First records of deep-sea Munnopsidae (Isopoda: Asellota) from the Kuril Basin of the Sea of Okhotsk, with description of Gurjanopsis kurilensis sp. nov.

Abstract

The deep-sea Munnopsidae Lilljeborg, 1864 of the Kuril Basin of the Sea of Okhotsk, the Bussol Strait, as well as the western abyssal slope of the Kuril-Kamchatka Trench (KKT) off the Bussol Strait were studied. The material was collected during the expedition SokhoBio (Sea of Okhotsk Biodiversity Studies) in the summer of 2015. The first data on the composition and distribution of the family Munnopsidae from the SokhoBio samples are presented. In total 2190 individuals of Munnopsidae from 53 species, 26 genera and seven subfamilies have been collected at 19 of 21 C-EBS stations at all 11 sites of the SokhoBio expedition. The most abundant subfamily in the samples was Ilyarachninae Hansen, 1916 (36%), followed by Eurycopinae Hansen, 1916 (29%). In the Kuril Basin 39 species of 20 genera and 5 subfamilies were found, the main portion of munnopsids here was represented by the Ilyarachninae (39%), followed by the group of genera incertae sedis (31%) and Eurycopinae (27%). The abyssal munnopsid fauna of the Kuril Basin is an intermediate in terms of diversity and species richness between the adjacent studied abyssal areas, the Sea of Japan and the open abyssal of the KKT. Half of the collected species, 27 species (51%) are shared with the KKT area, 22 species (41.5%) are common to the Kuril Basin and the Pacific sites. About 80% of the collected species are new to science. One of the new species, Gurjanopsis kurilensis sp. nov. is described herein. GurjanopsisMalyutina and Brandt, 2007 is the only genus within the Munnopsidae having a posteromedial notch in the pleotelson containing tiny uropods and the anus. A similar notch in the pleotelson containing uropods within Janiroideа Kussakin, 1967 is known only in species of Jaera Leach, 1814 (Janiridae G.O. Sars, 1897). The male pleopods of Gurjanopsis which cover the pleopodal cavity of the pleotelson are unusual for the family. This “operculum” is formed by the small pleopods 1 and 2 and the enlarged exopods of pleopods 3. This is similar to the pleopodal structure found in the primitive asellote superfamilies Aselloidea Latreille, 1802 and Stenotrioidea Hansen 1905, while in Janiroideа only pleopods 1 and 2 are operculate. The new species is the third species of the rare genus Gurjanopsis and the first record of the genus, previously only known from the deep-sea of the Arctic and the Antarctic, for the Pacific Ocean. The finding a species of Baeonectes Wilson, 1982 in abyssal depths of the Kuril Basin is the deepest record of the genus.