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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 .
Fragilariopsis cylindrus is a pennate raphid diatom with a retangular cell with an elongated apical valve ranging from 15 to 55 μ and a transapical axis ranging from 2.4 to 4 μm [9]. Like other diatoms, F. cylindrus presents a cell wall composed of two biogenic silica valves, the frustule. It is also possible to note the presence of an ...
Some pennate diatoms are capable of a type of locomotion called "gliding", which allows them to move across surfaces via adhesive mucilage secreted through a seamlike structure called the raphe. [60] [61] In order for a diatom cell to glide, it must have a solid substrate for the mucilage to adhere to.
Diatoms generate about 20 per cent of the oxygen produced on the planet each year, [12] take in over 6.7 billion metric tons of silicon each year from the waters in which they live, [13] and contribute nearly half of the organic material found in the oceans. Diatoms are enclosed in protective silica (glass) shells called frustules.
Dead diatoms drift to the ocean floor where, over millions of years, the remains of their frustules can build up as much as half a mile deep. [64] Diatoms have relatively high sinking speeds compared with other phytoplankton groups, and they account for about 40% of particulate carbon exported to ocean depths. [60] [65] [62]
The migration occurs when organisms move up to the uppermost layer of the water at night and return to the bottom of the daylight zone of the oceans or to the dense, bottom layer of lakes during the day. [2] DVM is important to the functioning of deep-sea food webs and the biologically-driven sequestration of carbon. [3]
The diatom lineage may go back 180 to 250 million years ago (Mya). About 65 Mya, diatoms survived a mass extinction in which roughly 85% of all species perished. [6] Until 1994, the genus was known as Nitzschia, but was changed to Pseudo-nitzschia because of the ability to form chains of overlapping cells, as well as other minor morphological differences. [8]
Pseudo-nitzschia australis is a pennate diatom found in temperate and sub-tropic marine waters, such as off the coast of California and Argentina. This diatom is a Harmful Micro Algae [1] that produces toxic effects on a variety of organisms through its production of domoic acid, a neurotoxin. Toxic effects have been observed in a variety of ...