[Microsporidia of the Simulium larvae: systematic, cytochemical, pathological and ecological data].

At present, 10 microsporidian species belonging to the genera Nosema, PLeistophora, Thelohania, Stempellia, Octosporea, Weiseria and Caudospora are known as parasites in Simuliids larvae. Acid mucosubstances fixing alcian blue and proteinic granules rich in -SH groups appear during sporogony in various species of Thelohania, Pleistophora, Stempellia. The microsporidan contracts intimate relations with larval host-cells of the type host-parasite complex and lengthens larval state as well for the size (a morphological aspect) as for the respiratory rate (a physiological aspect). This is a very good condition for the development of the parasite. The incidence of parasitism does not exceed 8%. It looks independant from various physical and chemical factros (stream velocity, temperature, oxygen concentration) but it rises with the perimaginal population-age because of the lengthening of larval life by the parasite.