一个自配型梨形四膜虫的接合及其细胞学过程

自从Elliott和Nanney(1952)描述了四膜虫(Tetrahymena sp.)的接合过程以后,国外对于四膜虫的接合型(mating types)特性以及接合的细胞学过程做了很多研究。Nanney(1953),Elliott和Hayes(1953)分别研究了自配型(selfers)和接合型梨形四膜虫(T.pyriformis)的接合过程。Elliott和Nanney都曾指出,自配型四膜虫的两接合体(Conjuga-nts)在完成核交换后不能分开,即使人力强使分开,二接合体也将解体而不能存活。Elliott(1973)认为,自配型四膜虫接合产生的后代不能存活这一特性,是四膜虫种群排除不稳定的自配型的一种途径。

CONJUGATION IN TETRAHYMENA PYRIFORMIS S1, A SELFER STRAIN FROM SHANGHAI

A selfer strain of Tetrahymena, believed to be a species of T. pyriformis complex, has been established and maintained in axenie culture. By starvation, more than 90% of the cells in clone culture could be induce d to conjugate. The offspring of the ex-conjugants grew very well. It was remarkable that before conjugation, the precon-jugants agglutinated into groups of no more than 60 individuals. After 2-3 hours of agglutination, the cells emerged from the groups individually, and only after an interval of active swimming which lasted about half an hour did they conjugate in pairs. The external form of the preconjugants changed considerably during the period of agglutination. The anterior third of the cell became much narrowed with its terminal end truncated and bending towards the oral surface. At the end of conjugation, a copious secretion of viscous fluid was seen between the two separating con-jugants. The process of agglutination is believed to be a mechanism of mutual recognition, the detail of which needs to be further studied. The nuclear differentiation occurred early in the first postzygotic division when one of the division products became enlarged markedly and divided into two macronuclei, while the other one remained dense and small, the division of which gave rise to a mieronuclear anlage and one which degenerated soon. The early differentiation of nuclei is considered to be of significance in the segregation of mating types in the offspring of the conjugating pairs.