THE ULTRASTRUCTURE OF MITOSIS IN THE FREE-LIVING KINETOPLASTID BODO-CURVIFILUS

The nuclear division of a free-living bodonid flagellate was investiga ted at the ultrastructural level for the first time. Transmission elec tron microscopy of serial ultrathin sections shows that nuclear divisi on of Bodo curvifilus occurs by closed mitosis with an intranuclear sp indle, as in trypanosomatids and cryptobiids. The nucleolar material o f B. curvifilus persists during the nuclear division and seems to be s hared between the daughter nuclei. The spindle consists of one compact bundle of approximately 30 microtubules running through the nuclear c entre: most of the microtubules continue from one pole to another. Mic rotubule-organising centres of the mitotic spindle lie at the opposite poles, and they are not distinguished morphologically. The spindle of B. curvifilus is associated with at least 10 pairs of kinetochore-lik e dense plaques. In sections only the plaques can be seen at different stages of migration towards the poles as chromosomes are not condense d during mitosis of kinetoplastids.