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''Alexandrium catenella'' is a dinoflagellate.〔(【引用サイトリンク】url=http://www.orhab.org/education/Alexandrium_sp.htm )〕 It is among the group of ''Alexandrium'' species that produce toxins that cause paralytic shellfish poisoning, and is a cause of red tide.〔(【引用サイトリンク】url=http://www.red-tide.org/new_site/ac.htm )〕 These organisms have been found in the west coast of North America, Japan, Australia, and parts of South Africa. ''Alexandrium catenella'' can occur in single cells (similar to ''A. fundyense''), but more often they are seen in short chains of 2, 4, or 8 cells. The organism is typically 20–25 µm in length and 25–32 µm in width. The cells are compressed both in the anterior and posterior ends of this specimen. ''Alexandrium'' has two flagella that enable it to swim. While one flagellum encircles the cell causing the cell the rotate and move forward, the other extends behind the cell and controls the direction. In some instances, these organisms can appear like small trains moving in the water under a microscope. The dinoflagellate produces saxitoxin, which is a highly potent neurotoxin. If consumed, this toxin can cause paralytic shellfish poisoning (PSP).〔(【引用サイトリンク】url=http://www.sccoos.org/data/habs/species.php?specie=Alexandrium%20spp )〕 By ingesting saxitoxin, humans can suffer from numbness, ataxia, incoherence, and in extreme cases respiratory paralysis and death. The toxin was discovered in 1927 in central California. Shellfish poisoning affected over a hundred humans, and now saxitoxin is recognized as one of the most deadly algal toxins. These algal blooms have caused severe disruptions in the fisheries of these waters, and have caused filter-feeding shellfish in affected waters to become poisonous for human consumption. Because of this, A. ''catenella'' is categorized as a Harmful Algal Bloom (HAB) species. While in some areas the causes of HABs appears to be completely natural, in others, they appear to be a result of human activity, which is often coastal water pollution and over-fertilization. Some important limiting factors include growth that is stimulated by the supply of ammonia and inorganic nitrogen. The optimal growth conditions for ''A. catenella'' include a cool temperature of around 17 to 23 °C, a medium light illumination of 3500 to 4000 lux, and a high salinity of around 26 to 32 percent. == References == 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Alexandrium catenella」の詳細全文を読む スポンサード リンク
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