Abstract

Plasma levels of thyroid hormones (T4 and T3) and pineal AANAT activity exhibited prominent diurnal rhythms during all the four phases (quiescent, progressive, breeding, and regressive) of the fish, Clarias gariepinus. During all the four phases, we observed that (i) the acrophase (peak) of the circadian rhythm of both T3 and T4 occurred around midday, while the acrophase of AANAT activity rhythm was recorded during midnight, (ii) a significant negative correlation existed between plasma levels of the thyroid hormones and AANAT activity, and (iii) a direct relationship existed between water temperature/daylength and plasma levels of thyroid hormones, and an inverse relationship between water temperature/daylength and AANAT activity. On the basis of these findings, we conclude that an inverse relationship exists between the diurnal rhythms in plasma levels of thyroid hormones and pineal AANAT activity. The observed inverse relationship between the levels of thyroid hormones and pineal AANAT activity seems to be maintained by seasonal changes in water temperature and daylength.

Full Text
Paper version not known

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.