Abnormalities in Nuclear Behavior and Mating Type Determination in Cytoplasmically Bridged Exconjugants of Doublet Paramecium aurelia*

Abstract

SYNOPSIS Exconjugant clones of Paramecium aurelia stock 51S, syngen 4, which fail to separate prior to the 1st fission have numerous cytologic and mating type determination anomalies. The doublets have abnormal distribution of macronuclear anlagen, fewer macronuclear fragments per cell, and abnormalities in numbers of micronuclei. Despite apparent cell fusion and mixture of cytoplasm, the singlets arising from each side of the doublet may be of opposite mating types, and mating type determination may remain unstable for 1 or more fissions in contrast to the usual pattern of mating type determination before the 1st postconjugation fission.

Nuclear and Cortical Regulation in Doublets of Paramecium: II. When and How do Two Cortical Domains Reorganize to One?

“…6B), in which the two cells were not fused along their entire length, either the proter or the opisthe could bud off singlets. This was the mode briefly reported by Butzel (1973) in P. tetraurelia , and was observed in line M of FT II of P. tetraurelia. However, for the most part we obtained doublets from electrofusion that were fused along their entire length (Fig.…”

“…Yet, in P. bursaria , cortical balance can be maintained for over a year of cultivation: doublets start out perfect and revert to singlets by formation and deepening of an anterior notch at a defined position with subsequent lateral separation, as in the back‐to‐back spirotrich doublets (Sato, Endoh, and Watanabe 1991). Such separation also was observed in P. tetraurelia by Butzel (1973) and in this study (Fig. 6), but in both of these cases such doublets were imperfect (i.e.…”

“…Subsequently, Kaczanowska and Dubielecka 1983 described two different pathways of regulation of doublets of P. tetraurelia. A third pathway was described by Butzel (1973) in P. tetraurelia and by Sato, Endoh, and Watanabe (1991) in P. bursaria. Both Sonneborn 1963 and Kaczanowska and Dubielecka 1983 observed third cytoprocts, but not third oral structures, originating within the narrower surface of regulating Paramecium doublets.…”

Studies on the Macronuclei of Doublet Paramecium tetraurelia: Distribution of Macronuclei and DNA at Fission*

“…thesis, Univ. of Hong Kong, 1969) in small samples of exconjugants and exautogamonts, and by Butzel (6,7 ) in newly formed doublets (cytoplasmically bridged pairs) growing in axenic culture. In both cases about the same frequency of abnormal distributions of anlagen was observed as in the present study with fully formed doublets.…”

Mating-Type Inheritance

“…The presence of the cytoplasmic factors was initially shown by a change of mating type which occurred after the exchange of cytoplasm between con-jugants (Sonneborn 1947;Butzel 1973). Direct evidence of cytoplasmic E-determining factors has been obtained by transplanting E cytoplasm into 0 cells just before development of the new macronucleus, which induced transformation of o to E in the progeny clones.…”