First record of sea urchin-associated Epizoanthus planus from Japanese waters and its morphology and molecular phylogeny

抄録

The species Epizoanthus planus is the only known described zoantharian with an association with echinoderms, and it is known to live on the spines of living sea urchins from the family Cidaridae. This species has been reported from 741 to 1019 m in the Indian Ocean and the East China Sea. However, diagnostic characters are lacking in both the original description and subsequent studies. The present study reports the first record of E. planus from Japanese waters (300–400 m) based on a newly collected specimen, and this record slightly extends the species distribution range in the northwest Pacific Ocean. This new record increases the number of Epizoanthus species in Japanese waters to at least five species. Although many taxonomy and diversity studies have focused on specimens from SCUBA-based collections in Japanese waters, few studies have focused on zoantharians in deeper waters below SCUBA diving limits. The results of the present study highlight the importance of examining specimens from deeper waters to better understand the overall diversity of the order Zoantharia.