A New Gastrotrich Species of the Genus Ptychostomella (Macrodasyida, Thaumastodermatidae) from South Korea

摘要

A new marine gastrotrich species, Ptychostomella jejuensis n. sp. belonging to the family Thaumastodermatidae, is described on the basis of the specimens from subtidal sand bottom at about 6-7 m depth of Jeju Island, South Korea. Ptychostomella jejuensis n. sp. is distinguished from its congeneric species with smooth cuticular armature by the character combination: (1) small body up to about 160 pm in length; (2) presence of knob-like cephalic tentacles; (3) absence of dorsal and ventral adhesive tubes; (4) bifid pedicles; (5) pyriform copulatory organ. Under scanning electron microscopy, numerous epidermal gland openings were observed in the new species, characteristically flanking a bristle. Taxonomic accounts on the affinities, some brief remarks on the epidermal gland openings and the cooccurrence with P orientalis Lee and Chang, 2003 are also presented with detailed illustrations and scanning electron photomicrographs.