ИСТИНА

Order Desmoscolecida comprises free-living marine nematodes featured by simple and thin cuticle with prominent rings covered by clay particles, large vesicular amphids, paired reddish ocelli, peculiar locomotion by means of body setae, parental care of eggs attached to the female body, etc. Molecular data support relationship of Desmoscolecida to the order Monhysterida; both taxa share also outstretched female gonads and non-spiral amphids. Desmoscolecid species occur worldwide in marine sediments from supralittoral belt to the maximal depths of the deep-sea; a few species inhabit even soil and freshwater sediments. However, the desmoscolecid species look very similar everywhere regardless of the geographical region and milieu. Diet of desmoscolecid species remains unknown thus far. All the specimens examined, either from shallow or from deep-sea, showed no content in the intestine. Percentage of desmoscolecids in nematode assemblages reaches about 10% in deep-sea silty sediments whereas the highest taxonomical diversity is documented in shallow medium sands. Study of desmoscolecids in Angola Basin (SE Atlantic, about 5500 m deep) reveals 16 species of Desmoscolex, one species of Protricomoides and one species of Tricoma (altogether 7.5% of all nematode specimens). 16 species of them are new for science while one species of Desmoscolex and one species of Protricomoides were described formerly from SE Pacific deep-sea. Deep-sea fauna of Desmoscolecida is characterized by high comparatively high abundance, low species diversity with dominant genera Desmoscolex and Tricoma, and widespread to cosmopolitan distribution of species in World Ocean abyss. (Support: RUSSIAN FOUNDATION FOR BASIC RESEARCH, grant number 18-04-00237). – M.V. Lomonosov Moscow State University, Moscow, 119991, Russia. E-mail: AVTchesunov@yandex.ru