沖縄島中城湾に出現するドロクイ属2種の仔稚魚の形態変化

Two species of the genus Nematalosa, N. japonica and N. come, are the valuable target species for local fisheries in the Okinawan region of southwestern Japan. We examined the morphological development in larvae and juveniles of these two species collected in Nakagusuku Bay, Okinawa Island. Totally, 59 N. japonica, 89 N. come and 2 their hybrids were identified by morphological, ecological, and molecular methods. Their larvae and juveniles can be distinguished from those of other clupeid species by the number of myomers or dorsal and anal fin rays, location of dorsal fin base and anus, and pigment patterns. Two closely related species also appeared very similarly in general morphological characteristics such as body shape, dorsal and anal fin rays, and pigment pattern on body. Although morphological analyses showed differences in number of myomers between two species, their hybrids were difficult to identify. Accordingly, accurate identification of their larvae and juveniles could be achieved by a combination of distributional, morphological, ecological, and genetic tools.