Gametic nuclear exchange during the conjugation of Paramecium polycaryum

Abstract

The migratory gametic nuclear exchange is an important event during the conjugation of ciliates. So far, it is unclear whether this process occurs in Paramecium polycaryum, and there are also some other contradictory descriptions of this species. To clarify this issue, we studied the conjugation process in the Chinese strain of P. polycaryum by means of a modified protargol technique. The reciprocal gametic nuclear exchange and the formation of fertilized nuclei were observed in detail. The results indicated the following: 1) P. polycaryum has cross-fertilization during its conjugation. 2) The transfer of migratory gametic nuclei into the partner cell seems to be an active process. 3) The process of fertilized nuclear formation includes the attachment of a migratory gametic nucleus to a stationary one, membrane fusion of two kinds of gametic nuclei with separate nucleoplasm, and the fusion of the nucleoplasm of two gametic nuclei to form a typical fertilized nucleus.