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As a result, after each division cycle, the average size of diatom cells in the population gets smaller. Once such cells reach a certain minimum size, rather than simply divide, they reverse this decline by forming an auxospore, usually through meiosis and sexual reproduction, but exceptions exist. The auxospore expands in size to give rise to ...
Pinnularia, like most diatoms, can reproduce by simple cell division. Nuclear division occurs by mitosis and cell divides into two parts. Each daughter receives one of the parent cell's thecae, which becomes that cell's epitheca. The cell then synthesizes a new hypotheca. Thus, one daughter is the same size as the parent, and one is slightly ...
Three diatom species were sent to the International Space Station, together with the huge (6 mm length) diatoms of Antarctica and the exclusive colonial diatom, Bacillaria paradoxa. The cells of Bacillaria moved next to each other in partial but opposite synchrony by a microfluidics method.
In diatoms, fertilization gives rise to a zygote termed auxospore. Besides sexual reproduction and as a resting stage, the function of an auxospore is the restoration of the original cell size, as diatoms get progressively smaller during mitotic cell division. Auxospores divide by mitosis.
The M phase can be either mitosis or meiosis depending on the type of cell. Germ cells, or gametes, undergo meiosis, while somatic cells will undergo mitosis. After the cell proceeds successfully through the M phase, it may then undergo cell division through cytokinesis.
Some pennate diatoms also exhibit a fissure along their longitudinal axis. This is known as a raphe, and is involved in gliding movements made by diatom cells; motile diatoms always possess a raphe. In terms of cell cycle, vegetative cells are diploid and undergo mitosis during normal cell division.
Following mitosis, two daughter cells form inside the parent cell, with the nucleus of each daughter cell moves to the side of the diatom where the new hypotheca will form. A microtubule center positions itself between the nucleus and the plasma membrane above which the new hypotheca will be placed.
Consequently, each division cycle decreases the average size of diatom cells in a population. When its size becomes too small, a dividing diatom cell produces an auxospore to expand its cell size back to that which is normal for vegetative cells. [2] Auxospores can also play a role in sexual reproduction in diatoms, and may be formed after ...