Trypanosoma cruzi populations: more clonal than sexual.

The ancient question of trypanosome sexuality has recently been reactivated in view of important observations in the African species Trypanosoma brucie, in which Mendelian sexuality has been proposed as a working hypothesis on the basis o f indirect isozyme evidence. Subsequent experiments have confirmed that recombination can occur in T. brucei under defined experimental conditions and suggest that this parasite undergoes meiosis. In this article, Michel Tibayrenc and Francisco Ayala discuss the intraspecific variability of another species, Tyapanosoma cruzi - causative agent of american trypanosomiasis or Chagas disease. They interpret the variation revealed by extensive isozyme analysis and restriction endonuclease analysis of kinetoplast DNA, to suggest that T. cruzi is diploid, genetically very polymorphic, and has a clonal structure that manifests a lack of (or very restricted) sexuality.