned eggs give color to many otherwise chalky or transparent live worms. Other species, however, acquire carotenoids or other pigments, giving their bodies yellow ish, pinkish, or orange colors. Most fishes harbor digeneans and some have several different species. Even though many show specificity toward a single or few hosts, they, as a group, exhibit less Figure 146. Dorsal fin ofAtlanticcroakerwith specificity than monogeneans. encysted digenean specimens (a meta In addition to harboring adult digeneans, cercaria) between finrays. If the croaker Is fishes also host a variety of larval digeneans eaten by the proper predator, the larval fluke will mature. (metacercariae). Usually the small worms are encysted and cannot be seen without a posits dark pigment around the cysts. critical microscopic examination (Figure Fishermen know this condition as "black 146). Exceptions occur when the host de- spot" disease, and several nonrelated 70 Marine Maladies?

Figure 147. Black spot resulting from pigmentation (melanization) around larval Figure 148. Melanophores In the skin of a cysts of a strlgeoid fluke in the tidewater fish. These are part of a complex system of silverside. A variety of freshwater and marine chromatophores which regulate colors and parasites can cause black spot. color changes in fish. This pieceof sectioned tissue had an overabundance of pigment digeneans cause it. In the southern U.S., surrounding a lesion. most casesof black spot result from strigeoid Heterophyids have many similarities infections. Most strigeoid species utilize a with the microphallids already discussed freshwater snail and a fish-eating bird in the earlier as digeneans infecting the blue crab cycle. The tidewater silverside from the and shrimp. Small species infect birds and estuaries in Mississippi, however, also mammals, often in very large numbers. A possesses a strigeoid species. The one in the sample of 14 brown pelicans from Louisi photo (Figure 147) came from the ana averaged about 12,000 specimens of Pascagoula estuary. One large easily Phagicola longus per bird. Both digenean visible hemiurid (Stomachicola magnus) families have a large numberof species, and, encysts in the flesh andelsewhere in a variety in bothgroups, the second intermediate host of fish. The white (sand) seatrout often has is usually more specific than the final one. many. If the curious finder pricks at this Adult heterophyids appear very similar in black object in a fresh fillet, out will pop appearance to microphallids, but minor a pinkish-colored worm. differences in their genitalia and other Normally, chromatophores (Figure 148) features set them apart. Differences in their expand, spreading out their associated free-living larvae (cercariae) accentuate the melanin to give a fish a dark color. differences even more. From a more practi Contraction produces a pale color. Other cal point of view, heterophyids use fishes chromatophores bear different pigments as second intermediate hosts and micro for different colors. Most diseases in which phallids use crustaceans. pigments are deposited, however, involve The key silverside shown in Figures 150 melanin. and 151 has damaged fin rays caused by an Less easy to see than the above hemiurid, encysted metacercaria (of an acanthostome). a small heterophyid (Phagicola longus) in One important fact concerning these in fects the flesh and viscera of mullets along fections is that the fish is rareandconsidered the Gulf and southeastern Atlantic states. endangered. Found in a pond in the Florida A diagram (Figure 149) shows the life cycle. Keys, the fish has to contend with a parasite In addition to herons, a large number of in addition to man's encroaching develop other birds and mammals, including man, ments. The final link in the cycle, either the can probably act as final hosts. Although no American crocodile or the American human infections have been confirmed, alligator, also has status as an endangered many people throughout the world who species. eat raw fish harbor zoonotic* species related Another group of digeneans or closely to this tiny worm. Most infections produce related worms is the aspidogastrids. These symptoms hardly more serious than have a conspicuous ventral loculated hold diarrhea and mild irritation; however, fast organ and a life history lacking asexual serious complications occasionally develop. reproduction. Although prevalent in some Fishes 71

Figure 149. A heterophyid fluke (Phagicola longus)lifecycle. This large family of flukes hasadults that Infect theintestine of birds andmammals andlarvae thatencystin fishes. Theencystedstage shown here infects predominantly mullet. 72 Marine Maladies?

Figures 150 and 151. Two specimens of the Figure 152. A preadult aspidogastrid key silverside infected with cysts of the (Cofy/ogasfer basiri) from the rectum of the metacercaria of an acanthostome digenean. sheepshead. Presumably acquired from a Bottom, close-up view showing nature of mollusc, this worm matures in a few fishes damage to caudal fin rays. Cysts also occur including the sheepshead. elsewhere on these and otherspeciesof fish. A crocodilian completes the cycle for the showed completion of one aspidogastrid parasite. cycle utilizing a freshwater clam as the only freshwater clams and turtles, aspidogastrids necessary host and the ability for turtles include species that also infect marine feeding on the clam to maintain an infec fishes. The most common Gulf species (Lo- tion; many biologists assumed that species batostoma ringens) occurs in the intestine to be representative of the group. Actually, of a variety of fishes, but if a person really a vertebrate appears to be necessary for desires to obtain a specimen, he (used in the maturation of most species, including antiquated sense to include also females) Cotylogaster basiri and Lobatostoma will have the best chance by examining a ringens, rather than just an adjunct host Florida pompano. Fish apparently acquire helpful as a dispersing agent. the worm by feeding on coquina clams in the surf, but it may be harbored by other molluscs. The most attractive aspidogastrid Roundworms (Multicalyx cristata) resides in the bile "Roundworm" is a common name for a ducts of large rays, sawfish, and other nematode. Not all nematodes parasitize elasmobranchs. Growing over 10 cm long, animals. Some infect plants and others live the narrow pale yellow body contrasts free without hosts in water or soil. They sharply with a bright reddish holdfast all have separate sexes, a digestive tract, a organ. The elasmobranchs may acquire lough cuticle (outer layer of worm), and infections by feeding on bony fish with internal longitudinal muscles. The reason juvenile worms (checkered puffer, southern for mentioning this last feature is that kingfish, and others) which in turn picked nematodes, unlike earthworms, and cater up the worms from a mollusc. A preadult pillars, move in a whiplike fashion. Most specimen (Cotylogaster basiri) from the other animals that are called "worms" have rectum of the sheepshead illustrates an a layer of circular muscles that allow a aspidogastrid (Figure 152). An earlier study coordinated inchworm-type of locomotion. Fishes 73

Figures 153-155. Some views of two adult roundworms from the intestine of fish. Left, anteriorend of camallanid (Splrocamallanus cricotus) showing spirally ribbed buccal capsule used for attach ment to gut. The capsule is hard and golden-tan to orangish In life and followed bya long muscular . Middle, a male tail of the same worm showing the winglike flaps (caudal alae) with sensory papillae used in grasping the female during mating. Right, anterior end of ascaridoid (Thynnascaris Inqules) from a cobia. Attachment by this worm is achieved by the three large lips. The distinct ringed cuticle is not as dominant in related species.

The size and arrangement of the longitu A few intestinal worms also deposit lar dinal body musculature in nematodes vae rather than eggs. An especially notable dictates the type of slashing movement it one also has a reddish color. It was men will have. Before reading this guide, a reader tioned earlieras a nematode larva in penaeid may have never thought about parasitic shrimp. This camallanid (Spirocamallanus nematodes, even though he may have cricotus, Figures 153 and 154) infects the pondered "vinegar eels" (Turbatrix aceti) intestine of at least 13 different estuarine thrashing about in plant juices or vinegar. and nearshore fishes. When an intestine ofa Those small free-living worms had been fish is swollen, filled with liquid, or par incorrectly credited in the past with the tially transparent, these relatively large acetic properties of vinegar. worms (up to 3.2 cm long) can be seen Parasitic nematodes occupy a wider wiggling within the uncut gut. The reddish variety of habitats than most worms in fish. worm's activity, especially when several The adult forms in fishes occur mostly occur together, readily distinguishes it from along the alimentary tract, whereas most any food contents. larval forms inhabit the mesentery. These Why is Spirocamallanus cricotus red? larvae usually have thin cystsencapsulating Many worms, and other animals including them. One family of nematodes worth the beautiful flamingo acquire their reddish mentioning for its unusual locations is the color from components in their diets Philomeiridae. Members of this group (mostly carotenoids). Such is not the case for usually appear reddish. Some reside in the Spirocamallanus cricotus and some other body cavity, and others occur in the gonads, reddish nematodes. Unlikemost nematodes, between fin rays, under the skin, and in these worms have hemoglobin* just like muscle tissue. Rather than releasing eggs man and fishes. Properties of the hemo like most nematodes, these worms release globins from Spirocamallanus cricotus, young larvae. Philometrids infect a variety however, differ some from those of its of local fishes including the Atlantic Atlantic croaker host. The worm attaches to croaker, redfish, tripletail, and southern the gut wall with its golden colored, flounder. spiralled, scleritized* buccal capsule(Figure 74 Marine Maladies? 153) and feeds on host blood. The worm atypical feature for members of that genus, quickly digests the host blood, and a possi but not for members of a related genus. bility exists that its components help to Thynnascaris inquies, often present in the form the worm's own hemoglobin. hundreds in a large cobia, occasionally Strangely though, properties of this causes ulcerated lesionsatsites whereseveral hemoglobin in males differ from those in individuals attach clustered together. female worms. Other ascaridoids occur in the northern Fish can acquire infections of this reddish Gulf, and one (Thynnascaris reliquens) is colored nematode by feeding on copepod occasionally common in inshore fishes. intermediate hosts. The penaeid shrimps This worm, up to 13 cm long, may also also act as intermediate hosts and quite occur in the hundreds in the intestine and possibly as paratenic (transfer) hosts. elsewhere along the alimentary tract of I have seen worms in the common small sheepshead and a few other hosts. In several squid (Lolliguncula brevis), and other other hosts, however, only few specimens animals may also serve as paratenic hosts. A occur. When a host has been caught and paratenic, or transfer, host is one in which landed or otherwise placed under severe nodevelopment to the nextstageoccurs, and stress, the worms vacate the host, leaving paratenic hosts have and will be discussed through the mouth, gill cavities, and again under other sections. This type host anus, hence the Latin name reliquens re should not be confused with a reservoir ferring to the abandonment. Additional host* in which any stage could occur. species in martin and other billfish also Spirocamallanus cricotus takes several leave in mass. Such an activity, disgustingas months to mature and can live in a fish for it may appear, should have no bearing on longer than a year. Since individuals grow whether a person eats the fish. Even though relatively slowly, they probably do not some species may be harmful to man, the cause excessive mortalities in . escaping stage is easily visible, it is an adult, Several specimens crowded into one fish the worms are discarded when removingvis might causedisease, and related species have cera, and their eggs need several days before killed their hosts. The ripe female of one of becoming infective and then not to people. these (Camallanus oxycephalus) sticks its Nevertheless, cooking the fish alleviates any reddish body out theanusof a striped bass or potential threat. More information on other of its hosts. These can be commonly public health aspects occurs below. seen in estuarine bayous and freshwater Something should be said about the sex habitats of both Mississippi and Louisiana. life of nematodes, since reproduction ac When fully gravid, the protruded female counts for most of their expended energy. ruptures explosively and releases her larvae. The figured copulating pair shows the Copepods serve as the intermediate host, curled tail of the male wrapped about the and small fishes serve as paratenic ones. female, the inserted right spicule, and a Different groups of nematodes attach to their host usingdifferent anteriorstructures. Philometridsdo notdevelopa very elaborate anterior end because they embed in tissue. The camallanids have scleritized bivalve- shaped or barrel-shaped buccal capsules, and adult ascaridoids possess three strong lips. Common ascaridoids from local Gulf fishes include members of the genus Thynnascaris. Figure 155 shows the power ful lips of a species (Thynnascaris inquies) Figure 156. A male nematode (Thynnascaris from the stomach and pyloric caeca of the reliquens) mating with the female. A mucoid cobia (lemonfish). Actually, the con band girdles the female immediately spicuously-ringed cuticle constitutes an posterior to her genital opening. Fishes 75

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Figure 157. Generalized ascaridoid roundworm life cycle. Three different types of final hosts are illustrated, and each harbors members of a different genus. Nevertheless, the life histories of the worms show the same general patterns. Depending on the species Involved, eggs deposited in the water either produce free-swimming or encased infective larvae. Copepods or other crustaceans act as primary hosts for most species, allowing development of the stage infective for the vertebrate hosL Some crustaceans do not supportcomplete development of the larva, but be come eaten by a fish or other invertebrates in which development does occur. Forsome species, free-swimming larvae eaten directly by fish will develop to a stage infective for the final host. Usually, improper fish hosts that eat fish with infective larvae will maintain and accumulate infec tions. Depending on the species of parasite, the length of these larvae range from the span of a headof a pinto thatof a finger. Acoiledandstraightspecimen of alarval Thynnascaris sp. is figured to the right of theintermediate hosts.With minormodifications, all ascaridoid larvae appearsimilar. 76 Marine Maladies? mucoid band about the female (Figure 156). intermediate or paratenic host iseaten by the The male's tail in this worm and all other proper definitive host, the worm matures in nematodes has some type of a modification die alimentary tract and deposits eggs to to cup or clasp the female. It is usually start another cycle. lined ventrally with a specific pattern of Larval species of and other sensory papillae (see Figure 154 of the male genera infective to marine mammals act as tail of Spirocamallanus cricotus). Once potential threats to public health and the properly aligned, the inserted spicule or primary cause of marine nematode spicules allow passage of sperm to fertilize zoonoses*. Even though species belonging the ova. The position of the female opening in genera that normally infect non- and other aspects of both the female and mammalian hosts may infect man, they are male reproductive systems vary considerably not as large and most are harmless. At least among different groups of worms and com one species of Thynnascaris from both prise important taxonomic characters. fishes and invertebrates can infect labora While still concerned with ascaridoids tory mice, and it was discussed earlier as a and their biology, I will discuss general life shrimp parasite. Fortunately, few cycles of species of three different genera. mammalian-type larvaeoccur in the inshore Mammals (porpoise), birds (pelican), and coastal regions. fishes (Atlantic croaker) act as hosts for Less dangerous to man, but nevertheless members of Anisakis, Contracaecum, and discomforting to fishermen, are large Thynnascaris, respectively, as exemplified species of larval Contracaecum. These in Figure 157.Actually, several species exist cream-colored to yellowish to reddish in each of these three and related genera of worms coil up or occur straight, either free parasites, and most probably have similar or encysted in their hosts. The species in cycles. The major difference among the different mullets (Contracaecum "robust- three relates to the members' infecting a um") most often infects their kidneys and mammal, a bird, or a fish, respectively, as liver. A related species in the redfish and a their definitive hosts. Eggs are released with few other hosts infects the same sites, but feces from the host. Usually an eggdevelops also commonly resides in the mesentery. Be in a few days, and a small larva is released. If cause an individual of both species can a proper crustacean feeds on the wiggling extend over 2 cm when uncoiled and the little larva, the worm develops into a stage worms heavily infect some fish, they con infective for the final host. Alternatively, if stitute a logical cause for unnecessary worry. an appropriate fish feeds on the free- The tested worms have not infected experi swimming larva of some species, the worm mental mammals, are usually discarded can develop without the copepod. On the normally when cleaning fish, can be easily other hand, some copepods do not promote avoided, and are killed with heat. development in the worm, but still allow a Past history, including the great depress fish to acquire the larva by feeding on them. ion of the 1930's did much to influence the Whether infective as a free larva or within likes and dislikes of eating mullet on the a crustacean, some species can complete the Gulf Coast. Since smoked mullet was a pri cycle to maturity by utilizing a fish mary protein source for many years, main- intermediate. Although usually not highly people still prepare mullet in this and a vari host-specific, an ascaridoid will not infect ety of other ways. For this same reason, nor develop in all fishes. In order to assure many people would be happy never to see completion of cycles, however, many fishes another mullet or can of Spam. Actually, in and invertebrates can act as paratenic hosts. the 1800's many inland farmers made an As discussed earlier, they acquire infective nual fall trecks to the Florida coast to catch larvae by feeding on other hosts with the and salt large quantities of mullet to last same stage larva. No development takes through the year. Before that, Indians made place in the new host, but accumulation and similar annual trips to catch, salt, and transference assure a greater supply of in smoke the fish. If fresh mullet is cleaned fective larvae in the entire habitat. Once an immediately, I recommend it highly. Fishes 77

Figures 158-160. Skinned mink with the giant kidney worm (Dloctophyma renale). Left, greatlyen larged right kidney with enclosed nematodes. Middle, same kidneycutopen toexpose worms. One worm exhibits a post-mortem deflated condition and an extruded filled with eggs. Note the bony spicules supporting theempty kidney capsule. Right, seven worms all removed from the body cavity of the single adjacent mink. Note the externally affected, but not infected, right kidney. According to the trapper, this mink was a healthy-appearing, active individual. Herbivorous (plant eating) fish like mullet, host's right kidney and totally devour all just as their herbivorous terrestrial counter the interna] cellular material, often leaving parts deer and cattle, quickly decrease in only the kidney's capsular wall reinforced quality if not immediately eviscerated. by some freshly-deposited bony spicules. In Larval ascaridoids, although usually not fections probably occur primarily in the harmful to adult fish, can kill juveniles right kidney because the placement of the because of their relatively large size in duodenum and liverallowsdirect migration comparison with that of the small fish's of the larva. Occasionally an adult infects vital organs. This danger exists in the the body cavity, perhaps because the migrat natural environment because many small ing larva did not have direct access to the fishes feed on infected copepods. Conse kidney. In any event, the large reddish quently, the possibility for fish fry to get colored worm is destructive, as can be seen infected may depend on whether copepods by the photographs of two minks, one with harbor appropriate worms at a time when an infected right kidney (Figures 158 and and a place where fry are present. 159) and the other with worms removed Many other groups of nematodes use from the body cavity (Figure 160). fishes as intermediate or paratenic hosts. The life cycle of Dioctophyma renale is Members of most of these are small and rather straightforward (Figure 161), but necessitate critical examination to find and described improperly in many textbooks. to identify. One conspicuous exception is Eggs exit in host urine and embryonate. the dioctophymatids. These large red worms Specific aquatic oligochaetes ingest eggs can be found taking up most of the space in with the developed larva; this larva develops a killifish's or some other small fish's further in the worm's ventral blood vessel. body cavity. Since mustelids, canines, and other carni The giant kidney worm (Dioctophyma vores seldom feed on small oligochaetes, renale) in mink (Figures 158 to 160) and most of these mammals depend on paratenic other mammals represents a well-known hosts for their infections. Some small fish member of the group because it can reach feeding on theoligochaetes acquire the larva over a meter long in an appropriate host. and even support considerable growth, but Once ingested, a few specimens enter the not maturation, of the worm. The nematode 78 Marine Maladies?

—•**>= ,r

'ii'i

Figure 161. Life cycle of giant kidney worm (Dioctophyma renale) of carnivores. A mink or other acquires an infection by eating anyofseveral, minute,aquatic, free-living worms or more often by eating a fish that has eaten one of those worms. Once in the mammal, the worm typically migrates to the right kidney. It penetrates into that organ and devours all the tissue, growing to over a meter long, if theanimal hasa large enough kidney. Eggs are deposited with urine and aftera short developmental period are infective to the aquatic worm. can grow many times longer than the Eustrongyloids appear similar except the fe oligochaete once in a fish. male has her genital opening in the Even though primarily a freshwater posterior end rather than anteriorly. Adults disease, I have seen several wormy mink that infect the intestine, stomach, or proven- had been trapped from estuarine marshes triculus of herons and some other water in Louisiana, including those photo birds. In a few birds, they embed in the graphed. stomach wall, partly degenerate, and pro Most large reddish-colored worms duce an abundance of eggs. In others, they encountered in both fresh and estuarine inhabit the intestine without apparent harm fishes, however, are not the kidney worm, to the host. The life cycle is the same as that but close relatives (Eustrongyhides spp.). for the kidney worm. Fishes 79

Eustrongyloids penetrate out of the flesh of dead infected paratenic hosts. Striped bass maintained in a pond at GCRL as well as mosquitofish, killifish, and tadpoles all had worms escaping after a large scale mortality in the pond. Whether the worms had any influence on the mortalities was not established, but investigating the re lationship would be a good problem. Striped bass held in aquaria and fed gambusia acquired larval Eustrongyloides sp., whereas others not fed fish did not, suggesting the ability of the worm to be maintained by a series of paratenic hosts. Larval eustrongyloids have been implica ted in deaths of herons and egrets. Actually, when a variety of birds feed heavily on in fected fish, death can follow. Numerous red-breasted mergansers in Virginia died a day or so following engorgement on infect ed mosquitofish and silversides trapped be neath a thin sheet of ice on a brackish pond. Migrating worms reduced the birds' liver, proventriculus, and air sacs to a bloody pulp.

