Ophiuroidea of the Emperor Seamount Chain – diversity, distribution and biogeography

Data on brittle stars from the Emperor Seamount Chain (ESC) are presented, including their distribution across the seamounts of the region, characteristics of their vertical distributions, biogeographical characters, and dominance in macrobenthic communities. This study is based on the results of work with a collection of more than 100 samples and the analysis of more than 70 h of video material obtained during two expeditions on the R/V Akademik Lavrentyev (2019 and 2021) using the ROV Comanche 18. Representatives of 29 species, 17 families, and 21 genera of the class Ophiuroidea have been identified, and their association with different types of substrate (sandy sediment with silt and outcrops of the underlying rock, solidified lava and rocky bottom) on the ESC have been revealed. Dominant species found on different seamounts are Ophiocreas sp., Ophiocten hastatum, Ophiura leptoctenia, Ophiomusa lymani, Ophiopholis aculeata, Ophiura ooplax. The benthos of the ESC was found to contain a large number of brittle star taxa, which were dominant or significant components of the communities. A correlation between different brittle star taxa and specific substrate types was identified. Due to the spatial extent of the ESC, communities contain groups of brittle stars with very different biogeographical characteristics. The Bray-Curtis similarity analysis confirmed the presence of a biogeographical boundary around 37°N, where the North Pacific ophiuroid set of species intersects with that of Central Pacific origin.