伍氏游仆虫二分裂和接合生殖期间的形态发生

STUDIES ON MORPHOGENESIS ACCOMPANYING BINARY FISSION AND CONJUGATION IN EUPLOTES WOODRUFFI (CILIATA, PROTOZOA)

用改进的银浸法和黑色素法研究了伍氏游仆虫在二分裂和接合期间的形态发生。在二分裂期间前仔虫继承亲体的口围带和口侧小膜。新伸缩泡开口起源于两组额腹横棘毛原基中的第5棘毛场。看清了接合期间两次形态发生的细节。在营养期口围带上见到的小膜第三排动体的骤然变换,已被证明起源于接合时第一次形态发生的不完整的口围带后端的保留。讨论了游仆虫与其它腹毛类在形态发生上的同源问题。

Using modified silver-impregnation technique and Nigrosin method, the morphogenesis during binary fission and conjugation in Euplotes woodruffi has been investigated. The cortical morphogenetic patterns in both reproductive cycles are similar to those of other members of the genus Euflotes reported by other authors, but some details which were overlooked formerly have been clarified in the present species. During fission the proter inherits the parental adoral zone of membranelles and paroral membranelle as well as the parental cytopharynx apparently unchanged. The contractile vacuole pores for future daughter cells originate separately from the 5th cirral field in the fronto-ventro-transverse primordium at early stage. During conjugation the cytoplasmic fusion between the two conjugants is restricted within a rhomboid area situated in the anterior left corner inside the AZM, Where the wound is healed by thin and dense ac-tinoid silver line network after the conjugants separate. Two steps of morphogenetic reorganization were found in conjugant and exconjugant. The first step initiates dedifferentiation of the entire ventral ciliature including the oral apparatus and redifferentiation of a new set of cirri and the anterior part of the new AZM. The paroral membranelle and its associate cyto-pharynx as well as the buccal cirrus are missing from this step. The membranellar pattern exchanging site which is seen in the vegetative AZM exists in the posterior portion of the incomplete AZM of the exconjugant. The 2nd step involves replacement of all the cirri including the buccal one, and completion of the oral apparatus by redifferentiation of the posterior half of the AZM and of the paroral membranelle with its associate cytopharynx in an additional buccal pouch. The morphogenetic similarities between Euplotes and Stylonychia are summarized and it is proposed that the homology in conjugational morphogenesis between Eu-plotes and other hypotrichous ciliates should not be neglected in consideration of new systmatics of ciliated protozoa.