Figure 162. Proboscises of juveniles of two Thorny-headed Worms related thorny-headed worms (acantho Acanthocephalans, or thorny-headed cephalans). Large one on left is Tegorhyn- chus turcatus that commonly infects the worms, are all parasitic, even though living southern kingfish, and the smaller one is worms presumably shed from fish do occur Dollfusentls chandler! that commonly in benthic samples. They look superficially infects the Atlantic croaker. Even though like roundworms. Actually, they have no both can be transmitted by amphipods from gut, they have a protrusiblc proboscis with near high salinity beaches, Dollfusentls chandler! usually infects estuarine hosts hooks, and their reproductive and most that feed on amphipods from low salinity other systems differ considerably from those habitats. of roundworms. They, like roundworms, have separate sexes. orange-colored species (Pomphorhynchus Several different species occur in local bulbocolli) may makea stronger impression fishes. The sheepshead minnow hosts one on an observer from this low salinity-fresh (Atactorhynchus verecundum) and the water habitat because its bulbous proboscis cobia (= lemonfish) hosts another permanently embeds in the gut of the (Serrasentis sagittifer). In order to see the bowfin (= mudfish, Amia calva) and a few first species, a microscope is necessary, but other fishes. the latter species stands out conspicuously As an extremely common estuarine when one cuts into the intestine and pyloric example, Dollfusentis chandleri portrays a caeca of a cobia because it frequently grows characteristic thorny-head (Figure 162). longer (but substantially narrower) than a This species infects the rectum of the finger. Many other species occurcommonly, Atlantic croaker, spot, and a variety of other even in the fresh-brackish water interface fishes. It is quite similar to a larger species where one (Leptorhynchoides thecatum) in (Tegorhynchus furcatus, Figure 162) which fects most members of the sunfish family as embeds in the intestine of the southern well as a variety of marine intruders. An kingfish (= ground mullet, Menticirrhus 80 Marine Maladies? Dollfusentis chandleri (Figure 164) does not need a transfer host in its life cycle be cause its definitive hosts eat amphipods. A few unrelated amphipods from habitats ranging from nearly-fresh to full-strength seawater can host it (reported from Lepi- dactylus sp., Grandidierella bonnieroides, and Corophium lacustre). Up to three cystacanths, each folded over on itself and longer than the amphipod, can inhabit the same host (at least for the closely-related Figure 163. Typical example of a nearly Tegorhynchus furcatus in Lepidactylus mature acanthocephalan egg. The shell of sp.). Tegorhynchus furcatus appears to most species looks like a diatom and thus a cause an increase in the host's size; evidence source of food for the inter suggests infections may even make the af mediate host. The nearly infective acanthor fected amphipod a more accessible item of can be seen inside the shell. prey. Most croaker usuallyacquire Dollfusentis americanus) and a few other fishes. In both chandleri in low salinity bayous about early cases, many individuals can infect a single host. Indeed, over 450 specimens of summer. The worms can remain in this principal final host for over a year, but Dollfusentis chandleri crowded into the females usually restrict egg-production to a rectum of a relatively small (as long as a short period sometime in or near summer. hand) Atlantic croaker without any appar Unlike many acanthocephalan species, ent harm to the host. males and females remain in equal Life cycles show one basic pattern, numbers. Many species of both acantho- whether for species infecting fishes or other cephalans and nematodes undergo a loss of vertebrates. Developed eggs are sorted and males following fertilization, but this shed by the female worm; they leave the host acanthocephalan acts as an exception. with its feces. Aquatic ones look similar to a diatom (Figure 163) and consequently simulate a food source for arthropod intermediate hosts. After being eaten by the Crustaceans proper arthropod, the larva (acanthor) Crustacean parasites from fishes evoke forms another stage (acanthella) which more interest than most parasites because gradually develops into an infective juve they are readily visibleand show such a wide nile. Finally, the arthropod with the worm variation in appearance. Isopods can be is eaten by and the worm infects the proper extremely large and fierce-looking, whereas vertebrate host. In the case of acantho- copepods come in all sizes and shapes. Both cephalans from fishes, most either use an groups have large numbers of nonparasitic or an amphipod host, but few use relatives. The parasitic ones have evolved copepods, isopods, and other hosts. Since several features to assure their livelihood. the cobia and many other host-fish do not Some have evolved to the point where, with feed on such small crustaceans, the reader out examining larvae and mouthparts. one may wonder how the cycle is completed. could hardly classify them as crustaceans. Once again, the paratenic host becomesa vi Crustaceans have a protective, external, tal link in those cycles. Consequently, some nonliving cuticle which sheds during ma biologists call the host a transfer host. turation. This molting process was Fish usually fill this role and, in the case of described earlier in conjunction with crab Serrasentis sagillifer which matures in the symbionts. Most parasitic crustaceans also cobia, the Atlantic croaker, inshore lizard possess a variety of appendages the same as fish, lane snapper, and other fishes function nonparasitic ones (see figure 48 of a brown as the transfer hosts by harboring juveniles shrimp). (cystacanths) in their mesenteries. Structures of the isopod (Lironeca ovalis) Fishes 81

Figure 164. Life cycle of acanthocephalan (Dollfusentls chandleri). Male and female worms live and mate in the rectum of the Atlantic croaker and other fishes. Specific amphipod crustaceans feeding on deposited eggs acquire a stage that ultimately produces a juvenile worm. Croaker be come Infected from eating these amphipods; however, some other acanthocephalans utilize different as hosts, and some use additional transfer hosts to bridge the apparent gap between an arthropod and a predator that feeds on relatively large prey. most commonly observed on the gills of a cussion on bacteria and lymphocystis). variety of fishes have been modified much When one isopod infests each side of a host, less than those on the bopyrid discussed the debilitation must beconsiderable. Three earlier from under a grass shrimp's cara views (Figures 165 to 167) illustratea sheeps pace (see Figures 82 and 83). Effective claws, head with twosuch unwanted "passengers." however, do hold that asymmetrically Some other isopods display themselves shaped parasite to the gills or adjacent more conspicuously when a host dies. regions of its fish-host. Oftentimes, most of Occasionally a large percentage of a stock the filaments from several gills erode away of Gulf menhaden (pogy) will have a large and secondary infections ensue (see dis species (Olencira praegustator) attached to 82 Marine Maladies?

Figure 168. An isopod (Nlroclla acuminata) attached to the dorsal fin of the sea catfish. The same isopod commonly infests the tail and also the fins of a few other fishes. Externally-located species gain the attention of divers in clear tropical waters. An infested sergeant major in Panama or a squirrelfish in the Virgin Islands stand out obviously. Actually, a striped species (Nirocila acuminata), common on sea catfish and remoras, is just as conspicuous (Figure 168) in the northern Gulf. Ap parently these may stay attached for long periods because a small fish has a small isopod and a large fish has a large one. A species (Anilocra acuta) on the spotted gar either debilitates that host considerably or selectively infests an already weakened fish. Sick fish with extensive lesions associated Figures 165-167. Three views of a young with the isopod, especially on or near sheepshead with an isopod (LIroneca ovalls) the bases of their fins, can be picked out of in each gill chamber. Top, side view. Middle, the water with bare hands or a dip net. top view showing bulge. Bottom, ventral The life cyclefor most of these isopods has (underside) view showing protrusion. Normally, the opercula do not protrude from not been investigated. Whereas a few species body. may not utilize an intermediate host, most do, and different species of fishes apparently the roof of the mouth. Actually, that is the act as those hosts for several species. In the female; smaller males and juveniles feed on Bahamas, nearly 100 tiny immature isopods the gills, but can occur in the mouth. All can be seen crawling about on the skin of a these come crawlingouton the deck or sort moderate-sized . Intermediate hosts ing tray of a fishing boat as the fish die. for most species harbor fewer larvae. Pre Some evidence suggests that many infested sumably these larvae do not mature until or otherwise injured menhaden cannot attaching to the next proper host. In the function with their normal school and Gulf, the immature form called Aegathoa therefore recuperate by swimming with oculata probably represents several different slower youngerschoolsor remain nearshore isopod species. Usually just one or two of during summer and fall. these large individuals infest a single host. The isopods situated in the oral cavities Copepods evoke curiosity because of their of pigfish and southern kingfish take more range of modifications. Indeed, two evolu effort to find than simply opening the tionary lines of nonrelated copepods have mouth as in menhaden and some other counterparts that superficially resemble fishes. each other. These lines range from looking Fishes 83

{•\.4f.t m \\ : Figure 170. Modified antenna of female ** Ergasllus sp. used for clinging to the gills of its host. A variety of species infests Figure 169. Adult caligid copepod from gills estuarine Gulf species. of sheepshead. The view shows the under side (ventral aspect) with the egg sacs trailing posteriorly. clinging by their pair of antennae to the gills of many Gulf fishes as well as fresh nearly like free-living copepods to looking water species. Mullet and killifish both act like blobs. as prime hosts for observing specimens. A large number of copepod species infests Since the mullet is larger, hundreds of the fishes in the northern Gulf, but only a few white specks binding to the bright red gills will be mentioned. Easy to see on the skin of presents a conspicuous spectacle. They ran the southern flounder, sea catfish, and a damage their hosts by digesting and rasping variety of other fishes including the Atlantic mucus and tissue from the gills. Pond- croaker, a transparent copepod (Caligus reared hosts appear more vulnerable to praetextus) presents a common example of a mortalities; striped mullet in their normal non-permanently attached copepod. The habitat often have most of their gills copepod scampers about actively in large covered without showing any obvious numbers when the host is pulled out of the ill effects. Possibly fewer secondary infec water. Sharks have other copepods (pan- tions occur in wild fish than in pond- darids) which can be spotted becauseof their reared individuals. Ergasilid copepods brownish cast against the greyish-colored probably attach to other species of copepods hosts. These copepods also have little as intermediate hosts. corrugated padlike objects on their limbs. A common species (Lernaeenicus The mature females of the caligids, panda- radiatus)that looks nothing like those men rids, and most other copepods can be tioned above infests a wide variety of local quickly separated from the males because fishes. Its anterior end extends into the the females have long posterior egg sacs host's flesh so that its head, which forms (Figure 169). antler-like appendages, can cling around a Members of another family of copepods vertebra or some other structure adjacent to (ergasilids) look like free-living species a rich blood supply. Blood appears to be a except the antenna of the female is modified primary food source. The head structure into a powerful prehensile grasping organ varies according to where and how it (Figure 170). The antennule remains as a attaches. Without carefully removing this sensory structure. These small female para internal portion, a confirmed identification sites, without their mates, can be seen is impossible. An observer still clearly sees 84 Marine Maladies? the long neck, body proper, and egg strings T^mm^mimismssk which change in color from transparent to reddish-brown as the larvae (nauplei) develop. Red blood from the host can also tfJ:-'-?$UX<* be observed flowing back and forth within the external body. During specific years, the Gulf menhaden has heavy infestations of Lemaeenicus radiatus, whereas in other years, oneor more species of anchovy show up heavily infested. During most years, a few croaker, seatrout, killifish, gobies and others may turn up with an embedded worm or two. In the case of Lemaeenicus radiatus, the rock seabass, primarily in high salinity water, harbors the ••; ••:•••' i,:.fi!;;$p larval stage (chalimus) attached and free on its gills; thus the abundance of the seabass governs the ultimate number of adult in festations in other fishes. Obviously, the adult parasites can kill their hosts if vital organs are disturbed or if too many Figures 172 and 173. Larval copepod (chalimus stage) on tip of Florida pompano's individuals infect a host. fin. Top, entire view. Bottom, close-up of In addition to beingable to harm the host, frontal filament that attaches copepod to Lemaeenicus radiatus is itself vulnerable host. to undesirable symbionts. Figure 171 shows filament of the copepod attached to the fin a hydroid attached to and presumably of its host. Fertilization often takes place at killing one of two individuals. this stage when a male breaks the filament A few related copepods occuron mackerel and finds a female. The female will then and other fishes. Examples from other geo break away and it or both male and female graphic regions are also well known. One infest the gills or flesh of the proper from a whale grows about 60 cm (2 feet) definitive host. When a chalimus infests a long, and Eskimos feed on another from the larval or juvenile fish, as it occasionally gills of the that has a body- does, it probably makes the host more proper about 5 cm (2 inches) across. vulnerable to predation. The Florida pompano acts as an inter Many other weird-looking copepods can mediate host for an unidentified chalimus be seen on local fishes. Look at the gills of a (Figures 172 and 173). Note the frontal redfish or black drum for the experience of trying to decipher what kind of organism is present. (It may be Lemanthropus longi- pes.) Parasitic copepods constitute an im portant dietary source for some "parasite pickers." A variety of fishes and shrimps have evolved behaviors allowing them to feed on monogeneans, crustaceans, dead tissue, and other items that could poten tially aggravate the host if not removed. Some of these pickers feed exclusively on parasites, whereas others do not. Most Figure 171. Two specimens of a copepod popularized pickers display bright colors (Lemaeenicus radiatus) embedded in the bay anchovy. The anterior individual, and inhabit tropical reefs; however, juvenile however, has been totally encrusted with a sea catfish and some cyprinodontid fishes hydroid. appear to pickmaterial off local fishes. Also, Miscellaneous Hosts 85 the colored dots are an argulid (Argulus fuscus), occasionally numbering up to a dozen per fish and involvingabout 10to 30% of the pompano and Gulf kingfish among the breakers along the Mississippi barrier islands and northwestern Florida beaches. Some species show more host specificity than others. An exceptionally large species (Argulus funduli) infests the relatively small killifish, a smaller one (Argulus lepidostei) occurs in large numbers on the spotted gar, another small one (Argulus flavescens) commonly infests the southern flounder and several other fishes, and several other species also infest local fishes.

MISCELLANEOUS HOSTS The American Alligator The establishment of an alligator season in Louisiana made several large parasites more accessible to hunters and other Figure 174. Argulids such as the one shown interested people. If interested, one could here have acquired the common name "fish probably see four ascaridoid nematode lice." They are not copepods. Note the two compound eyes and cuplike suckers species in the stomach, a variety of modified from mouthparts. Eggs are laid in digeneans from several families in the strings rather than carried like copepods, intestine, a pentastome (Sebekia and argulids can damage their hosts. oxycephala) in the lungs and liver, and a some diskfishes cat parasitic copepods ofl large leech (Placobdella multilineata) on their primarily pelagic hosts. the skin and in the mouth. The leech acts as Another external crustacean that appears an especially good indicator that the superficially like a caligid copepod, but infested gator was from or had recently belongs to the group, often goes resided in freshwater. Actually, most of the by the name argulid or "fish " (Figure gator's parasites are acquired in freshwater, 174). In the typical argulid figured, note the but somecome from brackish water(e.g., the compound eyes and the modified mouth- acanthostome digeneans). All the major parts forming two disks. This attractive groupings have been discussed previously little disk loses most of its intrigue when it except the pentastome, or tongue-worm, reproduces in an aquarium. Females lay which belongs in a separate phylum. eggs on a hard substratum and development Pentastomes have arthropod-1ike nymph of young ensues without intermediate hosts. larvae. Adults possess four powerful Quickly, the piercing stylet, or "sting," anterior hooks (Figures 175 and 176) used and proboscis of these active young for embedding their mouth region into host symbionts can overpower aquarium fishes, tissues. They feed on tissue-fluids and blood occasionally producing an ulcerated de cells. The nymph of the alligator species pression where the argulid can reside. (Sebekia oxycephala) infects a variety of When snorkeling among a school of fishes. Even though not parasitic to man, its Florida pompano, a diver might think his relative from rattlesnake lungs has a nymph eyes are playing tricks on him. Are small that can infect mice, and that nymph could brownish specks moving about on the sides potentially infect man. of some of the fish? They are real! Actually, Pentastomes typically infect the lungs of 86 Marine Maladies?

Figure 177. A mating pair of feather from a royal tern. Some species cause their hosts to deplume themselves.

Figures 175 and 176. A pentastome (Sebekia oxycephala) from the lungs and liver of the American alligator. Forming a group of their own, pentastomes produce young nymphs that infect an intermediate host. The one from the alligator develops in a fish. Most pentastomes mature in the lungs of reptiles. Top, anterior side view. Bottom, anterior frontal view of a chemically cleared Figure 178. Feather louse on breast feather specimen. of clapper rail. Lice are generally quite specific to their bird hosts and those from reptiles. An exception (Reighardia sternae) marine birds do not cause human disease. infects the air sacs and body cavity of local gulls and terns. This bloodfeeder may including the conjunctival sac of the eye, bypass an intermediate host and infect the bursa of Fabricii, and kidney. bird directly. Shore, marsh, and marine birds host a variety of parasites that do not infect fish; most of these are arthropods: nasal mites, Birds feather mites (Figure 177), hypopial mites As the reader may suspect, birds harbor from subcutaneous tissues, lice (Figure 178), many members of the same groups of and others. and ticks seldom infest parasites as do the other mentioned hosts. I aquatic birds. noted above that the air sacs are a site for Just the thought of lice and other pentastomes. Several nematodes and arthropods crawling over a person handling digeneans also infect these sacs, but other an injured or dead bird may cause itchiness. species additionally infect a number of sites Actually, even the bird-handler who fre not present or seldom infected in fishes, quently contacts birds seldom receives a rash Miscellaneous Hosts 87 from handlingaquatic or marsh birds. A few able specificity toward a single species or arthropods on non-aquatic birds do cause group of birds, one can speculate with some rashes. The tropical fowl (Ornithonys- assurance that both birds and their lice have sus bursa) from the English sparrow often evolved together. Since little about occasionally bites man, causing a rash bird evolution can be deduced positively (dermatitis). That mite, however, cannot from modern evidence, that evidence live longer than 10days without the sparrow provided by parasites becomes especially- or a few otherdomestic fowl which can host important. Evolution of lice should parallel it. Chiggers, or "red bugs," also cause irrita and reflect that of birds. As an example, tion, but seldom infest aquatic hosts. flamingos have been placed with storks and Searching for avian arthropods can be herons. Some species of feather lice on fun. Try looking for eggs of feather lice flamingos, however, have relatives that attached to the feathers. The female of these occur elsewhere only on swans, geese, and biting lice usually lays her eggs in rows on ducks. Lice on storks and herons show no flight feathers safe from regions reachable relationship to any of the lice on the other by the bird's bill. After 3 or 4days of develop indicated birds. Apparently the ancestors of ment, the nymph molts and undergoes the duck-lice were present before a common growth for about a month at which time the ancestor gave rise to flamingos and modern adult emerges. Some species feed directly on ducks. Thus, maybe flamingos should be feathers whereas others puncture the quill placed more closely with ducks than with to take blood and central pulp. herons! Lice reveal much about a host. If many- Some biting lice also seriously harm their individuals infest a bird, it is probably so hosts. Juveniles of the while pelican and weak that it cannot keep them in check by double-crested cormorants in their rookeries preening. The lice then can irritate and may be killed by a species (Piagetiella weaken the bird further. The number of peralis) that heavily infests the oral cavity. individuals on a healthy host seldom varies Attached to the tissue of the pouch and roof throughout the year like it does for many- of the cavity, over 500 of these 3 to 6 mm worms. Often several species of lice infest a long, transversely-striped lice can cover single bird. The colorof these usually varies most of the mouth's available space. directly with the color of host; dark colored Additional immature forms occurelsewhere lice infest dark colored hosts and so forth. on the body surface. Young white ibis in The reason for so many species of lice has rookeries also host a troublesome biting been thought to reflect evolution of the louse. Secondary bacterial infections group spreading to a variety of unutilized (Staphylococcus sp.) often accompany the ecological niches* during the period when louse infestation, and an infected young birds first evolved. Apparently, ancestral bird looks as if it has . The host- lice lived in trees and later started eating parasite balance between young of nesting tissue-debris on reptiles. As feathers evolved aquatic birds and theirarthropod symbionts from the scales of reptiles, more habitats needs further investigation. became available for rapid of A final comment on bird parasites these lice. Some later spread to mammals. concerns white patches commonly found in Lice also seem to indicate evolutionary- the breast of surface-feeding ducks, but also patterns of their hosts. Birds evolved in birds from at least 21 other families. rapidly, so rapidly that few traces of the These cysts infect heart, leg, and neck primitive arrangements of and muscles, and they are all the same species muscles remain, and few fossils exist for ( rileyi). A definitive host for this birds during this period when the funda coccidian protozoan has not been mental changes occurred. Thefragile nature determined, but it is possiblya raptorial bird of the bones of birds is not conducive to or carnivorous mammal. A related species fossilization. Since so many lice species in the muscles of a cow utilizes the intestine infest birds and since they show consider- of man or as a final host. 88 Marine Maladies?

