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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 3654

Stephen F. NG; Persistence of Oral Structures in the Sexual Process of Amicronucleate Paramecium tetraurelia. J.Protozool. 35(2):321-326, 1988

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In the sexual process, amicronucleate Paramecium tetraurelia, unlike micronucleates, fail to reproduce an oral apparatus, but resorb the pre-existing one. Exceptions were found in some amicronuleate cell lines in which about 1% of the cells possessed oral structures, including pieces of oral membranelles, sometimes complete with buccal cavity, after autogamy or conjugation. By following oral development in the sexual process in some detail, the present study supports the view that these oral structures are derived from the pre-existing oral apparatus and not newly developed from the oral primordium. The possible involvement of the micronucleus and the pre-existing oral apparatus in oral resorption is discussed. The possession of a functional oral apparatus after the sexual process may open up a new evolutionary avenue to the amicronucleates.