•

IIIC'At

Identification I Host Sites

and Biology of Parasites

Infecting Juvenile (So/mo s%r) , , • in the Miramichi River s.'Jstem •• • by G.M. Hare • M.D. B. Burt '.

FISHERIES AND MARINE SERVICE SERVICE DES PECHES ET DES SCIENCES DE LA MER TECHNICAL REPORT No. RA PPORT TECHNIQUE N° 581 1975 Environment Environnement 1+ Canada Canada Fisheries Service des peches and Marine el des sciences Service de la mer Technical Reports

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'I".OCHNICAL REPORl' NO. 581 RAPPORl' TOCHNI(XJE !P. 581

(Numbers 1-456 in this series were issued (Les nt.lItEros 1-456 dans cette serie furent

as Technical Reports of the Fisheries utilis~s oamme Rapports Techniques de l'office Research Board of Canada. The series des r echerches sur les p€cheries du canada name was changed with Report nunber 457) • Le nom de la serie fut change avec Ie rapport numero 457).

Identification, Host Sites and Biology of Parasites Infecting Juvenile Atlantic Salnon (Sa lmo sa lar ) in the Miramichi River System, I'Jew Brunswick 1

by

G. M. Hare Department of the Environment Fisheries and Marine Service Biological StatiOi.1, St. Andrews, N. B. Effi 2XO and M. D. B. Burt Departrrent of Biology University of New Brunswick Fredericton, N. B.

This is the eighty-seventh Ceci est Ie quatre-vingt septiE:!rcE Technical Report fran the Rapport Teclmique de la Direction de la Research and Developuent Directorate Recherche et Developpernent BiolC>g'ical Station Station biolC>g'ique St. Andrews, N.B. St-Andrews, N.-B.

1975 lBased on part of a thesis by G. M. Hare sul::mitted in partial fulfilJ.nEnt of the requirarents for the degree of Doctor of Philosophy in the Department of Biology, University of New Bnmswick, Fredericton, N. B. i i

TABLE OF CONTENTS

Introduction 1

Materials and Methods ...... 1 l. Collection of hosts 1 2. Examination of hosts 1 3. Preservation and identification of parasites ...... 4 4. Recording of parasite da ta ...... 4 5. Analysis of parasite data 4

Results and Discussion ...... 6 Phylum Protozoa ...... 6 Subclass Peritrichia ...... 6 Phylum Platyhelminthes ...... 8

Class Trematoda ...... ~ ...... 8 Class Nematoda 17 Class 23 Class Acanthocephala ...... 24 Phylum Annelida ...... 2 7 Class Hirudinea ...... 27 Phylum Arthropoda 28 Class Arachnoidea ...... 28 Phylum Mollusca ..•...... 29 Class Pelecypoda 29

References 30 iii

LIST OF TABLES Page

Table 1. Localities, dates of capture, life stages and numbers of Atlantic salmon examined for parasites 3

Table 2. List of parasites infecting Atlantic salmon collected from the Miramichi River system 7

Table 3. Number and percentage of sagittata on the gill arches of Atlantic salmon, 1970 and 1971 10

Table 4. Number and percentage of on the left and right sides of the branchial basket of Atlantic salmon, 1970 and 1971 10

Table 5. Number and percentage of Discocotyle sagittata on the inner and the outer hemibranchs of Atlantic salmon, 1971 11

Table 6. Number and percentage of Discocotyle sagittata on the dorsal, median and ventral segments of the gills of Atlantic salmon, 1970 and 1971 11

Table 7. Number and percentage of mature specimens of Crepidostomum farionis in different regions of the intestine of Atlantic salmon, 1970 and 1971 15

Table 8. Number and percentage of Capillaria salvelini in different regions of the intestine of Atlantic salmon, 1970 and 1971 18

Table 9. Number and percentage of Raphidascaris sp. in different regions of the alimentary tract and liver of Atlantic salmon, 1970 and 1971 20

Table 10. Number and percentage of Sterliadochona tenuissima in different regions of the alimentary tract of Atlantic salmon, 1970 and 1971 22

Table 11. Number and percentage of Neoechinorhynchus rutili in different regions of the alimentary tract of Atlantic salmon, 1970 and 1971 25 i v "

LIST OF FIGURES

Page Figure 1. Miramichi River system showing locations where Atlantic salmon were collected for parasitological examinations. 2

Figure 2. Diagram of gills on the left side of the branchial basket of Atlantic salmon showing divisions of the gill arches examined for parasites 5

Figure 3. Trichodina sp. showing conspicuous "toothed" disc (Modified after Hoffman, 1967) 6

Figure 4. Gyrodactylus sp. showing posterior anchors, embryo and absence of eye-spots 8

Figure 5. Discocotyle sagittata, (A) posterior end showing and clamps and (B) high power view of clamps 9

Figu~e 6. Crepidostomum farionis, anterior end showing large ventral sucker in relation to smaller oral sucker 13 .. Figure 7. Seasonal difference in the percentage of Crepidostomum farionis in different regions of the intestine of Atlantic salmon collected from Trout Brook in 1971. The figures in parentheses are the number of parasites in each sample 14

Figure 8. Diplostomum spathaceum, metacercaria showing distinct hindbody 17

Figure 9. CapiUaria salvelini, (A) posterior end of male specimen and (B) posterior end of female specimen (Modified after Threlfall and Hanek, 1969) 18

Figure 10. Specimen of Raphidascaris sp. larva showing posterior esophageal caecum 19