Marine Mammals also invade the brain. Marine and estuarine mammals harbor a A lungworm (Halocercus lagenorhynchi) multitude of parasites, and the discussion inhabits the air passages of the lungs. This for most, just like for most birds, is beyond nematode may cause severe bronchitis. the scope of this guide. Because of the Possibly because an infected porpoise has pleasant and almost humanoid natureof the a poorly developed cough reflex, it cannot Atlantic bottlenose dolphin and the fact that discharge resulting fluid. A healthy this porpoise commonly makes its presence porpoise seems able to control the parasite, known in the Gulf, a few comments on some but a very young or stressed host apparently of its parasites seem warranted. The federal often allows numerous individuals to government protects marine mammals, mature and thereby contribute to its death even when dead, reducing the chance of or a serious disease. A heavy infection of a seeing their internal parasites. The pene related worm in the auditory capsule can trating odors transmitted with oils in the cause deafness. blubber make cutting into a beached Conspicuous to someone admiring the mammal dead only a few hours a rather antics of the bottlenose dolphin alongside unpleasant experience, anyway. If some his vessel are the skin disorders of some inspired person in the northern Gulf does individuals. Cuts and sores from fishing get the opportunity to see a fresh stomach nets, shark attacks, or even self- or peer- lining of a porpoise, he would probably induced trauma may progress into see two species of digeneans and possibly a debilitating infections. When a dominant mass of nematodes. Large numbers of a porpoise bites its subordinate companion, rather strange looking fluke (Braunina the rake marks of its teeth orient parallel cordiformis) about the size of a marble (Figure 179). Many animals also show a attach firmly to the stomach and can live for variety of healing wounds, often with up to 3 years. The other digenean (Pholeter secondary infections (Figure 180). Other gastrophilus) is smaller, but cannot be seen types of lesions occur on the skin. Some because a nodular cyst larger than the previous fluke forms around the worm and hides it. The nematodes belong to one or more species of Anisakis, the larvaeof which when present in raw seafood have been implicated in severe human gastric disease. Its life cycle was diagrammed earlier(Figure 157). A few other worms commonly infect the porpoise. One elongated fluke (Nasitrema delphini) inhabits the lateral air sinuses of the head near the internal ear. Less commonly, a campulid fluke species infects the pancreatic ducts. The reason for mentioning this infection is that worms in this family have been implicated in some strandings of marine mammals. Several dolphins that had stranded singly along California beaches had livers badly damaged by a campulidand hadextensively damaged brains apparently resulting from easily diagnosed campulid eggs. Eggs and occasionally adults pass through the Figures 179 and 180. Lesions on the Atlantic pancreatic duct and ultimately invade bottlenose dolphin. Top, flipper with deep various tissues including the brain, causing wounds made by another dolphin. Bottom, them to degenerate. A few nematodes can secondary infection of wound in dorsal fin. Miscellaneous Symbionts 89 result from bacterial or fungal infections large numbers of eggs, and are free- and the cause of some remains unknown. swimming or otherwise readily available People who work with porpoises refer to to infect the hosts, some act as good agents some common dark colored patchy lesions for biological control of pests. as "tattoos." These do not appear to harm In order to appreciate better these the host, but their cause should be investi potential biological control agents, I gated. present a brief life history of one Because marine mammals reach gigantic (Perutilimeris culicis) from the saltmarsh sizes, a reader might expect a giganticworm . Free-living females lay thou to infect large whales. One exists! Blue and sands of eggs in the substratum, and the fin whales have a nematode (Crassicauda small preparasitic larva hatches and sp.), the males of whichoccur in the penisor penetrates an early instar* mosquito larva. clitoris. The much larger female worm It does not grow, but remains dormantuntil extends from this region down the ureter, the mosquito pupates. At that time, the through the kidneys, into blood vessels, and larva migrates to the abdomen and enlarges occasionally to the liver. This is a long rapidly soon after the mosquitomaturesand worm. obtains a blood meal. The host becomes sterile and then dies when the internal postparasitic stage with its lance-like tooth MISCELLANEOUS perforates an escape hole. Once in the water, the nematode molts, mates, and lays eggs. SYMBIONTS Some other species produce eggs that must Nematode larvae and larval nematode- be eaten and larvae that enlarge in the larval like organisms infect and other host. hosts in addition to fish and the mentioned Not to be confused with mermithids, but shellfish. Because people can see these also infecting insects and other arthropod worms, they deserve some comment. Fairly common large nematode larvae in insects may be mermithids. If so, farmers refer to them as "cabbage ." The infected midge in Figure 181 from an estuarine bayou exemplifies a local infection. Spiders, leeches, crustaceans, and other invertebrates harbor specific mermithid larvae, some of which reach 50 cm in length. Because they have lifecycles adapted to their specific hosts, produce

Figures 182 and 183. A horsehair worm (Gordlus robustus). Top, several males Figure 181. Mermithid roundworm aban that had been found wiggling together In a doning a midge larva. Mermithid nematodes shallow pond. Juveniles parasitize grass have a parasitic larva which In some cases hoppers and a varietyofotherhosts. Bottom, acts as a biological control agent to keep posterior tip of a male worm. The female of populations of annoying insects under this species has a rounded rather than a check. lobed tail. 90 Marine Maladies?

hosts are immature "horse-hair" worms (Figures 182 and 183). These nemato- morphs, or gordiacean worms as they are also called, appear superficially like long dark-brownish nematodes. The digestive tract is vestigial in nearly all species, and adults do not feed at all. Juveniles secrete digestive enzymes through their tegument and absorb host-nutrients directly back through their body with little damage to the host. Development occurs gradually from larva to juvenile without metamor phosis. When someone sees a larva in a , or an adult in a water trough or in their yard, some unnecessary anxiety usually develops. A few marine parasitic nematomorphs exist; one ( agile)even infects the hemocoel of a grass shrimp along the northeastern United States coast in which it Figure 184. A commensal triclad flatworm reaches at least 10 cm in length. The (Bdelloura Candida) from base of leg of the of females with ova shrink and become horseshoe crab. Note the eyespots opaque, but the host is not killed. Horse anteriorly, the large protruded feeding hair worms that I have seen in the northern pharynx near the middle, and the adhesive holdfast organ posteriorly. Separated from Gulf belong to a freshwater species ( the host, these worms can be kept alive for robustus), even though some individuals extended periods with liver or other sources occur in brackish areas. Thespecimens have of nutrients. all been encountered during early winter and summer, but they can probably be found during most warm months. A juvenile worm emerges from its host while in water, becomes sexually-mature, and mates; the slightly mobile females occur in grassy regions or in water near shore, whereas about an equal number of males swim actively in the deeper adjacent regions or wiggle in the grass. The male appears to search out the female. After the ova are fertilized, the female lays stringsormassesof eggs. When a larva hatches from the egg, it penetrates any of a variety of hosts and undergoes its entire development as a parasitic stage. If not in a properhost, it may encyst. If a person or fish eats an infected host, the larva maydevelop, usually without damage to the new host. Figure 185. A large tuberculated leech A few symbionts have been mentioned (Stlbarobdella macrothola) on the anal fin of because they can be maintained alive with a large bull shark. Commonly encountered little effort when separated from their hosts. on sharks, it also occurs on other animals and substrata in high saline waters. The The ease with which one can collect photographed specimen hadbeen preserved polyclad flatworms from oysters, barnacles, and lost its greenish-grey coloration. Note and other hosts for study or observation the encircled area where the large posterior exemplifies this. A related triclad flatworm sucker had attached to the fin. Miscellaneous Symbionts 91 (Bdelloura Candida, Figure 184) is also an shrimps and as a vector of blood parasites. inviting organism to study. This large Even though several other leeches occur in worm can be found on most large specimens the northern Gulf, one (Figure 185) deserves of the horseshoe crab (not actually a true attention because of its large size and its crab) by looking where the legsattach and at elasmobranch hosts. The tuberculated leech the book gills (named because the leaf-like (Stibarobdella macrothela) can reach a lamellae on the breathing appendages length of about 15 cm, but most measure suggest a book). about 3 cm long. It typically infests the Leeches have already been mentioned as mouth, fins, claspers, and skin of any of symbionts infesting the blue crab and several sharks, as well as of the guitarfish, crabs, shells, andoccasionally bony fishes. It occurs worldwide in high saline habitats. Barnacles have already been discussed as symbionts showing various degrees of association with crabs. Barnaclesalsoattach and have commensal relationships to other living organisms, but often they attach because the organism acts as a solid sub stratum rather than a symbiotic partner. Three species that attached to a plastic band arounda sharkdemonstrate this. Twodusky Figure 186. Medium-sized sharks off Pensacola, Florida, became encircled by a commercial plastic packing encircled within commercial plastic band. Barnacles attach to the band. packing bands (Figure 186). A close-up

Figures 187-190. Barnacles attached toplastic packing bands encircling thedusky shark. Top left, notethe damage causedthe shark atitsgill slits, structures through which water passessothatthe shark can obtain oxygen. Top right, acommon gooseneck barnacle (Lepas anatlfera) covered bya filamentous green alga. Bottom left, therabbit ear whale barnacle (Conchoderma aurltum) which often attaches to sessile barnacles on whales. Bottom right, rare in the Gulf, another related barnacle (Conchoderma vlrgatum) often attaches directly to fish and their parasitic copepods 92 Marine Maladies? photograph (Figure 187) reveals the damage caused to the body near the gill slits by the band. Similar harm caused to other fishes will be discussed later, and I will focus my attention here on the barnacles. A common goose-neck barnacle (Lepas analifera) frequently attaches to drifting wood and other objects. One individual on the plastic band (Figure 188) had become covered by attached filamentous . Another stalked species (Conchoderma auritum, Figure 191. Underside of a biting gnat Figure 189) has the common name "rabbit ( hollensls).Th\8 large gnat is one of the twocommon gnatsin thesoutheastern ear whale barnacle" because it has been U.S. that breed in salt marshes and bite peo collected off whales. Actually, many ple. It is most prevalent in March-April and specimens collected during modern times October-November and occurs throughout come from hulls of ships that transit the day. The otherspeciesIs discussed in the tropical and subtropical Atlantic and text. Mediterranean waters, but their common to propagate. presence on whales seems more than The two indicated species commonly bite accidental. Another species (Conchoderma people along the Gulf Coast and Atlantic virgatum, Figure 190), even though often seaboard. Like mosquitoes, only the female attaching to ships and flotsam, does attach gnat sucks blood. Effects of the irritating directly to small living organisms. Not bite may persist for days in some people, common in the Gulf, it has been reported whereas all symptoms disappear within there from the dorsal fin of a halfbeak and a few hours for others. Along the northern on a parasitic copepod (Lemaeolophus Gulf, adults of the larger (Culicoides sultanus) embedded in the flesh of a cobia. hollensis, Figure 191) appear from mid- Considering such rare sightings of this March through April and also during barnacle, a rather unique combination of October and November. They feed heavily conditions seem to be required for its throughout the day on people, domestic development. Perhaps one of these mammals, and probably other animals. On conditions is a wound. the other hand, a smaller species (Culicoides Whether one considers as parasites insects furens) occurs predominantly from May that must feed on blood to produce eggs is through September, biting near sunrise and a matter of individual interpretation and again from about an hour and a half before interest. Because biting gnats, even more sunset until after the sun sets. Both species than mosquitoes, have such a dramatic breed among the salt marsh vegetation. influence on people's daily outdoor Larvae of some other species develop in activities, I include a few comments on freshwater habitats and those of one them. (Culicoides melleus) develop in brackish From a human point of view, gnats (at intertidal sandy regions. Fortunately, the least Culicoides furens and Culicoides coastal Gulf pests transmit no known hollensis), also called "no-see-ums," human diseases. "punkies," and "sand ," can vector true parasites and often make collecting parasites or just being outside miserable. FISH-KILLS AND One species (Culicoides furens) acts as the intermediate host for Ozzard's MISCELLANEOUS ( ozzardi) in and DISEASES the West Indies. Because people in North America have not been found to harbor the Fish-kills are not restricted to finfishes; thin worm in their mesentery, the gnat in they also involve shellfishes. In general, the northern Gulf apparently has nothing shellfish mortalities present more difficulty Miscellaneous Kills and Diseases 93 in assessing because the hosts are smaller occur along Bcllefontaine Beach and and moreeasily overlooked, are more readily Gulfport, Mississippi. Perhaps the cause of preyed upon, and seldom swim to the these differs from that for the jubilee in surface. Several examples of diseases that Mobile Bay because the conditions related have not been overlooked have already been above do not necessarily coincide with those discussed in the earlier invertebrate sections. encountered in Mississippi. Many fish die, Fish-kills occur for a variety of reasons. but neither involved fishes nor the complete Most cases have not been thoroughly- state of the water from jubilees has been in investigated, but residents usually know vestigated. Plankton* blooms have been when to take advantage of them. People fill observed during some of the mortalities. washtubs with fresh fish following a rapid If algal toxins cause the mortalities, perhaps temperature drop or during certain other investigators should ascertain if affected conditions. hosts can be safely eaten. When water temperature gradually drops Devastating "red " result from during the winter, fish usually have time to blooms of a few species of toxic planktonic acclimate or move into deep or offshore dinoflagellates (primarily water. When the drop is rapid and when fish brei'e). They occur periodically along the are additionally stressed such as by the west coast of Florida and less often along the presence of low salinity water, some fish western Gulf and perhaps elsewhere. When come to the surface and die. Those that sink a red occurs, large numbers of fish and to the bottom slowly bloat with gas and rise invertebrates die. an irritating aerosol to the surface after about 2 to 3 weeks when occurs throughout the nearby coastal areas, the water has warmed and algae has begun and less often, contact-rashes occur in to cover them. When these fish surface, humans. The noxious tides alarm tourists people often worry unnecessarily about and residents alike. another fish-kill not associated with low The alga secretes a neurotoxin that kills temperatures. Dying fish or those in a coma any fish if exposed to a sufficient amount. make a safe product to eat if cooked and not Fish also die from oxygen depletion result otherwise contaminated. ing from decomposing fish and algae. Other naturally-occurring water condi However, other mechanisms of death seem tions may also provide another source of to occur. Two of these are long term neuro- food for the table. Residents in the northern imoxication and long term blood disease. Gulf call the major condition a "jubilee." Different fishes respond differently, and, The eastern shore of Mobile Bay has gained consequently, only specific fishes die from a a reputation for its summer jubilees. Once, group of several species. As examples, low when the coastal region was less populated, levels of toxin affect the ladyfish's neuro observers would notify their neighbors logical system and the mullet's blood. The about these events; they usually occur just mullet's blood clots slowly and the cells before sunrise. Now it is almost everybody break apart. Resulting deaths usually occur for himself, and biologists seldom hear a few weeks following a subsided red tide. about jubilees until all the fish arc collected. Typically one or more fish of either species Rarely do animals die unless confined like from a large school under continuous ex crabs in traps or sessile like oysters; most posure to the toxin exhibits a frenzied become stunned for several hours and make behavior and dies while others of the same a dip net an easy means to gather them. kind remain normal until they too are Apparently a combination of specific winds terminally affected. Some birds, primarily and tides allows water with a low concentra the lesser scaup, also die following red tides. tion of oxygen to stratify and to move along Perhaps this is because they feed on the bottom of specific areas. Crabs and molluscs which concentrate the algae, and bottom fishes like flounders and eels move thus the toxin. Man can also show symp shoreward and evade this encroaching water toms of mild neuromuscular intoxication mass which soon overtakes them. following ingestion of contaminated shell Summer kills also referred to as jubilees fish. 94 Marine Maladies i Probably the most common cause of fish- kills in the northern Gulf is oxygen depletion. This can occur naturally after several days of overcast skies. Decreased sunlight reduces photosynthesis* and thereby oxygen production, and this, in conjunction whith the loss of oxygen from decomposing organic material, results in an oxygen concentration too low to support most fish life. Domestic wastes and organic wastes from industrial plants intensifyalgal blooms and the amount of matter to be de composed. Consequently, the number of Figure 192. Reversal of a fringed flounder. mass mortalities caused by oxygen The fish on the right is normal, whereas the depletion, especially in harbors and en one on the lefthas itseyeson the right side of the body. closed areas, increases with increased population growth. and the lack of pigment is patchy. Replica Other kills result from fishing practices, tion of the eyed-side color pattern on the toxic materials, and combinations of blind-side of is termed "ambi natural and man-controlled factors. Many coloration." The hogchoker (Trinectes fish, occasionally entire catches, may be maculatus) in the northern Gulf often has spilled from seines or "culled" from shrimp extensive shading or pigmentation on the catches. Pesticides, herbicides, and chemi blind-side, but ambicoloration is infrequent cals may be accidentally or carelessly in these and other Gulf of Mexico flatfishes. introduced into a system and kill organisms. Reversal indicates the occurrence of eyes Several other anomalous conditions and pigmentation on the usual blind side. A might be considered diseases. Unless fish are normal (right) and reversed (left) fringed confined in a rearing facility or in a stressed flounder (Etropus crossotus) illustrate this habitat, most of these conditions are seldom condition (Figure 192). observed. Predators eat most affected fish be By visiting a fish hatchery' where large fore their genetic, nutritional, and injury- quantities of fry are produced, one may be caused diseases become conspicuous to able to observe a variety of genetically de fishermen; however, a few affected fish can formed young fish. In the natural environ be seen, and I will briefly mention a sample. ment, many of theseabnormal fish would be Anomalies seen by most shrimpers eaten. Still, increased heated effluents include albinism, ambicoloration, and re and pollutants in the environment probably versal of flatfishes. Even though most are produce an increasing number of congenital defects, some anomalies can be abnormalities. In order to investigate that caused by trauma during early develop likelihood, eggs and embryos have been mental stages of the fish. When examined for chromosomal anomalies. develop normally, one eye migrates to the Those of the Atlantic mackerel from pol opposite side resulting in both eyes being luted New York Bight show a high number on the top or ocular side. This side possesses of all sorts of chromosomal damage with a pigmentation which can be controlled to tendency for more damage to occur in the vary in coloraccording to the background so more degraded regions. that both predators and prey looking down The striped mullet illustrated in Figure have difficulty detecting them. The blind 193 might have been a genetic anomaly, a underside of the fish lacks pigment and pro nutritionally-deprived fish, a parasitized vides a difficult target against the water's individual, or an individual confronted reflecting surface for a predator from below. with excessive stress during early develop When fish lack pigments in their normal ment. A variety of pollutants such as regions, that is "albinism." Usually some sulfuric acid, herbicides, and pesticides pigments occur on the head or elsewhere can produce such stress. Miscellaneous Kills and Diseases 95

Figure 193. Anomalous striped mullet with sideways curvature of the spine (scoliosis). This condition, usually resulting from a nutritional deficiency, can result from a variety of causes.

Figure 196. Fibrous tumors in a striped mullet. This type of growth appears to be increasing in prevalence in polluted estuarine habitats during the past few years.

be reversed, and the liver will resume its normal character after proper food is eaten. Fatty livers, however, can also result from pollutants. Some contaminants also induce cancer in fishes and other aquatic animals. So far, in the northern Gulf, few tumors have been re ported from fishes. Probably the most prevalent one in estuarine fishes involves fibrous outgrowths in the striped mullet (Figure 196). Usually less than \% of a catch Figures 194 and 195. A stained section of of fish reveals these externally protruding fatty liver tissue from the striped mullet. The special stain (Sudan black B) stains the lipid tumors. They, however, have been seen only darkly, distinguishing the condition from in polluted regions of Galveston and that of excessive glycogen. Top, double Corpus Christi, Texas; Pensacola, Crystal layers of liver cells radiating normally from River, and Miami, Florida; and Ocean central vein. Bottom, close-up of large Springs, Mississippi. Long-time mullet stained fat globules in cells. The condition can be reversed in most instances;excess fat fishermen say they have seen the tumorous occurs in the liver during starvation, certain fish only in recent years, further suggest vitamin deficiencies, spawning, and a few ing a relationship to increasing pollution. other conditions. Young fish in aquaria fed Composition of the growths apparently exclusively on a diet of a single animal often differs among geographical regions. Those develop a fatty liver and die. in Mississippi fit most, but not all, of the Fatty livers, livers with cells occupied criteria of malignant cancers. with lipid material (Figures 194 and 195), Most tumors on fishes are benign; that is, commonly occur in naturally starved fish they do not grow fast, invade tissues, nor during cold spells, in fish during their metastasize. The most common of these, a spawning periods, and in fish maintained papilloma somewhat similar to a wart, on inadequate diets. Usually the processcan occurs occasionally on a few fish, the black 96 Marine Maladies? (Figures 186 and 187). A reader should also realize that plastic bags, even though they may mess up a boat, do a lot of damage to the intestinal tract of a sea turtle or other animal that normally- feeds on jellyfish and other such items resembling the bags. If someone is bent on throwing garbage in the water, a can might be the easiest to rationalize. Most cans pro vide shelter for small gobies and blennies which in turn harbor some harmless para sites which most certainly should be perpetuated. Figure 197. Large black drum with benign tumorous growth on chin. This papilloma, similar to a wart, rarely occurs on fish from the northern Gulf. This fish from a public aquarium developed the growth while in a large display tank. TECHNICAL ASPECTS

