Mating‐Type Polymorphic Variation in Euplotes minuta (Ciliophora: Hypotrichida)1

Abstract

An investigation was carried out to probe into the mating‐type structure of a local population of the marine ciliate, Euplotes minuta. From this population, nine different mating types belonging to a unique set were isolated. The nine type‐representative wild stocks analyzed were found to be heterozygous at the mating‐type (mat) locus and provided, together with their sexual progeny, a total of 15 pure mating types. In E. minuta, the high‐multiple nature of the basic mating system controlled by a series of peck‐order alleles at a single locus should be considered a virtual certainty. The relationships among the genetic economies of the similar bottom‐dwelling marine ciliates of the genus Euplotes, the E. vannus‐crassus‐minuta group, are discussed.