Alexandrium Catenella

Alexandrium catenella is a dinoflagellate species that produces the potent neurotoxin saxitoxin, the cause of paralytic shellfish poisoning in humans who eat shellfish that have accumulated the toxin, and of the reddish discoloration in seawater known as a red tide. It is found in cold coastal waters at temperate latitudes, including along the west coast of North America, Japan, Australia and parts of South Africa, and its cells, typically twenty to thirty micrometers across, often link together into short chains. It spends much of its life cycle as a dormant cyst resting on the seafloor in dense accumulations called cyst beds, which germinate into motile, photosynthesizing cells when conditions warm. Its toxin, first identified during a 1927 poisoning outbreak in California that sickened more than a hundred people, can cause numbness, loss of coordination and, in severe cases, fatal respiratory paralysis.