SYMBIOSIS Textbooks on parasitology are beginning to treat many host-parasite associations more generally as symbiotic ones. The variability in the amount of dependency of a particular symbiont on its host under different conditions makes a more general ized symbiotic approach the most practical one. Texts treating a variety of types of symbiotic relationships include those by- Figure 198. A rubber band girdling an Henry (1966;l967), Read (1970), Noble and Atlantic croaker. Tissue has grown around Noble (1971), Cheng (1973), and Schmidt the hole In the dorsum and separated some of the fish's tissue ventrally. and Roberts (1977). Few texts of any sort emphasize marine relationships. Those that drum being an example (Figure 197). The do usually stress diseases (e.g., Sindermann, drum acquired the growth of a long-time 1970). resident displayed in a public aquarium. Dales (1957) presented a review of some Anomalies also result from injuries. commensal relationships, listing numerous Examples of wounds have already been hydroids and anemones with their partners. presented. Chitinoclastic (chitin-attacking) Several additional uncited associationsexist bacteria essentially tattoo woundson crusta in the Gulf. ceans. Fishes on occasion lose their tails or The example of Clytia sp. on Donax other helpful but nonessential structures. roemeri protracta and other species of Many of these fish survive, if sheltered from Donax noted above points out problems predators. One local example of wounding in assigning a specific form of symbiosis, concerns an Atlantic croaker which in this case phoresis, to any particular caught itself in a rubber band. After a period symbiotic couple. A strict definition of of time the fish apparently grew around the phoresis demands that neither party be band, leaving the band to perforate and physiologically dependent on the other. disfigure its body (Figure I98). Unfor The hydroid may depend on the clam. It tunately, plastic beer can holders, rubber rarely infests any other substratum. Richard condoms, and other items slow to degrade Heard has found it on old large specimens of may cripple many fishes. A packing strap the mole crab Emertia talpoida in around a shark has already been illustrated Georgetown, South Carolina, but why does Technical Aspects 97 it not attach to other hard items along high other reviews on the behavioral aspects of energy sandy beaches? Maybe it does. If so, the relationships. maybe when it does, the item washes ashore The terms "zooxanthellae" and or becomes otherwise unable to support the "zoochlorellae" have no taxonomic signi hydroid or the hydroid's character changes ficance when applied to invertebrate-algal such that biologists consider it a different relationships. The names refer to the green species. Loesch (1957) reported an absence or brown colored algae just as "cyanellae" of digenean parasites in clams with the refers to a blue-green colored mutualist. hydroid or an attached alga. Tiffany (1968), Actually dinoflagellates, , however, did not obtain similar results. He , blue-green algae, , and found coquina over 25 mm long all had other algae have been reported as symbionts. digeneans, whether commensals were pre Henry (1966) presented many examples. sent or not. Actually, Loesch encountered The inability to culture most algal species few infected clams, and the suggested loose and to extract them from living hosts has form of mutualism based on the hydroid's affected the understanding of associations. preventing parasitic infections is doubtful. Smith (1973) presented a brief review of In an unpublished study, Joyce (1961) algal associations, drawing mostly from the suggested that the hydroid Podocoryne examples of corals and their zooxanthellae, carnea (actually Podocoryne selena, see hydra and its chlorclla, molluscs and their Mills, 1976) in Cedar Key, Florida, required chloroplasts, anda small platyhelminthand a living snail shell, whereas Hydractinia its alga, a normal componentof the adjacent echinata "preferred" a shell occupied by a phytoplankton. In the case of the flatworm, hermit crab. Matthews and Wright (1970), other related algal species can be established Defenbaugh and Hopkins (1973), and in it, but if the normal symbiont is then Mercando (1976) provided additional exposed to it, the worm ejects the alien alga observations. AH three works reported a and acquires the usual one. The symbiotic tendency for hydroids to live on shells oc interaction involves more than nutritional cupied by Pagurus longicarpus and processes! Taylor (1974) discussed the Pagurus pollicaris, but not other hermit of all described symbiotic marine crabs. The first authors noted that colonies algae and presented information on their of Hydractinia echinata were usually- biology. A very useful paper, it will help moribund when on shells occupied by the anyone initiating a study on algal crab Clibanarius vittatus. When deprived of symbionts. a shell, 80%of the specimens of Clibanarius In the two species of Zoanthus from vittatus refused a shell covered with that Florida, I found the typical golden-brown hydroid, and those that accepted the shell vegetative stage of a dinoflagellate removed the polyps before entering it. resembling those of the genus Apparently Clibanarius vittatus is more Gymnodinium or Exuviaella (probably sensitive to stinging than species of Gymnodinium microadriaticum) within Pagurus, and those pagurids have an advan the gastrodermis. Embedded in the tage over the more abundant Clibanarius epidermal tissue occurred bacteria, diatoms, vittatuswhen there isa fight over possession and what may be another algal symbiont of a shell. Laboratory experiments could which did not fluoresce light. However, the shed some light on this intriguingproblem! presence of chlorophyll a, as determined Anyone interested in the anemone-crab with a Beckman DK-2 spectrophotometer, relationship will find that several such was confirmed in tissue stripped of diatoms. relationships have been examined. Indeed, Internally, a few species of colorless Ross (1974) gathered together most of the flagellates resided. One large flagellate information known on the behavior, phys extended over 40 p. in length not including iology, , and zoogeography of the the flagellum, and another stored consider partners and used that information to able starch. Even the vegetative stage of the formulate ideas on the evolution of the dinoflagellate occurred in a flagellated associations. He (e.g., 1967) has presented motile carrier cell. 98 Marine Maladies?

A method of observing objects with haps these organisms are vital to the life of a chlorophyll is to use fluorescent micro zoanthid, and perhaps their presence or scopy. I found thedinoflagellate to fluoresce abundance varies according to locality or red, and, under a squash preparation, a few season. individuals showed dividing stages. This knowledge would provide a Fluorescent microscopy also revealed remarkable understanding of a very- elongated homogeneous boat-shaped complex "simple animal." Even with the objects that differed some between the two help of E.J.F. Wood and John F. Kimball, zoanthids. Instead of being red like that of I was unable to culture any of the internal most chlorophyll, the fluorescence was a symbionts using several modifications of chartreuse green similar to that produced methods used by McLaughlin and Zahl by members of , dinoflagellates (1957) and Provasoli, McLaughlin, and that possess armor in their motile stage. Droop (1957). Perhaps someone using more This material appeared to be packaged from modern techniques and approaches can granular material in mesogleal cells and was succeed in this task. transported throughout the organism. Its function is unknown. Considerable work has already been conducted on zoanthid feeding. Trench THE AMERICAN OYSTER (1974) provided an extensive study on the The American oyster, Crassostrea photosynthetic contribution of the virginica, acts as a host or substratum for a intracellular Gymnodinium species and large number of symbionts. The "bible" on how it passes that material on to "Zoanthus all aspects of the oyster (Galtsoff, 1964) sociatus." Ultimately the algal cells presents considerable information on most apparently undergo senesence, but still are of these. Cheng (1967), Sindermann and not digested by the host. Rosenfield (1967), and Sprague (1970b) Food other than the photosynthate from provide more recent compilations on the alga also is utilized. Digestion occurs symbionts from molluscs in general. Other intracellularly after cells engulf small pertinent reports dealing with Crassostrea particles. Sebens (1977) assumed that the virginica include those by Sprague (1971) zoanthid studied by Trench was actually and Sindermann (1977). MacKenzie (1977) Zoanthus solandri. The taxonomy remains discussed some oyster symbionts in to be clarified. In any event, what Sebens conjunction with an appraisal of the oyster considered Zoanthus sociatus feeds on fishery and an aquacultural program to smaller items than Zoanthus solandri. rehabilitate damaged reefs in Mississippi. These include small crustaceans, Citations referring to work on specific , and apparently detritus. organisms occur in all theabovearticles and When not provided this external source of others are cited below. Several infectious food, both mentioned species lost weight. and noninfectious diseases that involve Some other zoanthids tested by Sebens did oysters from the Gulf have not been treated not lose weight, suggesting that they, unlike here. the two species of Zoanthus, derived all their Parasites of another oyster, the smaller energetic needs from their algal symbionts. Gulf oyster (Ostrea equestris), have not been Reimer (1971) also studied different feeding reported as extensively. Thisoysteroccurs in behaviors of zoanthids, but she used Pacific high salinity regions, has rows of small species. "teeth" bordering the inner margins of the Other than Trench (1974) who reported valves, and lacks pigmentation on the aggregates of unidentified bacteria on the adductor muscle scar. cuticle, no other authors to my knowledge Overstreet and Howse (1977) provided a have reported more than the single brief review of the public health aspects of dinoflagellate symbiont in a host. The eating raw oysters and of coming into identification, function, and interaction of contact with polluted waters in Mississippi. other symbionts needs investigation. Per Unquestionably, the most dreaded disease Technical Aspects 99 from eating raw oysters locally is hepatitis, Losses as high as 85%of planted oysters from but others, primarily bacterial and viral, some regions along the northeastern U.S. also can be contracted. A few other types of coast have been attributed to this disease, may also have potential now known to be caused by the haplo public health significance (Harshbarger, sporidan Minchinia nelsoni based on Chang, and Otto, 1977). evidence by Couch, Farley, and Rosenfield Much of theecological information about (1966). Both it and Minchinia costalis cause Dermocystidium marinum came from a disease and have attracted considerable study by Quick and Mackin (1971) in attention concerning their morphology Florida. Other extensive investigations have (Perkins, 1968; 1969), reduced reproductive been made by Ray (1954), Andrews and capacity of infected oysters (Couch and Hewatt (1957), and Mackin (1962). For those Rosenfield, 1968), and mortalities caused by interested in classification of the organism, the two haplosporidans (Andrews, Wood, the species has been transferred from and Hoese, 1962; Farley, 1975; Kern, Dermocystidium and was known as 1976). Even though most oysters in a reef Labyrinthomyxa marina for several years. may be killed, survivors and their progeny- After some uncertainty, Perkins (1976a; appear to develop a resistance. Conse 1976b), using ultrastructural evidence, quently, either transplanting uninfected considered it a coccidian or related oysters into an enzootic region or protozoan, and Levine (1978) has now introducing an infected oysterinto a region established it as a protozoan named free of the haplosporidan disease can have after Perkins. short-term devastating effects! Several other species exist in oysters and Apparently more than two species of other molluscs; Quick (Dow Chemical sporozoan gregarines infect the oyster. Company, Frecport, Texas, personal Spores of Nematopsis ostrearum lodge communication) estimates at least four or primarily in the mantle, and those of five Labyrinthomyxa-like organisms affect Nematopsis prytherchi and perhapsanother the oyster alone. Most of these usually occur undescribed species primarily involve the in low numbers and do not harm the oyster gills. Quick (1971) encountered uniden unless it experiences other stresses. Upon tifiable spores near the digestive tissues of culturing with thioglycollate and other oysters from central but not northern media, these organisms respond in a variety Florida. Decapod hosts for Nematopsis of different ways and morphological types. ostrearum include several mud crabs, Often more than one species will infect the whereas the host for spores in the gills is the same individual oyster. Much more effort stone crab. Mackin (1962: 203-205) should be given to understanding these questioned whether any of these species organisms and their relationships with their causes oyster-mortalities as suggested by invertebrate hosts and their environments. several authors. Nematopsis spores, In fact, Labyrinthomyxa patuxent, first generally larger than those of described in 1921, a potentially-lethal Dermocystidium marinum, can be seen in pathogen, and the focus of considerable histological sections or in fresh tissue research (Mackin and Schlicht, 1976), may partially digested for about a minute in a be related to what many authors consider few drops of 10% sodium or potassium neoplastic (tumor) diseases of molluscs. hydroxide solution. Whether that organism, with its incom Nematopsis ostrearum appears to be plete response to thioglycollate medium, involved in a dynamic equilibrium in occurs in the Gulf has not been firmly- oysters from Virginia (Feng, 1958). That is, established. The method for the improved when oysters heavily or lightly infected get culture medium has been documented and transplanted to other regions with oysters discussed by Quick (1972). having light and heavy infections, A disease not discussed above because it respectively, the transplants alter the apparently does notaffect oysters in theGulf intensity to assume average levels for the is "MSX" (for Sphere X). region. Such ideas should be investigated 100 Marine Maladies? further using oysters in the Gulf. The small pyramidellid gastropod along At least two species of Stylochus plus the edge of an oyster shell can be identified other polyclads occur in oyster beds of usingAbbott's(1974) book. Hopkins (1956c) Mississippi (Hyman, 1940). Stylochus and Allen (1958) both discussed the ellipticus, a cream to brownish worm Odostomia impressa-oyster relationship. reaching about 25 mm long, is much more Oyster growth shows a relationship with prevalent than the grayish 50 mm long bucephalid infections (Menzel and Stylochus frontalis. The latter, much more Hopkins, 1955), although more extensive common in Florida, was studied by Pearse studies are needed. and Wharton (1938), who presented The pathogenic effect by normally ecological and biological data on it as the commensal inhabitants to stressed oysters synonym Stylochus inimicusas well as some has not been well documented in most cases. data on Stylochus ellipticus under the name Stress from high temperatures apparently Eustylochus meridianalis. The latter causes dermo to harm the host. Other withstands water of lower salinity and examples also exist. Ciliates occasionally temperature than Stylochus frontalis and infect a healthy oyster, but may become a is less specific toward oysters. Both species complicating factor in weakened hosts as a lay single layers of egg-masses on oyster secondary invader (Mackin, 1962; Pauley, shells or other hard surfaces. Chew, and Sparks, 1967).The latter workers The oyster crab rarely occurs in most Gulf observed a ciliate to infect heavily the Pacific regions, but because students often wonder oyster after they injected turpentine, but not about problems they could undertake, I a nonirritant, in the adductor muscle or in think it worthwhile to mention here that connective tissue. several species of small pinnotherid and Even though burrowing organisms affect porcellanid crabs associate with a variety of oysters and other molluscs, few studies have invertebrates and provide an easily visible treated them in detail. Alfred Chestnut at animal to study. If a person collects GCRL provided most of the information on pcnshells or scallops, digs up burrows of the oyster burrowing clam, or martcsia mud shrimps (callianassids). or investigates (Diplothyra smithii), used here. His the tubes or burrows of , dissertation will present details of the holothurians, or sipunculids, he will biology of this intriguing clam. The mud probably encounter several species of \ka worm Polydora websteri can be easily- crabs. They can probably be identified using identified using Blake's (1971) key. Another the keys by Williams (1965) or Felder (1973). species, Polydora ligni, also excurs in oyster Many questionsconcerningeach different reefs, but forms fragile tubes of silt rather could be asked. Are young than burrowing in shells. It. however, can produced over long periods? Does the first reproduce rapidly and smother the oysters. stage crab always invade the host? Are young Hartman (1958) presented a taxonomic individuals chemically attracted to hosts? treatment on the several species of bur What is the dependency and pathological rowing sponges, and Wells, Wells, and effect of the crab on the host? What is the Gray (1960) added sizesof perforations in the longevity of both sexes? Will additional shell in addition to other characteristics. females enter an already occupied habitat? Hopkins (1956a; 1956b) reported ecological When several females associate with a host, data on the different species. He considered will some migrate to nonassociated hosts the presenceof Cliona celatato indicate that when they change into a hard stage? Can the salinity remained below 10 ppt about one crabs survive harsher conditions than their fourth of the time and that of Cliona truitti, hosts? Do attached hydroids aid the crabs? A a species favoring high salinity, to indicate place to initiate a literature search for any that the salinity seldom dropped below such investigation could be articles by 15 ppt. For those interested in animal- Christensen and McDermott (1958), Haven burrowing, an entire issue of American (1959), Davenport, Camougis, and Hickok Zoologist (Carriker, Smith, and Wilce, 1969) (1960), and Sastry and Menzel (1962). provided many specific and general articles Technical Aspects 101 treating the subject. Ameson michaelis nor Loxothylacus The section on predation by Galtsoff texanus, both internal parasites, infect (1964) can be amplified by reading the Callinectes similis. I tried to infect a few interesting findings of McDermott (1960) individuals with the microsporidan without who studied predation of oysters by mud success. On the other hand, I have seen a crabs. Kay McGraw has been investigating nonencysted larval cestode plerocercoid predation by the blue crab in her doctoral extensively invading the skeletal muscles of work on growth and survival of hatchery- the lesser blue crab (Figures 26 and 27). but reared oysters. McGraw and Gunier (1972) have never seen it in the regular blue crab. investigated predation by the drill in On the basis of examining muscle tissue Mississippi. Larval development of this from numerous specimens of Callinectes most important predator, Thais sapidus. both Phyllis Johnson and Richard haemastoma, was described by D'Asaro Heard (personal communication) have each (1966). seen but a single specimen of a larval ces tode. Heard's specimen was encountered in the Florida Keys. Most external symbionts THE BLUE CRAB infest both crabs, and their presencedepends The blue crab fishery in Mississippi has on ecological variables. The remaining been discussed by Perry (1975). Others have discussion relates entirely to infections in treated it in adjacent regions in the Gulf Callinectes sapidus. (e.g., Darnell, 1959; More. 1969; Jaworski, The first of four viruses infecting eastern 1972; and Adkins. 1972). Tagatz and Hall blue crabs, according to Phyllis Johnson (1971) presented an annotated bibliography (1977b), is a reolike virus found in on Callinectes sapidus, Pyle and Cronin hemopoietic tissues, hemocytes, glia of the (1950) described its anatomy, Phyllis central , and other cells. If Johnson is finishing a histological study, infected hemolymph is injected into the and Overstreet and Cook (1972) discussed body- cavity of a crab, the crab may die soft-shelled crabs and their potential for within 3 days, probably from neurological further exploitation. involvement, compared to 12 to 32 days for So far I have not said anything about the crabs fed injected tissue. The second is a lesser blue crab, Callinectes similis, or. as herpeslike virus mainly in hemocytes some fishermen call it, the Gulf or scissor (Figures 44 and 45) which takes about a bill crab. It also occurs in the northern Gulf month to kill a confined crab and perhaps and the eastern U.S. seaboard (Williams. much longer to kill or severely affect an 1974) and helps make up a part of the blue unstressed host in its natural environment. crab fishery. It, however, does not reach the Crabs do not appear distressed until near size of Callinectessapidusand can be further death, at which time their hemolymph turns separated from it by possessing two large chalky white. The third is a picornalike and two small "teeth" projecting along the virus infecting primarily neurosecretory front of the carapace between the eyes rather cells, , and bladder than just two large ones. This count does and secondarily invading blood cells and not include the projections where the other tissues. After about a month, the crab, eyestalks protrude. Also, small specimens of affected by an altered molting pattern and Callinectes similis have a blue patch at the sometimes by blindness, may die. The "elbow" and where the claw articulates, fourth is a baculovirus infecting the hepa- rather than being red like on Callinectes topancrcas that does not appear to cause sapidus. overt disease. Most of these and other viruses The parasites infecting the two crab probably affect the blue crab in the Gulf. species also differ in some cases. A critical Infections to date have been confirmed study of all the parasites of the two has not solely on the basis of ultrastructural been made, even though numerous papers examination of specimens from theAtlantic cover individual species infecting seaboard (P. Johnson, 1977b). Callinectes sapidus. As far as I know, neither A variety of chitinoclastic bacteria have 102 Marine Maladies? been isolated from crabs and shrimp in blue crab as well as other hosts have been Mississippi (Cook and Lofton, 1973). One treated by Sprague (Bulla and Cheng, 1977). strain, Beneckea type I. was isolated from all I am presently working on another species. necrotic lesions, making it suspect as a Sprague recently changed the name of the primary causative agent that invades most prevalent species, Ameson michaelis, wounded hosts. Shell disease in the blue when he transferred it from the genus crab, caused by one or more opportunistic Nosema. Some aspects of its development organisms, has only been reported relatively have been described by Weidner(1970; 1972). recently (Rosen, 1967; Sandifer and Overstreet and Weidner (1974) suggested Eldridge, 1974), but has long been con that the muscle disintegration induced by sidered a problem to crabbers who maintain Ameson michaelis may be more severe and crabs in floating cypress cages or who leave extensive than that caused by several other crabs in traps for extended periods. microsporidans because the spores of this Overstreet and Howse (1977) discussed the species lack a surrounding pansporoblast. need to investigate the relationship between A growth chamber bounded by one or more stress and causative agents. membranes, the pansporoblast may trap Crabs collected by (rapping, , or potentially harmful metabolites. dredging typically have systemic bacterial If in the future the crab industry rears its infections which are undetectable other product for the soft-shelled crab market, than by culturing the bacteria. Many such means to prevent and control infections of crabs with bacteria in their hemolymph microsporidans will be necessary. Steps in appear to be, and probably are. relatively these directions have already been made healthy (Colwell. Wicks, and Tubiash, 1975; (Overstreet. 1975; Overstreet and Whatley, Sizemore, Colwell, Tubiash, and Lovelace, 1975; Sindermann, 1977). 1975). Most of these bacteremias are A helpful listing of many protozoans probably transient, and some may be from decapods was presented by Sprague misdiagnoses based on cultures of con and Couch (1971). Many other papers treat taminants from thecuticle. Disease typically different aspects of infections and their ensues only when the organism is especially causative agents in detail, and a few of these virulent or when the host is stressed. Heavy will be mentioned. P. Johnson (1977a) infections can kill crabs (e.g., P. Johnson, critically investigated paramoebiasis; the 1976). Overstreet and Howse (1977) report agent has been adequately described by mortalities of crabs in traps caused by Sprague, Beckett, and Sawyer (1969) and by- Vibrio parahaemolyticus. Perkins and Castagna (1971). Newman and Vibrio parahaemolyticus, a gram C. Johnson (1975) reported the dino negative, rod-shaped, motile bacterium has flagellate Hematodinium sp., and Couch also been implicated in human disease. (personal communication) has additional Many strains live and multiply rapidly in studies in progress. Newman, Johnson, and marine waters, especiallyat the human body- Pauley (1976) described the Minchinia-like temperature of 37°C. In contrast, most haplosporidan. Three papers (Couch, 1966; strictly human pathogens cannot reproduce 1967; 1973) treated the ciliate Lagenophrys in seawater. These organismsconcentrate in callinectes, and Overstreet and Whatley marine organisms near sewage outfalls and (1975) reported the internal "holotrich." give most raw seafood products an Bland and Amerson (1973a; 1973b) undeserved poor reputation. Just like reported the fungus Lagenidiurn callinectes several other bacteria though, Vibrio from crustacean ova, and continuing work parahaemolyticus usually produces by Bland's group has developed control symptoms of nausea, diarrhea, vomiting, measures (Bland, Ruch, Salser, and and mild fever. It hasalso been implicated in Lightner, 1976). infections of the skin. Lee (1973) discussed In a dissertation on microphaiiid information that seafood processors should digeneans of fiddler crabs, Richard Heard know about the organism. (1976) additionally treated some species Most of the microsporidans infecting the from the blue crab and from other Technical Aspects 103 crustaceans. He corrected and added data to to cyprid stage of Octolasmis muelleri takes the earlier reports on Microphallus about 2 to 3 weeks at 21 to 27°C and less for basodactylophallus (= Carneophallus the other barnacle. Development to that basodactylophallus) by Heard (1967) and cyprid stage, the stage which attaches to the Bridgman (1969). Even considering the host, prolongs considerably in cooler water. nomenclatural treatment of the species in a Diet also controls development, and the monograph by Deblock (1971), problems pedunculate barnacle necessitates a much still exist, as pointed out by Heard. Heard more specific diet. Observations on that also elucidated additional aspects of the life species from North Carolina were cycle of Levinseniella capitanea, a worm documented long ago (Coker, 1902). described by Overstreet and Perry (1972). However, whether or not specimens from The cycle progresses much the same as the blue crab in America comprise a Microphallus basodactylophallus; however, geographic population and a synonym of fewer mammals and birds probably host the the cosmopolitan Octolasmis lowei has not worm than for many microphallids, since I been established decisively (e.g., Newman, could not establish specimens in mice, rats, 1967). or baby chicks. Ecological studies of Loxothylacus Many microphaiiid metacercariae, texanus in the northern Gulf were presented including those discussed, produce eggs in some detail by Ragan and Matherne when maintained in warm saline. This (1974) who additionally cited most of the ability reflects the lack of much biochemical references on that species in their biblio dependency on the host for egg production graphy. The only other reported host in in those microphallids. The important addition to Callinectes sapidus is aspect of the life cycles of those species seems Callinectes ornatus. Gordon Gunter has to be the need for adults to produce eggs seen that crab infected along the west coast quickly, a maneuver allowing infection of of Florida (Christmas, 1969), and I haveseen intermediate hosts if the definitive host is many in the shallow hot regions of BearCut one that would soon migrate from the in Miami, Florida. Lawler and Shepard region and thereby leave potential inter (1978) present a fairly complete biblio mediate hosts behind. graphy on all rhizocephalans. From Various histological studies treating the Mississippi, Christmas (1969) reported hyperparasite Urosporidium crescens from infected blue crabs and also mentioned the the Atlantic coast list digeneans of the blue presence of what he tentatively considered crab other than Microphallus basodac Loxothylacus panopaei in mud crabs. tylophallus as probable hosts (De lurk, Loxothylacus panopaei is an important 1940; Sprague, 1970a; Perkins, 1971; Couch, example of introduced species. After many 1974a); however, Heard and I have oysters in Chesapeake Bay died from examined specimens of trematodes from Minchinia nelsoni, oysters from the Gulf of infected crabs from Virginia and found Mexico were introduced in 1963 and 1964 to them to be Microphallus basodactylo help reestablish the population. Incidental phallus, the same as in the Gulf. On the to the oysters occurred mud crabs infected other hand, additional digeneans are with the rhizocephalan. By 1965,native mud suitable hosts for this haplosporidan crab populations started revealing includingMicrophallus choanophallusand infections of Loxothylacus panopaei for the Levinseniella capitanea. first time (see Van Engel. Dillon, Zwerner. The acorn barnacle, Chelonibia patula, and Eldrtdge, 1966; Daugherty, 1969). and the pedunculate barnacle, Octolasmis Couch (personal communication) has also muelleri, have been reared in the laboratory found Eurypanopeus depressus infected in by Lang (1976a; 1976b). Those works Chincoteague Bay (Figure 36). suggest that distribution of both species Soon after first being introduced, a depends on temperature. Breeding and successful species often produces excessively larval development ceases below about large populations until such time that an I5°C. Development from the first naupliar equilibrium becomes established. Whether 104 Marine Maladies? infections of Loxothylacus panopaei spread abdominal (tail) segment. The white explosively has not been established, but the shrimp lacks these, but not the pink shrimp, apparent abundance of mud crabs declined. which may additionally have a distin Possibly the parasite did not influence the guishing brownish lateral spot on the population structure of the crabs, but, second and third segments. Cook and nevertheless, introductions of one Lindner (1970) and Lindner and Cook species may result ultimately in a decline in (1970) presented good summaries of data on other species in the new habitat. Before the brown and white shrimps to which introducing any animal or plant, the need could be added a paper on burrowing and for it and the possible side-effects from the daily activity of shrimp by Wickham and introduction should be carefully evaluated. Minkler(l975). Christmas and Etzold(1977) Humes (1942) presented an extensive edited a report on a regional fishery treatment on the nemertean Carcino- management plan for penaeid shrimp. nemertes carcinophila. which was later The parasites and diseases of commercial followed byapapcron itsuscasan indicator penaeids, more than those of most any other of host spawning (Hopkins, 1947) and select group of marineorganisms, have been another on its larva (Davis, 1965). studied in some detail. A considerable The fact that the common leech number of questions remain unanswered, Myzobdella lugubris uses a fish to obtain but recent findings and summaries of blood and a crab on which to deposit previous works have been presented by cocoons has been recognized only recently Overstreet (1973), Feigenbaum (1975), S. (Daniels and Sawyer, 1975; Sawyer, Lawler, Johnson (1971; 1975), Lightner (1975). and and Overstreet, 1975). The latter reference Couch (1978). Couch broadened his paper goes into considerable detail on salinity- further by including the response of shrimp tolerances of the adultanddeveloping leech. and their tissues to a variety of toxic Hutton and Sogandares-Bernal (1959) chemicals and heavy metals. The obser reported the association between the leech vations on the tumorous growth, a and crab mortality. Some data on the hamartoma, discussed above were made by branchiobdellid Cambrincola mesochoreus Overstreet and Van Devender (1978). were reported in an unpublished honor's thesis by Blackford (1966), but more Couch (1974b) first observed the viral inclusion bodies in shrimpand followed his extensive work could be done on that and report with a series of studies assessing the other branchiobdellids of both the crab relationship between stress and disease and crayfishes in the northern Gulf region. (Couch, 1974c; see citations by Couch and The authority on that group is Perry C. Holt Courtney, 1977). The virus was charac at Virginia Polytechnic Institute and State terized by Summers (1977). Flagellate and University. ciliate protozoans additionally involved some of the dying larval shrimp, but no doubt exists about the increased presence of the inclusion bodies in shrimp exper PENAEID SHRIMPS iencing certain stresses.

