Effect of five dietary carotenoids on gonad development, antioxidant capability and pigmentation of adult female Chinese mitten crab (Eriocheir sinensis)

Carotenoids are a group of natural lipid-soluble bioactive pigments produced by photosynthetic organisms such as plants, phytoplankton, algae, bacteria and some fungi. Except for typical pigmentation properties in crustaceans, extensive studies have shown there are numerous benefits of carotenoid for crustaceans, including growth performance, antioxidant activity, immune system, environmental stress tolerance and disease resistance, and these findings suggested that carotenoid is of primary importance to the crustacean health. Although more than 600 carotenoids in nature have been defined, only a few of them can be absorbed and stored in animal tissues and fluids. Among the carotenoids used in aquaculture feeding, the best-known and well-studied carotenoids include astaxanthin (Axn), β-carotene (β-car), canthaxanthin (Cxn), zeaxanthin, zeaxanthin (Zxn) and lutein (Lut). This study was designed to determine the effect of different dietary carotenoids on growth, gonad development, color parameters, and carotenoid composition of adult female Chinese mitten crab Eriocheir sinensis. Six diets were formulated to contain one of five carotenoids (Axn, β-car, Cxn, Lut and Lut) at about 100 mg/kg and a control treatment was also studied without any carotenoid supplementation. The results showed that: ① Feeding different carotenoids did not result in any notable difference in gonad development, tissue index and survival of adult female E. sinensis among treatments, but significant promotion of lipid content was observed in the hepatopancreas of carotenoids supplemented treatments. ② Indicators of antioxidant capacity (T-AOC, MDA), immunity (AKP, ACP) and physiological status (GPT, GOT) significantly improved in the hepatopancreas and hemolymph of carotenoid supplemented treatments with the order of Axn > Cxn ≈ β-car > Lut ≈ Zxn. ③ For colour enhancement, Axn and Cxn had a better effect on redness value improvement of ovary and hepatopancreas of E. sinensis, and β-car and Lut had a better effect on the yellow value improvement of adult female E. sinensis. ④ In terms of carotenoid composition, all kinds of carotenoids can be effectively deposited and Axn has the highest deposition efficiency in the ovary. No matter what kind of carotenoids were supplemented in the diet, Axn and β-car were the highest carotenoids in the carapace and hepatopancreas, respectively. In conclusion, results from this study suggested that the effectiveness of carotenoids as dietary pigment or as dietary antioxidant depends on their types, and the Axn was better than other carotenoids either in the antioxidant properties or colour enhancement of adult female E. sinensis. The results of this study can not only provide important information for understanding the physiological function of carotenoids, but also provide a basis for the development of functional fattening diet for E. sinensis.