New Species of Scale-worms (polychaeta: Polynoidae) from the Hydrothermal Rift-area of the Mariana Back-arc Basin in the Western Central Pacific

•Polynoid polychaetes collected by the Mariana Back-Arc Basin Expedition in the western Central Pacific in 1987 are described. They include four new species belonging to three subfamilies and four genera of Polynoidae: Macellicephalinae: Levensteiniella raisae; Lepidonotopodiinae: Lepidonotopodium minutum; and Branchinotogluminae: Branchinotogluma burkensis and Opisthotrochopodus marianus. Included also is a brief summary of the subfamilies, genera, and species associated with deep-sea hydrothermal vents, deep seep-sites, trenches, abyssal basins, experimental deep wood panels, and caves. In her revision of the genera and species that had been grouped in Macellicephalinae Hartmann-Schröder, 1971, containing mostly abyssal species, Pettibone (1976) separated Macellicephalinae and five additional subfamilies: Macellicephaloidinae (four species), Macelloidinae, Bathyedithinae, Polaruschakovinae (two species), and Bathymacellinae. In the remaining Macellicephalinae, in addition to Macellicephala (seven species), six new genera were added: Bathykermadeca, Bathyeliasona (three species), Bathyvitiazia, Bathyfauvelia, Bathycatalina, and Bathykurila. Subsequently, additional new subfamilies, genera, and species have been added. Pettibone (1979) emended and added to Macellicephalinae Bruunilla natalensis (Hartman, 1971). Levenstein (1975) added two new species oí Macellicephala from the deep-sea trenches in the Antarctic: M. tricornis and M. grandelytris. The latter species was later transferred to Bathyfauvelia by Levenstein (1978a:77). Levenstein (1975) also added the new species Macellicephaloides sandvichensis. Levenstein (1978b) added the new species Macellicephala alia from the Palau trench and the new genus Bathymariana for B. zebra from the Ryuku trench. The latter genus was placed in Bathyedithinae by Levenstein (1984). From the deep Canadian basin in the Arctic Ocean, Levenstein (1981) added the new genus Bathypolaria for B. carinata in Macellicephalinae; the new species Bathyedithia tuberculata in Bathyedithinae; and the new genera Bathymiranda for B. microcephala and Bathycanadia for B. diaphana in Polaruschakovinae. In the same subfamily, Loshamn (1981) added the new genus Diplaconotum for D. paucidentatum (Eliason, 1962) from the Skagerrak. From the Japanese trench, Levenstein (1982a) added a new species of Macellicephaloides, M. villosa. From the Tasman trench, Levenstein (1982b) included a key to the genera of Macellicephalinae and added two new genera: Bathytasmania for B. insólita, and Bathynotalia for B. perplexa. The latter genus and species were referred to Harmothoinae by Pettibone (1985a: 130), based on the figure of the prostomium showing long lateral antennae (not mentioned in the text): the prostomium is harmothoid, with cephalic peaks; prostomial lateral antennae are lacking in Macelli138 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON cephalinae. From the Kurile-Kamchatka trench, Levenstein (1983) added a new species of Macellicephaloides, M. improvisa, and included a key to the seven species of the genus. Levenstein (1984) summarized the distributional patterns for the 19 genera and 38 species of polynoid polychaetes belonging to the six deep-sea subfamilies covered in Pettibone (1976), along with the additional genera and species indicated above. They were widely distributed on the abyssal plains and in the deep-sea trenches. The Macellicephalinae had the greatest number of genera (10) and species (21). Three subfamilies were represented by fewer genera and species: Macellicephaloidinae (one genus, seven species), Bathyedithinae (two genera, three species), and Polaruschakovinae (four genera, five species). Two subfamilies were monotypic: Macelloidinae and Bathymacellinae. These groups were defined as ancient or primary abyssal because all the representatives lived only in abyssal depths except for a few that ascended secondarily. Members of the Macellicephalinae showed the greatest vertical range and panoceanic distributions, mostly in the Northern Hemisphere. This group appeared to be the most ancient of the abyssal polynoids. Since the summary of the group by Levenstein (1984), additional new subfamilies, genera, and species have been added, chiefly in connections with studies on the hydrothermal vents in the northeastern Pacific, deep seep-sites in the Gulf of Mexico, and deep wood panel and cave studies in the northwestern Atlantic. From the hydrothermal rift-area off western Mexico at 21°N, Pettibone (1983) added the new subfamily Lepidonotopodiinae for Lepidonotopodium fimbriatum. From the Galapagos vent, the new subfamily Branchipolynoinae for Branchipolynoe symmytilida, commensal