Effects of thyroxine and thiourea on the development of larval red sea bream Pagrus major

The role Of thyroid hormone on the development of larval and early juvenile red sea bream was studied by administrating thyroxine (T4) and thiourea (TU) as an anti-thyroidal agent. T4 treatment accelerated the appearance of black stripes on the body and the change in the habitat from the surface to the bottom of the aquarium. In contrast, TU treatment caused stasis of black stripes formation and delayaed the change in the habitat. These results indicate that thyroid hormone plays the role of an inducer in the morphological and behavioral transformation from post-larva to juvenile in red sea bream.