The sensitivity of glass eels to water temperature changes
김완수; 윤성진; 이태원
The oxygen consumption rate (OCR) of glass eels Anguilla japonica was measured to determine the effects of water temperature changes on their endogenous and exogenous rhythms. The glass eels were exposed to different water-temperature patterns during simulated 12-, 14-, and 24-h cycles. The OCR of wild glass eels, freshly collected from estuaries, exhibited a clear endogenous circatidal rhythm while kept in constant darkness and temperature (1 ± 0.1°C). However, if the temperature was variable, the glass eels OCR coincided with the gradually increasing water temperature (∆t = 1°C/12-h or 24-h) in the experimental chamber. This minor variation in water temperature (∆t = 1°C/12-h or 24-h) was significant enough to affect the rhythmicity of glass eels' OCR. When the glass eels were exposed to a cyclic increase or decrease in water temperature (0.5°C/14-h), the OCR peaks displayed a clear rhythmicity at 14-h intervals. The results indicate that glass eels' OCR is controlled not only by an endogenous circatidal rhythm, but also by exogenous rhythms related to small environmental changes, such as water temperature changes of as little as 0.5°C.