Hybrid formation between African trypanosomes during cyclical transmission

Trypanosomes of the species Trypanosoma brucei reproduce primarily by binary fission, but the frequency of enzyme elec-trophoretic variants in natural populations of T. brucei has provided indirect evidence for the existence of a sexual cycle1-3. These studies, coupled with studies of restriction fragment length polymorphisms of genes encoding glycolytic enzymes4, have also provided evidence for T. brucei being diploid. Here we report direct evidence of gene exchange between two different clones of trypanosomes after mixed infection and full cyclical development in the tsetse fly vector.