Cellular immune responses and FAD‐glucose dehydrogenase activity of Mamestra brassicae (Lepidoptera: Noctuidae) challenged with three species of entomopathogenic fungi

Abstract

Abstract. Cellular immune responses and glucose dehydrogenase activity are examined in the larvae of Mamestra brassicae (Lepidoptera: Noctuidae) injected with three entomopathogenic fungi, Beauveria bassiana, Nomuraea rileyi and Paecilomyces tenuipes. Total haemocyte count and the number of spherulocytes increase significantly over 2 h in larvae infected with N. rileyi, the most virulent fungal pathogen of M. brassicae. However, glucose dehydrogenase is not activated in the haemolymph of larvae inoculated with N. rileyi. By contrast, P. tenuipes, the least virulent fungal species, but with the highest proteolytic activity, activates glucose dehydrogenase and the number of nodules formed is significantly larger in larvae inoculated with P. tenuipes. It is suggested that the different virulence of each fungal species is caused by specific immune responses in the larvae. Haemopoiesis is affected by the fungal conidia and this is investigated by culture of the haemopoietic organs of M. brassicae in vitro. The proportion of spherulocytes discharged from the organs is typically high after all of the fungal treatments. In addition, the anterior and posterior haemopoietic organs, according to the histological locations in larva, show different patterns of haemopoiesis in response to fungi.