Fluctuations of haemocytes and phenol oxidase enzyme in the greater wax moth larvae, Galleria mellonella injected with Heterorhabditis bacteriophora and Steinernema feltiae

Insect immunity comprises behavioral, physical and innate immunity. In this study, innate immune response of the greater wax moth larvae, Galleria mellonella against two species of entomopathogenic nematodes, Heterorhabditis bacteriophora and Steinernema feltiae, as important biocontrol agents were studied. Total haemocyte count in larvae injected with H. bacteriophora increased immediately. In this case, plasmatocytes and granulocytes were the prevalent haemocyte types. The response of injected larvae with S. feltiae was different. There was no significant increase in haemocyte population by 15 min until 4 h after injection. Haemocyte populations in hemolymph of G. mellonella larvae after injection by both nematode species was decreased 8 and 12 h after post injection. In humoral response, H. bacteriophora caused a significant increase in phenoloxydase activity by 15 min until 8 h after injection to hemoceol. In contrast, phenoloxydase activity against S. feltiae showed lower fluctuation rather than those in treated larvae by H. bacteriophora. The result of cellular and humoral immune response of the larvae suggested that H. bacteriophora induced stronger reaction of the insect as compared with S. feltiae. The latter species not only evades of host immune response but also can suppress the immune responses, successfully. These, eventually suggests a weak interaction between the pathogen with host immune system.