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Articles
Published: 2019-10-21

First observation of the "double-faced X-framed cup ossicle" extracted from a deep sea holothurian in Japan

Wakayama Prefectural Museum of Natural History, Funo 370-1, Kainan, Wakayama 642-0001, Japan
Research Center for Subtropical Fisheries, Seikai National Fisheries Research Institute, Fisheries Research and Education Agency, Fukai-Ohta, Ishigaki, Okinawa 907-0451, Japan
Biodiversity Genomics Research Group, Department of Applied Chemistry and Biochemistry, National Institute of Technology, Wakayama College, 77 Noshima, Nada, Gobo City, Wakayama 644-0023, Japan
Biodiversity Genomics Research Group, Department of Applied Chemistry and Biochemistry, National Institute of Technology, Wakayama College, 77 Noshima, Nada, Gobo City, Wakayama 644-0023, Japan The University Museum, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 133-0033, Japan
Echinodermata Cucumariidae Dendrochirotida DNA barcoding molecular phylogeny

Abstract

A New type ossicle form, “double-faced x-framed cup ossicle” is discovered from the undescribed deep sea holothuroid. To give a definite view on the substantial qualities of this ossicle, a SEM observation on the ossicles and a DNA barcoding analysis are conducted. Although the most internal and external morphologies of the present species agree well with the characteristics of the family Cucumariidae Ludwig, 1894, the ossicles morphologies mostly does not agree with the congeners of Cucumariidae. On the other hand, our molecular study indicates a possibility that the specimens are not cucumariids, but belong to a sister group of Cucumariidae. In our present observation, some of the peri-oral ossicles show a very similar property with the small x-framed cup-shaped structures (which sometimes occurs in cucumariids). Therefore, the double-faced x-framed cup ossicle probably could be considered as the results of derivation from the x-body: in which four extra-arms developed on the bottom face of a cup ossicle, and finally these arms equipped with an extra-rim.