Cholesterol, as an indispensable nutrient, regulates molting and growth in crustacean. As crustaceans are unable to biosynthesize
cholesterol de novo, it is central to understand how
dietary cholesterol affects molting in crustaceans. An 8-week feeding trial was conducted to evaluate the effects of
dietary cholesterol level (0.12%, 0.43%, 0.79%, 1.00%, 1.30% and 2.50%) on growth,
cholesterol metabolism and expression of genes related to
lipid and
ecdysone metabolism in female swimming crabs (Portunus trituberculatus). A total of 192 crabs (1.41 ± 0.05 g) were randomly distributed into 192 aquaria. Each treatment had 4 replicates with each replicate containing 8 crabs. Crabs fed the 1.00%
cholesterol diet showed best growth performance, and thus based on percent
weight gain, the optimal
dietary cholesterol requirement was calculated at 1.01%. Tissue
cholesterol concentrations were positively correlated with
dietary cholesterol level. The contents of functional
fatty acids in hepatopancreas significantly increased as
dietary cholesterol increased from 0.12% to 2.50% (P < 0.05). The expression levels of genes related to lipogenesis pathway,
lipid catabolism and
fatty acid oxidation were significantly down-regulated with increased
dietary cholesterol level (P < 0.05). The highest expression levels of
cholesterol transport genes,
low-density lipoprotein receptor (ldlr) and
low-density lipoprotein receptor-related protein 2 (lrp2) occurred in crabs fed the 1.30%
cholesterol diet. Moreover,
hormones related to molting such as
crustacean hyperglycemic hormone (CHH),
methyl farnesoate (MF),
molt-inhibiting hormone (MIH), and
ecdysone in hemolymph were significantly influenced by
dietary cholesterol level (P < 0.05). The highest expression levels of
ecdysone receptor (ecr) and
chitinase 1 (chi1) in eyestalk and hepatopancreas were found in crabs fed the diet containing 1.00%
cholesterol (P < 0.05). In conclusion, the optimal dietary level was beneficial to functional
fatty acid accumulation, regulated lipid metabolism, promoted the
ecdysone signalling pathway by improving the
cholesterol transport, and improved the molting rate and growth of swimming crabs.