A Rare Flatfish, Samaris spinea (Teleostei: Pleuronectiformes: Samaridae) from the Ogasawara Islands, Japan, with Notes on Its Distribution, Taxonomy and Sexual Dimorphism

抄録

A single specimen of the samarid flatfish, Samaris spinea Mihara and Amaoka, 2004, was collected off the northwest coast of Ototo-jima Island, Ogasawara Islands, Japan. This specimen represents the third occurrence of this species and the second record from Japan and the Northern Hemisphere. We report morphological characters of the specimen in detail with discussion of small spines along the dorsal and ventral margins of the caudal peduncle and the intermuscular bones. We confirmed the small spines coming out from large, plate-like scale. It is also revealed that distributional patterns of intermuscular bones of S. spinea are different from those of the congeneric species, S. cristatus: epimerals are absent and hypomerals are present only on abdominal and anterior caudal vertebrae in S. spinea. Although the present specimen bears a testis, male character as prolonged anterior dorsal- and pelvic-fin rays on ocular side is not appeared. This may be related to the presence of a single isopod parasite in the gill. The taxonomic confusion on gender of the generic name is also fixed.