Figure 11. Ster liadochona tenuissima, (A) posterior end of male specimen and (B) posterior end of female specimen (Modified after Choquette, 1955) 22

Figure 12. Specimen of Proteocephalus sp. larvae 23

Figure 13. Neoechinorhynchus rutili, anterior end showing small cylindrical shaped proboscis and large hypodermal nuclei 24

Figure 14. Echinorhynchus lateralis, (A) whole specimen showing proboscis withdrawn and (B) high power view of partly everted proboscis 26 • v

Figure 15. Specimen of Piscicola punctata 27

Figure 16. Mounted specimen of Trhypochthoniellus sp. 28

Figure 17. Glochidia encysted in gill filame nts 29 vi

ACKNOWLEDGMENTS

We thank Dr. P. F. Elson, Mr. J. W. Saunders and the staff of the Biological Station's Curventon and Trout Brook counting fences for assistance in fish collections, laboratory facilities, equipment, and accommodations; the staff of the Fisteries and Marine Service, Resource Development Branch, Newcastle, N. B., for assistance in collecting fish samples: the Atlantic Salmon Association, the Fisheries and Marine Service, and the National Research Council for financial support: Dr. D. Barr, Royal Ontario Museum, for identifying the mites found in this study; Dr. W. L. Bullock, University of New Hampshire, for collaborating on acanthocephalan nomenclature: Mr. P. W. G. McMullon for preparing the illustrations; Mrs. M. Irwin for typing the manuscript; and Drs. D. W. McLeese and J. S. Scott for reviewing the manuscript. vii

ABSTRACT

Hare, G. M., and M. D. B. Burt. 1975. Identification, host sites and biology of parasites infecting juvenile Atlantic salmon ( salar) in the Miramichi River system, New Brunswick. Fish. Mar. Servo Res. Dev. Tech. Rep. 581: 34 p.

Fourteen parasite species (1 protozoan, 10 helminth, 1 annelid, 1 arthropod and 1 mollusc) were collected from 1710 juvenile Atlantic salmon (Salmo salar) in the Miramichi River system, New Brunswick, Canada, during 1969-1971. This report provides information on the identification, host sites and biology of the parasites. It is noteworthy that (1) adult mites, Trhypochthoniellus sp., were collected from a vertebrate host for the first time; ' (2) Discocotyle sagittata~ Crepidos­ tomum farionis~ Capillaria salvelini~ Raphidascaris sp., Sterliadochona tenuissima and Neochinorhynchus rutili commonly infected specific host sites; and (3) the seasonal maturation of D. sagittata and C. farionis indicated annual cycles of infection.

RESUME

Hare,G. M., and M. D. B. Burt. 1975. Identification, host sites and biology of parasites infecting juvenile Atlantic salmon (Salmo salar) in the Miramichi River system, New Brunswick. Fish. Mar. Servo Res. Dev.Tech. Rep. 581: 34 p.

De 1969 a 1971, quatorze especes de parasites (1 protozoaire, 10 helminthes, 1 annelide, 1 arthropode et 1 moll usque) ont ete prelevees a partir de 1,710 saumons atlantiques juveniles (Salmo salar) proven ant du bassin de la Miramichi, Nouveau-Brunswick (Canada). Ce, rapport donne des renseignem~nts sur l'identification, Ie site d'inf~ction chez l'h6te et la biologie des parasites. Les points saillants de l'etude peuvent se resumer comme suit: 1) C1est la premiere fois que des acariens adultes, Trhypoch­ toniellus sp., sont isoles sur un vertebre; 2) Discocotyle sagittata~ Crepidostomum farionis~ Capillaria salvelini~ , Raphidascaris sp., Sterliadochona tenuissima et Neochirorhynchus rutili infectaient generalement des parties specifiques de leurs hates; et 3) la maturation saisonniere de D. sagittata et de C. farionis laissent souPronner l'intervention de cycles d'infection annuels. - 1 -

INTRODUCTION

The purpose of this report is to provide information on the identification, host sites and biology of parasites infecting juvenile Atlantic salmon (SaZmo saZar) in the Miramichi River system, New Brunswick, Canada. Although literature on the parasites of Atlantic salmon is extensive (see bibliography by Pippy, 1968; Pippy, 1969a, 1969b, 1970; Hicks and Threlfall, 1973; Hare and Frantsi, 1974; McCarthy, 1974; Kennedy 1974), there are no intensive parasitological surveys of this host within a limited geographical area except for the study by Heitz (19l7).

The information contained herein was collected during studies on the potential use of the parasites as biological tags (Hare and Burt, 1974) and on the population dynamics of the parasites (Hare and Burt, 1975).

