Nezumia burragei

Comments on Japanese record of Nezumia burragei

(Fig. 180)

Kamohara (1937) recorded N. burragei (Gilbert, 1905) from Japan based on a single 350 mm long specimen obtained at the Mimase fish market, Kochi. This is a very rare species, which elsewhere is known only from the holotype from Hawaii at a depth of 543–603 m (USNM 51641, 44.2 mm HL, 254+ mm TL; examined here). The occurrence of N. burragei in Japan is quite dubious, considering that no additional specimens have been obtained despite the relatively shallow occurrence of the species and extensive trawl surveys in southern Japan over the past several decades. Citing Kamohara’s (1937) record, all subsequent authors have believed N. burragei to occur in Japanese waters (e.g., Matsubara 1955; Okamura 1970a, 1984b, 1988; Nakabo 1993, 2000, 2002; Shinohara et al. 2001; Nakabo & Kai 2013). Unfortunately, the voucher specimen of Kamohara (1937) was apparently lost during the WWII, which makes it difficult to reconfirm the Japanese record of this species.

However, Kamohara’s (1937) specimen appears to be attributable to a different species of Nezumia, due to notable differences between his figure (Fig. 180) and the holotype of N. burragei (see Gilbert 1905: fig. 260). Kamohara (1937) illustrated his specimen as having the ventral surface of the snout only narrowly naked above the upper lip, and the posterior margin of the naked area not extending beyond a vertical through the anterior rim of the orbit. In contrast, the ventral surface of the snout and the lower half of the suborbital area are completely naked in the holotype of N. burragei, with the hind margin of the naked area extending to above the posterior margin of the upper jaw. The difference between the two specimens is also evident in the dorsal contour of the head. Kamohara’s (1937) figure shows that the predorsal contour of his specimen was prominently humped over the nape, whereas in the holotype, the dorsal contour of the head is straight from above the orbit to the first dorsal-fin origin.

It is most likely that the record of Kamohara (1937) represents a misidentification of N. rara sp. nov. described here. Many features of his specimen, including fin-ray counts, head squamation, and the general appearance, agree well with those of the new species. Another possibility is that his specimen was a representative of N. proxima (Smith & Radcliffe in Radcliffe, 1912), a moderately common species at upper and mid-slope depths in the Pacific off southern Japan. Although Kamohara extensively surveyed the deep demersal fishes of Tosa Bay and adjacent waters, he did not record N. proxima during his career. Nezumia burragei appears to be confined to the Hawaiian Archipelago, and is unlikely to occur in Japanese waters. Therefore, this species is excluded from the list of Japanese grenadiers in this study.