This paper elucidates the developmental profiles of iodide and thyroid hormones, thyroxine (T₄) and triiodothyronine (T₃) in hatchery-reared rabbitfish (Siganus guttatus) during early larval development. The study evaluated the levels of iodide, T₄ and T₃ tissue content in rabbitfish larvae at 0, 10, 20, 30, 40 and 50 days after hatching (DAH). Under normal rearing conditions, iodide (11.98 ± 4.3 nmol g⁻¹) and thyroid hormones (T₄: 0.09 ± 0.01 nmol g⁻¹; T₃: 0.01 ± 8.5E-05 nmol g⁻¹ were already detected from newly-hatched larvae and their presence has been attributed from maternal origin. Iodide level sharply peaked at 10 DAH (1416.43 ± 149.6 nmol g⁻¹) which is significantly higher compared to the iodide levels in the larvae at 20, 30, 40 and 50 DAH. The levels of THs gradually increased as the larvae developed with T₄ (0.96 ± 0.05 nmol g⁻¹) and T₃ (0.03 ± 0.004 nmol g⁻¹) exhibiting a peak on 20 and 30 DAH, respectively, which coincided with the onset of metamorphosis. Thyroid hormone levels gradually decreased which coincided also with the completion of metamorphosis. The present findings indicated a pattern of the rise and fall in iodide and thyroid hormone levels during larval development and its role in metamorphosis of rabbitfish larvae. The study has reported for the first time, the changes in iodide and thyroid hormone levels during the early developmental stage in hatchery-reared rabbitfish and the results are in agreement with those vital actions of thyroid hormones in other fish species.

本文阐明了孵化场孵化的兔子鱼（Siganus guttatus）在早期幼体发育过程中碘和甲状腺激素，甲状腺素（T ₄）和三碘甲状腺素（T ₃）的发育情况。该研究评估了孵化后（DAH）0、10、20、30、40和50天兔子鱼幼虫中碘化物，T ₄和T ₃组织含量的水平。在正常饲养条件下，碘化物（11.98±4.3 nmol g ^-1）和甲状腺激素（T ₄：0.09±0.01 nmol g ^-1 ; T ₃：0.01±8.5E-05 nmol g ^-1已从新孵化的幼虫中检测到它们，并且其存在是由于母体来源引起的。碘化物水平在10 DAH时急剧达到峰值（1416.43±149.6 nmol g ^-1），与20、30、40和50 DAH时幼虫中的碘化物水平相比明显更高。随着幼虫在T ₄（0.96±0.05 nmol g ^-1）和T ₃（0.03±0.004 nmol g ^-1）发育时，THs的水平逐渐升高。）分别在20和30 DAH上出现一个峰，这与变态的发生相吻合。甲状腺激素水平逐渐下降，这也与变态的完成相吻合。目前的发现表明，在幼体发育期间碘化物和甲状腺激素水平的上升和下降模式及其在兔鱼幼虫变态中的作用。该研究首次报道了孵化场饲养的兔子鱼在早期发育阶段碘和甲状腺激素水平的变化，其结果与其他鱼类中甲状腺激素的重要作用相吻合。