ИСТИНА

We present the first report on deep-sea enteropneust fauna in the Bering Sea. Three species were recorded: Torquaratorid-1 and Torquaratorid-2 from Torquaratoridae, and Saxipendium sp. from Harrimaniidae. It is the northernmost locality in the Pacific for torquaratorids and the first record of Saxipendium beyond the East Pacific. Torquaratorid-1 is a bathyal epibenthic species found on the Volcanologists Massif slope (Figs. 1A, 2 green). It dominated the soft-sediment community at depths 1830–2290 m, but also was found on hard substrate. Its faecal trails were mainly meandering or rarely a combination of meandering and switchback patterns. Torquaratorid-2 is an abyssal species known from the Volcanologist Massif and Komandorsky Graben (Figs. 1B, 2 magenta) with a spiral counter-clockwise pattern of trails. It is common on soft sediments at depths 3334–4277 m, but did not reach high densities. Our results suggest that the taxon specificity may be the main factor shaping the pattern of trails, meandering or spiral, in torquaratorids. Saxipendium sp. is a bathyal-abyssal species occurring on the Volcanologists Massif slope (1930 m) and north-west of the Volcanologists Massif (3334–3931 m) (Figs. 1C, 2 white). Animals were often recorded with their posterior parts buried in sediment between rocks and with anterior parts exposed on the substratum. Morpho-anatomical analysis of Torquaratorid-1 allows clarifying the diagnosis of Torquaratoridae. It demonstrates several new features: collar coelomoducts, axial complex with pericardial coelom and a stalk skeleton comprising two plates. One character in Torquaratorid-1 – the opening of the collar coelomopores directly into the exterior – is shared with other class of Hemichordata, Graptolithoidea. This morphological condition makes Torquaratorid-1 an important link for understanding the evolution of Hemichordata and Deuterostomia.