DNA measurements and ploidy determination of different stages in the life cycle ofSarcocystis muris

The DNA contents of different stages within the life cycle ofSarcocystis muris were measured cytophotometrically using DNA-specific Feulgen staining. Stages of gamogony were obtained by the transfer of isolated cyst merozoites into cat kidney-cell cultures. For calculation of absolute DNA contents, the amounts of DNA in the parasites were compared with those in chicken erythrocytes, which are known. The measurements revealed that all investigated stages ofS. muris contained haploid DNA except the early zygotes, which were diploid. The further development of the zygotes started with a nuclear division, resulting in two daughter nuclei that again revealed haploid DNA values. The results confirm the existence of zygotic meiosis; thus, a haplo-homophasic life cycle is proposed for the Sarcosporidia.Dedicated to Prof. Dr. G. Piekarski on the occasion of his 80th anniversary (October 5, 1990)Supported by the Deutsche Forschungsgemeinschaft (DFG)