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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.
Diatoms are divided into two groups that are distinguished by the shape of the frustule: the centric diatoms and the pennate diatoms. Pennate diatoms are bilaterally symmetric. Each one of their valves have openings that are slits along the raphes and their shells are typically elongated parallel to these raphes. They generate cell movement ...
For many years the diatoms—treated either as a class (Bacillariophyceae) or a phylum (Bacillariophyta)—were divided into just 2 orders, corresponding to the centric and the pennate diatoms (Centrales and Pennales; alternative names Biddulphiales and Bacillariales, as used e.g. in Lee, 1989). [9]
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]
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 ...
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 ...
Nitzschia is a common pennate marine diatom. In the scientific literature, this genus, named after Christian Ludwig Nitzsch, is sometimes referred to incorrectly as Nitzchia, and it has many species described, which all have a similar morphology. In its current circumscription, Nitzschia is paraphyletic. [1]
Sea ice pennate diatom populations can become very dense, reaching up to 1000 μg of chlorophyll per liter of seawater, compared to a typical maximum of 5 μg/L in the open ocean. Due to their high abundance in sea ice, pennate diatoms can profoundly impact the microecosystem within a brine pocket, such as DMSP production.