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Cells are attached to form long, straight, unbranched filaments that may be entangled to form a mass on substrates or are occasionally found free-floating. Filaments are straight throughout their length except for a possible slight tapering in the last few cells near the apex. Cell size is highly variable between species. Cells may be highly compressed against each other giving the impression of "stacked coins" or exhibit a small indentation at cell-cell juncture. No akinetes nor heterocysts exist in this genus. Filaments commonly exhibit oscillating, sporadic flexing or gliding movements under the microscope, especially near the anterior ends.
This organism is known to produce a family of toxins called microcystins. They are heptapeptides that primarily affect the liver in animals (hepatotoxins) by causing liver cells to dissociate leading to blood accumulation within the liver causing death by hypovolumic shock. Recent experimental evidence shows that at least one of the molecular mechanisms of action is consistent with certain known carcinogens. This information has led researchers to suspect these toxins as liver carcinogens, which could prove significant to humans following continuous, low level exposure.
Acute toxicity symptoms may take 30 minutes to 24 hours to appear, depending upon the size of the animal affected and the amount of bloom consumed. Microcystin toxicosis may exhibit jaundice, shock, abdominal pain/distention, weakness, nausea/vomiting, severe thirst, rapid/weak pulse, and death.
This information is from "Toxic Cyanobacterial Blooms - A Field/Laboratory Guide". This guide was written by Dr. M. A. Crayton from Pacific Lutheran University, Tacoma, Washington and edited by Dr. F. Joan Hardy, Washington State Department of Health. Used with permission.
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