Effects of astaxanthin in diet on antioxidant capacity and molting-related genes expression of larvae giant freshwater prawn (Macrobrachium rosenbergii)

This experiment was carried out to determine the effects of astaxanthin on reactive oxide species (ROS), anti-oxidant capacity as well as molting-related genes expression in larvae of giant freshwater prawn, Macrobrachium rosenbergii. A total of 90,000 larvae were assigned to five treatments with six replicates each. Astaxanthin mixed in steamed eggs with graded effective content as 0 (control, A(0)), 40 (A(40)), 80 (A(80)), 160 (A(160)) and 320 (A(320)) mg kg(-1) were fed to larvae for 14 days. The results showed that ROS of larvae in astaxanthin treatments was significantly lower than the control (P < 0.05). T-AOC, T-SOD and GR activities under astaxanthin treatments generally showed a downward trend and decreased significantly than the control (P < 0.05). No significant difference was observed towards CAT activities among A(40) and A(80), but the values were markedly greater than A(0), A(160), A(320) (P < 0.05). Larvae in A(80) exhibited stronger MDA content than the other (P < 0.05). GSH-Px activity was significantly highest in A(320) than the other treatments (P < 0.05). The expression of molt-inhibiting hormone (MIH) in A(40) and A(80) enhanced markedly than the control (P < 0.05). The elevated expression of Ecdysone receptor (EcR) was recorded only in A(160) and A(320) (P < 0.05). Chitinase (CHIT) expression among treatments was significantly downregulated than the control except for A(40). Heat shock protein (HSP21) and chitooligosaccharidolytic beta-N-acetylglucosaminidase-like expression increased dramatically in A(160) and A(320) (P < 0.05). For actin 6 gene, higher expression was happened only in A(40) compared to control, others presented drop expression in very low level (P < 0.05). This study provides a theoretical basis that 320 mg/kg astaxanthin was excessive level, and might decreased partial antioxidant indexes and influenced molting genes expression of larvae M. rosenbergii.