MATERIALS AND METHODS

1. Collection of hosts: During 1969, 1970 and 1971, 1,710 juvenile Atlantic salmon were examined from the Miramichi River system (Fig. I). The locations, dates of capture, life stages and numbers examined are given in Table 1. All finger­ ling and parr samples were collected by electrofishing. In mOst cases smolt samples were collected by a fyke and a modi­ 1- fied stake net (Hare, 1973). However, smolts from the Sevogle in 1970 were collected by electrofishing and those from the Bartholomew, the Northwest and the Miramichi estuary were collected at Resource Development Branch and Fisheries Research Board counting weirs. All juvenile salmon were transported in hatchery cans to a Fisheries Research Board field laboratory at the Curventon counting fence on the Northwest Miramichi and placed in tanks containing aerated water until examination. 2. Examination of hosts: In the initial stages of this work in 1969 and 1970, the following parts of each fish were examined: external surfaces, blood, eyes, gills,muscles, internal organs, gall bladder, visceral cavity, mesentries, sHim bladder and alimentary tract. The external surfaces were scanned with the naked eye and a wet-mount of a scraping from the skin of each fish was examined microscopically for pro­ tozoan and monogenean parasites. The muscle tissue and visceral cavity were examined with the naked eye. Blood smears, stained with Giemsa's stain, and wet-mounts from the gall bladder were examined microscopically for protozoa and trematode larvae. Examination of blood, muscles and gall bladder contents was discontinued in 1971 because no parasites were found in these · parts. The eyes, gills, swim bladder, internal organs and alimentary tract from each fish were placed in petri dishes - 2 -

" ~"" " '" :< :: ..: '.:. .' .... :.. ~' ::

Seal. - IiI .. o 10 20 50 I I I I

Figure 1. Miramichi River system showing locations where Atlantic salmon were collected for para­ sitological examinations. - 3 -

Table 1. Localities, dates of capture, life stages, and numbers of Atlantic salmon examined for parasites.

No. fish Locality Date of Capture ~ife stage examined

Trout Brook Oct. 4, 1969 Fingerling 14 Oct. 4-5, 1969 Parr 30 May 16-19, 1 970 Smo1t 16 June 1-20, 1970 Parr and smo1t 18 July 7-2 0, 1970 Parr 31 Aug. 12-1 9 , 1 9 7 0 " 18 Sept. 5, 1 9 70 " 18 Oct. 8-22, 197 0 " 38 Nov. 10-23, 1970 " 28 May 19-:!3, 1971 Parr and smo1t 38 June 1-9, 1 9 71 " " " 28 July 10-19, 1 9 71 Parr 33 Aug. 12-17, 1971 " 32 Sept. 11, 1971 " 28 Oct. 10, 1971 " 25 Nov. 11, 1971 " 24 Northwest Miramichi R. Oct. 11, 1969 " 21 " May 18-June 5 , 1970 Smo1t 59 " May 23-June 7, 1971 " 125 Sevog1e R. Oct. 18, 1959 Parr 17 " June 3-9, 1970 Smo1t 26 " May 26-29, 1971 " 81 Little Southwest Miramichi R. Oct. 19, 1969 Parr 14 " May 28-June 1, 1970 Smo1t 36 " May 30-31, 1971 108 Renous R. May 29, 1970 16 " June 2-4, 1971 71 Dungarvon R. June 15, 1970 8 " June 1-7, 1971 84 Bartholomew R. May 25-June 1, 1970 102 " May 31-June 3, 1971 42 South"flest Miramichi R. June 11, 1970 18 " June 2-3, 1971 -" 130 Cains R. June 5, 1970 " 21 " May 30, 1971 " 112 Miramichi Estuary May 26-June 3, 1970 " 200 - 4 -

containing 0.85% saline, and examined for parasites. The alimentary tract of parr and smolts was divided into six regions: esophagus, stomach, pyloric ceca, anterior intestine, . posterior intestine and rectum. The gill arches were numbered 1-4 anteroposteriorly with each gill being divided into a dorsal, median and ventral region, and the hemibranches were divided into an outer and inner surface (Fig. 2).

During 1969 and 1970 all fish were examined immediately after death. In 1971, only those fish from Trout Brook were examined immediately. The remaining f ish were deep frozen after host data and parasite infections of the external surfaces, gills and eyes were recorded. Each fish in a sample was marked by a fin clip or a combination of these for later identification. Subsequently, 6-8 fish were thawed daily for parasite examinations.

A Wild M5 stereoscopic microscope with magnifications from 12 X to 50 X was used to detect metazoan parasites, and a wild M20 phase-contrast microscope was used for detecting protozoan parasites.

3. Preservation and identification of parasites: After tentative identification, random samples of different genera of parasites were fixed and stored in 5% formalin, with the exception of nematodes, annelids, arthropods and molluscs, which were fixed and preserved in 70% ethanol. Trematodes, cestodes and acanthocephalans were stained with Mayer's carmine, dehydrated in ethanol series, cleared in oil of cedar­ wood and mounted in Permount. Nematodes, arthropods, annelids and molluscs were cleared in glycerin alcohol or lactophenol and mounted unstained in glycerin jelly. Parasites were identified according to descriptions given by several authors which are referred to in the text.

4. Recording of parasite data: The site and number of each parasite species from each fish were recorded except for smolts collected from the Miramichi estuary where parasites were recorded as present or absent. In the Trout Brook study, the stage of maturity (juvenile, immature or mature) of each parasite was recorded whenever possible and the parasites were recorded as being dead or alive.

5. Analysis of parasite data: Chi-square analyses (Sokal and Rohlf, 1969) were used to determine whether the parasite species were homogeneoUsly or heterogeneously dis­ tributed on or in the host. The number of parasites of a species occupying specific sites in a body part was compared with an expected distribution of equal numbers of the species in each site of the body part. - 5 -

Dorsal Region Median Region

Ventral Region Outer Inner Surface Surface

Surface of Hemibranches

Fig. 2. Diagram of gills on the left side of the branchial basket of Atlantic salmon showing divisions of the gill arches examined for parasites. - 6 -

RESULTS AND DISCUSSION

Fourteen parasite species (1 protozoan, 10 helminth, 1 annelid, 1 arthropod, 1 mollusc) were collected from Atlantic salmon in the Miramichi River system (Table 2). Of the sites examined, parasites were confined to the body surfaces, gills, eyes, liver, esophagus, stomach, pyloric ceca, small intestine and rectum. The identification, host site(s) and biology of the parasites are given below.

