Cysts
Cysts of P. dubius. Arrow indicates a cyst wall (empty cyst) following excystment. © Agnieszka Pajdak-Stós, Institute of Environmental Sciences, Jagiellonian University, Poland, www.eko.uj.edu.pl
Like many ciliates, Pseudomicrothorax dubius can produce a dormant stage - the cyst. These are usually produced when environmental conditions become unfavourable, for example when there is a lack of available food.
Ciliate cysts may remain viable for long periods, several decades in some cases. They play an important role in the survival and dispersal of many free-living ciliates.
The cyst of P. dubius is usually dark brown and has a diameter of 40-50µm. The cyst wall is about 3µm thick and is more or less regularly sculptured by rounded cones. A major component of the cyst wall is chitin, which is also found in the exoskeleton of arthropods (Mulisch and Huasmann, 1989).