Effects of photoperiod on the melatonin cycle of Dybowski’s frog (Rana dybowskii)

ABSTRACT

There are few studies on the relationship between photoperiod and the melatonin cycle in amphibians. To elucidate the role of the photoperiodically modulated endogenous melatonin cycle in different tissues of Dybowski’s frog (Rana dybowskii), its serum, liver, whole brain, skin, and eyeballs were collected under five photoperiods, and the daily variation in melatonin concentration was determined via high-performance liquid chromatography. Compared with the control group (12 L:12 D), melatonin concentration was increased under photoperiods 0 L:24 D and 6 L:18 D in serum, and the concentration peaked at 00:00 under photoperiod 0 L:24 D. This trend was synchronized with the peak melatonin concentration in the retinal, liver, and whole-brain tissues. After 24 h of light exposure, no significant daily variation was observed under photoperiod 24 L:0 D. Furthermore, we observed a significant peak at 04:00 in the serum under photoperiod 18 L:6 D. However, we observed the opposite trend in the circadian rhythm of the skin tissue. Our results underscore the high sensitivity of melatonin content to different photoperiods. These findings may have real-world implications in terms of furthering our understanding of circadian rhythms disruption induced by exposure to different photoperiods.

KEYWORDS:

• Photoperiod
• melatonin
• circadian rhythm
• Dybowski’s frog
• Rana dybowskii

Acknowledgments

This work was supported by the Scientific Research Project of Liaoning Provincial Education Department under Grant number LSNQN202006; the Liaoning Provincial Natural Science Foundation of China under Grant number 2019MS274; the Liaoning Province Key Research and Development Project under Grant number 2019JH8/10200018; and the earmarked fund for Modern Agro-Industry Technology Research System under Grant number CARS-48.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Scientific Research Project of Liaoning Provincial Education Department; Liaoning Provincial Natural Science Foundation of China.