Effect of thyroid hormones on hatching in the tilapia, Oreochromis mossambicus

Incubation of fertilized eggs of Oreochromis mossambicus in media containing varying doses of T3, T4, and phenylthiocarbamide (PTC) indicated that the thyroid hormones delayed hatching, while the antithyroid drug accelerated it. Denuded eggs were also incubated in the above media and the media were assayed at various time intervals for hatching enzyme. The thyroid hormones delayed hatching enzyme release, while PTC enhanced it. The possible role of thyroid hormones in the control of the hatching process in fish eggs is discussed.