Larval identification following metamorphosis in the slender brown moray Strophidon ui from the western North Pacific

Abstract

Leptocephalus larvae collected from the western North Pacific, and characterized by yellow head pigmentation and many myomeres, were identified as the slender brown moray Strophidon ui following observations of metamorphosis in an aquarium. The leptocephali had 184–196 total myomeres (84–90 predorsal, 116–122 preanal) and 95–102 last vertical blood vessel myomeres. A horizontally elongate group of irregular melanophores before and behind the eye formed a poorly defined band. Some irregular melanophores on the iris encircled the pupil, and minute melanophores occurred ventrally on the spinal cord and along the dorsal and anal fin bases. Yellow pigments were present in anterior and posterior regions adjacent to the eye in fresh specimens. It was possible to clearly distinguish the leptocephali of S. ui from six unassigned leptocephalus types and Gymnothorax minor reported previously from the same region, owing to the lower total myomere counts (106–142) in the latter. This is the second description of specifically identified muraenid leptocephali from the western North Pacific.