Embryonic and Morphological Development of Larval and Juvenile Coral Trout, Plectropomus leopardus

Abstract

Embryonic and morphological development of larva and juvenile coral trout, Plectropomus leopardus, are described using specimens raised at Yaeyama Station (Ishigaki Island, Okinawa Pref.), Japan Sea Farming Association, from eggs spawned voluntarily by captive brood fish (14 females, 3 males). The eggs were pelagic and spherical, 0.82-0.93mm in diameter, and possessed single oil droplet and a narrow perivitelline space. Hatching took place 26 h 40min after spawning, at a temperature of 25.4-26.3°C. The newly-hatched larvae were 1.62mm in mean total length (TL) with 27 (9+18) myotomes and had an oil droplet in the posterior part of the yolk. Two days after hatching (2.70mm TL) the mouth opened. Five days after hatching (2.96mm TL), the pelvic fin spines and 2nd dorsal fin spine emerged. At 4.70mm TL, a spine formed at the angle of the preoperculum. At 6.10mm TL, the notochord was slightly flexed, and the hypural bones and caudal fin rays had begun to develop.At 11.8mm TL the adult complement of spines and soft rays was attained, except in the anal fin. At 18.7mm TL, the 1st anal fin soft ray had begun to transform into the 3rd anal spine. All fins had the adult complement of rays and spines. By 25.1mm TL, the body had become red, with some fish sleeping on the bottom at night. By 35.0mm TL, the fish had become completely demersal and when startled, sought shelter immediately. Two inflections in relative growth were found, at about 7 and 22mm BL. The first inflection coincided with the development of 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.