title: The nature of control of oral development by the micronucleus in sexual reproduction of Paramecium tetraurelia.
abstract: Twelve laser-irradiated cell lines and eight cis. platin-treated cultures possessing defective micronuclei exhibited micronuclear and oral abnormalities during autogamy. Micronuclear abnormalities were characterized by the failure of some of the cells to complete the micronuclear cycle resulting in the absence of either micronuclei or macronuclear anlagen, or both. Oral abnormalities included reduction in the length of the buccal cavity and oral membranelles, abnormal oral membranellar patterns and arrest of oral development at early and late stages. The present study demonstrated a close relationship between micronuclear and stomatogenic abnormalities during sexual reproduction. It is concluded that the micronucleus plays an important role in the specification of a normal oral pattern during sexual reproduction. The participation of postzygotic micronuclear activities in the control of sexual stomatogenesis is discussed. In contrast to the situation in sexual reproduction, the development of the oral apparatus was normal during asexual propagation of the cell lines possessing defective micronuclei. This paradoxical situation forms the basis of speculations on the nature of micronuclear control of oral development in sexual reproduction. It is probable that micronuclear genes are involved.
authors.affiliation: Zoology Department, University of Hong Kong, Hong Kong.
authors.forename: M F
authors.initials: MF
authors.lastname: Chau
authors.forename: S F
authors.initials: SF
authors.lastname: Ng