Mating Types in Paramecium caudatum

Abstract

Three noninterbreeding groups of 2 opposite mating types each were found in 41 clones of P. caudatum collected from Yunnan lakes. A 4th group of 2 opposite mating types was produced in the laboratory by exconjugants of one of the naturally occurring groups. This new group was not a reversion to ancestral type, nor was it formed by sex reversal since there was no evidence of endomixis. Mating reaction could be correlated neither with form of micronucleus nor with geographic distribution.