MARINE FAUNA and FLORA of BERMUDA a Systematic Guide to the Identification of Marine Organisms

MARINE FAUNA AND FLORA OF BERMUDA A Systematic Guide to the Identification of Marine Organisms Edited by WOLFGANG STERRER Bermuda Biological Station St. George's, Bermuda in cooperation with Christiane Schoepfer-Sterrer and 63 text contributors A Wiley-Interscience Publication JOHN WILEY & SONS New York Chichester Brisbane Toronto Singapore ANTHOZOA 159 sucker) on the exumbrella. Color vari many Actiniaria and Ceriantharia can able, mostly greenish gray-blue, the move if exposed to unfavorable condi greenish color due to zooxanthellae tions. Actiniaria can creep along on their embedded in the mesoglea. Polyp pedal discs at 8-10 cm/hr, pull themselves slender; strobilation of the monodisc by their tentacles, move by peristalsis type. Medusae are found, upside through loose sediment, float in currents, down and usually in large congrega and even swim by coordinated tentacular tions, on the muddy bottoms of in motion. shore bays and ponds. Both subclasses are represented in Ber W. STERRER muda. Because the orders are so diverse morphologically, they are often discussed separately. In some classifications the an Class Anthozoa (Corals, anemones) thozoan orders are grouped into 3 (not the 2 considered here) subclasses, splitting off CHARACTERISTICS: Exclusively polypoid, sol the Ceriantharia and Antipatharia into a itary or colonial eNIDARIA. Oral end ex separate subclass, the Ceriantipatharia. panded into oral disc which bears the mouth and Corallimorpharia are sometimes consid one or more rings of hollow tentacles. ered a suborder of Scleractinia. Approxi Stomodeum well developed, often with 1 or 2 mately 6,500 species of Anthozoa are siphonoglyphs. Gastrovascular cavity compart known. Of 93 species reported from Ber mentalized by radially arranged mesenteries. muda, 76 are included here; the remain Mesoglea a mesenchymal or fibrous connective ing 17 are deep-water or rare shallow tissue. Adult body sizes range from water species. Scleractinia of 2 mm diameter to whip-like Antipatharia 7 m long. Colonies of OCCURRENCE: Throughout the world Scleractinia may also reach several meters oceans from the Arctic to the Antarctic, in diameter and weigh several tons. Most from the intertidal to hadal depths (10,700 anthozoans, however, measure between 3 m), and in temperatures of - 1° to 30°C. In and 50 em. Most orders possess some kind general, more species occur in the shallow of inorganic supporting structure, such as water tropical and subtropical regions as a calcareous or horny axis or microscopic sociated with coral reefs, but virtually all calcareous sclerites distributed throughout benthic marine habitats are exploited. Full the tissue. Some gorgonians and pen oceanic salinity is usually required, but natulids have both supporting axes and some scleractinians and gorgonians can sclerites, whereas the Actiniaria, Coral tolerate brackish water of 1.7% salinity. limorpharia, Zoanthidea and Ceriantharia Some zoanthids and actinians thrive in pol have no such supporting structure. Antho luted areas. Substrate type is an important zoans are among the most colorful animals factor governing distribution; some in the reef environment. Unfortunately species require mud, others sand or hard the pigments are rarely retained in pre substrates, and others are epizoic or served specimens and, although distinctive epiphytic. Anthozoans are usually patchy in some species, color is not usually a reli in distribution, often abundant in coral able taxonomic character. Anthozoans are reef habitats where conditions of substrate, predominantly sedentary animals, often light and current combine to create highly firmly attached to the substrate. The only productive areas. Densities of 27-30 col locomotion involved in most life cycles is onies of Scleractinia or Gorgonacea per in the planktonic larval stage. However, square meter are not unusual in reef envi- 160 KINGDOM ANIMALIA ronments, whereas antipatharians rarely identification relies on a great number of exceed 2-3 colonies/m~. characters and methods. Most intertidal and shallow-water An The basic structural unit of alllhozoans is the thozoa can be collected with the aid of a polyp, which may exist alone or in a colonial aJTan~e hammer and chisel while snorkeling or ment, all contiguous polyps tracing their ancestry through asexual budding to a single founder polyp. SCUBA diving. A wooden spatula or flat The polyp usually has a short, squat, cylindrical body bivalve shell is good for detaching (column) with a flattened oral end (oral disc). The anemones. Burrowing actinians, cerian mouth occupies the center of the oral disc and is sur thids and pennatulids may be obtained by rounded by several rings (cycles) of hollow