2020 年 49 巻 p. 67-73
Two specimens (67.5–75.1 mm standard length; SL) of Plectranthias maekawa Wada, Senou and Motomura 2018 (Serranidae: Anthiadinae), previously recorded only the Tokara Islands, Kagoshima Prefecture, Japan, were collected from Okinawa-jima and Yonaguni-jima islands, Okinawa Prefecture, Japan. The present specimens, described herein in detail, represent the first records of the species from Okinawa Prefecture. Although the body depth (% of SL) has been regarded as one of diagnostic characters between P. maekawa and two closely-related congeners (Plectranthias helenae Randall, 1980 and Plectranthias wheeleri Randall, 1980) in the original description of P. maekawa, that of the present new specimens was overlapped with the latter two species (viz., 33.5–37.7% of SL in P. maekawa, 35.5–38.7% SL in P. helenae, and 35.6–37.9% of SL in P. wheeleri). The number of serration on the margins of subopercle and interopercle in P. wheeleri and P. maekawa has also been regarded as a diagnostic character for the two species, but additional specimens described in this study showed that the number of serration changed ontogenetically, and it overlapped in the similar-sized specimens of the two species. However, the validities of other diagnostic characters given in the original description of P. maekawa are reconfirmed in this study (viz., number of pectoral-fin rays, scales on above and below lateral line, morphometrics of body width, head length, third dorsal-fin spine length, caudal-peduncle length and depth, and both coloration of fresh and preserved conditions). In addition, three specimens of P. wheeleri (71.3–83.7 mm SL) from the Okinawa Islands, are reported here as the first records of the species from Okinawa Prefecture; it has been previously recorded from Japan (Sagami Bay, and Tokara and Amami islands), Taiwan, Indonesia, and Australasia.