Controlled gonad development: effects of environmental factors on sexual maturity in red swamp crayfish, Procambarus clarkii

Because development of crustacean gonads can impede growth potential, a balance between growth and gonad development is necessary to promote the healthy and sustainable development of aquaculture. We report growth and gonad development in red swamp crayfish Procambarus clarkii at six temperatures between 16 °C and 36 °C, and conduct experiments to investigate the impact of light intensity on growth, gonad development, and survival at 36 °C. Growth in crayfish first increased, then decreased with increased temperature. Above 28 °C, 10%-30% of gonads were mature, but the survival rate of crayfish above 28 °C was significantly lower than that below 28 °C. Hemolymph vitellogenin (VTG) content increased significantly with increased temperature; expressions of vtg gene and molt-inhibiting hormone (MIH) in hepatopancreatic and ovarian tissues gradually increased; and expression of vitellogenesis-inhibiting hormone decreased significantly. At 36 °C, crayfish treated with 400-500 lx light (50% relative light intensity, RLI) showed significantly higher weight gain and survival rates than controls (800-1,000 lx, 100% RLI), and gonad development was slightly lower; hemolymph VTG contents of treatment crayfish were lower than that of controls; vtg expression decreased significantly in the ovary but not in the hepatopancreas; expression of vitellogenesis-inhibiting hormone in the hepatopancreas gradually increased; and expression of molt-inhibiting hormone did not differ significantly. Therefore, growth promotion and delayed gonad development can be achieved by decreasing light intensity during crayfish culture at high temperature, reducing VTG accumulation rates in ovaries.