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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 4743

Valentina G. Kovaleva; The Pronuclei of the Lower Ciliate Tracheloraphis totevi (Karyorelictida). Arch.Protistenk 134:367-377, 1987

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Multiple formation of pronuclei occurs during conjugation in the lower ciliate Tracheloraphis totevi: 4 functional pronuclei (two migratory and two stationary) are differentiated in each of the conjugating cells. The migratory pronuclei lie opposite to each other close to the surface of junction of the two conjugants, and the stationary ones always lie deeper in the cytoplasm. The two types of pronuclei show morphological differences in respect to their shape, size and the presence of a specialized zone of cytoplasm which exists only around the migratory pronuclei. There is no direct cytoplasmic continuity (no cytoplasmic bridges) between the conjugants which only display a zone of intercellular junction. Due to this, the migratory pronuclei, with a minimum amount of surrounding cytoplasm, temporarily assume an extracellular position while passing into the other conjugant.