Effects of Steinernema carpocapsae (Weiser) on immunity and antioxidant responses of Glyphodes pyloalis Walker

Abstract

The effect of Steinernema carpocapsae (IRA18) infection was studied on the mortality, immunity and antioxidant responses of Glyphodes pyloalis Walker larvae. The LC₅₀ value of 582.9 infective juvenile per mL with confidence limit of 359.1-811.5 was obtained via bioassay against the larvae. Injection of S. carpocapsae increased the number of total hemocytes after 1-6 h compared to intact and Ringer-injected larvae while the highest numbers of plasmatocyte and granulocytes were recorded after 1 and 3 h. Although intact larvae had a steady activity of phenoloxidase at different time intervals but those injected by S. carpocapsae showed the elevated enzymatic activity at 3-12 h. Nematode injection significantly increased the activities of superoxide dismutase and catalase compared to intact and Ringer-injected larvae, while no significant difference was observed in peroxidase activity. The injection with S. carpocapsae caused the highest activity of glutathione s-transferase using CDNB as reagent, but the enzymatic assay with DCNB showed no statistical differences among treatments. Also, activities of ascorbate peroxidase and glucose-6-phosphate dehydrogenase significantly increased in the nematode-injected larvae. Intact and Ringer-injected larvae showed no statistical differences in the concentration of malondialdehyde but the highest amount was recorded in nematode-injected larvae. Results of our study indicate that native isolate of S. carpocapsae cause mortality on the larvae of G. pyloalis and It interferes in the immune and antioxidant responses.