DNA MEASUREMENTS AND PLOIDY DETERMINATION OF DEVELOPMENTAL STAGES IN THE LIFE-CYCLES OF THEILERIA-ANNULATA AND THEILERIA-PARVA

The relative DNA levels of different developmental stages of Theileria annulata and T. parva in the cow and the tick were measured by the cy tophotometric DNA technique using the fluorochrome Hoechst 33258 as a staining dye. The results revealed that sporozoites, merozoites, gamon ts, and gametes were haploid, whereas multinucleated intralymphocytic schizonts were poly ploid. No difference was observed between T. parva and T. annulata in these stages. For both Theileria species, the DNA measurements revealed that fusion of gametes occurred in the gut of th e final host, thus providing evidence of sexual reproduction. However, differences were observed between the two parasites in the tick. Wher eas T. parva zygotes underwent a two-step meiotic division, a comparab le reduction division could not be unequivocally detected in T. annula ta. Differences could also be detected in the further development of k inetes, indicating that Theileria species are not characterized by onl y one life cycle, which is specific for this genus.