Mitosis and cytokinesis in the dinoflagellate Amphidinium carterae

Mitosis and cytokinesis are described in the free-living dinoflagellate, Amphidinium carterae Hulburt. In prophase, invaginations of the nuclear envelope form into tunnels which enclose bundles of microtubules. No centrioles or spindle organizers are present but microbodies are situated at the ends of the bundles of microtubules. The dividing chromosomes are attached to the tunnels, and microtubules connect to the nuclear envelope adjacent to the chromosomes by means of kinetochore-like structures. At anaphase, daughter chromatids are pulled apart as the nucleus extends but there is little change in the pole to chromosome distance. Cytokinesis is brought about by pinching-in of the cytoplasm adjacent to the equatorial region in an area where many microtubules lie under the plasmalemma. The account adds further details to the earlier descriptions of mitosis in other dinoflagellates.