FINE-STRUCTURE OF THE NUCLEI OF THE KARYORELICTEAN CILIATE TRACHELORAPHIS-FLEXUOSUS FROM THE JAPAN SEA

The nuclear apparatus of the Japan sea population of Tracheloraphis fl exuosus RAIKOV et KOVALEVA 1968 consists of a longitudinal row of 20-3 0 macronuclei and 10-15 micronuclei usually arranged into groups of tw o macronuclei and one micronucleus in each. The nuclear groups lie in a voluminous perinuclear lacuna, the proximal membrane of which tightl y applies to the nuclei leaving around them only a thin rim of ground cytoplasm. This membrane encircles each nuclear group separately and a pparently holds the nuclei together. The micronuclei are filled with s pongy condensed chromatin and limited by a conventional envelope with pores. The micronuclear chromatin is resistant to bleaching with BERNH ARD'S EDTA. Young macronuclei occur in some groups and contain small s cattered chromocentres but no nucleoli; the chromocentres are readily bleached with EDTA. Adult macronuclei contain several nucleoli of usua l structure (fibrillar core, granular cortex), several chromocentres a nd rarely a small sphere. The chromocentres are heterogenous: each one shows a dense cap. They become bleached with EDTA even after short ex posure whereas nucleoli and the sphere retain contrast. The nuclei of Tracheloraphis flexuosus are smaller than those of T. dogieli, the sim ilar European form.