Biodiversity of echiurans (Echiura) of the Kuril-Kamchatka Trench area

Abstract

During KuramBio and KuramBioII (Kuril Kamchatka Biodiversity Studies) expeditions of 2012 and 2016 years, 12 sites across the Kuril-Kamchatka abyssal plain and 11 sites along Kuril-Kamchatka Trench area (KKT) were surveyed and sampled and benthic communities were investigated. Samples, which comprised over 300 echiurans from 12 species of 11 genera belonging to the family Bonelliidae and Thalassematidae, were collected. The family Bonelliidae is most common in abyssal and hadal environments in the world ocean with high abundances in all investigated regions, while Thalassematidae is reported first time from the hadal depth. Species identified as representative of the genera Maxmuelleria have been noted first time in Pacific. Previously known echiuran Bonellia pacifica suggested to be Pseudoikedella achaeta. The description of deep-water echiurans from the investigated areas is the second one based on complete specimens with living colouration. The descriptions provide new information on the distribution, abundance, morphology and taxonomic details of the species, which were previously noted from the northwestern Pacific and described from damaged or incomplete specimens. The knowledge of the geographic ranges of these genera are expanded and discussed.