Phylum PROTOZOA Subclass PERITRICHIA Calkins, 1933 Order GYMNOSTOMATIDA Butschli, 1889 Family URCEOLARIIDAE Dujardin, 1841 Trichodina sp. (Fig. 3)

Fig. 3. Trichodina sp. showing conspicuous "toothed" disc (Modified after Hoffman, 1967).

Identification: Trichodonids are small, circular protozoans with a con~picuous "toothed" disc within their bodies. Generic identification was based upon the absence of an offshoot pointing anteriorly from the central part of each tooth (Bykhovskaya-Pavlovskayaet al. 1962). - 7 -

Table 2. List of parasites infecting Atlantic salmon collected from the Miramichi River system.

Protozoa - Peritrichia - Trichodina sp. Helminth - Trematoda - GyrodactyluD sp. - Discocotyle sagittata - Crepidostomum farionis - Diplostomum spathace um - Nematoda - Capillaria salvelini - Raphidascaris sp. - Sterliadochona t enuissima - Cestoda - Proteocephalus sp. - Acanthocephala - Neoechinorhynchus rutili - Echinorhynchus lateralis Annelida - Hirudinea - Piscicola punctata Arthropoda - Arachnoidea - Trhypochthoniellus sp. Mollusca - Pelecypoda - Glochidium - 8 -

Site: Gills

Biology: Unknown

Phylum PLATYHELMINTHES Class TREMATODA Order suborder MONOPISTHOCOTYLEA Odhner, 1912 Family Cobbold, 1864 GYY' odacty lus sp. (F ig. 4 )

Fig. 4. Gypodactylus sp. showing posterior anchors, embryo and absence of eye-spots.

Identification: Generic identification was based upon the absence of eyespots, its hap tor bearing a single pair of large hooks and 16 marginal hooks, and the presence of larvae in the uterus (Hoffman, 1967).

site: Gills

Biology: The life history of GYY'odactylus has been reviewed by Bychowsky (1957). In essence, its basic peculiarity appeared to be the absence of a special morphological dif­ ferentiating stage which served for infection of new hosts. - 9 -

Infection occurred by fully mature parasites wh i ch transferr e d from one host to another when they came in c lose cont a ct . He reported that the life span of an individua l p arasite l a sted not less than 12-15 days during which at lea st 3-4 n ew individuals were born.

Suborder POLYPISTHOCOTYLEA Family Price, 1 93 6 Discocotyle sagittata (L e uckart, 1842 ) Diesing , 1850 (Fig. 5)

A

Fig. 5. Disco c otyle s agi ttata , (A) posteri or end showing hap tor and clamp s and (B) high powe r v iew of clamps.

Identification: Species identification was based upon the description given by Price (1943) for Discocotyle salmonis Shaffer, 1916, a species which he c ons ide r e d, however, as a synonym of D. sagittata .

Site s: D. sagittata was heteroge n eously distributed (P<.005) on the gill arches of Atlantic salmo n (Table 3 ) . Most parasites we re found on the first gill arch with the infection progressively declining from the fir s t to the f ourth arch. These observations agree with those of Llewe l lyn and Owen (1960) and Slinn (1963) who reported a preference by D. s agittata for the first gill arch of (Sa lmo t rut ta) . - 10 -

Table 3. Number and percentage of DiscocotyZe sagittata on the gill arches of Atlantic salmon, 1970 and 1971.

No. of No. (%) on gill arches 1 to 4 x 2 parasites 1 2 3 4 (3 d. f. ) P

331 202 92 21 16 272.75 <0.005 (61. 03) (27.79) (6.34) (4.83)

The parasites were randomly distributed (P>O.lO) between the left and right sides of the branchial basket (Table 4).

Table 4. Number and percentage of DiscocotyZe sagittata on the left and right sides of the branchial basket of Atlantic salmon, 1970 and 1971.

No. (%) on sides of No. of branchial basket parasites Left Right (1 d.f.) p

331 154(46.53) 177 (54.47) 1. 60 >0.10 - 11 -

Significantly more parasites were found on the inner hemibranches than on the outer (P<.005) (Table 5).

Table 5. Number and percentage of Discocotyle sagittata on the inner and outer hemibranches of Atlantic salmon, 1971.

No. of No. (%) on hemibranches parasites Inner Outer (1 d.L) P

112 86(76.79) 26( 2 3.21) 32.14 <0.005

A similar preponderance of monogeneans on the inner hemibranches has been noted by Frankland (1955) for Diclidophora denticulata on the cod (Gadus virens), by Llewellyn and Owen (1960) for D. sagittata on the brown trout, by Wiles (1968) for Diplozoon paradoxum on the bream (Abramis brama) and the roach (Rutilus rutilus), and . by Suydam (1971) for Diclidophora maccallumi on the hake (Urophycis regius).

In the present study, the parasites were hetero­ geneously distributed on the segments of the gill filaments (P<0.005) and the majority of the specimens were found on the ventral segment (Table 6).

Table 6. Number and percentage of Discocotyle sagittata on the dorsal, median and ventral segments of the gills of Atlantic salmon, 1970 and 1971.

