Dimorphic nuclei of the karyorelictid ciliate Geleia nigriceps kahl: Fine structure

Geleia nigriceps has two somatic nuclei (macronuclei) of the diploid never-dividing type, which are very poor in Feulgen-positive material, and one compact generative nucleus (micronucleus) [10]. Each macronucleus contains a large central nucleolus and often a voluminous sphere of fibrous texture which, according to light microscopical cytochemistry, contains much RNA and some protein. There is very little condensed chromatin in the macronucleus, mainly in form of intranucleolar chromatin bodies. These bodies may decondense forming fibrillar centres. The macronuclear envelope is conventional and carries numerous pore complexes. The micronucleus is filled with spongy condensed chromatin and lacks nucleoli or nuclear bodies. Its envelope displays finger-like protrusions covered with two membranes without pore complexes. These occur only on regular parts of the micronuclear envelope.