Effects of microcystin-LR on behavior, histopathology, oxidative stress, non-specific immunity and gene expression of red claw crayfish (Cherax quadricarinatus)

Microcystin-LR (MC-LR), the most prevalent cyanobacterial toxin, poses a serious threat to the survival of aquatic animals. Herein, crayfish (Cherax quadricarinatus) were treated with MC-LR at 33.06 mu g kg-1 for 48 h, and the effects of MC-LR on behavior, histomorphology, oxidative stress, non-specific immunity, and gene expression were investigated to elucidate the molecular mechanisms underlying antioxidation and detoxification in crayfish. MC-LR caused vacuolation and disruption of crayfish hepatopancreatic cells, although no significant effect was observed on the structure of intestinal cells. Moreover, MC-LR increased the activity of antioxidant enzymes (SOD, CAT, GPx, GST) and up-regulated the expression of genes encoding antioxidant enzymes (ecCu,Zn-SOD, SOD, Se-GPx, GPx3P, GST). In addition, GSH was found depleted in the hepatopancreas and plasma. MC-LR activated the immune system, enhanced immunoenzyme activity (ACP, AKP) and induced the expression of immunity-related genes (C-LZM, proPO, hemocyanin). Furthermore, caspase and HSP70 genes were induced in the hepatopancreas of crayfish under MC-LR stress. Taken together, MC-LR was shown to cause a positive response in crayfish, and our findings suggested that the antioxidant activity and immune system play an important role in protecting crayfish from MC-LR stress by regulating gene expression and activities of antiox-idant and immune enzymes.