Pathogenesis of the hyphomycete Tolypocladium cylindrosporum in the mosquito Aedes aegypti

Abstract

A series of experiments were carried out to determine the pathogenesis of Tolypocladium cylindrosporum in larvae of Aedes aegypti. Host death in relation to larval feeding, molting, and fungal colonization of the hemocoel, and the principle sites of infection were determined. In addition, observations were made on conidial germination, fungal growth, and sporulation on surface or in submerged culture using scanning electron and light microscopy. The host-pathogen relationships are complex: Multiple infection sites occur which differ according to the host's growth stage; larvae seem most susceptible during their molting period; and conidia germinate and produce blastoconidia in the mosquito rearing medium. Molting larvae succumb to the fungus prior to fungal colonization of the hemocoel, primary infection sites being through the alimentary canal and the exocuticle. Intermolt larvae succumb to the fungus after fungal colonization of the hemocoel with primary infection sites at the base of the mandibles and maxillae and in the region of the anus.