Kinorhynchs (Kinorhyncha) from methane cold seeps in the Bering Sea, with biogeographical discussion and ecological notes

Abstract

Several species of kinorhynchs, including representatives of Pycnophyes schornikovi Adrianov, 1999 in Adrianov et Malakhov, 1999 and Condyloderes shirleyi Neuhaus et Higgins, 2019 in Neuhaus et al.2019, previously known from other localities in the Pacific Ocean, were found in detritus washed off the material of bacterial mats collected at the cold methane seeping area on the Chukchi bathyal slope in the Bering Sea. These specimens were studied and illustrated using light (DIC) and electron (SEM) microscopy to analyze morphological variations within representatives of these species collected from rather distant localities in the Pacific Ocean. Redescription of P. schornikovi is provided with careful mapping of all sensory spots, setae and glandular cell outlets, not sufficiently illustrated in the original description. Current taxonomic contributions have clearly showed the taxonomic significance of these structures, becoming a standard element in taxonomic descriptions of kinorhynchs. P. schornikovi appears to be the first eurybathic species of the Pycnophyidae in the Pacific, being distributed from shallow water to bathyal depth. C. shirleyi, characterized by a marked variation of some diagnostic morphological features even in the type locality in the North-East Pacific, appears only the second representative of the genus Condyloderes with the transoceanic (amphipacific) distribution. Both these species, P. schornikovi and C. shirleyi, constitute the first representatives of these genera in the Bering Sea. In the Pacific Ocean, kinorhynchs still have never been reported from the extreme environments of cold seeps. P. schornikovi and C. shirleyi appear to be the first representative of the genus found in the methane seepage area. Deep-sea communities of this cold seepage area are described and illustrated with ROV facilities. Biogeography discussion for both species and probable explanation of the transoceanic (amphipacific) distribution of Condyloderes shirleyi are suggested and illustrated.