Effects of light and food on the growth and lipid accumulation in Hippocampus kuda Bleeker

The aim of this study was to investigate the effects of light and food on the growth and lipid accumulation of Hippocampus kuda , and to analyze the role of biological clock genes in this process. H. kuda is a precious traditional Chinese medicine, and its lipid content was the main material basis for its pharmacological effects. The study selected healthy juvenile H. kuda and divided them into 3 groups, which were raised for 7 weeks under different photoperiod (16 L:8D, 12 L:12D) and fed different food (artificial compound feed (ACF), iced Mysis ). The results showed that G1 fed with ACF under a longer duration of illumination (16 L:8D) performed the best values in specific growth rate of body length (SGR L ), specific growth rate of body weight (SGR W ), and feed conversion rate (FCR), while G3 fed with iced Mysis showed the worst values under 12 L:12D. During this period, the biological clock genes showed significant rhythmic expression in the brain and liver of H. kuda , with G1 showing significantly higher expression levels than the other 2 groups. The expression levels of lipid metabolism related genes were also the highest in G1 among 3 groups, giving a conclusion that appropriate factors of light and food were conducive to the growth and lipid accumulation of H. kuda . The measured results of lipid contents confirmed that G1 had significantly higher accumulation levels of total cholesterol, free fatty acids, DHA, and EPA compared to the other 2 groups. In brief, the factors of a longer light exposure and artificial compound feed were more conducive to the growth and lipid accumulation in H. kuda , and the expression of biological clock genes and lipid metabolism genes played a key role in this process. This work provided a scientific basis for optimizing the breeding environment of seahorses and improving their breeding techniques. • Longer photoperiod(16L:8D) with AFC maximizes growth and feed efficiency in juvenile Hippocampus kuda. • Enhances lipid accumulation: cholesterol, fatty acids , DHA, EPA in H.kuda. • Rhythmic biological clock genes expression regulates growth and lipid metabolism. • Lipid metabolism and clock genes expression improve growth and lipid accumulation. • Insights to optimize seahorse breeding for production and conservation.