No. of No. (%) on segments of the gills parasites Dorsal Median Ventral (2 d.L) P

328 87(26.52) 92(28.05) 149(45.43) 21. 71 <0.005 - 12 -

The pattern 6f distribution of D. sagittata observed in tiis study may be related to the direction and volume of the gill ventilating current, as has been suggested by Llewellyn (1956) for gill monogeneans. The presence of most specimens of D. sagittata on the first gill arch and the gradual decrease in their numbers from the first to the fourth arch may be due to a greater volume of water flowing over the posterior arches which removes or prevents newly acquired parasites from secure attachment. The greater numbers of parasites on the inner hemibranches may be associated with protection from the ventilating current. Finally, the ventral surfaces of the gill filaments are more exposed to the external environment than are the dorsal and median seg­ ments, thus affording a greater chance for the parasite to attach to this segment.

Biology: IThe life history of D. sagittata involves the production and shedding of eggs by the adult, the hatching of a free-swimming, ciliated larva or oncomiracidium and its subsequent attachmeLt to the host gills. The newly hatched oncomiracidium possesses one pair of clamps when it leaves the egg (Bychowsky, 1957; Owen, 1970) and once attached to host tissue, there appears a second, third and finally a fourth pair of clamps which develop in a posterior to anterior succession. Adult parasites are firmly attached to the secon­ dary gill lamellae and they are relatively difficult to remove with forceps. Observations by Llewellyn and Owen (1960) indi­ cate that it is unlikely that adult D. sagittata can move around on the gills because, when they are forcibly detached, reattachment was usually incomplete with the attachment clamps on only one side of the worm being used.

Discoco tyZe sagitta ta infecting Atlantic salmon in Trout Brook has an annual life span which involves mortality of mature parasites and recruitment of juvenile parasites during mid-summer (Hare and Burt, 1975). The life span of D. sagittata on salmon is similar to that on whitefish (Coregonu8 Zavaretus) in Lake Ladoga, U.S.S.R. (Bauer and Nikolskaya, 1957) and on brown trout and Arctic char (SaZveZinus aZpinus ) in the Crummock waters of the English Lake District, U.K. (Paling, 1965), but it is considerably shorter than the 3-4 yr life span of this parasite on brown trout in the Windermere waters of the English Lake District (Paling, 1965).

In addition to the population of D. sagittata infecting salmon in Trout Brook, another population characterized by a longer life span, such as described by Paling (1965) for tro~t in Windermere, may infect this host. This hypothesis is based upon a report by Pippy (1969b) of two adult specimens of D. sagittata on 1+ sea-year from West Greenland waters. The absence of the parasite on grilse and 2 sea-year salmon examined from the Northwest Miramichi, a river in which D. sagittata was abundant on smolts (Hare and Burt, 1974), suggests that - 1 3 - the specimens from salmon in West Greenland waters are repre­ sentative of a different population of D. sagittata on the same host species.

Order DIGENEA Family ALLOCREADIIDAE Stossich, 1903 Crepidostomum farionis (MUller, 1784) Nicoll, 1909 (F ig. 6)

Fig. 6. Crepidostomum farionis, anterior end showing large ventral sucker in relation to smaller oral sucker.

Identificatio~: Mature specimens conformed to the specific diagnosis given by Hopkins (1934) for this species.

Site: The sites occupied by C. farionis in the intestine of juvenile salmon were seasonally dependent (Fig. 7). In salmon collected from Trout Brook during May, the majority (53.30%) of the parasites were found in the pyloric ceca. During June-September, the distribution of the parasites indicated a posterior movement in the intestine. However, in autumn (October and November), the parasites began to re-establish in the pyloric ceca. It is evident from these data that the - 14 -

II Pyloric Ceca ~ Anterior Intestine D Poste'rior Intestine ~ Rectum en Q) -en (2300) (2574) (97) (108) ~ 80 o CL. -o ... 60 Q) ..c E ::::I Z

-o 40 -~ o -20 Q) ICr' o c -Q) ...u Q) o CL. May June July - Sept

Fig. 7. Seasonal difference in the percentage of Crepidostomum farionis in different regions of the intestine of Atlantic salmon collected from Trout Brook in 1971. The figures in parentheses are the number of parasites in each sample. - 15 - pyloric ceca are the most commonly infected site. Also, when only mature parasites were considered, they showed a heterogeneous distribution (P<.005) in the intestine and the majority of the parasites were found in the pyloric ceca (Table 7).

Table 7. Number and percentage of mature specimens of Crepidostomum farionis in different regions of the intestine of Atlantic salmon, 1970 and 1971.

