Records of Indo-Pacific Echinoderms

Records of Indo-Pacific Echinoderms AUSTiN H. CLARKI THE ECHINODERMS recorded herein were for Indo-Pacific is very limited, especially in re the most part collected in connection with gard to the central Pacific area. Extensive the studies of the Pacific Science Board, Na work has been done only in Australia, the tional Research Council. They represent in Netherlands East Indies, the Malayan region, cidental activities of 15 members of survey the Philippines, and the Hawaiian Islands, parties, all ofwhom were intensively engaged and even here the records, though very nu in other work. It has seemed advisable to sup merous, are very spotty. plement these records with those of other About the large, high, forested islands specimens from the Indo-Pacific region not where the available nutrients in the sea are previously recorded which were received from enriched by a constant accession of vegetable 15 donors, most of whom were members of waste from the land, the fauna, both littoral the armed forces, chiefly during and after the and abyssal, is exceedingly rich and varied, war. The specimens from New Caledonia were with many large species and unusually large presented to the National Museum by the individuals of other species. A curious side late Lieutenant General Alexander McCarrell light on the importance of vegetable detritus Patch, Jr., through the National Geographic .is afforded by the flexible-shelled sea urchins Society. ofthe genus Araeosoma which occur at depths All the specimens listed are in the United of from 70 to 1,289 meters and are known to States National Museum. A large collection feed on the leaves of dicotyledonous plants. of echinoderms from the Marshall Islands, Even a· fossil Araeosoma from California was including 2,674 specimens resulting from the surrounded by leaf impressions. In the Pacific Navy's Operation Crossroads and the Bikini area Araeosoma occurs among the Malayan Scientific Resurvey, has previously been de Islands and the Philippines, off Tonga and scribed (Clark, 1952). This paper should be Fiji, offsouthernJapan, and offthe Galapagos consulted in connection with the present Islands and Panama, but not in the central contribution. Pacific or on the American coast except at All the sea urchins collected by Dr. F. S. Panama. The species of Araeosoma are large, MacNeil are dead tests. one ofthem up to 180 millimeters in diameter. Our knowledge of the details of the dis Although certain faunal subregions may be tribution of the littoral echinoderms of the distinguished in the region of the larger and higher islands from Ceylon eastward, these 1 Curator, Division of Echinoderms, United States National Museum, Washington, D.C. Manuscript re are not very distinctive, the tropical Austra ceived August 12, 1953. lian, including the Am Islands and the south 243. 244 PACIFIC SCIENCE, Vol. VIII, July, 1954 coast ofNew Guinea, being the most notable. the Hawaiian Islands. One species occurs from Northward and eastward among the low is the Gulfof California to Panama, and another lands, as conditions become less and less is known from off the Dry Tortugas, Florida. favorable for littoral echinoderms, the fauna No species is known from the central Pacific, becomes progressively poorer, and segrega though one may occur there, as there is an tion into definite faunal regions appears to old specimen in the Copenhagen Museum become more marked. said to be from Nukahiva in the Marquesas;. The majority ofthe Indo-Pacific species are but Dr. Mortensen regards the locality as small or at most of medium size and are. doubtful. Too much faith cannot be placed present everywhere, though many become on the absence of records of this genus, as fewer in individuals among the atolls. In some the species seem to be easily overlooked. The cases the individuals here are noticeably Caribbean species was not described until smaller. The large species in many cases dis 1934 and is still known only from the four appear or become segregated ,and confined original specimens. to special areas in which they may become Among the brittle stars, the very large and differentiated into recognizable subspecies or conspicuous basket stars of the family Gor even distinct .species. gonocephalidae, otherwisecosmopolitan,have The very large and heavy sea stars of the not been reported from the small islands, nor family Oreasteridae are especially character have any ofthe species ofTrichasteridae, with istic of tropical coasts, but, except for the many-branched arms. However, the species genus Culcita, the cushion stars, the most of these two families occur in water of from specialized of the family, ranging from east a few fathoms downward, not along the Africa eastward, they are absent from the shores, so, although they are frequently central Pacific area. The largest genus, Penta brought up on fishermen's lines, the ab ceraster, with 14 species, is found from the sence ofrecords is not necessarily