Considerable data have been published The normal bacterial flora of brown and on shrimp catches and shrimp biology. white shrimps was investigated by Perez Farfante (1969) provided a detailed Vanderzant, Mroz, and Nickelson (1970). taxonomic and ecological treatment and a Lightner (1975), who reported the epizootic review of all members of the genus Penaeus of virulent chitinoclastic bacteria, reviewed in the Western Atlantic. Of the twocommon bacterial diseases of shrimp in general. species in the northern Gulf, the brown Research on fungal diseases of crusta shrimp has a groove (lateral rostral sulcus) ceans has just begun to receive serious running along each side of the dorsal (top) investigation. Unestam (1973), Bland midline ridge on the "head" (cephalo- (1975), and Lightner (1975) provided good thorax) as well as one on the last (sixth) summaries of the problems. Technical Aspects 105

"Black gill disease" results from a variety typically replace muscle tissue and some of both infectious and noninfectious agents. times invade anteriorly-located tissues in Massive accumulations of hemocytes settle addition to the tail; they involve primarily within the gill filaments, ultimately white and brown shrimps. The third species associated with dysfunction, destruction, or from the host tail, Thelohania duorara, lies secondary infections. Lightnerand Redman between muscle fibers, most commonly in (1977) showed histologically that the pink shrimps. As with Pleistophora sp., it inflammatory responses typically involve occasionally invades heart and other tissues. melanin deposition following exposure of Spores measure 4.7 to 6.8 }i long by 3.0 to shrimps to cadmium, copper, and Fusarium 4.2 u wide (averaging 6.0 by 3.7 /<) with solani, as well as when shrimp have an uniformly wide polar filaments 97 to 142 // ascorbic acid deficiency, wounds, and a long; eight of them exist within each variety of undiagnosed conditions. pansporoblast. Inflammatory response in penaeid shrimp The last species (Agmasoma /= Thelo involves fixed phagocytes lining blood hania] penaei) invades tissue other than sinuses, phagocytes in loose connective the abdominal muscle. Prevalent in tissue, fibrocytes, and three forms of blood vessels, foregut, and hindgut, it also hemocytes. Solangi and Lightner (1976) infects and destroys the germinal tissue of followed the response to the fungus, the gonads. Infections seen through the Fontaine and Lightner (1975) described the carapace among the branchiostegal encapsulation, , and elimina epithelium and in the appendages originate tion of necrotic material as well as the from tissue of the blood vessels. Only in an healing process, Couch (1977) presented an abnormal situation have I observed an ultrastructural study of lesions in gills infection associated with abdominal exposed to cadmium, and Sindermann muscles (Overstreet, 1973). A pansporoblast (1971) reviewed the internal defenses of harbors a group of eight pyriform spores crustaceans in general. either 2.5 to 4.7 /c long by 2.0 to 3.5 fi wide The four common microsporidans differ or 5.5 to 8.2 ]i by 3.5 to 4.2;^. Both the small in several aspects (Overstreet, 1973) and will and large (megasporcs) spores occur in the be described because of the difficulty in same shrimp. Also, the polar filaments distinquishing them and because of their protrude 65 to 87 }i and have a thin distal receiving a recent resurgence of interest. portion contrasting with the thick proximal Spores of Ameson (= Nosema) nelsoni part. Other than some pond-reared pink and measure about 2.5 ;/ long by 1.5 fi wide brown shrimp, only white shrimp have (occasionally up to 3.5 ji by 2.3 ]i) with a revealed infections. Iversen and Kelly (1976) narrow polar filament 23 /< long. Thesingle apparently transmitted this or a related spore has no pansporoblast chamber, and species to postlarval pink shrimp by feeding masses of them surround the abdominal them feces from spotted seatrout that had muscle bundles of white, brown, and pink eaten infected shrimp. shrimps before eventually replacing them. Descriptions of the different North Pleistophora sp. may be especially difficult American gregarines of penaeids occur in to distinguish from the above species. works by Sprague (1954), Kruse (1966a; Chromatophores along the dorsolateral 1966b), Overstreet (1973), and Feigenbaum surfacesof shrimp infected with both species (1975). Kruse (1966a; 1966b) provided expand and produce a bluish-black information on the biology of a few species, appearance to the shrimp; however, the and Sprague (1970a) reviewed gregarines of appearance usually is darker when the crustaceans in general. shrimp is infected by Pleistophora sp. Descriptive data on most ciliates are Sporesof that species, 1.7 to3.0/< long by0.9 lacking. Couch (1978) gave a recent to2.5 n wide withpolarfilaments 42 to 125 y summary of most ciliate and flagellate long, develop in pansporoblasts containing species from shrimp, and papers by as few as 14 spores or as many as several S. Johnson (1974) and by Lightner (1975) hundred. The Pleistophora sp. infections provided additional information. The 106 Marine Maladies? relationship between Zoothamnium sp. and suggested brown shrimp may respond to the shrimp's gill has been studied by Foster, infections differently. When shrimp can be Sarphie, and Hawkins (in press), and the readily infected, these hypotheses can be possible detrimental effects caused by that tested. Overstreet (1973) did not detect a relationship were discussed by Overstreet decreased intensity of infectionsover the 2 to (1973). 3 month period shrimp were reared in Heard experimentally infected the shrimp Louisiana ponds. shown in Figure 68 and plans to report the Most investigators previous to or unaware results soon. Overstreet (1973) summarized of a study by Mudry and Dailey (1971) information on the other trematodes, assumed shrimp acquired infections from including a description of Opecoeloides small infected crustacean intermediate fimbriatus by Kruse (1959). hosts. That study suggested that in cycles using a crustacean and elasmobranch, the Most of the common helminths have been reported by Hutton, Sogandares-Bernal, crustacean acquired its infection directly by Eldred, Ingle, and Woodburn (1959), Kruse feeding on worm's eggs, whereas in cycles (1959), Overstreet (1973), Feigenbaum with a plerocercoid in a fish, the fish (1975), and Couch (1978). Feigenbaum acquired the infection from a crustacean. (1975) discovered two new trypanorhynch The first method may not be representative cestodes from the hepatopancreas and body for penaeid shrimp with Prochristianella cavity of Penaeus brasiliensis near Miami, hispida. Florida, and Corkern (1978) found an The larval ascaridoid from shrimp encysted cyclophyllidean larva in shrimps described by Kruse (1959), Hutton, in Texas. No one has seriously tried to Sogandares-Bernal, Eldred. Ingle, and determine the identity of the intestinal Woodburn (1959), and others as larval cestode. However, Tom Mattis has Contracaecum sp. can presently be completed much of a dissertation problem considered Thynnascaris type MA. Norris at the Gulf Coast Research Laboratory on and Overstreet (1976) brieflydiscussed itand the life history of Prochristianella hispida. differentiated it from type MB. Type MB is 1 Figure 70 illustrates his present under to 3 mm long with an esophagus 4 to 13%of standing of its cycle. Prevalence of that that length, a ventricularappendage 14to 68 species, previously referred to as times the length of the short intestinal Prochristianella penaei (see Campbell and caecum, and a spineless, bluntly-rounded Carvajal, 1975), has been treated by several tail. In contrast, type MA is 3 to 5 mm long, authors (Aldrich, 1965; Corkern, 1970; has an esophagus 14 to 15% of that length, Ragan and Aldrich, 1972; Overstreet, 1973), has a ventricular appendage 2 to 3 times as and Corkern (1970) also included data on long as the intestinal caecum, and possesses Parachristianella dimegacantha, a species a spiny projection on the tail. Norris and common in youngershrimp from Galveston Overstreet recognized three or four forms Bay, Texas. from penaeids. In white shrimp studied by Sparks and Adult Thynnascaris species infect a Fontaine (1973), larval Prochristianella variety of fishes. Norris and Overstreet hispida developed a dense cyst in the (1975) described two adult forms and hepatopancreas that was apparently soon Thomas Deardorff of GCRL hopes to be destroyed and resorbed by the host. When in able to correlate the adults of a few Gulf the hemocoel, the larva had a thinner cyst species with their larval forms by experi with less inflammatory response, mentally completing portions of their life suggesting a more preferable site. Those cycles. authors believed that worms are gradually Spirocamallanus cricotus was first lost in white shrimp. Because infections in tentatively reported from penaeid shrimp as brown shrimp do not reveal a decrease in Spirocamallanus pereirai (see Overstreet, intensity with age as assumed for those in 1973). Fusco and Overstreet (1978), however, white shrimp from some areas, the authors have now clearly established that the species Technical Aspects 107 commonly referred to as Spirocamallanus (1975) on shrimp diseases for those pereirai from the Atlantic croaker and spot culturing shrimp, S. Johnson (1977) also in the Gulf of Mexico constitutes a separate, provided a similar handbook on diseases closely-related species. Fusco (1978a) has of crayfish and freshwater shrimp. described the larval stages of that worm. Although not complete for diseases of grass Leptolaimus sp. (Leptolaimidae) from on shrimp, that pamphlet provides the only the gills and from both within the lumen of single source of parasites of that host. It and adjacent to the alimentary tract of contains much useful information, some brown and white shrimps was reported by taken from an earlier paper (S. Johnson, Overstreet (1973). 1974). Many of the protozoans symbiotic on Rigdon and Baxter (1970) first reported the grass shrimp were listed by Spragueand spontaneous necrosis of abdominal muscles Couch (1971). The findings of more species of penaeids, and that work has been plus completion of considerable detailed followed up by Lakshmi, Venkataramiah, biological studies on many protozoans of and Howse (1978), who showed that the grass shrimp and other crustaceans have lesions, presumably caused by muscle occurred since 1971. Clamp (1973) provided fatigue heal faster in oxygenated rather observations on Lagenophrys lunatus, and than aerated water. The cramped condition Phyllis Bradbury has worked up several was first reported by de Sylva (1954) and then other ciliate-grass shrimp relationships subsequently by Johnson, Byron, Lara M., including that for Terebrospira chattoni and Ferreira de Souza (1975). Venkata (see Bradbury, Clamp, and Lyon, 1974; ramiah, Lakshmi, and Biesiot at GCRL Bradbury and Goyal, 1976). Sprague (Bulla have found that crampingoccurs most often and Cheng, 1977) listed three micro in conditions of low salinity and tempera sporidans from Palaemonetes pugio and ture. They (personal communication) also more information on those have been determined that it results from an internal presented by Street and Sprague (1974) and ionic imbalance, and they- are presently- Overstreet and Weidner (1974). trying to identify the specific ion or ions The bopyrid Probopyrus pandalicola has involved. Both necrosis and cramping been studied by Richard Heard (unpub typically affects shrimps in tanks for bait lished). Also, its respiration in both larval dealers and in culturing facilities. As cul and adult stages has been investigated in turing shrimp becomes more widespread, relation to its two hosts (Anderson, 1975a; especially with heated or cooled water, these 1975b). Both the infested copepod and and other diseases will appear. One of these shrimp respired less than their respective others is gas-bubble disease (Lightner, control counterparts. This decreased use of Salser, and Wheeler, 1974), and it also oxygen may result from a lipid buildup in affects oysters and clams in water super infested hosts requiring less energy to saturated with oxygen or nitrogen. metabolize. When fish have parasitic Overstreet (1973) discussed the golden infections, they generally respire more, shrimp disease and also reported and which in turn increases their stressed reviewed some fouling organisms. Many condition. organisms foul shrimp, even a barnacle that settles on the blue crab (Dawson, 1957). Just like different tissues of all animals, FISHES those of shrimp degenerate at different rates after death. Lightner (1973) described these A general treatment of the biology of postmortem changes in the brown shrimpat fishes can be obtained from a multitude of different temperatures. books available in most any library. Identifications of most species from the northern Gulf of Mexico can be made using GRASS SHRIMP keys in a book by Hoese and Moore (1977). Walls (1975) also wrote a recent book on In addition to his illustrated handbook these fishes. A standardized list of common 108 Marine Maladies? and scientific names acceptable to the Bacterial flora including commensal and American Fisheries Society was published disease-causing organisms have been (Bailey etal., 1970), and anotheredition will investigated more thoroughly than viruses. update it in the future. These are common Horsley (1977) reviewed the bacterial flora of names used in most scientific literature, and fishes and concluded that the flora in a fish's not necessarily those used in specific alimentary canal was about the same as that geographic localities by fishermen. Older on the gills and skin, which, in turn, works, such as an article by Earll (1887) used depended on the state of the environment. for comments on the early mullet fishery, In other words, monitoring bacteria and often use scientific and common names no water quality in ponds should help predict longer in use today. potential disease outbreaks. Because of recent interest in elasmo The natural bacterial epizootic in the branchs and the potential for investigating northern Gulf was first reported by Plumb. evolutionary aspects of some highly specific Schachte, and Gaines (1974) and later elasmobranch parasites, I mention a few studied in more detail by Cook and Lolton references. A book edited by Gilbert, (1975). Overstreet and Howse (1977) dis Mathewson, and Rail (1967) covered most cussed some bacterial infections in aspects of elasmobranch biology except the Mississippi coastal areas. parasites. More current evaluation of inter A book with parts by G. Bullock, Conroy, relationships among elasmobranch groups and Snieszko (1971) and by G. Bullock has been presented by Zangerl (1973) and (1971) deals specifically with the methods of Compagno (1973; 1977). Means for critical working with bacteria from fishes. Two of identification of species have been given by several papers concerning identification of Bigelow and Schroeder (1948). bacteria are by Glorioso, Amborski, Larkin, No single source covers parasites from Amborski, and Culley (1974) and by Slums marine or estuarine fishes. Hoffman (1967). (1976). The primary reference is Bergey's however, covered parasites in North Ameri Manual (Buchanan and Gibbons, 1974). can freshwater species, and that book might be helpful for identifying some parasites. A rather extensive compilation of mullet Protozoans parasites and diseases (Paperna and Protozoology and even the study of Overstreet, in press) may also apply to a parasitic protozoans represent fields unto general investigation of conditions in any themselves. The advances in chemistry, fish. Control and treatment of freshwater ultrastructure, and culturing techniques diseases have been covered extensively have allowed a much better understanding (Hoffman and Meyer, 1974). Methods for of the relationships amongdifferent groups. diagnosing and controllingselected diseases In 1964, Honigberg and a group of others in , pompano, and striped bass have formulated the committee's revised been edited by Sindermann (1977), but the classification of the Protozoa. Since then same statements also apply to several other several major changes have been suggested host-disease relationships. such as those by de Puytorac and others (1974)and Corliss (1974a; !974b)forciliates, and by Sprague (Bulla and Cheng, 1977) for Microbes microsporans. Several books cover Plumb (1974) reviewed all known viral protozoans in general such as those by Kudo diseases of fishes from the Gulf region. (1966), Grell (1973), and Sleigh (1973). Lymphocystis from Atlantic croaker was Levines' book (1973) specializes in parasitic first described by Howse and Christmas forms primarily from domestic animals. (1970; 1971) and that from the silver perch Even though helpful, that book unfor by Lawler, Howse, and Cook (1974). A brief tunately did not treat species from fishes. review of infections including some new The biochemistry of parasitic forms has data was presented by Overstreet and Howse been summarized by Gutteridge and (1977). Coombs (1977). Several papers on specific Technical Aspects 109 species or groups are cited below. paucity of observations have influenced Lawler (1977) has shown that all but 6 of some biologists to assume that several rather over 80 tested fishes (different species) specific trypanosomes occurred in sonic- succumbed to heavy infestations of the regions. Ultrastructure of stages in the leech dinoflagellate Amyloodinium ocellatum. has been investigated by Desser (1976). Those six fishes usually appeared refractory Amoebae have been encountered in to the invader. Occasionally an individual marine fishes. Orias and Noble (1971) list of one of those species would become ed the four reported species. All but one infested or even die, but in those instances, inhabits the alimentary tract, and it occurs another less susceptible fish was usually in the branchial mucus and skin. None present. Lawler suggested the resistance appears pathogenic to the fish, but fresh of Cyprinodon variegatus, Fundulus water amoebae have been implicated in grandis, Opsanus beta, and others might mortalities, possibly in conjunction with relate to the ability of those fish to tolerate associates (Rogers and Gaines, 1975; low oxygen concentrations or to produce an Sawyer, Hoffman, Hnatli, and Conrad. abundance of mucus, either with or without 1975). Living individuals move about a repelling substance. Lorn and Lawler actively with their ; in some (1973) described the attachment mechanism cases they even feed on their own protective of the related Oodinium cyprinodontum cyst stage in addition to expected food parti which infests gills of killifish and other cles (W. Bullock, 1966). Critical examina cyprinodontid fishes along the Atlantic and tion of intestinal tissue and contents might Gulf coasts. Larger and more elongate than reveal many amoebae in marine fishes. Amyloodinium ocellatum, it harbors Based on other reports, individuals should chloroplasts. Rather than penetrating and be more prevalent when intestinal flagel digesting host tissue like that compared lates also cx-cur. and they probably occur in species, it attaches without harming the host clusters. Perhaps given appropriate and produces its own nutrients like a typical stimulation, some of the commensal plant. That Oodinium cyprinodontum has amoebae become virulent. such characteristics favor the host, since as Several books treat coccidiosis in general many as 2000 dinospores (about eight times (Kheysin, 1972; Levine, 1973; Hammond as many as for Amyloodinium ocellatum) and Long, 1973). A brief treatment by Lorn can form from one trophont. (1970) summarized much of the information Several chemical treatments cited in about piscine species, and many new species aquarium publications as curing Oodinium have been described since then. Lorn (1970) infestations have not been successful in also treated hemogregarines and other pro treating heavily-infested fish. Lawlei (1977) tozoans of fish, whereas Becker (1970) listed several of these and emphasized the confined his chapter in the same book to value of a short freshwater bath. protozoans in fish blood. Davies and A general treatment of piscine flagellates Johnston (1976) studied Haemogregarina (Becker, 1977) covered all different groups. bigemina, a species that reproduces Becker and I are presently studying some asexually in peripheral blood of a blenny blood parasites in fishes from Mississippi, and other hosts; they presented strong and comments on leeches as vectors for these evidence that the isopod Gnathia maxillaris occurred in the paper by Sawyer, Lawlei. acted as the vector. For someone interested and Overstreet (1975). Dealing specifically in the fine structure and locomotion of with trypanosomes. Khan (1977) showed hemogregarine gameiocytes, the most ob experimentally that at least Trypanosoma served stage in fish, Desser and Weller(1973) murmanensis in Newfoundland, Canada, provided an informative paper. Olscn's infected a variety of related and non- (1974) book presented a diagram of a life related hosts. After being transmitted by cycle for a species utilizing a turtle and a the leech, the trypanosome continuously- leech, and it also gave several references for increased in size for about 2 months. The obtaining information on all stages. difference in size of blood flagellates and Generally not considered pathogenic, 110 Marine Maladies?