No. (%) in regions of intestine No. of. Pyloric Anterior Posterior x 2 parasites ceca intestine intestine Rectum (3 d.L) P

394 192(48.73) 76(19.29) 83(21.07) 43(10.91) 127.60 <.oos

The distribution of c. farionis in the intestine of Atlantic salmon differs from its distribution in brown trout (Thomas, 1964) and in rainbow trout (Salmo gairdneri) Klein et al. (1969). Thomas reported that the post pyloric ceca region was the preferred site of C. farionis and that the pyloric ceca was the preferred site of a closely related species, Crepidos­ tomum metoecus. Klein et al. (1969) found young worms in the pyloric ceca, pyloric region, and gall bladder, while adult worms were usually concentrated in the large intestine. If differences occur in the gut physiology between Atlantic salmon and the other salmonids, it may account for a different distribution of C. farionis in salmon than in brown or rainbow trout. Another possible explanation for the difference between the distribution of C. farionis in salmon and brown trout may be that habitat segregation occurs because of interspecific com­ petition (see Holmes, 1973) between the two species in the latter host. Thomas suggested that C. farionis with its large ventral sucker was well adapted for existence in the post pyloric ceca region, whereas the smaller trematode C. metoeaus was provided with additional shelter in the pyloric areas. Thus, in the absence of C. metoecus, the pyloric ceca may also provide the better habitat for C. farionis in Atlantic salmon. The report by Klein et al. that adult worms were usually con­ centrated in the large intestine of rainbow trout is at variance with the present findings because 48.73% of the mature parasites were found in the pyloric ceca of salmon. - 16 -

Biology: Based upon the observations of Brown (1927), the first intermediate hosts are the fingernail clams, Pisidium amnicum and less frequently Sphaerium corneum. The cercariae develop in rediae which are attached to the mollusc gills. There is no sporocyst stage in the life cycle. The stylet­ bearing cercariae penetrate mayfly nymphs or amphipods, the second intermediate hosts. Brown found encysted metacercariae in the fat bodies and abdominal musculature of Ephemera danica, and Baylis (1931) reported encysted metacercariae from the amphipod, Gammarus pulex. Experimental infections by Crawford (1943) demonstrated that the life history of C. farionis involved Pisidium sp. as the first intermediate host and mayfly larvae, Ephemera sp. as the second intermediate host. Thus, fish may become infected by feeding on mayfly nymphs or Gammarus which have been infected by cercariae from the clams Pisidium or Sphaerium.

The life history of C. farionis infecting Atlantic salmon in Trout Brook involves the recruitment and maturation of parasites primarily during late autumn to early spring, and mortality of the mature parasites primarily during June and July (Hare and Burt, 1975). Their data suggest that the life span of C. farionis in Atlantic salmon is probably less than one year. Similar findings have been reported by Thomas (1958) and Awachie (1968) who observed that the developmental cycle of C. farionis and the closely related allocreadiid C. metoecus in brown trout was annual.

Order STRIGEATOIDEA Family STRIGEIDAE Raillet, 1919 Diplostomum spathaceum (Rudolphi, 1819) Braun, 1893 (F ig. B)

Identification: Larval identification was based upon the presence of a distinct hindbody (Hoffman, 1960).

Site: Vitreous hUmor and retina.

Biology: D. spathaceum (Syn. D. flexicaudum) requires a snail as the first intermediate host, fish as the second intermediate host and a piscivorous bird as the definitive host. According to Hoffman (1960), cercariae have been reported from pulmonate snails, principally Lymnaea spp., and the metacercariae and adults have been reported from various species of fish and birds respectively. - 17 -

Fig. 8. DipZostomum spathaceum, metacercaria showing distinct hindbody.

Class NEMATODA Order TRICHURIDEA CapiZZapia saZveZini Polyanski, 1952 (F ig. 9)

Identification: Male and female specimens agreed with the species diagnosis and measurements given by Bykhovskaya­ Pavlovskaya et al. (1962) and by Threlfall and Hanek (1969).

Sites: C saZvelini was heterogeneously distributed (P<.005) in the intestine and the majority of the specimens were found in the rectum (Table 8). - 18 -

B

Fig. 9. Capillaria salvelini, (A) posterior end of male specimen and (B) posterior end of female specimen (Modified after Threlfall and Hanek, 1969).

Table 8. Number and percentage of Capillaria salvelini in different regions of the intestine of Atlantic salmon, 1970 and 1971.

No. (%) in regions of intestine No. of Pyloric Anterior Posterior x 2 parasites ceca intestine intestine Rectum (3 d.f.) P

87 12(13.79) 7(8.05) 17(19.54) 51(58.62) 54.75 <.005 - 19 -

Biology: Unknown. Markevich (1951) reported that copepods or amphipods act as the intermediate host for three species of Capillaria infecting fish in the U.S.S.R.

Order ASCARIDEA Family HETEROCHEILIDAE Raphidascaris sp. (Fig. 10)

Fig. 10. Specimen of Raphidascaris sp. larva showing posterior esophageal caecum.

Identification: Generic identification of the larv~e was based upon the presence of a posterior esophageal cecum and the absence of an intestinal cecum (Hoffman, 1967). The species identification of this parasite requires mature nematodes obtained from experimentally infected fish.

Sites: Free and encysted :Larvae occurred throughout the alimentary tract and in the liver (Table 9). The pre­ ponderance (62.69%) of free larvae in the pyloric ceca and · the corresponding high percentage (47.83%) of encysted larvae in the pyloric ceca and in the liver may suggest that bile secretions in this region act as a stimulant to initiate the Table 9. Number and percentage of Raphidascaris Spa in different regions of the alimentary tract and liver of Atlantic salmon, 1970 and 1971.

Site of infection (No. _ and %) State of No. of Pyloric Anterior Posterior larvae parasites Stomach ceca intestine intestine Rectum Liver

N 0 Free 67 0 42(62.69) 12(17.91) 4(5.97) 1 (1. 49) 8(11.94) Encysted 184 19(10.33) 37 (20.11) 42(22.83) 29(15.76) 6(3.26) 51(27.72)

• • • - 21 - tissue migration of larvae. By analogy, MacKenzie and Gibson (1970) showed that the trematode PodocotyLe sp. was found predominantly in the anterior intestine of freshly caught flounders, whereas in starved flounders, they were predominantly found in the rectum. The force feeding of starved flounders initiated movement of the trematodes to the anterior intestine. This anterior migration was prevented by cutting the bile ducts, suggesting that the parasites were attracted to bile.

