Effects of green wavelength light on antioxidant and non-specific immune responses of the olive flounder, paralichthys olivaceus, exposed to different stocking densities

Abstract

The present study aimed to test the effects of green light on antioxidant systems and immunity in the olive flounder. Fish at three different stocking densities(900, 1350, and 2250 fish per 8-ton tank) were compared. The effects of green light were assessed by measuring survival rates, mRNA expression activity of antioxidant enzymes (superoxide dismutase and catalase), an oxidative stress-related parameter (hydrogen peroxide, H2O2), and immune-related parameters (lysozyme and melatonin). Overall, fish survival rate decreased over the 45-day period of the experiment, but survival rate were significantly higher among the groups of fish under green light. mRNA and activities expressions of antioxidant enzymes and H2O2 concentrations increased at 45 days however, in fish under green light, significantly lower levels of antioxidant enzyme expression was observed. By contrast, parameters indicating immune responses decreased at higher stocking densities groups, although in fish under green light treatment, significantly higher levels of immune responses were observed. A comet assay revealed that a high stocking density increased the rate of nuclear DNA damage however, treatment with green light reduced the frequency. These results indicate that although high density induces oxidative stress and reduces immune responses in olive flounder, green light inhibits oxidative stress and boosts the immune system.light were assessed by measuring survival rates, mRNA expression activity of antioxidant enzymes (superoxide dismutase and catalase), an oxidative stress-related parameter (hydrogen peroxide, H2O2), and immune-related parameters (lysozyme and melatonin). Overall, fish survival rate decreased over the 45-day period of the experiment, but survival rate were significantly higher among the groups of fish under green light. mRNA and activities expressions of antioxidant enzymes and H2O2 concentrations increased at 45 days however, in fish under green light, significantly lower levels of antioxidant enzyme expression was observed. By contrast, parameters indicating immune responses decreased at higher stocking densities groups, although in fish under green light treatment, significantly higher levels of immune responses were observed. A comet assay revealed that a high stocking density increased the rate of nuclear DNA damage however, treatment with green light reduced the frequency. These results indicate that although high density induces oxidative stress and reduces immune responses in olive flounder, green light inhibits oxidative stress and boosts the immune system.