Microcystis sp. Identification


Forms Used with permission; copyright Robin Matthewsclusters of cells (colonies) which may be spherical, lobed or an extensive reticulate mass. Suspended colonies often appear as small blue-green "clots" to the unaided eye. Individual cells are very small (3-5 mm diameter) with conspicuous, highly refractive pseudovacuoles that cause the colonies to be buoyant and float to surface. Cells of a colony are held together by a transparent, gelatinous matrix which may be difficult to discern under microscopic examination. Akinetes and heterocysts are absent. The photograph is the copyright property of Dr. Robin Matthews, Western Washington University, and used with her permission.

This organism is known to produce a family of toxins called microcystins. Named after this genus, they are heptapeptides that primarily affect the liver in animals (hepatotoxins). Current evidence suggests that the toxins alter the cytoskeletal components of hepatocytes leading to intercellular dissociation of hepatocytes causing blood accumulation within the liver and death by hypovolumic shock. Very 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.

Poisoning symptoms in animals

Symptoms may take 30 minutes to 24 hours to appear, depending upon the size of the animal affected and the amount of toxic bloom consumed. Microcystin toxicosis may include 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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