hemogregarines include a species artificially- cultured spores from the vege (Haemogregarina acipenseris) in a tative stage. Hoffman (1974), who has from the Volga River that apparently causes conducted much research on means to anemia and wasting in its host (seeShulman control whirling disease, reported on the use and Stein, 1962). of ultraviolet irradiation to control both it Microsporidans have been discussed in and a variety of other fish parasites. detail in the section on crustacean hosts. Treating ponds in order to control the di The best single source of review articles and sease is not always entirely effective references on all aspects of the group is the (Hoffman, 1976; Hoffman and O'Grodnick two volume work edited by Bulla and Cheng 1977). (1976; 1977). The myxosporidan cysts portrayed The extensive literature about myxo between the fin rays of the spot probably sporidans primarily deals with spore size are referable to the same species of and shape and with hosts. Increased num Henneguya that occurs between the soft rays bers of ultrastiuctural investigations on the of the dorsal and anal fins of the seatrouts spores and on developmental stages should Cynoscion nebulosus and Cynoscion enhance the knowledge of the group arenarius in Mississippi Sound and that considerably. Kudo (1920) and Shulman reported but never named from Cynoscion (1966) wrote the classic treatments on the regalis in New York and Virginia by group, and Paul Meglitsch of Drake Jakowska. Nigrelli, and Alperin (1954). University- has an ii|xlated monograph in Other than three species, one from an progress. , one from an insect, and one from a Lorn (1969), an active worker with digenean, all reported true myxosporidans myxosporidans. compared the development infect cold-blooded vertebrates. The patho of the polar filament and its external tube genic Fabespora vermicola from the thai is drawn into the capsule with the digenean Crassicutis archosargi and its similar process for nematoc yst development unusual ability to move by itself was re in cnidarians. He used this and other fea ported by Overstreet (1976a). If the fluke tures, all of which contrast with those of a harmed its sheepshead host, the myxo microsporidan and its polar filament and sporidan could be considered for possible with a ciliate and its extrudiblc organelles, use as a biological control agent. The fluke, to relate myxosporidans more closely with however, even though attaching to the cnidarians than with other protozoans. Both intestine by an unusual adhesive mech groups also have dissociated generative anism (Overstreet, 1976b), apparently does cells. not harm the fish. The possession of more than one cell References on ciliates in general were pre needs further explanation. When most sented at the beginning of this section. By disporous species develop (two spores culturing a few ciliates. applying the within a membrane), ten cells form the two protargol and silver impregnation tech spores and one forms the pansporoblast niques, maybe using an electron chamber. For a spore, one cell forms each microscope, and exercising considerable of the two valves and each of the two polar patience, students and other scientists can capsules including their contents. The still solve numerous economically and nuclei of a binucleate cell often fuse to academically important problems with produce the infective amoeboid stage. ciliates. Pathological alterations in Cyprinodon Trichodinids of marine fishes have been variegatus (sheepshead minnow) infected studied most extensively by Lorn, who with Myxobolus lintoni have been treated presented a nicely illustrated study (1973)on by Nigrelli and Smith (1938). Overstreet and their adhesive disk. They have been reported Howse (1977), and others. Articles on trout to cause mortalities in marine hatcheries with whirling disease probably surpass in (e.g., Purdom and Howard, 1971; Pearse. number those on any other myxosporidan. 1972), but dying fish often also harbor Recently, and Markiw (1976) have monogeneans, copepods, or dinoflagellates Technical Aspects 111 in addition to the ciliates that may help especially those resulting from Tetra- promote their multiplication. Several hymena corlissi. That facultative parasite species cause mortalities in freshwater killed fish, but fish could not be experi facilities. As examples (Meyer, mentally infected with it. 1970), trichodinids kill channel catfish fry- Specimens of the sheepshead minnow within an hour after hatching and keep from Horn Island infested with the young golden shiners from feeding. hypotric h were collected by Adrian Lawler. Red sore disease has been considered a and the progress of the disease was followed problem for some time to people with by the two of us (unpublished data). -ponds (Rogers, 1972). In addition to low oxygen concentration and Cestodes high organic content, other factors can Yamaguti (1959) compiled a book on all promote the disease. Esch, Hazen. Dimock, cestodes known at that time, providing and Gibbons (1976) studied the Aeromonas- keys to genera and higher groups. A more Epistylis complex in centrarchid fishes up-to-date set of keys was written by- from a cooling pond for a nuclear pro Schmidt (1970). but neither helps identify duction facility and found that more fish most larval forms. Some of these larvae from from the thermally-affected region had Gulf molluscs can be sorted out using a key red sores than did those from a region with by Gike (1976). Wardle and McClouds water of ambient temperature. Presumably, (1952) book on tajM-wonns remains the a variety of pollutants that stress the host classic for a general treatment. and encourage growth and reproduc lion of Aspects of the ecology and taxonomy of the ciliate and the bacterium will enhance the pseudophyilidean Anantrum tortum red sore disease. were presented by Overstreet (1968). Rees Overstreet and Howse (1977) studied the (1969) presented a more detailed account of attachment of the stalk's terminal plate to several of the characters of the same worm host tissue and suggested that the fibrillar using the junior synonym Acompsoceph- attachment complex of Epistylis sp. slowly alum tortum. Before this present report, infiltrates and erodes the host tissue leaving the worm had never been reported from the scale or bone as the only remaining sites on Gulf of Mexico, even though the worm is which to attach. Fish heavily infested often extremely abundant. I have confirmed that have exposed bones and extensive tissue it has operculated eggs. Recently Jensen and destruction and regeneration. Those Heckmann (1977) described a second authors point out that hemorrhaging species, Anantrum histocephalum, from a lesions seem to depend on the presence of lizardfish in California. That worm, scales. Catfish, without any scales, harbor however, has a mushroom-shaped scolex to dense growths of the same or similar species assure attachment within the gut of Epistylis without much hemorrhaging epithelium. even though bones may be exposed. Overstreet (1977b) reported the ecological The major group Holotrichia no longer aspects of infections of Poecilancistrium has acceptance in the recent classification caryophyllum in the spotted seatrout. schemes of de Puytorac and others (1974) Moreover, Tom Mattis has been investi and Corliss (1974a; 1974b). The term, gating the life-history of that worm and of however, still has some useful value in several other elasmobranch cestodes. He is nontaxonomic works because of its long the authority from the Gulf region on workable and familiar nature. An outbreak elasmobranch cestodes; others that work on of Cryptocaryon irritans in fishes from both elasmobranch cestodes are Ronald experimental and public aquaria was Campbell of Southeastern discussed by Wilkie and Gordin (1969). University and Murray Dailcy of California Hoffman, Landolt, Camper, Coats, State University at Long Beach. Dailey and Stookey, and Burek (1975) provided a key to Overstreet (1973) described the multi- "holotrichs" of freshwater fishes and strobilate forms of Cathetocephalus discussed pathological responses by hosts, thatcheri from the bull shark. 112 Marine Maladies?

Monogeneans to the fish's belly. It embeds its anchors into Rather than being most closely related to the host, but holds on primarily by suction. digeneans, monogeneans probably evolved Accessory hook-like structures anterior to from an ancestral form that gave rise to the anchorsactually prop up the central part cestode groups. Malmberg (I974) discussed of the holdfast making a cup. In some other his ideasand reviewed much of the literature species, the anchors penetrate more deeply on monogenean phylogeny. and hold the host in a manner similar to an A book by Yamaguti (1963a) provides keys ice long when the fish is active. When the to the families and genera of monogeneans fish slows down, some worms' marginal and listings of species. A more updated key hooks suffice for attachment (Lester, 1972). for North American genera by Schell (1970) Studies by Paperna (1964) provided an may prove more economical and up to date understanding of infestations by more than for a beginning student. one monogenean species in pond-reared Many laxonomic problems still need fish. He found that heavy infestations of attention, including numerous descrip vastator on young carpcaused tions of pathogenic species. In fact, Adrian increased growth of host tissue (hyper Lawler at GCRL plans to describe the new plasia) and created an unfavorable species of Dermophthirius that harmed its environment for two other monogenean sawfish host. Lawler and Cave (1978) species. The small worm can kill many already reported on Aspinatrium pogoniae fry, but fingerlings develop a resistance, so which built up infestations to thousands of that monogenean infestations in larger fish individuals and apparently killed a large include other less pathogenic species only. captive black drum. Large worms measured If the effect of temperature, salinity, and over 12 mm long, but most were smaller. other physical parameters on larval and Many species will multiply extensively in adult worms and the time when fry first cultured fish and kill or weaken them, but appear in ponds are understood, fish can be few cases have been reported in the properly managed to avoid infestations literature. (e.g., Paperna, 1963). A biologist, however, Some monogeneans that occur in must realize that not all monogeneans' eggs Mississippi may be near the limit of their have to hatch quickly; some develop- geographic range, being rare except under mentally inhibited larvae over-winter and specific conditions. The relatively rare hatch about the time young fish appear. Absonifibula bychowskyi may be an Another group of tiny monogeneans example of this (Lawler and Overstreet, (gyrodactylids) produces embryos rather 1976). We found that the intensity of than eggs, and many species can coexist on infestations related directly with water the same host (e.g., Williams and Rogers, temperature. 1971, for species on the sheepshead min The best understood monogenean now). Some species cause mortalities and infesting skin does not occur in local waters. others inhabit atypical sites. One species Still, a brief understanding of the biology of even infests the brood pouch of the male Entobdella solea from the ventral surface of Gulf (Holliman, 1963). the sole should inspire extensive investi A large number of the marine species in gations of local species (Kearn, 1971).This the northern Gulf have been reported or 5 mm worm moves about on the bottom of described in papers by Koratha (1955a; the flatfish, feeding on tissue overlying 1955b) and Hargis (1957, for summary). scales. It lays eggs with long sticky filaments Koratha (1955a) also suggested a possible on sand grains during the day when the host phylogenetic relationship between cobia is buried. Fish feed during dark hours, and and diskfishes indicated by their about dawn they return to partially bury in monogeneans. This relationship has been the sand. At that time, a ciliated questioned by several ichthyologists. monogenean larva (onchomiracidium) Several other groups of monogeneans are hatches and infests the exposed upper head also restricted to specific families or other of the sole. As it matures, the worm migrates groups of fishes. On the basis of Hargis' Technical Aspects 113 report on host-specificity, each of 67 mono ecological aspects of many parasites from geneans from the northern Gulf infested a the Atlantic croaker including digeneans. single host species, whereas only 8 parasi Courtney and Forrester (1974) reported on tized twoand 1 parasitized three. When more the worms from the brown pelican. Some than one host was infested, they belonged to heterophyids infect their intermediate hosts the same genus. Similar levels of specificity in large numbers. Paperna and Overstreet to single hosts occur in the White Sea, (in press) reported as many as 6,000 Barents Sea, , and Great Barrier heterophyid metacercariae per gram of Reef off Australia (Rohcle, 1977). tissue from some mullet in the Sinai. Even though fishes do notact as paratenic hosts for digeneans as frequently as for Digeneans cestodes, nematodes, and acanthocephalans, Yamaguti (1971) revised an earlier some still function in that role. So can compilation of all digeneans of vertebrates, (squids and related molluscs) giving keys to genera and families and which parallel fishes in many respects in listing species with their hosts. He (1975) addition to harboring the same digeneans also compiled most known data on life (Overstreet and Hochberg, 1975). cycles. Both lengthy works are extensively- For a fairly recent discussion on illustrated. Shell's (1970) key allows some phylogenetic and taxonomic relationships identifications and is much cheaper in price of digeneans, readers should refer to a paper than Yamaguti's book, but does not include by Cable (1974). I hope Raymond Cable will as many local marine and estuarine species. share more of his knowledgeabout cercariae A book by Erasmus (1972) deals with with us in the future. experimental investigations of trematodc Chuck Getter, a graduate student of biology, emphasizing larval stages. C. Richard Robins at the University of Lumsden (1975) reviewed the function and Miami has been investigating the endan structure of helminth teguments, including gered key silverside, Menidia conchorum. those of trematodes, and Overstreet (1976b) He sent me preserved material infected with described the unusual attachment to a fish acanthostomes. Specimens of sheepshead host by Crassicutis archosargi. minnow and sailfin molly also had For further discussion on some ol the infections. To date, only three examples presented, the reader can refer to acanthostomes have been reported from the the following works: Gibson and Bray United States, and the larva, based on the (1977) considered the giant fish stomach presence of 24 oral spines and other worm from a variety of hosts as the single characters, appeared most like species Hirudinella ventricosa until further Acanthostomuw. coronarium (see Brooks evidence confirms a second species, Iversen and Overstreet, 1977); however, we have and Yoshida (1957) reported the common studied no crocodilian worms from South occurrence of two specimens of that giant Florida and additional species with similar digenean per wahoo, and Watertor (1973) features may occur there. discussed variations in infections of it from Anatomical aspects of the four species of tunas. A general discussion on melanin- marine aspidogastrids in the northern Gulf containing cells in teleostswas presented by have been treated by Hendrix and Overstreet Roberts (1975), and Dubois' (1968; 1970) (1977). synopsis covered the taxonomy and life A review of American histories of most strigeoids. Overstreet including the pairing and encapsulation of (1970; 1971a; 1971b; 1971c; 1977a) treated individuals was presented by Sogandares- Metadena spectanda, Saturnius maurepasi, Bernal and Seed (1973). Literature on many and the digeneans illustrated in Figures 143 marine zoonoses (parasites, including to 145. digeneans, that could infect humans and, Some discussed works are still in progress. in some cases, pets) has been synthesized by Heard and I will describe the life history of Williams and Jones (1978). Phagicola longus, and I will report on 114 Marine Maladies?

Nematodes of Agriculture & Fisheries for Scotland. As he has done for other helminths, Aberdeen, Scotland). Yamaguti (196I) has compiled a listing of A general treatment of nematodes in nematodes parasitic in vertebrates, and he marine fishes by Margolis (1970) gave a included keys to genera and higher taxa. fairly complete idea of the different major These keys, but not the listings, have been groups infecting fish. More groups than superseded by a series of keys edited by- that, however, infect fish. A critical study Anderson, Chabaud, and Willmott (1974a, on the life cycle of Dioctophyma renale by 1974b. 1975a. 1975b). Number 1 in this Mace and Anderson (1975) emended someof series also includes a glossary which should the interpretations by Karmanova (1962). straighten out some of the confusion among who confirmed that earlier workers had terms. A series of books in Russian have indeed mistaken a gordiacean larva from the compiled much of the literature cm some branchiobdellid from crayfish as Diocto groups, and a few have been translated into phyma renale. The duck mortalities re English (e.g., Skrjabin, 1919; Ivashkin, sulting from their eating fish with Sobolev. and Khromova, 1971). A numberof Eustrongyloides sp. were described by- other books has been written on various Locke, DeWitt, Menzie, and Kerwin (1964). aspec ts of nematodes, and, for the present Rosenthal (1967) fed wild plankton to pur|K>ses, I mention those by Chitwood and larval herring and many of these young fish Chitwood (1950) and by Bird (1971) only. apparently started dying from larval Information on the striking reddish ascaridoid larvae after about 11 days. The camallanids in Gulf marine fishes has just worms grew rapidly and were quite active. been published (Fusco and Overstreet, After the fish reached 2 cm in length, they 1978). Spirocamallanus cricotus infects became less seriously affected by the worm. shallow inshore fishes. Actually more than More studies of this nature should be con the 13 reported hosts can harbor infections. ducted. Problems arise when using In water 27 meters and deeper, Spiro predatory fish, however, because they camallanus halitrophus infects at least typically cannibalize weakened individuals. bothid flounders and a cusk-eel. Fusco Consequently, several predatory fish cannot (1978b), using isoelectric focusing and occupy the same aquarium and at the same spectrophotometric characterization, has time provide meaningful results. differentiated hemoglobins of the Atlantic croaker, male Spirocamallanus cricotus, and female Spirocamallanus cricotus. He Acanthocephalans (1978a) also obtained experimental Yamaguti (1963b) listed the known infections of this worm in a harpacticoid acanthocephalans and presented keys to the copepod (Tigriopus californicus) and in the higher taxa. Golvan (1969) provided de white shrimp. scriptions and keys to the species of Adults of the common Thynnascaris paleoacanthocephalans, a major group reliquens were described by Norris and infecting fishes. Authorities do not agree Overstreet (1975). Those authors (1976) also about the higher classification of acantho reported larval members of that genus in cephalans, even though about 1000 species invertebrates and the ability of at least one have been described. W. Bullock (1969) dis member to invade mice. Ebert (1976) cussed the anatomy of these worms and examined this latter matter in more detail. discussed many features in relation to their Thomas Deardorff of GCRL hopes to relate use in classification and systematics. A more a few larval species of Thynnascaris with recent treatment on the phylum was pre their adult forms. Much has been written sented by Schmidt and Roberts (1977). about the disease anisakiasis, especially in One of several papers on acantho Japan. Oshima (1972) gave a good review cephalans covers most of the marine fish which has been updated by several workers species in the northern Gulf (W. Bullock, (e.g., Jackson, 1975; Margolis, 1977;and in 1957). Buckner, Overstreet, and Heard progress by John Smith of the Department (1978) reported intermediate hosts for Technical Aspects 115

