Photoperiod effects on growth, lipid metabolism, and lipidomics analysis of tilapia

To investigate the effects and underlying mechanisms of photoperiod on the growth and lipid metabolism of tilapia (Oreochromis niloticus).

Four photoperiod treatment groups were established: 10L:14D, 12L:12D, 14L:10D, and 16L:8D. Various analytical methods were employed, including tissue sectioning, blood lipid analysis, gene expression profiling, fatty acid profiling, and lipidomics, to assess the impact of photoperiod on lipid metabolism in tilapia.

In both females and males, the highest relative body weight growth rates were observed in the 16L:8D group, reaching 122.1% and 133.6%, respectively. As the photoperiod increased, the visibility of lipid droplets in the liver decreased. The expression levels of lipid synthesis‑related genes (fasn, acaca, srebp1, and aclya) were downregulated. Blood lipid concentrations, including cholesterol (TC), triglyceride (TG), low‑density lipoprotein (LDL), and non‑esterified fatty acid (NEFA) levels, were reduced. Saturated fatty acid (SFA) content decreased, whereas polyunsaturated fatty acid (PUFA) content increased. Lipidomic analysis revealed 54 significantly differential lipid metabolites between the control group (12L:12D) and the experimental group (16L:8D) (P<0.05), and candidate biomarkers for photoperiod‑regulated lipid metabolism were identified.

These findings suggest that a long photoperiod (16L:8D) effectively increases the growth rate of tilapia and reduces blood lipid concentrations and hepatic fat deposition, thereby promoting healthy growth. This study provides a theoretical foundation for healthy aquaculture practices in fish.