Studies the effect of exogenous thyroxine (T4) on marble goby (Oxyeleotris marmoratus Bleeker) larvae

Abstract

A study on the effect of the thyroid hormone, thyroxine (T4) on marble goby 0Oxyeleotris marmoratus) during the early larval development was carried out in hatchery unit, Kolej Universiti Sains dan Teknologi Malaysia. Thyroid hormones in the marble goby were detected at hatching even though the thyroid follicles were not yet developed. The first T4 cells were not recognized as follicles but appeared as domain of non follicular cells that appeared dark brown on anti T4 staining section. The first thyroid follicles in marble goby were observed at 13 days after hatching (DAH). T4 was detected in the larvae at hatching, and increased till 2 DAH indicating the onset of endogenous thyroid hormones production. T4 level started to decrease from 3 DAH till 7 DAH, and then increased again from 10 DAH onwards. The decrease of T4 level was consistent with the mortality pattern of marble goby larvae occurred at this stage, and showed that the larvae endocrine organs were not yet fully functional, even though production of THs has began. The increased of T4 level at 10 DAH onwards indicated that the endocrine organs began to function again but T4 level remained low.