Responses of growth and activities of antioxidant and detoxification enzymes of Misgurnus anguillicaudatus to transgenic Cry1Ab/Ac rice residues in water

A loach (Misgurnus anguillicaudatus) aquaculture experiment was conducted in phytotron with aquatic water added with straw power in different concentrations (10 mg·L^-1, 50 mg·L^-1, 100 mg·L^-1, 200 mg·L^-1) of different rice varieties, which were transgenic Cry1Ab/Ac rice variety of 'Huahui 1' (HH1) and non-Bt control rice variety of 'Minghui 63' (MH63). In the experiment, the loach basal fed without rice straw powder was set as the blank control. The specific growth rate, condition factor, and viscera somatic index as well as activities of antioxidant enzymes of superoxide dismutase (SOD) and catalase (CAT), and detoxification enzyme of glutathione-s-transferase (GST) of loach were investigated after culture for 100 days. The aim of the study was to explore effects of transgenic Bt rice on aquatic animal through simulating rice residues in paddy water. The results showed no significant differences (P > 0.05) in specific growth rate, condition factor, viscera somatic, and activities of SOD, CAT and GST between loaches cultured in aquatic water added with HH1 and MH63 straw powders with four concentrations. Compared with the blank control, the growth performance gradually decreased with increasing concentration of rice straw powder of both varieties. Furthermore, the specific growth rate, viscera somatic index and CAT activity of loach decreased obviously when loach was cultured in aquatic water with 200 mg·L^-1 of HH1 and MH63 straw powder. These results indicated that aquatic water with lower concentration of transgenic Cry1Ab/Ac rice straw powder had no obvious effect on growth performance and activities of antioxidant and detoxification enzymes of loach. When the concentration of rice straw powder was up to 200 mg·L^-1, the growth performance and activities of physiologic enzymes of loach decreased significantly, regardless of rice variety. It was suggested that higher level of rice straw powder in water hindered breathing of loach. In addition, the decomposition of rice straw powder in water induced decreasing of pH and dissolved oxygen.