It is long known that the process of macronuclear regeneration in
Paramecium aurelia is a mistake. Misreading the sequence of stages in
stained slides caused this error. See Sonneborn (Adv Gen 1: 263-358,
1947), and the most excellent modern view of macronuclear (MA)
development by M Nowacki et al (Curr Biol15:1616–1628, 2005.). Both
green fluorencent protein and FISH are very much underused in ciliate
studies.
When the MA starts to break down, a signal has gone through saying,
"wrong genotype for the old MA." If "same genotype" is the signal, the
old genotype can stay and thereby compete with any other MA anlagen.
Resorption of the old MA without fragmentation is possible, yet seems
unlikely. When MA fragments appear only in exconjugants the wrong
genotype signal might have come from the synkarion. All this is
speculation just as MA regeneration is.
Paul R Earl
