Circadian patterns and photoperiodic modulation of clock gene expression and neuroendocrine hormone secretion in the marine teleost Larimichthys crocea

ABSTRACT

The light/dark cycle, known as the photoperiod, plays a crucial role in influencing various physiological activities in fish, such as growth, feeding and reproduction. However, the underlying mechanisms of this influence are not fully understood. This study focuses on exploring the impact of different light regimes (LD: 12 h of light and 12 h of darkness; LL: 24 h of light and 0 h of darkness; DD: 0 h of light and 24 h of darkness) on the expression of clock genes (LcClocka, LcClockb, LcBmal, LcPer1, LcPer2) and the secretion of hormones (melatonin, GnRH, NPY) in the large yellow croaker, Larimichthys crocea. Real-time quantitative PCR (RT-qPCR) and enzyme-linked immunosorbent assays were utilized to assess how photoperiod variations affect clock gene expression and hormone secretion. The results indicate that changes in photoperiod can disrupt the rhythmic patterns of clock genes, leading to phase shifts and decreased expression. Particularly under LL conditions, the pineal LcClocka, LcBmal and LcPer1 genes lose their rhythmicity, while LcClockb and LcPer2 genes exhibit phase shifts, highlighting the importance of dark phase entrainment for maintaining rhythmicity. Additionally, altered photoperiod affects the neuroendocrine system of L. crocea. In comparison to the LD condition, LL and DD treatments showed a phase delay of GnRH secretion and an acceleration of NPY synthesis. These findings provide valuable insights into the regulatory patterns of circadian rhythms in fish and may contribute to optimizing the light environment in the L. crocea farming industry.

KEYWORDS:

• Larimichthys crocea
• photoperiod
• circadian rhythm
• clock gene
• neuroendocrine

Acknowledgments

The authors of this paper would like to thank Dr. Weiye Li from Zhoushan Fishery Research Institute for his assistance on fish sampling.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/07420528.2024.2315215.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [Nos. 42076130 and 32373111] and the “Pioneer” and “Leading Goose” R&D Program of Zhejiang [2022C02040].