北西太平洋初記録のハダカエソ科魚類Lestidium bigelowiボタンナメハダカ（新称）

抄録

The rare barracudina Lestidium bigelowi Graae, 1967 was reported for the first time from the northwestern Pacific, based on four specimens collected from the vicinities of Okino-torishima Island, Japan, and Guam, at depths of 85–150 m. Previous records of the species had been limited to east of the Seychelles in the western Indian Ocean (type locality), the eastern Pacific off Colombia, and the southwestern Pacific off New Caledonia. Lestidium bigelowi is the only paralepidid species known to have six small, round, discrete mid-ventral luminescent organs, evenly spaced from the isthmus to near the anus, whereas in other species of the family, the luminescent organ is absent or represented by an elongate slender duct (s) extending along the mid-ventral line from the chest to the anus. The following characters are also useful to distinguish the species from its congeners: dorsal fin origin and outer pelvic-fin base more-or-less vertically level, anal-fin rays 28–30, vertebrae 80 or 81, predorsal fin length 54.3–56.5% of standard length (SL), and prepelvic fin length 53.7–56.3% of SL. Because L. bigelowi was previously known only from juveniles, the morphology of much larger individuals (72.3–123.7 mm SL) is described herein. Two specimens collected southwest of Okino-torishima Island represent the first record of L. bigelowi in Japanese waters (within the Exclusive Economic Zone). The new standard Japanese name “Botan-namehadaka” is proposed for the species, being derived from the button-like luminescent organs (“botan”) and the Japanese name for barracudina (“namehadaka”).