Study on the Optimal Phospholipid Addition Levels for Button-Sized Juvenile Chinese Mitten Crab (Eriocheir sinensis): Survival, Growth, Physiological Parameters, and Neverland Expression

Abstract

A 50-day feeding experiment was performed to investigate the effects of dietary phospholipid (PL) addition on the survival, growth, serum, and hepatopancreas lipid indexes, calcium content, and neverland (Nvd) gene expression in button-sized juvenile Chinese mitten crab (Eriocheir sinensis). Five experimental diets were formulated with increasing addition of PL (0%, 1%, 2%, 3%, and 4%), which were named PL0, PL1, PL2, PL3, and PL4, respectively. Each diet was randomly assigned to four tanks of juvenile E. sinensis (initial weight: 5.00 ± 0.55 g), with eight crabs held in each tank. The results showed that PL addition significantly increased the survival rate (SR) but just slightly increased the weight gain rate (WGR) of juvenile E. sinensis. As the PL addition level increased, SR and WGR first increased and then decreased, with the highest values observed in the PL3 group. As the PL addition level increased, the activities of trypsin and cellulase significantly increased and then decreased, with the highest value observed in the PL2 group and PL3 group, respectively. As PL addition level increased from 1% to 2%, lipase activity increased sharply and then kept constant with a further increase of dietary PL. As PL addition level increased from 0% to 3%, the calcium content in the serum significantly increased from 7.96 to 12.43 mmol/L and then significantly decreased to 11.36 mmol/L with a further increase of PL addition. PL addition just slightly promoted the calcium content in the hepatopancreas compared with the control group. As PL addition level increased from 0% to 3%, the expression of Nvd in the hepatopancreas significantly increased by 1.47-fold and then decreased to basal level with a further increase of PL addition. In conclusion, 2%−3% addition of the optimal PL addition level was estimated to be 2%−3% for juvenile E. sinensis based on their survival, growth performance, and digestive enzyme activities. PL addition at a relatively higher level (3%) increased the calcium content and Nvd expression, the latter possibly facilitating cholesterol metabolism into vitamin D.