Five specimens of scaleless dragonfish of the genus Melanostomias (Stomiidae: Melanostomiinae) were collected off the Ogasawara Islands, southern Japan and Fukushima Prefecture, Pacific coast of northern Japan. The specimens conformed to Melanostomias nigroaxialis Parin and Pokhilskaya, 1978 as follows: tips of the upper and lower jaw teeth bifurcated; chin barbel distally expanded from midpoint, the dorsal and ventral expanded areas membranous and transparent, and including small luminous bodies; a single ovoid body without a terminal filament on terminal part of chin barbel; distinct luminous patch on dorsal surface of head absent; and axis of chin barbel almost entirely black, except terminal part. However, the present specimens had a shorter chin barbel than noted in the original description of M. nigroaxialis. Because a plot of barbel lengths (as % of standard length) versus standard length of the present specimens and three specimens examined in the original description indicated that barbel lengths tended to decrease with growth, the difference in barbel length between the two groups of specimens was consistent with intraspecific variation. In addition, the present specimens had different numbers of VAV, AC, IC, VAL and OA photophores compared with the original description of M. nigroaxialis, although the ranges were less than the those in many congeneric species, also indicative of intraspecific variation. Consequently, the present specimens were identified as M. nigroaxialis, previously known only from the Banda Sea, southern Philippines Sea and northern New Zealand. This is the northernmost record of M. nigroaxialis, and first from Japanese waters. The new standard Japanese name “Tomoshibi-kanten-tokagegisu” is proposed for this species.
