title: Observations on the mitosis and on the chromosome evolution during the lifecycle of Oodinium, a parasitic dinoflagellate.
abstract: The life cycle of the dinoflagellate Oodinium alternates between an ectoparasitic trophic phase and a phase of multiplication as free-living flagellates. The nucleus of the young ectoparasite has rod-like chromosomes similar to those of free-living dinoflagellates. As growth of the trophout proceeds the nucleus becomes increasingly homogeneous. When Oodinium leaves its host, nuclear reorganization processes occur rapidly; they correspond to a peculiar prophase of the first sporogenetic division. The following division stages are similar. A conspicuous fusorial system appears between two archoplasmic areas which are responsible for daughter-chromosome segregation. The nuclear envelope remains intact while the fusorial microtubules are attached at distinct, kinetochore-like structures onto the nucleus. As the chromosomes become more condensed the kinetochore-like formations disappear.
mesh_terms: D000818:Animals; D002875:Chromosomes / Q000648:ultrastructure*; D004141:Dinoflagellida / Q000254:growth & development* / Q000648:ultrastructure; D056890:Eukaryota / Q000254:growth & development*; D008854:Microscopy, Electron; D008870:Microtubules / Q000648:ultrastructure; D008938:Mitosis; D009685:Nuclear Envelope / Q000648:ultrastructure; D013170:Spores