Tolypin, the insecticidal metabolite of the entomopathogenic fungus of the genus Tolypocladium, causes knock-down effect followed by high mortality in treated Culex pipiens molestus larvae. Histopathological changes accompanying the knock-down symptoms were similar in all tissues. Mitochondria, the main target in the cells, were destroyed and consecutively changed into vacuoles with the remains of cristae and lysed internal structures. Despite destruction of the internal content of individual organelles, the membranes of the cell surfaces, the endoplasmic reticulum, the nuclei, and the covering membranes of tissues and organs, were not affected and remained intact until final autolysis of the tissues. Some mitochondria in intoxicated cells were destroyed completely, but others remained intact and apparently structurally unchanged.

Institute of Entomology Academy of Sciences Ceské Budĕjovice Czechoslovakia

Evaluation of histological techniques for the detection of fungal infections caused by Leptolegnia chapmanii (Oomycetes: Saprolegniales) in Aedes aegypti (Diptera: Culicidae) larvae