Partial redescriptions of three holothurians with 'hook papillae' (Apodida: Chiridotidae): Taeniogyrus japonicus (Marenzeller, 1882), T. dendyi (Mortensen, 1925), Scoliorhapis theelii (Heding, 1928)

摘要

New specimens of Taeniogyrus japonicus (Marenzeller) were collected from Iwami coast and Sado island of the Sea of Japan. According to detailed observations of external and internal organs, we transferred T. japonicus, T. dendyi (Mortensen), and Scoliorhapis theelii (Heding) to the newly revived genus Scoliodota, with a large retractor organ and hook papillae as major diagnostic characters. We also concluded that Scoliorhapis dianthus Solis-marin et al. is a synonym of T. japonicus. Our molecular phylogeny and genetic distance analysis showed that specimens from Iwami and specimens from Sado of T. japonicus form a monophyletic clade, indicating that they are most likely the same species despite their morphological variation. The phylogenetic analysis also indicated that T. japonicus forms a sister group relationship with Taeniogyrus verruculosus Yamana & Tanaka and Scoliorhapis sesokoensis Yamana & Tanaka, suggesting that Taeniogyrus is not monophyletic. Taken together, these results brought new insights to sea cucumber diversity in Japanese waters.