The Genus Euthalenessa (Sigalionidae: Polychaeta) from Thai and Japanese Waters

Abstract

Two species of sigalionid polychaetes of the genus Euthalenessa, i.e., E. festiva (Grube, 1875) and E. digitata (McIntosh, 1885), are reported from the Andaman Sea, southwestern Thailand and Tanabe Bay, Japan. The latter species is also reported from the Gulf of Thailand and is a new record from Thai and Japanese waters. The position of the ceratophore of the median and lateral antennae, the occurrence of stylodes on the anterior and posterior lower lobes of segment 2- 5, and the number of pairs of labial ctenidia are the main characters used for distinguishing these two species from other members of the genus.