琉球列島から得られたハナダイ科イズハナダイ属魚類Plectranthias inermisレンガハナダイ（新称）の日本初記録およびP. altipinnatusチゴハナダイとの形態比較

抄録

A single specimen of Plectranthias inermis Randall, 1980 (Perciformes: Serranidae), widely distributed in the eastern Indian Ocean from Christmas Island to the South Pacific Ocean and around Mauritius (western Indian Ocean), was collected from the Ryukyu Islands, Japan, thereby representing the first record of P. inermis in Japan and northernmost record of the species [previously documented northern limit being Luzon, the Philippines (type locality)]. The new standard Japanese name “Renga-hanadai” is proposed for P. inermis. A morphological comparison of P. inermis with the closely related species Plectranthias altipinnatus Katayama and Masuda, 1980 revealed that the former differed from P. altipinnatus as follows: first dorsal-fin spine longer than tenth spine [tenth dorsal-fin spine length 50.0–77.8% (mean 62.5%) of first spine length vs. 100.0–137.5% (111.2%) in P. altipinnatus]; second anal-fin spine relatively long [length 36.3–42.2% (38.7%) of head length vs. 27.8–34.0% (31.9%) in P. altipinnatus]; dorsal-fin base relatively short [length 46.9–51.4% (48.7%) of standard length vs. 51.7–56.3% (54.6%) in P. altipinnatus].