The aim of this study was to investigate the effects of exogenous triiodothyronine (T3) on egg hatching and early larval development in grouper Epinephelus coioides. The fertilized eggs and hatched larvae were immersed in seawater containing 0 (control), 0.1 and 1 ppm of T3 for 48 hours. The results showed that T3 treatment did not influence the hatching rate. Newly hatched larvae, which were immersed in both T3 solutions for 24 hours, generally had longer total length (TL) and larger oil globule area (OA) and yolk area (YL) than control, but only the TL of 1-ppm group was significantly different from that of control. However, on day 2 after hatching, all of the TL, YA, and OA in the larvae treated with T3 were not significantly different from those of control group. This showed that the enhancing effect of T3 on developmental rate of grouper larvae seemed to disappear gradually.
Key words: Epinephelus coioides, Triiodothyronine, Egg, Larva