tentacles. sieving of sand and mud, preferably after The mouth leads through a short, longitudinally ridged tube (stomodeum) into the ~astrovascularcav the animals have been spotted in the ex ity (coelenteron). The hollow tentacles are continuous panded condition. It is best to collect with this cavity. Sometimes the stomodeum is flat cerianthids at night or at dusk, when most tened, with one or both of the narrow edges modified species expand. Ifkept moist, and the tem into flagellated grooves (siphonoglyphs) that propel perature is controlled, anemones may live water into the polyp. The ~astrovascularcavity is ra dially partitioned by thin lamellae (mesenteries, for several days and even survive shipment septa) on which the gonads develop. The inner, free by mail. Deep-water (over 70 m) species edges of the mesentel'ies bear distinct, thickened are usually collected fortuitously by trawl rims, the (mesenterial) filaments, which perform the ing and dredging, or selectively by sub functions of digestion, absorption and excretion. mersible. These filaments generally have the form of a simple cord, often very sinuous in the lower part of the Some anthozoans are commercially or polyp. In Ceriantharia the filaments in the upper part pharmacologically important. Some gor of the polyp are bilobed, in Actiniaria and Zoanthidea gonians and zoanthids contain compounds trilobed. Mesenteries (except in Ceriantharia) are ar (prostaglandins and palytoxin, respec ranged in cycles of different order. They are termed tively) that are biologically very active perfect or complete if they are attached to the col umn, oral disc, base and stomodeum; imperfect or and of pharmaceutical value. Care must incomplete if they do not reach the stomodeum. The be taken when collecting the zoanthid inner, free edges of the imperfect mesenteries Palythoa in late summer because it contains (mesenterial filaments) are sometimes very sinuous a highly toxic substance (palytoxin) which and trilobed. Most anthozoan polyps are bilaterally is very irritating to the skin and open cuts, symmetrical, the axis bein~ determined by the siphonoglyphs or the flattened stomodeum. Two causing severe pain and long-lasting blis mesenteries may occur symmetrically on both sides of ters. Actinians, some scleractinians and the axis (coupled) and/or directly adjacent (in pairs). cerianthids are popular aquarium animals. The space between the mesenteries of a pair is called Finally, because anthozoans constitute an endocoel, the space between 2 pairs an exocoel. A most of the mass of coral and patch reefs, directive mesentery pair flanks a siphonoglyph. In some elongate actinians there may be 8 well they contribute to storm protection, tourist developed, fertile macromesenteries alternating with recreation and sand production, not to 8 smaller sterile micromesenteries. Nematocysts, tbe mention the habitats provided for innu characteristic "stinging capsules" of Coelenterata, are merable other animals, many of which are found on the tentacles, stomodeum, column and eaten by humans. The taking of corals for mesenterial filaments of all Anthozoa. The fine struc ture of nematocysts as well as the cnidom (types of souvenirs is strongly discouraged, and pro nematocysts in a species or higher taxon) are impor hibited by law in certain areas (Coral Reef tant criteria for classification. The body wall of an Preserves). anthozoan is composed of 3 layers: an outer ectoderm (epidermis), an inner endoderm (gastrodermis) and an intermediate mesoglea, composed of a mesenchy IDENTIFICATION: Because of the mor mal or fibrous connective tissue. The mesoglea of a phological diversity within the class, colonial anthozoan is collectively termed coenen- ANTHOZOA 161 chyme. Many species contain symbiotic zooxanthellae groove (fossa) that occurs between the collar and the (dinoflagellates) that enable many Scleractinia to be base of the capitulum. The scapulus and capitulum reef~building (hermatypic) in shallow, well-lit waters; are invariably smooth, but the scapus may bear a vari the other, non-reef-building (ahermatypic) Sclerac ety of special structures, such as vesicles, hollow, tinia, i.e., without zooxanthellae, are able to live in nematocyst-bearing outgrowths of the gastrovascular dark, cold deeper waters. cavity; acrorhagi, vesicle-like nematocyst batteries oc The following terms pertain to features ofindivid curring on the parapet or in the fossa; pseudotenta ual orders rather than the entire class. cles, large, branched, inflated, vesicle-like structures All gorgonaceans have a central supporting struc bearing acrorhagus-like nematocyst batteries; warts, ture, usually called the axis in Scleraxonia and the adhesive, generally brightly colored, button-shaped central core in Holaxonia. The axis

Load more