A New Record of Brittle Star <i>Ophiopsila</i> cf. <i>polyacantha</i> (Echinodermata: Ophiuroidea) from Southwestern Japan, with Notes on its Bioluminescence

Abstract

Two specimens of Ophiopsila cf. polyacantha H. L. Clark, 1915 are described from approximately 15 m water depth at Kakeromajima island, Amami Islands in southwestern Japan. The species occurs on sandy bottoms with the disc buried and the arms extended above the substratum. Bioluminescence and burrowing behavior are described. The specimens are clearly morphologically different from the two species of Ophiopsila Forbes, 1843 previously recorded from Japan. The new Japanese name "Kin-habu-toranoo-kumohitode" is proposed.

The campylogomphosis: A new kind of joint in echinoderms

“…8e) of the joint revealed the interlocking and curvature of the trabeculae into stromal pores. A campylogomphosis was also illustrated by Okanishi et al (2023) in distal (younger) vertebrae of Ophioteichus multispinum (their fig. 5h,i), but there was strong ankylosis of the suture in the ventral groove of proximal (older) vertebrae (their fig.…”

“…These restricted areas of ankylosis were also observed in O. filograneus and 14 other species by LeClair (1995) and were noted in other works by Hendler (2018) as a “callus of imperforate stereom” (e.g., Litvinova, 1989; Pearse et al, 1998). Areas of ankylosis on articular surfaces of proximal (older) and distal (younger) vertebrae are present in the ophiuroid Ophioteichus multispinum (Okanishi et al, 2023: fig. 5a,b,f,g).…”

The First Record of <i>Ophioteichus multispinum</i> (Echinodermata: Ophiuroidea) from Japan, with Notes on Its Ossicle Description and Ecology

“…Ophiuroids (Echinodermata) constitute the largest number of species within the phylum Echinodermata, and they inhabit nearly all marine habitats (Stöhr et al 2012;Okanishi 2016). Recent investigations by SCUBA diving have revealed many taxonomic discoveries of benthic invertebrates from the subtidal zone, usually at depths greater than 10 m in Japan (e.g., Kise et al 2017;Naruse and Yoshida 2018;Okanishi and Fujii 2020;Yamana et al 2022). Kushimoto is located at the southern tip of Honshu (the largest island in Japan) and is a warm region due to the Kuroshio Current flowing in its vicinity (Fig.…”

“…1). Kushimoto is the northern limit of tropical coral habitats in Japanese waters and is considered to have high biodiversity (Okanishi and Fujii 2020). The ophiuroid fauna at deeper than 10 m in Kushimoto is unexplored and potentially rich according to previous discoveries of benthic invertebrates in this area.…”