Biology: Studies on the biology of Raphidascaris are limited to R. acus. Moravec (1970) reported that this nematode, the adults of which are parasites of some economically important predatory fishes (pike, trout), is a frequent and widespread parasite in Europe and Asia. In referring to his earlier studies, he stated that "small fish of various families participate in the development of R. acus, these being infected either by eating reservoir hosts (invertebrates of various classes) or, more directly, by eating eggs containing second stage larvae". Based upon seasonal changes in incidence and intensity of infection, and maturation of the nematode, he showed that R. acus exhibited an annual cycle in brown trout in the River Bystrice, Czechoslovakia. In essence, larvae were present during September to May, egg producing adults were present during mid May to July, and no parasites were recovered during August.

Order SPIRURIDEA Family SPIRURIDAE Oerley, 1895 SterLiadochona tenuissima (Zeder, 1800) Spasskii and Roitman, 1959 (Fig. 11)

Identification: The specimens conformed to the emended generic diagnosis of SterL{adochona given by Maggenti and Paxman (1971). Measurements from the specimens agreed with those given by Sandeman and Pippy (1967) for Metabronema saLveLini Fujita, 1920, a synonym of S. tenuissima according to the former authors. .

Sites: S. tenuissima was found in the anterior portion of the alimentary tract; the majority of them being present in the stomach (Table 10). - 22 - ..

A B

Fig. lL Sterliadochona tenuissima, (A) posterior end of male specimen and (B) posterior end of female specimen (Modified after Choquette, 1955).

Table 10. Number and percentage of Sterliadochona tenuissima in different regions of the alimentary tract of Atlantic salmon, 1970 and 1971.

No. of No. (%) in regions of alimentary tract parasites Esophagus Stomach Pyloric ceca

5625 142(2.52) 4922(87.50) 561(9.97)

Biology: The life history of S. tenuissima involves a mayfly nymph as its first intermediate host and a fish as its definitive host. Choquette (1955) reported third stage larvae from the body cavity of the mayfly nymphs, Hexag e nia r e curvata and Polymitarcys sp., and fourth stage larvae from • .. • - 23 -

speckled trout. The feeding of infected nymphs of H. reourvata to trout resulted in the establishment of infection and development of adult worms in 60-70 days.

Sterliadoohona tenuissima infecting Atlantic salmon in Trout Brook has an annual life span which involves the recruitment and maturation of parasites during late autumn to spring and loss of parasites during summer (Hare and Burt, 1975). This seasonal pattern is similar to that reported by Moravec (1971) for Cystidiooloides tenuissima (=S. tenuissima) infecting brown trout in Czechoslovakia.

Class CESTODA Rudolphi, 1808 Order Mola, 1928 Family PROTEOCEPHALIDAE La Rue, 1911 Proteooephalus sp. (F ig. 12)

•

Fig. 12. Specimen of Proteooephalus sp. larvae.

Identification: Generic identification of the plero­ cercoids was based upon the presence of a round scolex unarmed with hooks and containing 4 suckers (Hoffman, 1967).

Site: Intestine

Biology: The procercoid develops in the hemocoel of crustacea.. the plerocercoid in small fish and the adults occur in freshwater fish (Hoffman, 1967). - 24 -

Phylum ACANTHOCEPHALA Van Cleave, 1948 Order NEOECHINORHYNCHIDEA Southwell and Macfie, 1925 Family NEOECHINORHYNCHIDAE Van Cleave, 1919 Neoechinorhynchus rutili Muller (1780) Hamann, 1892 (Fig. 13)

Fig. 13. Neoechinorhynchus rutili, anterior end showing small cylindrical shaped proboscis and large hypodermal nuclei.

Identification: Specimens of N. rutili agreed with the species diagnosis given by Petrochenko (1956) and Bykhovskaya­ Pavlovskaya et ale (1962). Despite the fact that all specimens in the present study were immature, the proboscis and hook measurements agreed with those given by the above·authors.

Sites: N. rutili was heterogeneously distributed (P <.005) in the alimentary tract of salmon (Table 11). The pre­ ponderance (59.74%) of worms in the posterior intestine suggests that this is the preferred host site. - 25 -

Table 11. Number and percentage of Neoechinorhynchus rutili in different regions of the alimentary tract of Atlantic salmon, 1970 and 1971.

No. (%) ln regions of alimentary tract

No. of Pyloric Anterior Posterior x 2 parasites ceca intestine intestine Rectum (3 d.f.) P

77 4(5.19) 13(16.88) 46(59.74) 14(18.18) 52.71 <.005

The distribution of N. rutili in the alimentary tract of salmon is similar to its distribution in brown trout (Thomas, 1964), and in three-spined stickleback (Gasterosteus aculeatus) (Walkey, 1967, Chappell, 1969). Thomas reported that the post pyloric ceca region was the preferred host site, and Walkey and Chappell reported that N. rutili was almost exclusively con­ fined to the posterior two-thirds of the gut of sticklebacks. The distribution of N. rutili in salmon, brook trout, and three-spined sticklebacks differs from its distribution in the minnow (Phoxinus phoxinus). Bibby (1972) reported that this parasite was found throughout the alimentary tract of minnows with the majority of the worms being present in the stomach. He suggested that the absence of gastric glands in the minnow may account for its distrib~tion in that host. However, Bibby suggested that the presence of these glands in the stomach of the three-spined stickleback could account for its absence in that site.

