Balancing act: How cholesterol and phospholipids influence juvenile mud crab Scylla paramamosain growth and lipid metabolism

A 2 × 3 two-factor experiment was designed to assess the effects of dietary cholesterol (CHO) and phospholipids (PLs) on growth and lipid metabolism in early juvenile mud crabs (0.01 g crab⁻¹). The experimental diets were designed with two CHO levels: 0.40 % (LCH) and 0.80 % (HCH), and three PLs levels: 1.80 % (LPL), 2.50 % (MPL), and 3.20 % (HPL). The 58-day aquaculture trial demonstrated that the LCH-HPL group achieved the best growth performance in mud crabs, characterized by the highest final body weight, weight gain, and specific growth rate. Regarding whole-body composition, dietary PLs increased total cholesterol (T-CHO), PLs, triglyceride (TG), and crude lipid content in the LCH groups. Mud crabs in the HCH groups had a higher proportion of saturated fatty acids, a lower proportion of monounsaturated fatty acids, and increased gene expression of sterol regulatory element binding protein 1c (srebp-1c) and fatty acid synthase (fas) compared to those in the LCH groups. As the dietary PLs increased, mud crabs in the LCH groups exhibited up-regulation in the expression of genes, including srebp-1c, fas, elongation of very long-chain fatty acid protein 4 (elovl4), elovl6, and Δ9-fatty acid desaturase (Δ9-fad). In the HCH groups, elevated dietary PLs resulted in the down-regulation of fatty acid binding protein (fabp) gene expression. In addition, high levels of dietary CHO and PLs (HCH-HPL) inhibited the catalase activity of mud crabs, resulting in a significant increase in the malondialdehyde content. Correlation analysis revealed that dietary CHO was positively correlated with the expression of long-chain polyunsaturated fatty acids synthesizing genes, and dietary PLs were positively correlated with the whole-body lipid content of mud crabs. Additionally, a positive correlation was found between the growth performance and whole-body content of crude protein, crude lipid, and antioxidant capacity in mud crabs.