First records of two morays, Gymnothorax mucifer and Gymnothorax niphostigmus (Anguilliformes: Muraenidae) from Japan

Abstract

Two species of the moray eels, Gymnothorax mucifer Snyder, 1904 and Gymnothorax niphostigmus Chen, Shao and Chen, 1996 are reported from Japanese waters for the first time. The former has been previously recorded from Australia, Taiwan, New Caledonia and Hawaii, and the latter from Vietnam and Taiwan. Two specimens of G. mucifer [356 mm and 392 mm of total length (TL), collected from Okinawa Island] conformed with the diagnostic characters and the presence of dark streaks on the branchial basket of the species. Although Gymnothorax mucifer is closely similar to Gymnothorax kidako (Temminck and Schlegel, 1846) in general body coloration and proportions, they differ in color pattern of the anal fin (whitish margin mostly continuous but posteriorly represented by separated spots in G. mucifer vs. entirely continuous in G. kidako), the pattern of the lower jaw (no defined patterned vs. obscured reticulation), and the presence of dark streaks on the branchial basket (present vs. absent or not obvious). One specimen of G. niphostigmus (514 mm TL, collected from Danjo Islands, western Nagasaki Prefecture) fully conformed with the diagnostic characters of the species. The color of the margin of dorsal fin was described as “darkish” for the species in the original description. However, the species including holotype and paratypes has a broken whitish margin on the fin. Although G. niphostigmus is closely similar to Gymnothorax intesi (Fourmanoir and Rivaton, 1979) in both proportional characters and coloration, the former is characterized by smooth edges of the teeth (vs. distinct serrations), the presence of mid-premaxillary teeth (vs. absent), and the margin of the dorsal fin coloration discontinuous whitish, the width less than the anal fin margin (vs. continuous whitish, the width similar to the anal fin margin). The new standard Japanese names, “Takanoha-utsubo” and “Watayuki-utsubo”, are proposed for G. mucifer and G. niphostigmus, respectively.