Biology: The life history of N. rutili has been reported by Merritt and Pratt (1964) and Walkey (1967). Walkey reported that the analysis of stomach contents of three-spined sticklebacks and experimental infections of food organisms showed that the ostracods Cypria ophthalmica and Candona candida were the intermediate hosts. Although it has been generally accepted that the aquatic larvae of the alder fly, Silas sp., served as an intermediate host for this parasite, Walkey found that this was not so. He suggested that previous records of Silas and of the leech Erpobdella may be of paratenic hosts, resulting from these organisms, both of which are voracious carnivores, having eaten infected ostracods. Variations in the occurrence of N. rutili were correlated with variations in the ingestion of ostracods by sticklebacks. Records of incidence, burden and degree of development showed that the parasite has an annual maturation cycle with new worms being recruited throughout the year. - 26 - •

Order ECHINORHYNCHIDEA Southwell and Macfie, 1925 Family ECHINORHYNCHIDAE (Cobbold, 1879) Yamaguti, 1963 Echinorhynchus ZateraZis (Leidy, 1851) Molin, 1858 (F ig. 14)

Fig. 14. Echinorhynchus ZateraZis, (A) whole specimen showing proboscis withdrawn and (B) high power view of partly everted proboscis.

Identification: The specimens conformed to the generic diagnosis of Hoffman (1967) and to the measurements given by Sandeman and Pippy (1967) for E. ZateraZis and by Petrochenko (1956) for AcanthocephaZus ZateraZis, a synonym of E. ZateraZis according to W. L. Bullock (University of New Hampshire, personal communication).

Site: Intestine

Biology: Unknown. Richardson (1936) suggested that the amphipod HyaZZ eZa knickerbockeri (syn. H. azateca) was the intermediate host of this parasite in Lake Edward, Quebec, and .. Hoffman (1967) records the intermediate hosts of parasites of the genus Echinorhynchus as amphipods. - 27 -

Phylum ANNELIDA Class HIRUDINEA Lamarck, 1818 Order RHYNCHOBDELLIDA Blanchard, 1894 Family PISCICOLIDAE Johnston, 1865 Piscicola punctata (Verrill, 1871) (Fig. 15)

Fig. 15. Specimen of Piscicola punctata.

Identification: Specimens were identified using keys given by Davies (i971) and Pennak (1953). The prime distinguishing . featt.re of this species was the absence of oculiform spots on the caudal sucker.

Site: Body surfaces and gills.

Biology: Leeches are monoecious organisms in which sperm is transferred to another individual in sperm · packets. Eggs are deposited in cocoons, which are usually attached to foreign objects. After hatching, the leech remains in wait to attack an unsuspecting host. There are neither larval stages nor an intermediate host (Meyer, 1954). In referring to Piscicola . geometra, Bauer (1958) stated that most leeches leave - 28 - the fish and deposit eggs in elongated cocoons during the summer and that the young leeches hatch and attack fish during the second half of summer. Piscicola punctata presumably follows the same pattern of development since specimens were only recovered from salmon during late summer and autumn.

Phylum ARTHROPODA Class ARACHNOIDEA Superfamily NOTHROIDEA Family TRHYPOCHTHONIIDAE Trhypochthoni e llus sp. (F ig. 16)

Fig. 16. Mounted specimen of Trhypochthoniellus sp.

Identification: These mites have been identified to the above genus by Dr. David Barr, Royal Ontario Museum.

Site: Gills

Biology: Unknown. A number of oribatids are known to be aquatic but none of them are known to have any association - 29 - with a vertebrate. Despite the fact that the specimens were encysted in the gill lamellae, they were alive when teased from the tissue. At present, it is difficult to determine whether or not these adult mites are parasitic because host gill tissue presumably elicits an immune response to any organism or foreign object. For example, Arey (1921) showed that aluminum clamps, when attached to the gill filaments, were covered by host tissue in the same manner as glochidia.

Phylum MOLLUSCA Class PELECYPODA Unidentified glochidia (Fig. 17)

Fig. 17. Glochidia encysted in gill filaments.

Site: Gills

Biology: Meyer (1954) hds given a general account of the biology of larval clams. The glochidia of most freshwater clams undergo part of their development in the gills of the - 30 - fema:e and when sufficiently advanced are expelled in large numbers and fall to the stream bottom. The disturbance caused by the fins of passing fish brings them in contact with the host. Larvae are usually drawn in through the mouth of the fish and distributed over the gills, although other parts of the body can be infected. Upon making contact with a suitable host, the larvae attack by closing their two valves on host tissue, thus beginning their parasitic phase. They are over­ grown by the host's tissues, which form a protective cyst within about a day. At the completion of the parasitic stage, the cyst is ruptured, freeing the young mussel, which begins growth on the stream bottom. Other salient features on the biology of glochidia are: (1) the hookless species usually become attached to the gills, hooked species to the fins or general body surface (Pennak, 1953) and (2) some forms are host-specific. The larvae infecting salmon in the Miramichi River system are of the hookless type and similar type larvae do not infect brook trout (Hare and Frantsi, 1974), a salmonid indigenous with Atlantic salmon in the Miramichi River.

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