FINE STRUCTURE OF CELL DIVISION IN CHLAMYDOMONAS REINHARDI

Abstract

Cell division in log-phase cultures of the unicellular, biflagellate alga, C. reinhardi, was studied with the electron microscope. The 2 basal ~ bodies of the cell replicate prior to cytokinesis; stages in basal body formation are presented. At the time of cell division, the original basal bodies detach from the flagella, and the 4 basal bodies appear to be involved in the orientation of the plane of the cleavage furrow. Four sets of microtubules participate in cell division. Spindle microtubules are involved in a mitosis that is marked by the presence of an intact nuclear envelope. A band of microtubules arcs over the mitotic nucleus, indicating the future cleavage plant. A third set of microtubules appears between the daughter nuclei at telophase, and microtubules comprising the "cleavage apparatus" radiate from the basal bodies and extend along both sides of the cleavage furrow during cytokinesis. Features of cell division in C. reinhardi are discussed and related to cell division in other organisims. It is proposed that microtubules participate in the formation of the cleavage furrow in C. reinhardi.