EMBRYONIC AND MORPHOLOGICAL DEVELOPMENT OF LARVAL AND JUVENILE CORAL TROUT, PLECTROPOMUS-LEOPARDUS

Embryonic and morphological development of larva and juvenile coral tr out, Plectropomus leopardus, are described using specimens raised at Y aeyama Station (Ishigaki Island, Okinawa Pref.), Japan Sea Farming Ass ociation, from eggs spawned voluntarily by captive brood fish (14 fema les, 3 males). The eggs were pelagic and spherical, 0.82-0.93 mm in di ameter, and possessed single oil droplet and a narrow perivitelline sp ace. Hatching took place 26h 40min after spawning, at a temperature of 25.4-26.3-degrees-C. The newly-hatched larvae were 1.62mm in mean tot al length (TL) with 27 (9+18) myotomes and had an oil droplet in the p osterior part of the yolk. Two days after hatching (2.70 mm TL) the mo uth opened. Five days after hatching (2.96 mm TL), the pelvic fin spin es and 2nd dorsal fin spine emerged. At 4.70 mm TL, a spine formed at the angle of the preoperculum. At 6.10 mm TL, the notochord was slight ly flexed, and the hypural bones and caudal fin rays had begun to deve lop. At 11.8 mm TL the adult complement of spines and soft rays was at tained, except in the anal fin. At 18.7 mm TL, the 1st anal fin soft r ay had begun to transform into the 3rd anal spine. All fins had the ad ult complement of rays and spines. By 25.1 mm TL, the body had become red, with some fish sleeping on the bottom at night. By 35.0 mm TL, th e fish had become completely demersal and when startled, sought shelte r immediately. Two inflections in relative growth were found, at about 7 and 22 mm BL. The first inflection coincided with the development o f larval behavior, in which an active movement and feeding on Artemia nauplii occurred. The second inflection occurred at transformation, as the larval habitat shifted from the surface and middle layers to the tank bottom.