Inhibition of early events of sexual processes in <i>Paramecium</i> by concanavalin A

Abstract

Abstract The lectin concanavalin A (ConA) inhibited specifically an early step of sexual reproduction (conjugation or autogamy) in Paramecium caudatum . ConA (50 μg/ml) did not prevent the initial agglutinative mating reaction in natural conjugation or a specific swimming behavior observed prior to the induction of conjugation by chemicals, but inhibited pair formation which usually occurs about one hour later. Cells pretreated by protease, ficin or papain increased in their sensitivity to the inhibitory effect of ConA. Conjugating pairs once formed were not separated by the treatment with ConA and underwent nuclear changes normally. The sensitive period to ConA was proximately the first 30 minutes from the onset of mating reaction or of the chemical treatment for induction of conjugation. The same kind of inhibition by ConA was observed in two other species, Paramecium trichium and Paramecium bursaria , but could not be demonstrated in Paramecium multimicronucleatum . ConA (4 μg/ml) completely prevented chemical induction of autogamy in an early step but did not if applied 60 minutes after initiation of the induction. The inhibition of conjugation and autogamy was completely released by α‐methyl‐D‐mannoside or mannose, competitive inhibitors of ConA. PHA had no effect on these sexual processes.