Morphological differences in Blastocystis cysts-an indication of different species?

Cyst forms of Blastocystis that show disparate morphology in relation to the previously described cysts were detected in faecal material from animal hosts. Transmission electron microscopy was performed without attempts to isolate or concentrate Blastocystis from the faecal material. Large, multinucleate cyst forms were found in faecal material from Macaca monkeys. These cyst forms measured up to approximately 15 microm in diameter and were often larger than vacuolar forms present in the same samples. Four or more nuclei were frequently seen in the cysts. Multiple individual cysts enclosed by a single fibrillar layer were found in faecal material from domestic chickens. Each individual cyst within the multiple cyst form measured approximately 3-4 microm in diameter and appeared to be uninucleate.