with the deep-sea mussel, was added by Pettibone (1984a). Also from the vents, Pettibone (1984b) added two new species oí Lepidonotopodium: L. riftense and L. williamsae and included a key to the species of the genus. From the North Atlantic, Pettibone ( 1985a) added to Macellicephalinae two new genera: Pelagomacellicephala for P. iliffei, from a cave in the Bahamas, and Bathybahamas for B. charleneae from off the Bahamas, associated with experimental wood panels, and a new species of Bathykermadeca, B. turnerae, from off the Virgin Islands, also associated with wood panels. Pettibone (1985b) added the new subfamily Branchiplicatinae for Branchiplicatus cupreus from the vents off western Mexico at 21°N. From the vents off the Galapagos and western Mexico, Pettibone (1985c) added the third new subfamily having arborescent branchiae, Branchinotogluminae for two new genera: Branchinotogluma, with three new species: B. hessleri, B. sandersi, and B. grasslei; and Opisthotrochopodus for O. alvinus. A key to the three branchiate subfamilies was included. Pettibone (1985d) added to Macellicephalinae the new genus Levensteiniella for L. kincaidi, and the new species Macellicephaia galapagensis from the Galapagos, and from the Santa Catalina Channel, the new genus Natopolynoe for A^. kensmithi. Included also was a summary of the polynoid polychaetes collected by DSRV Alvin in the Galapagos Rift in 1979 and East Pacific Rise at 21''N in 1982, along with a key to the subfamilies, genera, and species. From the deep seep-sites at the Florida escarpment in the Gulf of Mexico, Pettibone (1986) added a new species of Branchipolynoe, B. seepensis, commensal in the mantle cavities of the Gulf of Mexico mussels, along with a key to the two species of the genus. From the hydrothermal vents in the Northeast Pacific Explorer and Juan de Fuca Ridges, Pettibone (1988) added two new species: Lepidonotopodium piscesae in the Lepidonotopodiinae, and Opisthotrochopodus tunnicliffeae in Branchinotogluminae. VOLUME 102, NUMBER 1 139 A new species oï Macellicephala from the Antarctic, M. australis, was added by Wu and Wang (1987). Thus to the summary by Levenstein (1984), four new subfamilies have been added (total 10), nine new genera (total 28), and 20 new species (total 58). Four of the new genera were added to Macellicephalinae (total 14) and seven new species (total 28). Two of the new species were referred to Macellicephala, one to Bathykermadeca. Additional polynoids were collected by the Mariana Back-Arc Basin Expedition during April and May 1987, where active hydrothermal vents were found in the western Pacific off the Mariana Islands about 18°N and 144''E. The polynoid polychaetes were collected during dives of DSRV Alvin and sent to me for study by Robert Hessler, along with information on the collecting sites. Four species of polynoids were collected on two Alvin dives: dive 1836, referred to as Snail Pits in Burke Field (1 species), and dive 1843, designated as Alice Springs (3 species). The polynoids agree with some of the subfamilies and genera that were previously described from the hydrothermal vents in the eastern Pacific. Burke Field {Alvin dive 1836, 27 Apr, 18°10.9'N, 144°43.2'E, 3660 m) was an extensive area of low temperature vents at the southern end of an active spreading zone and dominated by pillow basalts. The Snail Pits vent had a water temperature of 15°C, with small, dense aggregations of "hairy" snails that clogged the vent openings. The hot vent water was crystal clear. The single polynoid collected is described below under Branchinotogluminae: Branchinotogluma burkensis, new species. Alice Springs {Alvin dive 1843, 4 May, 18°12.6'N, lAA'AlA'E, 3640 m) was an extensive area dominated by pillow basalts with sharp cliffs up to 40 m high. Some low temperature vent sites (10-25°C) were characterized by cloudy, particle-filled water and dense concentrations of white anemones. Some high temperature vents (up to 250°C) had dense aggregations of "hairy" snails, crabs, and shrimps, with emerging crystal clear water. The three species of polynoids collected are described below under three subfamilies: Macellicephalinae: Levensteiniella raisae, new species (1 specimen): Lepidonotopodinae: Lepidonotopodium minutum, new species (9 specimens); and Branchinotogluminae: Opisthotrochopodus marianus, new species (12 specimens). The types are deposited in the National Museum of Natural History, Smithsonian Institution (USNM). Subfamily Macellicephalinae Hartmann-Schröder, 1971 emended Pettibone, 1976 Levensteiniella Pettibone, 1985 Levensteiniella was erected for the single species L. kincaidi from off"western Mexico at 2rN and the Galapagos Rift (Pettibone 1985d:741). An additional species is added from the Mariana Back-Arc Basin. Levensteiniella raisae, new species