80 VENUS 69 (1–2), 2010 ©Malacological Society of Japan First Record of the Genus Megadenus Rosén, 1910 (Gastropoda: Eulimidae), Endoparasites of Sea Cucumbers, from Japan Ryutaro Goto Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-Nihonmatsu-cho, Sakyo, Kyoto 606-8501, Japan;
[email protected] The gastropod family Eulimidae is characterised northward extension of the distribution of this genus by its parasitic associations with various in the Pacific. Based on field observations, echinoderms (Warén, 1984). Megadenus Rosén, ecological data on this gastropod species are also 1910 is a genus of the Eulimidae that forms provided. endoparasitic associations with holothurians, although biological information on these snails is Material and Methods limited. Four species have been described in the genus, while additional collection records suggest I collected Stichopus chloronotus at Itton, Kasari the presence of two undescribed species (Warén, Bay, Amami-Oshima Island, southern Japan 1984). The type species of the genus, Megadenus (21°25´N, 129°36´E; Fig. 1A), during 26–29 May holothuricola Rosén, 1910, was described from 2009, and dissected them to search for endoparasitic specimens living in the respiratory tree of gastropods. Stichopus chloronotus is a common Holothuria mexicana Ludwig, 1875 in the Bahamas holothurian species living in shallow waters (Rosén, 1910). Humpreys and Lützen (1972) throughout the tropical Indo-West Pacific. If suggested that another Megadenus species had been gastropods were present, I recorded their number, collected from the respiratory trees of an position and posture in the holothurians. Before unidentified holothurian species in Luzon, the dissection, I measured the volume of the host Philippines, but it was assigned to the genus Stilifer holothurians using a graduated cylinder in the field.