Binary fission and encystation of Opalina sp. in axenic medium

金沢大学理工研究域自然システム学系Opalina sp. were cultivated under an anaerobic condition in the complex medium containing DME/F-12 HAM mixture (Sigma) as a basic medium, and fetal bovine serum and autoclaved rumen fluid as additional components. In the medium, the opalinid cells reproduced by binary fission, and in the longest case they were maintained for more than one month, following successive transfers. When cells collected from the host in breeding season were cultured in the same medium, encystation occurred after rapid cell divisions. In this case, the population obtained from the frog had contained a sub-population of cells with small number of nuclei and small cell size. The sub-population might have been in the phase of palintomy that is a rapid sequence of binary fissions without cell growth and finally produces small cysts. Our successful maintenance of the opalinid cells can offer the first step for the establishment of the in-vitro culture method