伪尖毛虫Oxytricha fallax的形态学研究

MORPHOLOGICAL STUDY OF OXYTRICHA FALLAX

伪尖毛虫Oxytricha fallax系原生动物门、纤毛虫纲、腹毛目、尖毛虫科的一种常见的单细胞动物。一般认为分裂间期的伪尖毛虫具有两个长圆形大核和两个圆球形小核。虫体腹面生有八根额棘毛、五根腹棘毛及五根肛棘毛,周缘左右两侧还生有缘棘毛,背面则有五列背触毛。 伪尖毛虫是原生动物中高度进化的类型,大、小核有显著的分化,细胞表面的纤毛小器官复杂而又明显,因此它是用以进行研究的一种良好材料。对它的核器与纤毛小器官以及它们在无性分裂过程中的发生和变化进行认真的探讨,可以使我们较详细地掌握该虫的形态特征,同时也能为进一步的研究提供一些资料。

Generally speaking, there are two macronuclei and two micronuclei in inter-phase Oxytricha fallax;and there are eighteen ventral cirri arranged in a pattern of 8, 5, 5, and two rows of marginal cirri. The development and changing, under cultural condition, of nuclei and ciliary system of the organism in asexual cycle were observed in detail experimentally. During cell division the two macronuclei reorganized separately before they fused into a single one, then divide twice, and the resulted four new macronuclei were equally distributed into two daughter cells. The micronuclei divided only once. Owing to their unequal distribution between daughter cells and the occational untouched condition of some of the original micronuclei during dividing process, the number of micronuclei varied from oto 5, instead of 2, while that of macronuclei was quite normal. Conceivably, the unequal distribution of the micronuclei is one the possible ways, through which the amicronuclear organism originates in nature. During asexual divition, the ciliary system undergoes a series of changes and renews itself entirely. When food is amply, owing to "over feeding", the size of the organism would increase drastically accompanied with the increasing of its surface area, the whole ciliary system would then be thrown into great confusion, the number of ventral cirri would increase and appear to be "fluctuating". The pattern and extent of those variations and the frequency of the "abnormal" organisms are all surprising. Such a phenomenon would continue for several generations, even if normal feeding condition is restored. No direct relations between various changes of ciliary system and the state of nuclei can be found.