Identification of first recorded ophichthid larvae of Ophichthus celebicus and O. macrochir (Anguilliformes; Ophichthidae) from Japan, based on morphometric and genetic evidence

Two types of ophichthid larvae collected from Japanese coastal waters around Kyushu and Shikoku were identified by DNA barcoding as Ophichthus celebicus (Bleeker 1856) and O. macrochir (Bleeker 1852). These two species have not been reported from Japan previously. The leptocephalus of O. celebicus was found to have melanophore spots or streaks on the eighth to last myosepta on the midline of the body. The metamorphic larva of O. macrochir was found to have subcutaneous melanophore distributed along myosepta in every first to fifth myomeres on the midline of the body. The larvae of those two species were distinguishable from other ophichthid larvae reported from Japan by these morphological features. The new standard Japanese names, "Torinoko-umihebi" and "Kuronaga-umihebi", are proposed for O. celebicus and O. macrochir, respectively.