ABSTRACT
Genetic studies on the coccidia are inherently difficult for several reasons. These include the complex nature of the life cycles, the absence of straightforward methods by which, with the exception of Toxoplasma, cloned populations can be obtained, and the absence of techniques to isolate purified gametes. Coccidial parasites have for some years been considered to be eukaryotes because they possess a cytoplasm delineated into membrane bound organelles such as nuclei, mitochondria, and Golgi. The nature and mechanisms of the regulators of sex differentiation are obviously topics worthy of investigation and Toxoplasma would seem to be the coccidian of choice given that it can be grown in vitro with relative ease. Comparatively few coccidial enzymes have been extensively characterized although O’Donoghue et al., working with Sarcocystis spp., obtained excellent resolution with 15 to 39 enzymes analyzed on cellulose acetate gels. Only a few studies on enzyme variation have been undertaken with other coccidia and most work has been done with Sarcocystis.
