Echinoderms of the Kuril-Kamchatka Trench

Abstract

Echinoderms collected in the Kuril-Kamchatka Trench (KKT) at depths greater than 6000 m by expeditions onboard RV Vityaz and Sonne (KuramBio II) are listed, with some taxonomic and biogeographic remarks. The echinoderm fauna of the KKT (>6000 m) includes 44 species, of which 29 were determined to the species level and 15 to the generic level; 14 species and 6 genera (Echinosigra, Gephyrothuria, Mesothuria, Molpadia, Molpadiodemas and Sonnetrochus) were recorded for the KKT for the first time. The KKT echinoderm fauna mainly comprises species (86%) from the cosmopolitan genera. Of the 29 identified species, 11 (38%) are endemics of the hadal zone, including 6 (21%) endemics of the KKT. Species of holothurians make up more than half of all known echinoderm species in the KKT. The number of echinoderm species at depths 6000–7000 m is 29, which decreases sharply to 16 at depths 7001–8000 m, stabilizes at 17 at depths 8001–9000 m and further declines to 8 from 9001 to 10,000 m. The proportion of holothurians increases with depth from 48% to 87%. The number of species in the KKT echinoderm fauna is much greater than in any other trench. The second–highest echinoderm species richness (19 species) is known from the South Sandwich Trench. Both trenches are located in areas of high primary productivity and are characterized by a high abundance of benthic invertebrates in trawl catches.