Mating‐type‐specific loss of conjugation competence by irritation in Euplotes vannus

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Abstract
In order to characterize differences in mating types in Euplotes vannus, two cell populations of complementary mating types were mixed and exposed to a pattern of irritation (switching schedule of agitation and rest). Cells costimulate each other, as is seen from courtship behavior during still intervals, but do not pair. Prolonged periods of treatment cause distinctly reduced cell interactions. After 72 hr they have ceased completely: Overstimulated cells have lost their ability to conjugate. However, with fresh cells of mating types, which are different from both constituents of the mixture, overstimulated cells mate normally as judged by time course, cycloheximide‐sensitivity, and concanavalin A (ConA) binding. Conjugation competence thus is selectively lost only for that mating type which has been the partner in the perturbated mixture. The required classification of pairs with regard to mating‐type combinations were confirmed by several identification procedures using amicronucleates and doublets. The observed phenomena during the mating‐type‐specific loss of conjugation ability are consistent with the concept that this is due to a physiological disappearance of a specific mating substance, which might correspond to the receptor side of the extended gamone‐receptor hypothesis of Miyake ('81).
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