A propos des stratégies d’infestation chez les protozoaires parasites ou endocommensaux des amphibiens anoures du Cameroun

Résumé En

The way protozoan parasites and commensals enter the intestinal tract of Anurans is still poorly understood. The observations and preliminary experiments reported in this paper were made in Cameroon, whose rich and varied Amphibian fauna opens new possibilities to test the hypothesis so far put forward. The favoured, if not unique, hosts of these protozoans are the tadpoles. Not a single case of transmission at the egg stage was noticed. Contamination of adult animals is unlikely, except for Xenopine frogs. Encystment was seldom observed, never within the intestinal tract itself. On the contrary, some experiments tend to indicate that cysts enter the host by ingestion at the tadpole stage, and remain quiescent until metamorphosis. An aquatic environment seems to be a necessary condition for the transmission of these parasites ; they were never found in species whose eggs undergo direct development. The case of those tree frogs of genera Chiromantis, Afrixalus and Hyperolius which build foam-or leaf-nests is typical ; young tadpoles hatching from eggs laid in natural conditions were never found infected with protozoan parasites. As for the protozoans which are restricted to adult’s intestinal tracts, they have to enter their hosts before metamorphosis, at the tadpole stage, and remain quiescent for a time. Adult Phrynodon sandersoni, a species whose tadpoles have a non-functional gut, never harbour parasitic protozoans.