In zebrafish, like many other teleost species, the development and differentiation of many
major organs continue unabated into the yolk-sac larval stage before culminating in a free-
swimming larva capable of exogenous feeding. We investigated the role of thyroid hormone
(TH) in this important embryonic to larval transitory phase. Thyroid hormone receptor (TR) α
and β mRNAs are expressed during the early stages of zebrafish embryonic development.
Beginning from the midblastula stage, the level of TRβ mRNAs increases dramatically and is …