A complementary experimental study of cell division in the dinoflagellate Prorocentrum micans

Cell division in Prorocentrum micans was studied with TEM, SEM and with fluorescence microscope techniques to visualize cytoskeletal structures. The cleavage furrow consists of the plasma membrane and two valvar vesicles. Its leading edge is lined with actin filaments. The completion of cytokinesis (like in some other dinoflagellates) is inhibited by extremely low doses of cytochalasin D. Under the influence of this drug cleavage vesicles fuse into large cleavage cavities. New valvae are formed, however, with an irregular, warty surface, caused by a surplus of membrane material and/or lack of stretch and possibly influenced by a predetermined pattern of the cell surface. At the end of mitosis individual or small groups of chromosomes are surrounded by the nuclear envelope.