Tegorhynchus furcatus and Dollfusentis species remains incomplete. Menzies, chandleri, and Overstreet is preparing a Bowman, and Alverson (1955) pieced several-year ecological study on the latter together the cycle of Lironeca convexa on species in the Atlantic croaker. the Pacific bumper. Presumably free- swimming juveniles find the appropriate host, infest and feed on gill tissue, molt Crustaceans into a male, transform into a female, mate, Kabata (I970) and Schmidt and Roberts and produce young as a commensal in the (1977) treated many aspects of crustacean host's mouth. A similar progression does parasites. Kabata also has other books in not occur for all species. progress which should be classics. Schultz's Two of the most troublesome copepod (1969) key can be used to identify most groups to identify and understand arc the American isopods, and Yamaguti's (1963c) ergasilids and caligids. Roberts (1970) and book lists and illustrates most piscine Johnson and Rogers (1973) provided keys copepods. and data on the tiny ergasilids, and Paperna The example discussing altered behavior and Zwcrner (1976) gave a good example of of infested menhaden was by Guthrie and ecological aspects of an infestation of Kroger (1974), and that on infested and de labracis on the striped bass. bilitated gar was by Overstreet and Howse Margolis, Kabata, and Parker (1975) pro (1977). vided a catalogue and synopsis on the many- Life cycles of isopods on fishes need species of Caligus, and Cressey (1967) considerable attention, especially in light of reviewed pandarids from elasmobranchs. the potential economic loss to cultured fish Myron Loman has investigated caused by isopods. A group of isopods not Lemaeenicus radiatus in my laboratory. mentioned in the first section because mem Using the rock seabass as an intermediate bers do not appear to be a problem in the host, he obtained results similar to Shields northern Gulf of Mexico is the Gnathiidae. (1970), who used the black seabass from the They may be a threat in south Florida. In Atlantic coast. Copepodid larvae infest the the Red Sea, one isopod that can bring fish fish, pass through a chalimus stage, mate culture to a halt has been investigated (the male breaks its frontal filament and (Paperna and Por, in press; Paperna and transfers its spermatophores to the female), Overstreet, in press). The larval gnathiid leave within 3 to 5 days, infest another fish, (praniza), unlike the adult, obtains a blood mature, and produce eggs within a week. meal from almost any fish, leaving that fish The Gulf killifish acted as a good final host, with integumentary wounds, anemic, and but readily succumbed when more than a often dead. The larva feeds on fluid from a couple of individuals infected it. Since over fish's gills or skin for about 2 to 4 hours at 100 infective larvae can infest a bass at one night and may do this three times before time, a few killifish left with a bass in an molting into an adult. A variety of fish aquarium will usually die unless removed at species maintained in cages near shore in proper intervals. 1 to 2 meters of water attracted the isopod, Considerable data concerning biological but those in cages from deeper water of 6 to aspects of copepods have been gathered. 8 meters about 100 m offshore did not. Once Cressey and Collette (1970) provided a good attacked, an individual fish rarely becomes example of copcpod-needlefish relation infested again. After obtaining the blood ships which could act as a guide for further meals, the isopod molts to an adult in about works on other copepod-host relationships. a week. Eggs develop in the female's brood By examining the stomach contents of re- pouch for about 3 weeks and then the larvae, moras, sharksuckers, and other diskfish, numbering about 90 in a full-sized female, Cressey and Lachner (1970) discovered that emerge. Larvae feed on fish after about 9 to copepods appeared to play different roles 10 days of development and live in the mud as the food source for different diskfish. in shallow habitats. Also, age of fish determined food prefer Information on life cycles of cymothoid ences. Young Remora remora ate more 116 Marine Maladies? parasites than older individuals, whereas By considering natural phylogenetic older Remora osteochir ate more than groups of both crocodilians and crocodilian younger fish. Bernett-Herkes (1974) found digeneans, Brooks (dissertation in progress. that the presence of some copepods from University of Mississippi) presented evi dolphin (fish) appeared to be influenced by dence that both groups evolved together. size of host and by the presence of other About 200 million years ago all land masses copepod species. that harbor crocodilians today were joined Many argulids prove difficult to identify together as one body of land (North using old literature. Most likely, such pro America, South America, Africa, Asia, blems should be solved by preliminary and and Australia). By the end of the next 50 future keys by- Cressey (1972). million years, that land mass had com pletely broken up. Because several species of the worms belonging to the same genera occur dispersed in most regions today and MISCELLANEOUS HOSTS because intermediate hosts of most groups The American Alligator cannot tolerate saltwater, the actual or The alligator harbors parasites that, for ancestral digeneans appeared to already be the most part, can be seen with the naked infecting crocodilians 200 million years eye. Large nematodes in the stomach may- be ago. one or a combination of at least four adult A stronger relationship between croco ascaridoids. A new species of Goezia is being dilians and birds than between crocodilians described by Deardorff and Overstreet, and and other reptilians is suggested by the the other three are being reviewed by John presence of strigeoids, clinostomes, and Sprent of the University of Queensland. His echinostomes inhabiting both crocodilians works will include most known crocodilian and birds, but not other reptiles. Brooks nematodes. will provide details of the association in the The most conspicuous digeneans are the near future. acanthostomes. Sometimes hundreds of The presence of the turtle leech the nearly 1cm long species inhabit a single Placobdella multilineata on the alligator alligator. Brooks and Overstreet (1977) has been reported only recently (Forrester described or presented supplemental data on and Sawyer, 1974) and then from Florida. In the three known species from the United Louisiana, it can be seen commonly on States. Other digeneans occur in lesser gators in freshwater. Just as in Florida, the numbers in hosts inhabiting fresher waters. hosts have a species of Haemogregarina Brooks, Overstreet, and Pence (1977) report in the blood which could be transmitted by ed the proterodiplostomes, and Brooks and that leech. Overstreet (1978) described the only The pentastome Sebekia oxycephala liolopid. The digenean Odhneriotrema occurs sometimes in large numbers in the incommodum from southern Florida de lungs of alligator hosts. It also occurred in serves comment because of its unusual the liver and mesentery of some hosts. The location even though it does not infect alligator acquired its infections from a alligators in Mississippi and Louisiana. variety of fishes (Venard and Eangham, This large worm attaches firmly to the 1941; Dukes, Shealey, and Rogers. 1971). pharynx or buccal cavity of its host, and an Self (1969) presented a review and biblio observer can see it by using extreme care. Its graphy of pentastomes in general. life cycle presents a good example of a parasite that infects a specific sex of host. The Florida gar (Lepisosteus Birds platyrhincus), which does not occur in Symbionts and diseasesof birds have been Mississippi, harbors the encysted meta- treated extensively in a book edited by- cercariae primarily in the ovary, hence a Davis, Anderson, Karstad, and Trainer preponderance of infections in the female (1971). Another general book byRothschild gar (Leigh, 1960). and Clay (1957) placed more emphasis on Technical Aspects 117 the arthropods. In order to appreciate the the direction of Pence. wealth of information available on the Pence (1973a) reported the pe-ntastonu- helminths of just the Anatidae. one can in Reighardia sternae from gulls and terns in spect the bibliography and catalogue by- Louisiana. It also infects the lungs and air McDonald (1969a; 1969b). Sources to sacs of at least the- laughing gull and identify helminths are basically the same common tern in Ocean Springs. Rather as for helminths infecting fishes. unique in that it infects birds, it may also Marine and estuarine fish play an im be unusual in not requiringan intermediate- portant role in transmitting helminths to host (Riley. 1972a). However, like the birds. As already shown earlier, they readily species in the alligator. Reighardia sternae transmit numerous digeneans and nema may also be transmitted by fishes (Bakke. todes to birds. To a lesser extent, these 1972). Those interested in the variety of fishes transmit cestodes, acanihoccphalans. feeding mechanisms that parasites use- to and other helminths. As an example, ingest host blood should consult papers by killifishes can be cited for hosting cestodes Riley (1972b; 1973) who reported observa belonging to the genus Parvitaenia tions and described the method used by this which infect ibis, herons, pelicans, and pentastome. other birds as determined by Richard Heard In order to identify and study arthropods, (personal communication) and the roughly a reader could initiate his literature search 5 cm long acanthocephalan Arhythmor- using publications by Emerson (1972a: hynchus frassoni which infects the clapper 1972b; 1972c) for lice. Coolc-y and Kohls rail (Nickol and Heard, 1970). (1945) for ticks. Pence (1972) for subcu Much information known about parasites taneous hypopial miles, and Pence (1975) of local birds has been reported by Danny- for nasal mites. The reference to the bloody- Pence of TexasTech University whostudied ulcers produced by a louse in the- mouth of the numerous nasal mites from Louisiana the white pelican was by Wobeser, Johnson, birds (Pence, 1973b; 1975). In addition to and Acompanado (197-1) and that to the those parasites, he reported on a variety of possible evolutionary history of flamingo- worms that have- importance foi different lice- was by Rothschild and Clay (1957). reasons. As examples, the digenean This latter relationship among the Amphimerus elongatus occurred in the flamingos and other gioups it-mains un thousands in the- bile ducts of the- double- settled. Osteological evidence based on a crested cormorant, causing extensive combination of characters of fossil cirrhosis and other pathological alterations flamingolike waders from the Lower Eocene (Pense and Childs. 1972), and the nematode supports the- relationship of flamingos Tetrameres aspinosa encysted in pairs in the with anseriforms (ducks) and also with proventriculus of the snowy egret (Pence, charadriiforms (shorebirds) (Feduccia. 1973c). Nothing was particularly notable 1976). In fact, similarities in cestodes occur about that tetramerid infection except that between flamingos and shorebirds (Baer, anyone examining the proventriculus and 1957). However, the consensus of most stomach of any birds should be aware of the present-day ornithologists (Oscar T. Owrc, presence of those encysting nematodes. The personal communication) supjxms Sibley embedded blood-red female, rather than and Ahlquist (1972) who believe that fla looking nematode-like, is extended greatly mingos, while related to ducks, align closer about the midbody. Either the males occui with Ciconiiformes (herons), and that, as encysted with the females in fibrous cysts or suggested by Mayer and von Keler (see re free in the stomach or proventriculus, de view by Sibley and Ahlquist). the lice pending on the species. The conspicuous transferred recently from waterfowl to cysts with red worms can be seen through flamingos. As possible tools to help solve host tissue, appearing at first glance like the problem, the affinities of quill mites hemorrhagic lesions. An extensive review (syringophilids) and nasal mites (derman- of the group is in preparation by Tony yssids) from flamingos should be investi Mollhagen (1977. abstract) working under gated. 118 Marine Maladies? Some important protozoans, bacteria, and host-mosquito, it can be handled easily, and viruses of wild birds have been treated in the preparasitic juvenile can be reared and some detail by Davis, Anderson, Karstad, collected in large numbers. Preliminary- and Trainer (1971). Levine (1973) covered field applications of 1000 larvae per square many more protozoans, including meter killed most of the mosquitoes, and the Sarcocystis rileyi. worm became permanently established in some of the sites (Petersen and Willis, 1972). The illustrated midge with the mermithid Marine Mammals came from Simmon's Bayou near Ocean Marine mammalian parasites have been Springs when the salinity was 6 ppt (14 described in a book (Delyamure, 1955) and April 1977)and the associated animals con compiled into a checklist (Dailey and sisted primarily of estuarine species. Brownell, 1972) in another book that pro A classic work on nematomorphs by May vides a wide range of diverse information on (1919) described the life histories of two these mammals (Ridgway. 1972). An an sjx»cies, and both Pennak (1953) and Cheng notated treatment of porpoise parasites (1973) provided a general treatment of the (Zam, Caldwell, and Caldwell, 1971) group. Born (1967) reported Nectonema supplements a review on this host's com agile from the grass shrimp. mon diseases encountered by veterinarians The leech Stibarobdella macrothela was (Sweeney and Ridgway, 1975). Lowery recently treated by Sawyer, Lawler, and (1974) discussed marine mammals in the Overstreet (1975) and by Penner and Raj northern Gulf, Gunterand Overstreet (1974) (1977). A few turbellarians were discussed reported parasites from a dwarfsperm whale as symbionts of oysters; Jennings (1974) in Mississippi Sound, and I have seen all the discussed many more and showed pro dolphin parasites discussed earlier in hosts gressive stages from totally free-living from Mississippi. David Gibson and Rod to parasitic. Bray have designed a display of the large Barnacles from bands on the dusky shark species of Crassicauda for the British were collected by Tom Mattis while in Museum (Natural History). search of elusive tapeworms. William A. The possible role of campulids in single Newman of Scripps Institution of Oceano stratidings was suggested by Ridgway and graphy identified Conchoderma auritum Dailey (1972). Perhaps multiple strandings and Cindy van Duyne of North Central could result from a dominant leader being College in Naperville, Illinois, identified affected by parasites and the subordinates the other two. According to Newman (per following that leader to beach themselves sonal communication), Conchoderma regardless of the consequences. Other auritum usually attaches to sessile parasites also have the potential to interfere barnacles on whales, but sometimes occurs with the "sonar" system in these animals. on baleen or on the teeth of toothed cetaceans when their lips are damaged. Newman got one off a submarine. Dawson (1969) previously reported the only recordof MISCELLANEOUS SYMBIONTS Conchoderma virgatum from the Gulf of A review of the mermithids was presented Mexico and listed cases in other parts of by Nickle (1972). Petersen (1973) is one of the world where the organism attached several who have reported on the use of these directly to fishes and to parasitic copepods. nematodes in controllingmosquito popula Unexpectedly, all hosts are not those that tions. Presently, one species, Reesimermis bask or remain in surface water where one nielseni, has been especially fruitful for might consider the barnacle's larvae most this purpose. It feeds on the hemolymph of able to infest hosts. and kills over 20 species of mosquitoes. The Biting gnats (Culicoides spp.) that occur larva can successfully infect a large in the northern Gulf have been studied from percentageof a mosciuitopopulation. Since several localities, and their activities differ the worm does not feed after it leaves its some from place to place (Khalaf, 1967. Technical Aspects 119

1969; Kline and Axtell. 1976). Because there tides (tides with smallest differences between was a dense population of Culicoides high and low tide occurring after the first hollensis last fall (1977) and because the and last quarters of the moon) at night weather has been so nice during the early between late June and early September. Us weeks of this spring, the present population ually rain precedes them, and the well-de of gnats has me satisfied being inside fined affected water has a tea color. Ap writing this booklet rather than being parently the proper nutrients allow suc outside. cession of a phytoplankter that might According to Robert C. Lowrie, Jr. produce a similar toxin to that of dino *r (personal communication. Delta Primate flagellate blooms of a red tide ora condition Center), our populations of gnats have not that otherwise creates an unhealthy water been implicated in transmitting viruses nor mass. These jubilees certainly demand cri hosting any local filarid nematodes. Lowrie tical investigation! has examined many individuals and never Numerous papers deal with red tide. Not seen natural filarial infections; however, he until recently, however, has anyone found local gnats toexperimentally support critically examined dead and dyinganimals. some exotic filaria. Quick and Henderson (1974, 1975) report such findings, and Forrester and others (1977) go into more detail and speculation concerning an epizootic affecting lesser scaup. FISH-KILLS AND Sources of pollution are being examined MISCELLANEOUS DISEASES more extensively in recent years Ixxause of Often a fish-kill results from a an increased concern for the environment. combination of factors. Comments on the Overstreet and Howse (1977) briefly- physiology of fish related to a cold-kill were reviewed pesticides, heavy metals, and other treated by Overstreet (1974). Guntcr (1941) sources of pollution and possible stress- and Moore (1976) are two of several who related diseases in Mississippi estuaries. have reported on fishes killed by the cold in Pollution-sources from other regions have Texas where such mortalities occur more also been documented (e.g., Alabama by frequently than in Mississippi. May (1973) Crance, 1971). More extensive studies have reported on the occurrence of jubilees in dealt with potential and actual problems in Mobile Bay and how the first account was in Chesapeake Bay (McErlean, Kerby, and 1867 even though he searched documents Wass, 1972). Sindermann (personal dating back to 1821 which should have communication) is preparing a review of mentioned early periodic fish-kills if they various diseases associated with aquatic had been present. According to May, the pollution. reason for the increasing frequency of Deaths and disease in the natural marine jubilees appears to be the decreasing ability environment are hard to document and the for the water of Mobile Bay to transport, causes even harder to determine. Usually a deposit, dilute, and assimilate the amountof combination of factors act together. One of organic matter in the bottom water. Most of those factors is often temperature. Some the matter comes from natural sources of fish, especially pelagic ones, swim faster wood and leaves, but is supplemented by the when the temperature is either raised or increased amount of domestic wastes. decreased under experimental conditions The jubilees in Mississippi, according to (Olla, Studholme, Bejda, Samel, and Charles Lyles (personal communication, Martin, 1975). Increases in localized water Gulf States Marine Fisheries Commission), temperatures are rapidly becoming normal and possibly those in Alabama, too. result biproducts of modern technology (e.g.. from plankton blooms. Lyles has observed Cairns, 1972). Primarily because of power many jubilees along Bellefontaine Beach plants, critical research has been conducted since the late 1930'sand found several items on the effects of fish by increased tempera common to all. They occur during neap ture combined with chlorine (Meldrin, 120 Marine Maladies?

Gilt, and Petrosky. 1974) and with other genetics and mutagenesis of fishes goes into chemicals (Cairns, Health, and Parker, considerable detail on many aspects of 1975). genetics (Schroder, 1973). Investigations In addition to natural mortalities caused into chromosomal anomalies in marine by a rapid drop in temperature, mortalities fishes have been recent and very fruitful can also result from sudden rainfall and (Longwell, 1976). Apparently LongwelTs storms. Dawson (1965) documented deaths methods of detecting anomalies allow of the (Branchiostoma caribaeum) evaluation of material from museum in Mississippi following heavy rains with a collections and thereby a means of subsequent drop in salinity. Most likely- comparing collections from past years when other animals also die under sue h adverse the water was relatively clean with those conditions. Storms can kill fish, especially collected recently from the same regions transient species not normally occupying after water-quality had deteriorated. She shallow inshore regions (Robins. 1957).The (personal communication) has been fishes accumulate sediment in their gill compiling much more extensive data that chambers, and their gills fray. Regular corroborate her earlier findings. inhabitants of shallow, wind-exposed Nutrition of fish has been covered in regions appear capable of withstanding detail in a book edited by Halver (1972),and considerable turbulence. that book gave a number of examples and Human activities have now stressed the references which should guide any student environment to a greater degree than interested in different aspects of nutrition. corresponding means have been designed to Examples of scoliosis (spinal column protect that environment. Our wastes and twisted in a sideways direction) such as that other activities are taking their toll on the shown for the striped mullet (Mugil environment. Unfortunately, only when cephalus) as well as cases of lordosis (spinal fish die in large numbers do people worry curvature tending toward a vertical about the problems. Would many people be direction) are presented. Diets deficient in concerned about dumping sewage sludge in or ascorbic acid produce both the New York Bight had not there- been an conditions experimentally as does a lack of extensive kill (Bullock. 1976)? Dredging, calcium phosphate or an infection with a bulkheading, and filling in natural marshes few different bacteria and parasites. Another seldom cause extensive fish-kills, but those book (Neuhaus and Halver, 1969) also activities nevertheless decrease numbers of covered nutrition, metabolism, genetics, animals (e.g.. Trent, Pullen, Proctor. 1976). and cancer. Representatives of most tumors Even flushing detergents intoour waters has from fishes that have been studied scientifi serious effects (Abel, 1974), but these effects cally have been deposited in the "Registry of seldom meet public view. Man needs Tumors in Lower Animals" at the National sounder management programs, and Museum of Natural History. John perhaps these should be oriented toward Harshbarger, who directs that registry and protecting important ecosystems rather identifies most of the neoplasms, has than protecting specific species. Cairns published extensively on the available (1975) commented on this strategy and on material (e.g., 1977).That paper occurs with the fact that our actions do not match our several others in a volume on "Aquatic public statements. In order for substantial Pollutants and Biological Effects with changes to occur, the life styles of people Emphasis on Neoplasia" (Kraybill, Dawe, must also change. Harshbarger, and Tardiff, 1977). Edwards As pointed out several times, the most and Overstreet (1976) reported on the important factor in transforming an neoplasms in the striped mullet, and infection into a disease is stress. A readable Overstreet and Edwards (1976) also reported book by Wedemeyer, Meyer, and Smith benign fibromas in the southern flounder (1976) on this problem provides a valuable and sea catfish and reviewed the obser background in regard to fishes. vations of other tumors from the northern A recent compilation of contributions on Gulf. Acknowledgments 121

