ABSTRACT
Deep-sea hemichordates Torquaratoridae gen. sp. reach high abundance up to 12 spec. m-2 at the depths of 1830-2130 m on the slope of the Volcanologists Massif in the south-western part of the Bering Sea, dominating in the benthic community at these depths. Their abundance exceeds by two orders the values recorded earlier. In order to clarify this phenomenon, we examined the gut contents of Torquaratoridae gen. sp. The detritus particles and frustules of planktonic diatoms Thalassiosira, Coscinodiscus, Actinocyclus, Chaetoceros, Neodenticula, and Grammatophora were the most common in the gut, as well as the remains of skeletons of benthic invertebrates with little admixture of mineral particles. According to obtained data, Torquaratoridae gen. sp. are mobile deposit feeders with high selectivity to fresh phytodetritus, able to compete with holothurians occupying similar trophic niche. Unusually high abundance of acorn worms is apparently related to high organic matter flux to the seafloor as a result of spring phytoplankton bloom in the surface water layer of the Bering Sea.
Subject(s)
Invertebrates , Phytoplankton , Animals , SeasonsABSTRACT
An annotated species list of all macrobenthic invertebrates inhabiting the Siberian sector of the Arctic Ocean is presented. The area considered includes the Kara, Laptev and East Siberian seas and the adjacent region of the deep-sea Central Arctic. Entries on species occurrences in the database are supported by corresponding references. Species of Polychaeta, Crustacea and Echinodermata in addition contain information on bathymetric distribution. Apart from published data, 12 taxa were identified in the area for the first time. In total 1574 macrobenthic species were recorded within the considered area. The most species rich was the Kara Sea with 1184 species. The Laptev and East Siberian seas and the Central Arctic showed lower species richness with correspondingly 1105, 780 and 268 species. The much smaller numbers of species in the East Siberian Sea and in the deep-sea Central Arctic can be related to taxonomic impoverishment or/and much smaller study effort in those regions.
ABSTRACT
Histological examination of a specimen of a deep-sea enteropneusts that belongs to a yet undescribed species (Torquaratoridae gen. sp.) revealed numerous trunk coelomoducts. They open into the genital wing coelom as a typical funnels; short ducts communicate with environment through pores located on the outer side of the genital wings. Total number of coelomoducts in a specimen is estimated at several thousand. Trunk coelomoducts have not been found earlier in any member of the phylum. We believe that the release of the male gonad products occurs through coelomoducts of Torquaratoridae gen. sp.
