A new species of Aspidiophorus (Gastrotricha, Chaetonotida) from the Russian Far East with a key to marine species of the genus.

The Russian gastrotrich fauna is virtually unknown, particularly the marine fauna. In the ocean, investigations have beenrestricted to the White Sea, from where only three fully described species have been reported so far. In this study we describea new species of Aspidiophorus found in a sandy sample collected from off of Vladivostok (Peter the Great Bay, Sea of Japan).Aspidiophorus oculatus n. sp. is the first marine chaetonotid gastrotrich described from Russia and the first representative of theorder Chaetonotida reported from the Sea of Japan. Specimens of the new species are characterized by a body up to 147.5 mmin total length; enveloped by 57 alternating columns of 6570 keeled, elongate scales. Pharyngeo-intestinal junction at U27;the head bears cephalion, hypostomion, pleuria and a pair of eye-spots; the furca is 20 mm long including the 12-mm longadhesive tube; the ventral interciliary field is naked, with the exception of a pair of elliptical, keeled scales occurring near theanus. Morphological differences between the new species and the other 13 marine con-generic taxa are discussed. A key tothe known marine species of the world based on easily identifiable traits, visible in both living and formalin-fixed specimens isprovided.