ABSTRACT

Effects of different photoperiods (9L-15D, 12L-12D and 15L-9D at a constant temperature 25 ± 1°C) and simulated temperatures (15°C, 25°C and 35°C under a common photoperiod 12L-12D) were investigated on the circadian rhythms of plasma levels of thyroid hormones [thyroxine (T₄) and triiodothyronine (T₃)] and pineal arylalkylamine N-acetyltransferase (AANAT) activity in the fish, Clarias gariepinus during winter and summer seasons. Irrespective of the seasons, plasma levels of thyroid hormones (THs) and pineal AANAT activity exhibited circadian rhythm under all the photoperiodic regimes and simulated temperatures. The levels of THs were found to be directly related to the length of photoperiod as well as temperature. In contrast, pineal AANAT activity was inversely related to the length of photoperiod and temperature. On the basis of these findings, we suggest that photoperiod and temperature jointly regulate the inverse temporal relationship between the circadian rhythms of plasma levels of THs and pineal AANAT activity in C. gariepinus.

摘要

不同光周期（恒温 25 ± 1°C 下的 9L-15D、12L-12D 和 15L-9D）和模拟温度（普通光周期 12L-12D 下的 15°C、25°C 和 35°C）的影响分别为研究了鱼， Clarias gariepinus血浆中甲状腺激素 [甲状腺素 (T ₄ ) 和三碘甲状腺原氨酸 (T ₃ )] 和松果体芳基烷基胺 N-乙酰转移酶 (AANAT) 活性的昼夜节律在冬季和夏季。无论季节如何，甲状腺激素 (THs) 的血浆水平和松果体 AANAT 活性在所有光周期机制和模拟温度下都表现出昼夜节律。发现 THs 的水平与光周期长度和温度直接相关。相反，松果体AANAT活性与光周期长度和温度成反比。基于这些发现，我们建议光周期和温度共同调节C. gariepinus血浆 THs 水平的昼夜节律与松果体 AANAT 活性之间的逆时间关系。