Crasiella clauseni, a New Gastrotrich Species (Macrodasyida, Planodasyidae) from Jeju Island, South Korea

A new gastrotrich species of the genus Crasiella (Planodasyidae) is described from the sublittoral sandy bottom of Jeju Island, South Korea. The family Planodasyidae and the genus Crasiella are recorded for the first time from East Asia. Crasiella clauseni n. sp. differs from its congeneric species by the combination of characters: absence of cephalic sensory pits; unseparated arrangement of anterior tubes and ventrolateral tubes, comprising about 120 adhesive tubes along whole body length; 5-7 horizontal rows of adhesive tubes and a pair of TbV in the anterior part of pharyngeal region; bifid pedicles with 8-11 posterior adhesive tubes; and tube-shaped seminal receptacle and copulatory organ. This paper deals with description of the new species, and provides a key to the species of genus Crasiella.