New squat lobsters (Galatheidae) from the Pacific Ocean: Mariana Back Arc Basin, East Pacific Rise, and Cascadia Basin

Abstract

Three species of squat lobsters new to science are described and illustrated. Munidopsis marianica, collected with the aid of DSRV Alvin from a hydrothermal vent area in the Mariana Back Arc Basin in the western Pacific, is distinguished from a northeastern Pacific species, M. tufts; Ambler, by the erectness of its eye spines and ornamentation of the body, form of telson plates, and spination of dactyls on walking legs. Munidopsis lignaria, collected in association with submerged wood with the aid of RV Yaqu;na in trawl samples from the eastern Pacific Cascadia Basin off Oregon and DSRV Alvin from the East Pacific Rise off south central Mexico, is distinguished from its nearest congener, M. ciliata Wood·Mason, by blunter ornamentation and smaller body size. Munidopsis granosicor;um from Cascadia Basin is represented by a unique specimen, the carapace of which has a distinctive unspined ornamentation but a much more broadly triangular rostrum and more pronounced anterior elevation than that of its apparent closest relative, M. follirostris Khodkina. On a recent Alvin/Atlantis II expedition to the Mariana Back Arc Basin in the western Pacific, 28 dives were made, 6 of them entirely devoted to biology. Those dives focused on 3 active low temperature (loo-25°C) vent sites at which anemones, mollusks, shrimps, squat lobsters, crabs, and other invertebrates were observed or collected (R. Hessler!; Hessler et a1. 1988). We here describe a new species of M-unidopsis collected during 3 of the dives. A subsequent At-vin/Atlantis II expedition (Cruise 118, Leg 32) focused on geological exploration of the East Pacific Rise between lat. lOo55'N and 11°55'N. Small fields of past and lRobert Hessler, Scripps Institution of Oceanography, La Jolla. CA 92093, pers. commun. September 1987. Austin B. Williams, Systematics Laboratory, National Marine Fisheries Service. National Museum of Natural History, Smithsonian Institution, Washington, D. C. 20560. Keiji Baba, Kumamoto University, Faculty of Education, Kurokami 2-chome, Kumamoto, 860 Japan. Manuscript Accepted May 1989. Fishery Bulletin, U.S. 87: 899-910. present hydrothermal activity were found along the axis of this region, and among samples of biological specimens collected from both vent and nonvent environments was a piece of wood colonized by a variety of invertebrates, including a species of Mu,nidopsis (see Van Dover 1988). These specimens are identical to specimens taken during extensive collections of benthic megafauna made at stations of the RV Yaqui-na on the Oregon continental margin and nearby abyssal plains from 1962 to 1983 (Ambler 1980; Carney and Carey 1982; Carei A pattern of stations was sampled to determine the distribution and abundance of mega-epifauna and to study the ecological influence at sea of radionuclides originating from the Hanford (WA) Nuclear Reservation. Collections at these and other study areas in the region were made with a 7.1 m semiballoon otter trawl (1.3 cm mesh) and with a 3 m beam trawl 0.3 cm mesh) equipped with paired odometer wheels (Carey and Heyamoto 1972). We reviewed all of this material and here describe the species as new. Finally, a unique but fragmentary specimen of Munidopsis from Professor Carey's sampling program is described. Specimens studied, except where otherwise indicated, were from the Oregon State University Benthic Invertebrate Museum (oSUBI), Corvallis, OR; the Museum of Comparative Zoology, Harvard University (MCZ), Cambridge, MA; and the Division of Crustacea of the United States National Museum of Natural History, Smithsonian Institution (USNM), Washington, DC. Types of new species are deposited in crustacean collections of the USNM and OSUBI. Munidopsis marianica New Species Figures 1, 2a, 3a, b Mate'rial studied.-Western Pacific Ocean, 2A. G. Carey, Jr., College of Oceanography, Oregon State University. Corvallis, OR 97331, pers. commun. September 1988.