Diatom Reproduction
Vegetative cell division is the predominant method of reproduction in diatoms. Like many other eukaryotes, diatoms are diploid during the vegetative stage of their life cycle, dividing by mitosis and cytokinesis. Mitosis first begins as the nucleus migrates to a specfic location-- usually somewhere along the bisecting valvar plane. The exact site is characteristic for each species. The nucleus then proceeds through mitosis, with the small chromosomes condensing and forming a ring around a typically cylindrical core of microtubules by metaphase. The chromosomes separate, towards opposite sides of the cell, after which diatoms undergo cytokinesis. More typical of animal than plant cells, diatoms undergo cytokinesis by progressive closure of a cleavage furrow, which pinches the cytoplasm in two. Each daughter cell, now associated with one of the halves (theca) of the parental cell wall, makes and secretes one new cell wall half (theca), thus regenerating a cell wall of two thecae. After formation of the new half of the cell wall, the daughter cells grow and separate from one another.
