Genetic evidence that metacyclic forms of Trypanosoma brucei are diploid.

The hypothesis that metacyclic trypanosomes are haploid has been tested genetically. Five cloned stocks of Trypanosoma brucei (each having four known isoenzyme markers and six known restriction fragment length polymorphisms) have been independently transmitted through tsetse flies. Fifteen individual metacyclic organisms were taken from flies with mature cyclical infections and used to establish fresh clones. All the sub-clones from all the flies proved to be identical to the starting (parental) stocks, with respect to all the markers examined, including those markers which were heterozygous in the parental stocks. We conclude that metacyclic trypanosomes are diploid, and are not the product of an obligatory meiosis.