ISSN:
0362-2525
Keywords:
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
In a study of the nuclear behavior of Paramecium aurelia, a process of self-fertilization, autogamy, has been discovered and traced through its essential steps. Autogamy is the counterpart, in a single animal, of conjugation. In autogamy, three micronuclear divisions lead to the formation of the gametic nuclei. These divisions are considered to be maturation divisions. The first division is characterized by a great increase in the size of the two vegetative micronuclei and the occurrence of long thread-like crescents. The second division results in the formation of eight nuclei, variable numbers of which continue to divide giving rise to the potential gametic nuclei. Two of the latter unite to form a synkaryon. The old macronucleus disintegrates. The fusion nucleus divides twice: two of the daughter nuclei become macronuclear anlagen, while the other two remain micronuclei. The macronuclear anlagen are distributed to two daughter cells at the time of the first cell division, when the micronuclei divide.The macronuclear changes in hemixis can be classified into three main types: (1) the extrusion of a relatively small number of spherical chromatin fragments; (2) the splitting of the macronucleus into two (generally) large independent portions - accompanied, or not, by the extrusion of smaller spherical bodies; (3) the complete disorganization by fragmentation of the macronucleus.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jmor.1050590103