That many tumors and other diseases are (1962) and Moore and Posey (1974) described caused by environmental contaminants is and reviewed many abnormalities in the based almost entirely on circumstantial hogchoker. Norman (1934) and Gudger evidence. Aquatic examples have been (1934) laid the foundation for discussing documented primarily from freshwater anomalies in flatfishes, and that foundation habitats because such habitats are often continues to be built upon today. excessively polluted and because specimens Est ut omne hoc vobis stercus sit, are easier to collect from these confined sed mihi panis et butyrum est. regions than from open marine and estuarine ones. Edwards and Overstreet (1976) suspected the tumor on mullet might result from pollutants. Mearns and Sherwood (1976) also considered this ACKNOWLEDGMENTS possibility for skin tumors in a southern California flatfish, but did not think I am grateful lo the many people who helped make improvements in municipal waste treat this guide possible, and the addresses of those not from the Gulf Coast Research Laboratory are indicated. ments would reduce the prevalence of Several people read different portions of the text and tumors unless the improvements increased made comments. C.E. Dawson. A.R. Lawler. and the number of young fish. They (Sherwood R.W. Heaid (Dauphin Island Sea I.all) read the entire and Mearns. 1977), however, presented text; J.A. Quirk. Jr. (Dow Chemical Company. strong observational and experimental Freeporl. Texas). P.T. Johnson (National Marine Fisheries Service. Oxford. Maryland), and J.A. Couch evidence linking chlorinated hydrocarbon (Environmental Protection Agency. Gulf Bree/c, pollutants (e.g., DDT) with fin-erosion in Florida) read the portions on invertebrates; and others the same flatfish exposed to the discharged read specific- pans: F.M. Bayer (Smithsonian Institu municipal waste water. tion) (zoanthids); H.M. Perry (blue crab): I'M. Van Many examples of injuries that cause Devcnder (penaeid shrimps); W.J. Demoran. E.W. Cake. Jr.. J.T. Ogle. A.P. Chestnut, and K.A. McGraw anomalies have been indexed in the (oyster); T.L. Deardorff and T.E. Mattis (fishes): and bibliographies by Dawson(l964; I966; I97I) D.B. Pence (Texas Tech University, Lubbock. Texas) and Dawson and Heal (1976). Bird (1978) (birds). Other assistance was provided by R.G. Palmer. reported straps encircling carcharhinid T.A. Miller. R.E. Buxton. T.L. Deardorff. T.E. sharks, including a postscript on the Mattis. D.R. Brooks, A.C. Fusco. M.A. Solangi. L.A. Toomey, S.L. Shepard. I..B. Ross, and V'.D. Jones affected dusky sharks mentioned in the (Mississippi-Alabama Sea Grant Consortium). present treatment of barnacle symbionts. CA. Foster and R.E. Buxton pi (pared most of the The Atlantic croaker with its rubber band black and white prints. Negatives or other prints were was reported by Oversteet and Lyles (1974). provided by J.A. Couch (Figs. 36. 46. 47. 19. and 50). Even though a few fishermen may P.T. Johnson (Figs. 44 and 45). A.P. Chestnut (Figs. 15 and 16). CA. Foster (Fig. 63). M.A. Solangi (Figs. 13. deliberately place a band about a fish as a 54 - 57. and 72). and T.E. Mattis (Figs. 186 - 190). joke, most fish ring themselves naturally. B.C. Heard (Dauphin Island. Alabama) drew Figs. 23. Lamont (1961) pointed out the abundance 28, 70. 78. 82. 86. 113, 149, 157. 161. and 164 and of mackerel ringed with contraceptives D.L. Ilolcomb drew Figs. 5 and 48. occurring near sewage effluents. Permission lo reproduce the same or similar figures from previously published works was granted by Dawson's bibliographies cited references Academic Press — Figs. 56 and 57 from Solangi and to all types of anomalies, including those of Lightner (1976) and Overstreet and Van Devender flatfish. According to the literature, reversal (1978); The American Microscopical Society — Fig. in Eutropus crossotus is rare. Taylor, 145 from Overstreet (1971a); American Society of Stickney, and Heard (1973) reported the first Ichthyologists and Herpetologisls — Figs. 91 and 93 from Lawler. Howse, and Cook (1974); American case from Georgia, and James Ray Warren Society of Parasitologists — Fig. 109 from Overstreet in the Fisheries Section at the Gulf Coast (1976a). Fig. 117 from Overstreet (1977b). Figs. 141 and Research Laboratory, who found the 142 from Overstreet (1976b), Fig. 143 from Overstreet specimen photographed above in Back Bay (1970). and Fig. 144 from Overstreet (1971 b);fluc/W«>io/ Marine Science — Fig. 196 from Edwards and of Biloxi has found only one other example Overstreet (1976); Cambridge University Press — Figs. of a reversed fringed flounder, and it 129 and 193 from Overstreet and Paperna (in press); occurred in a pass off Horn Island. Dawson Gulf Research Reports — Figs. 194 and 195 from 122 Marine Maladies?

Overstreet (I974) and Figs. I98 from Overstreet and of the Ascaridoidea, by G. Hartwich. 15 pp. Lyles (I974); The Hclmitithological Society of Farnham Royal: Commonwealth Agricultiiial Washington — Fig. 162 from Buckner. Overstreet. and Bureaux. Heard (1978); The New York Academy of Sciences — ANDERSON. R.C. A.G. CHABAUD. AND S. Figs. 88. 89. 103. and 105 from Overstreet and Howse WILLMOTT (eels.). 1975a. CIH Keys to the Nema (1977); Springer-Verlag — Fig. 80 from Overstreet and tode Parasites of Vertebrates. No. 3. Keys to Genera Weidner (1974); and The Wildlife Disease Association of the Order . Part I. Camallanoidra, — Figs. 25. 51. and 52 from Cook and Lofton (1973). liracunculoidea. Gnathostomatoidea, Physalopter- A number of people provided specimens for me to oidea, Rictularioidea and , by A.G. photograph: A.P. Chestnut (Figs. 12 and 14), D.W. Chabaud. 27 pp. Farnham Royal: Commonwealth Cook (Figs. 25. 51. and 52). T.M. Van Devcnder (Figs. Agricultural Bureaux. 75-77). CD. Getter (Rosenstiel School of Marine and Atmospheric Science. Miami, Florida) (Figs. 150 and ANDERSON, R.C, A.G. CHABAUD. AND S. WILLMOTT (eds.). 1975b. CIH Keys to the Nema 131). R.W. Heard (Figs. 68 and 178), A.R. Lawler(Figs. 90-93. 96-99. 137. and 165-168).M.J. Loman(Fig. 171). tode Parasitesof Vertebrates. No. 1.Keysto Generaof the Order Spirurida. Part 2. , Habrone- . Inc. (Gulfport. Mississippi) (Figs. 130and matoidea and Acuartoidea, by A.G. Chabaud. 58 197). T.E. Mattis (Figs. 71. 114-116. and 121-128). K.A. pp. Farnham Royal: Commonwealth Agrkuliuial McGraw (Figs. 6-11. 17-21). K.R. Melvin (Figs. 33. 35, and 112). J.T. Ogle (Fig. I). 1I.M. Perry (Figs. 30, 31. Bureaux. and 39). J.R. Warren (Figs. 32. 34, 39. and 192). and ANDREWS, J.D. AND W.G. HEWATT. 1957. Oyster some others by summer students. mortality studies in Virginia. II. The fungus disease caused by Dermocystidium marinum in oystcis of Chesapeake Bay. Ecological Monographs 27(1): 1-25. LITERATURE CITED ANDREWS, J.D., J.L. WOOD. AND H.D. HOESE, 1962. Oyster mortality studies in Virginia: 111. ABBOTT. R.T.. 1974. American Seashells. The Marine Epizootiology of a disease caused by Haplospor- of the Atlantic and Pacific Coasts of North idium costaleWood and Andrews. Journal of Insect America. 663 pp. New York: Van Nostrand Pathology 4(3): 327-343. Reinhold. BAER, J.G., 1957. Repartition el cndemieitc des ces ABEL. P.D., 1974. Toxicity of synthetic detergents to todes chez les reptiles, oiseaux et mammifii'-s. In fish and aquatic invertebrates, journal of fish Premier Symposium sur la Specificite Parasitaue des Biology 6(3):279-298. Parasites de Verlebres. International Union of ADKINS. C 1972. A study of the blue crab fishery in Biological Sciences Series B 32:270-292. Louisiana. Louisiana Wild Life and Fisheries Com BAILEY, R.M. (ch.). J.E. FITCH, E.S. HERALD. E.A. mission Technical Bulletin No. 3:1-57. LACHNER. CC LINDSEY. C.R. ROBINS. AND ALDRICH. D.V., 1965. 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S.F. caridean shrimp Palaemonetes pugio to infection by Snieszko). American Fisheries Society Special che adult epibranchial isopod parasite Probopyrus Publication No. 5:82-100. pandalicola. Comparative Biochemistry and P/»y- BECKER. CD.. 1977. Flagellate parasites of fish. In «ofogy52(lA):201-207. Parasitic Protozoa, Vol. 1, pp. 357-416. New York: Academic Press. ANDERSON. R.C, A.G. CHABAUD, AND S. WILLMO'IT (eds.), 1974a. CIH Keys to the Nema- BIGELOW. H.B. AND W.C SCHROEDER. 1948. lode Parasites of Vertebrates. No. 1. General Sharks. In Fishes of the Western North Atlantic. Introduction, Glossary of Terms, by S. Willmolt, Memoirs. Sears Foundation for Marine Research I Keys to Subclasses, Orders and Superfamilies, by (Pi. l):59-576. A.G. Chahaud. 17 pp. Farnham Royal: Common BIRD, A.F., 1971.The Structure of Nematodes. 318 pp. wealth Agricultural Bureaux. New York: Academic: Press. ANDERSON. R.C., A.G. CHABAUD. AND S. BIRD, P.M., 1978. Tissue regeneration in three WILLMOTT (eds.). 1974b. CIH Keys to the Nema curcharhinid sharks encircled by embedded straps. tode Parasites of Vertebrates. No. 2. Keys to Genera Copeia !978(2):345-349. Literature Cited 123 BLACKFORD, S.K., 1966. A Study of Certain Aspects BUCHANAN. R.E. AND N.E. GIBBONS (eels). 1974. of the Ecology and Morphology of lirancliiobdellid Sergey's Manual of Determinative Bacteriology. Annelids Epizoic on Callinectes sapidus. Honors 8th ed. 1268 pp. Baltimore: Williams and Wilkin*. Thesis. Newcomb College. New Orleans. Louisiana. BUCKNER. R.L.. R.M. OVERSTREET. AND R.W. 34 pp. HEARD. 1978. Intermediate hosis for Tegorhynchus BLAKE, J.A., 1971. Revision of the genus Polydora furcatus and Dollfusentis chandleri (Acantho- (torn the east coast of North America (Polychaela: cephala). Proceedings of the Helminthological Spionidae). Smithsonian Contributions to Society of Washington (in press). Zoology No. 75:1-32. BULLA, L.A., JR. AND T.C CHENG (ids.). 1976. 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Axehoel), pp. Ml. vations on Lagenidium callinectes: Isolation and Jersey City: T.F.H. Publications. sporangia! development. Mycologia e>5(2):310-320. BULLOCK. G.I... DA. CONROY. AND S.F. BLAND, C.E., D.C. RUCH, B.R. SALSER, AND SNIESZKO. 1971. Bacterial Diseases of Fishes, D.V. LIGHTNER, 1976. Chemical control of Book 2A. In Diseases of Fishes (eds. S.F. Snic-s/ko and Lagenidium, a fungal pathogen of marine H.R. Axelrod). pp. 1-151. Jersey City: T.F.H. Publi Crustacea. 38 pp. UNC-SG-76-02. Raleigh: Univer cations. sity of North Carolina Sea Gram Piogram. 1235 BULLOCK. W.l... 1957. The acanihocephalan Burlington I.aboratories. North Cirolina Slate jKirasilesof the fishes of the Texas coast. Publications University. of the Institute of Marine Science l(2):278-283. BORN, J.W., 1967. Palaemonetes vulgaris (Crustacea, BULLOCK, W.L., 1966. gadi sp.n. from ) as host for the juvenile stage of the rectum of lite pollock. Pollachius virens (I... Neclonema agile (). 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Gulf of Mexico. Proceedings of the Helminthologi shrimp and the blue crab (Callinectes sapidus). cal Society of Washington 43(2): 160-171. Journal of Wildlife Diseases 9(2):154-I59. CAMPBELL. R.A. AND J. CARVAJAL. 1975. A COOK. D.W. AND S.R. LOFTON. 1975. Patho revision of some trypanorhynchs from the western genicity studies with a Streptococcus sp. isolated North Atlantic described by Edwin Linton. 77ie* from fishes in an Alabama-Florida . Journal of Parasitology 61(6>:)016-1022. Transactions of the American Fisheries Society CARRIKER. M.R.. E.H. SMITH. AND R.T. WILCE IO-l(2):286-288. (eds.). 1969. Penetralion of calcium carbonate COOLEY. R.A. AND G.M. KOHLS. 1945. The genus substrates by lower plants and invc-itc-biates. Ixodes in Noith America. National Institute of American Zoologist 9(3. ed. 2):629-1020. Health Bulletin. U.S. Public Health Sen-lie 181: CHENG. T.C. 1967. Marine molluscs as hosts for 1-216. symbioses wilh a review of known iKirasitt-s of CORKERN. CC. JR.. 1970. 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Parasitic barnacles in newly pioposed phylogenelic scheme- of classifi Mississippi estuaries wilh special iclcie-nee- lo cation for the pioiistan phylum Ciliophora. Loxolhylaius texanus Boschma in the blue crab Systemalu Zoology 23(1):91-138. (Callinectes sapidus). Proceedings of the Twenty- CORLISS. J.O.. 1974b. Remarks on theconi|iositiou of Second Annual Conference. Southeastern Associ the huge ciliate class Kinelofiagmophoia de ation of Game and Fish Commissioners, pp. 272-275. Puyiorac et al.. 1974. and recognitor! of several new CHRISTMAS. J.Y. AND D.J. ETZOLD (eds.). 1977. taxa therein, wilh emphasis on the ptimiiivc order The shrimp fishery of the Gull of Mexieo United I'riiiKHiliaticla n. ord. The Journal of Protozoology Stales: A regional management plan. Gulf Coast 2l(2):207-220. Research Laboratory Technical Report Series COUCI I, J.A.. 1966.'Two peritrichousciliates fiom the No. 2:1-128. gills o( the blue crab. Chesapeake Science 7(3): CLAMP. J.C, 1973. 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GLOSSARY

The following definitions are included to carapace - The hard outer protective cover aid those not familiar with technical terms. ing of some animals. In crustaceans, it One desiring more information on specific covers the head and gill region. terms dealing with parasites should refer chitin - A skeletal material of arthropods to one of the cited works or some other and other invertebrates that decomjDoses treatment of the group in question. Too to specific chemicals (glucosamine and large a number of vertebrate and inverte acetic acid), if boiled with concentrated brate host-groups are mentioned in the text hydrochloric acid. When impregnated to discuss or classify here; therefore, a reader with calcium salts, it may help form a wanting more information on a host should firm exoskeleton. examine an encyclo|X"dia. a book on ihe chlorophyll - Any of several pigments general group in c,uestion, or specific capable of jjhotosynthesis. They provide papers, several of which have been cited in the green and yellow colors of many the text. plants. apron of crab - The thin abdomen which is chloroplast - The structure containing folded forward on the crab's underside; chlorophyll embedded in a cell. it is sometimes called the tail. chromatophore - A pigment-containingcell benthic - Living in. living on. orreferring to that by exjjansion or contraction can ihe bottom. change the overall color of an organism. 138 Marine Maladies? community (biotic) - The group of species humoral-cellular mechanisms - When re of plants and animals living in and char ferring to , responses are both acteristic of a given habitat. blood-mediated (humoral) and cell- cuticle - The noncellular (therefore non mediated. Antigenic responses involve living), usually horny, protective outer both systems. covering of many invertebrates produced hyaline - Refers to being translucent or by the animal. transparent without the presence of fibers disease - z\n abnormal condition of an or granules. organism or part that impairs normal hyperparasite - An organism which para physiological functioning. sitizes another parasite. estuary - The brackish water regions of and /mycelium - The mycelium is the near river mouths influenced by tides. vegetative filamentous stage of a fungus, and an individual branch is called a fibroblast -A connective-tissue cell that can hypha. produce collagen, the primary compon ent of scar tissue. inclusion body - A particulate body found in cells of tissue infected with a virus. fish)fishes - "Fish" may be singular for a species or an individual or plural when infection!infestation - An infection is the referring to more than one individual of invasion or state resulting from an inva one or more species. "Fishes" is used sion by a parasite or a pathogen into a when referring to two or more species, host. An infestation is an external rather disregarding the number of individuals. than internal invasion. If both internal The term for a group of individuals com and external organisms occuron one host, prising a variety of species used herein is all the associations are collectively refer "fish." but some ichthyologists prefer the red to as infections. Some biologists, how term "fishes." ever, restrict the term "infestation" to either internal or external associations free-living - An organism or stage not with metazoans. Neither an infection nor symbiotic with a host; the organism may an infestation necessarily implies disease. be parasitic during one stage in its life history and free-living in another. instar - A larval stage of an insect character ized by the animal's size and form between gamete -The maturesperm orovum capable molts. of participating in fertilization. intermediate host - A host in which a larval hemoglobin - One of several pigments parasite develops, but not to sexual used to transport oxygen, consisting ofan maturity. iron-complex coupled to a protein. It long-line - A usually main occurs in the red blood cells of most tained by an anchor and buoy with vertebrates and in body fluids or cor numerous, spaced, hooked lines. puscles of a variety of nonrelated invertebrates. lorica - A secreted noncellular (therefore non-living) protectivecase. Theexamples hemolymph!hemocytes - Hemolymph is in the text all involve ciliate protozoans. the circulatory fluid that bathes tissues of some invertebrates that do not have the measurements - For those confused about closed found in verte metric units, the following aids might brates. It is functionally comparable to help. blood and lymph of vertebrates. The multiplied by blood cells are called hemocytes. the following number is host-specificity - The degree to which a parasite can mature in more than one centimeters 0.3937 inches host species. If a parasite infects only a inches 2.54 centimeters single species, it is highly host-specific. feet 30.48 centimeters Glossary 139 liters 0.2642 gallons prevalence! incidence - Prevalence is the gallons 3.785 liters degree to which a disease or infective 1 meter = 100 centimeters (cm) = agent occurs. It is often measured as the 39.37 inches percentage of a population affected with a 1 cm =10 millimeters (mm) = particularorganism ata given time. Many 0.394 inches biologists define incidence identically. 1 mm = 1000 microns (u) More precisely, the term "incidence" 0.039 inches indicates the rate of occurrence of new- cases of a particular infection in a The diameter of a human headhair varies population. among individuals; those of a few friends range from 60 to 80 // wide. reservoir host - An organism serving as a source of infection for a specificorganism A common wooden pencil is about 7 mm by harboring the infectious agent. (5/32 inch) wide. resistance - The ability of an organism to A penny is 19mm wide by about 1mm thick. withstand the effects of physical, chem A stick of gum is 75 mm (7.5 cm or about ical, and biological agents which might 3 inches) long. otherwise debilitate it. A 10 ounce (about 0.3 liter) Coca-Cola bottle salinity - The sum of the various salt is 24.5 cm (9 21/32 inches) high. components in seawater usually repre metabolic - Pertaining to the complex of sented as parts per thousand (ppt). Open physical and chemical processesinvolved ocean salinities remain about 35 ppt (3.5% in maintaining life. salt), and in Mississippi Sound, salinity necrotic - Refers to the pathologic death of values usually range between 6 and 15 living tissue while still on a living body as ppt depending primarily on the direction opposed to that which continually dies and force of the wind. and is sloughed. sclerotized - Hardened by substances other niche - The position or status of an than chitin. organism within its community resulting serum!plasma - Plasma is the watery fluid from structural adaptations, physiolo containing salts, proteins, and other gical responses, and innate or learned organic compounds in which blood cells behavior. are suspended. After the blood clots and photosynthesis - The synthesis of simple loses many constituents, the clear organic matter from carbon dioxide and remaining fluid is serum. water, using light as the energy source. sign'symptom - A sign is any objective phylogenetic- Referring to theevolutionary evidence of a disease or disorder, as development of a plant or animal. opposed to a symptom, which is the phylum (pi. -la) - A primary taxonomic subjective complaint of a patient. division of the animal (or plant) king sp. - Abbreviation for species, and when dom. As an example, snails, clams, used in conjunction with a generic name, , and octopus all belong to it indicates the identification of the different classes in the phylum Mollusca. species is unknown or uncertain. If more plankton- Thefloating anddrifting aquatic than one species of a genus is being organisms whose primary movements referred to, spp. is used. result from water movement rather than spent - Referred to in above context as their swimming efforts. depleted of most reproductive products. prepotent period - That period between spore - A term defining a different structure invasion by a disease-agent and demon for different organisms. Typically a stration of disease ora parasite in the body single - or few-celled resting or resistant (such as by eggs or cysts in feces). stage produced asexually. 140 Marine Maladies? substrate/substratum (pis. -tes, -ta) -A vector - An invertebrate or in some cases substrate is the material or substance . wind, water, or other agents which upon which a chemical enzyme acts, transmit a parasite or disease organism, whereas a substratum is the underlying usually to a vertebrate recipient. If material on which an organism grows or development of a parasite occurs, the host attaches. is called an intermediate host unless systemic - Pertaining to the entire body, development includes sexual repro such as an infection with a bacterium duction and then it is called an dispersed through the body by the blood invertebrate host. Man is actually the stream. intermediate host for malaria organisms which have their sexual stage in tumor'cancer - "Tumor" refers to a mosquitoes. swelling serving no physiological func tion; it may be a neoplasm, a parasitic zooid - An individual forming part of a outgrowth, or any other growth. A colony in the Protozoa, , and neoplasm may be benign or malignant, other groups. A zooid can specialize in the latter being characterized by its ability reproduction, feeding, food capture, to invade tissue and metastasize to new protection, or locomotion. sites. Typically, only a malignant zoonosis - A disease of invertebrates or neoplasm is referred to as a cancer. vertebrates other than man which may be transmitted to man.