The first record of Asellota (Isopoda) from hydrothermal vent biotopes of the submarine Piip Volcano, Bering Sea, with descriptions of two new species of Munnopsidae

Abstract

Three species of asellote isopods (Crustacea) were found in hydrothermal vent biotopes on the submarine Piip Volcano, Bering Sea, at the depth of 373–472 m. Collection was obtained during 82−nd cruise of the R/V Akademik M.A. Lavrentyev using ROV Comanche-18. One species of the family Janiridae was tentatively identified as Janiralata cf. bilobata. Two species of the family Munnopsidae, Eurycope andreyi sp. nov. and Ilyarachna piipaensis sp. nov. were described as new to science. Both new species differ from their congeners by the unusually broad pleotelson: in Eurycope andreyi sp. nov., it is not narrower than pereonite 5, in contrast to all other species of the genus; in Ilyarachna piipaensis sp. nov., the pleotelson is broader than pereonite 7 and cephalon, while the other Ilyarachna species show opposite proportions. The broad pleotelson is associated with the increase in the size of the pleopods occupying the entire internal volume of the pleotelson from its ventral side. Pleopods have a respiratory function and their increase can be an adaptation to the reducing conditions of hydrothermal biotopes on the volcano. Photos and video records of underwater landscapes and benthic hydrothermal communities showed that Eurycope andreyi sp. nov. is the most abundant macrobenthic species on the Southern summit of the volcano, where it reaches a density of up to 40 individuals per square decimeter on bacterial mats.