The impact of betaine regulation on ovarian development and protein synthesis promotion in the Chinese mitten crab, <i>Eriocheir sinensis</i> H. Milne Edwards, 1853 (Decapoda: Brachyura: Varunidae)

Abstract We examined the effects of dietary betaine on ovarian development and protein synthesis in the Chinese mitten crabs (Eriocheir sinensis H. Milne Edwards, 1853). Four diets containing 0 g kg−1 (control), 0.5 g kg−1, 1 g kg−1, and 1.5 g kg−1 betaine were administered to crabs over seven weeks. Crabs fed 1 g kg−1 betaine exhibited significantly higher relative feed intake and feed efficiency ratio compared to other groups, with no significant differences observed among the other supplementation levels. The gonadosomatic index (GSI) and hepatopancreas index (HSI) were significantly higher (P &amp;lt; 0.05) in crabs receiving 1–1.5 g kg−1 betaine than in the control, but no difference was found in groups fed 0.5 g kg−1 . Vitellogenin (Vtg) levels were significantly elevated (P &amp;lt; 0.05) in the hepatopancreas of crabs fed 1 g kg−1 betaine. Vtg levels in the ovary increased with higher betaine supplementation, peaking at 1.5 g kg−1, although no significant differences were detected between supplemented groups. Estradiol levels were significantly higher (P &amp;lt; 0.05) in the 1 g kg−1group. Moreover, expression of the enzymes cytochrome P450 family 11 subfamily A member 1 (CYP 11a1) was elevated in crabs fed 1 g kg−1 but tended to decrease at 1.5 g kg−1, while cytochrome P450 family 19 subfamily A member 1 (CYP19a1) levels were higher in all supplemented groups compared to the control. Gene expression of Vtg in the hepatopancreas was upregulated across all betaine-supplemented groups, with ovarian Vtg expression significantly higher (P &amp;lt; 0.05) in crabs fed 1.5 g kg−1. Additionally, cathepsin D and cyclin B genes were upregulated in betaine-fed crabs. The phosphoinositide 3-kinase gene showed increased expression in crabs fed 1–1.5 g kg−1 betaine, while the mammalian target of rapamycin expression rose with betaine levels up to 1 g kg−1 but declined at 1.5 g kg−1. Dietary betaine, particularly at 1 g kg–1, thus enhanced ovarian development and protein synthesis in E. sinensis.