significant. Red Sea and eastern Africa to Australia, New Among the more conspicuous and char Guinea, New Britain, New Caledonia, and acteristic of Indo-Pacific sea urchins are the Samoa, and also on the coast of China, in the limpet, pavement, or helmet urchins of the Philippines, among the Ryukyu Islands, in genus Colobocentrotus. These are of fairly large southern Japan, in the Hawaiian Islands, and size and live in the surf zone, usually in large on the west coast of Central America. The colonies, so that they are not easily over species found in the Hawaiian Islands and on looked. One species, C. atratus, occurs at the American west coast are very similar. The Zanzibar, Natal, Madagascar, Mauritius, the genus Protoreaster, with four species, ranges Seychelles, Christmas Island,Java, Timor, and from eastern Africa to western Australia, New Amboina, and also in the Hawaiian Islands, Guinea, the Bismarck Archipelago, New Cale though not between the Moluccas and Ha donia, the Mariana Islands, the Palau Islands, waii. A related species, C. pedifer, is confined Yap, the Ryukyu Islands, and southernJapan. to the Tuamotus. A third species, C. mertensi, If species of these two or related genera is found in the Bonin and Mariana Islands. occurred among the atolls, they could scarcely A related genus with normal instead ofmodi be overlooked and certainly would be known fied spines, ZenocentrotuJ, occurs in Tonga and to the natives. Samoa. The latter, first described in 1931, Among the sea urchins the genus Astropyga may have a more extended distribution as it is characteristic of tropical regions in from 5 is easiiy confused with sea urchins of other to 88 meters. The species are large, up to 180 families. millimeters in diameter. They range from Among the largest, most conspicuous, and eastern Africa to Australia, New Britain, and most characteristic of the Indo-Pacific sea Indo-Pacific Echinoderms - CLARK 245 urchins are the two species of slate-pencil or from the Marshall Islands recorded in the cigar urchins ofthe genus Heterocentrotus. One following pages. ofthese, H. mammil/atus, occurs from the Red In the Atlantic, Echinometra lucunter reaches Sea and Tanganyika, Madagascar, Mauritius, its maximum size on the northern and south and Rodriguez to the Cocos-Keeling Islands, ern limits of its range in Bermuda and Brazil northwestern Australia, New Guinea, Torres (Clark, 1933: 83), and Brissus brissus.in the Strait, the Philippines, New Caledonia, and Mediterranean reaches nearly twice the size Fiji, and also in the Mariana, Bonin, Ryukyu, that it does in the Caribbean (ibid., p. 91). and Hawaiian Islands. It appears to be absent The largest known specimen of Linckia guild from the central Polynesian region except for ingii, with a radius of 215 millimeters, is from Johnston Island and the Tuamotus, where it Bermuda. was recently found by Dr. Morrison. From the zoogeographical and historical The other more specialized species, H. tri- . points of view, the most interesting andsig~ gonarius, occurs at Zanzibar, Natal, Madagas nificant echinoderms are not to be found in car, Mauritius, Rodriguez, Java, the Philip the warm and brilliantly illuminated tropical pines, Tonga, Samoa, and throughout littoral, but in the dimly illuminated and Polynesia. cooler zones from 5 or 6 fathoms downward Both species occur at Madagascar, Mauri to the depth, which differs indifferent areas, tius, Rodriguez, the Philippines, the Tuamo where a localized fauna, if present, begins to tus, and Johnston Island. merge into the increasingly widespread abys As both species have apparently the same sal fauna. That such an intermediate fauna habits, living normally in holes and crevices may be of much significance is indicated by in the reefs and sometimes together in the the genus Psychocidaris, the only representative same group, the reason for the difference in of the family Psychocidaridae, related to the distribution in the extreme western and in the Cretaceous Tylocidaris, known only from the eastem part of theinanges is obscure. It may, Bonin Islands in about 100 fathoms. ofcourse, be due in part to insufficient knowl edge oftheir distribution among the atolls; COLLECTION DATA H. mammillatus may be more generally dis Onotoa Atoll, Gilbert Islands tributed here than the records available at present indicate. The localities in the Onotoa Atoll, Gilbert It appears somewhat paradoxical that, al Islands, are listed by numbers. The data for though large species and large individuals for each numbered locality are as follows. the most part do not extend into the groups G.O.C.-24. Toward the southern end of a of small Polynesian islands, a few species lee reef stretch known as Rakai Ati, in an reach their maximum size in this area, on the area of small coral patches fairly thickly in northeastern periphery of their range. The terspersed on lime sand and coral debris; the largest specimen of Heterocentrotus trigonarius bottom is at depths of 3-4 feet at low tide.

Load more