Thyroid regulation in teleost embryonic and larval development - can it be a promise for aquaculture?

The role of thyroid hormones (THs) in fish development is often overlooked and particularly neglected for the embryonic and larval stages of fish. We used a set of experiments to elucidate the importance of TH in embryonic to early larval development in zebrafish. In the first set of experiments we used morpholino antisense oligonucleotides to knock down TH downstream genes and showed that the depletion of TH in early development resulted in severe deformities, developmental delay, and pigmentation, which could be quantitatively recovered by subsequent TH treatments. In the second set of experiments, blocking TH deposition into zebrafish eggs by treating parental fish with goitrogens resulted not only initial low TH content in eggs, but also subsequent loss of egg laying ability. Overall, these data strongly suggest a key role of TH in early development in fish, providing its worth to be investigated for effective use in reproduction and larviculture.