The cryopreservation of some large ciliate entodiniomorphid protozoa taken from the rumen.

Large entodiniomorphid ciliates taken from the rumen cannot be reliably kept in vivo, and cryopreservation was investigated as an alternative approach to storage. Three species of large entodiniomorphid ciliated (Polyplastron multivesiculatum, Epidinium ecaudatum forma caudatum and Ophryoscolex caudatus forma tricoronatus) were cryopreserved by one-step freezing, with mean recoveries of 43, 51 and 80%, respectively. For Ophryoscolex caudatus forma tricoronatus two-step freezing was investigated. The mean recovery was 30%, and of tested parameters, the equilibration time and temperature of the cryoprotective additive of dimethyl sulphoxide and the length of holding phase at -40 degrees C were found to be critical for the success of the method.