Cells united to form a straight, unbranched filament which tapers slightly toward both ends. Filaments usually clustered to form a bundle of parallel filaments (looking like a bundle of straw), which is free- floating. These bundles appear to the unaided eye as prominent, blue-green, "lens-shaped bodies" suspended in the water sample. Individual cells are at least twice as long as wide (5-6 mm diameter, 8-12 mm long). Each filament shows a slight tapering toward the ends with the cells near the ends being much more elongated and "empty" looking. There may be one centrally located akinete and heterocyst per filament. Akinete is sausage-shaped (8 mm diameter, 60-75 mm long) and located near the center of a filament. Heterocyst is oblong to cylindrical (7mm diameter, 12-20 mm long) and located in the mid- region but not adjacent to akinete. Akinete and/or heterocyst may be absent at times.
This organism is known to produce two of the same toxins as "Paralytic Shellfish Poison" produced by red tide organisms in marine habitats. Saxitoxin and neosaxitoxin are neurotoxins which block sodium channels of nerve cells making them incapable of generating a nerve impulse. They are effective in extremely small amounts; thus only a small amount of toxic bloom needs to be ingested to cause illness or death in animals.
Neurotoxins are notoriously rapid-acting poisons. Onset of symptoms and death
to the animal may occur within a few minutes to few hours, depending upon size
of animal and amount of toxic bloom consumed. Saxitoxin/neosaxitoxin toxicosis
may exhibit weakness, staggering, loss of muscle coordination, difficulty in
swallowing, labored respiration, complete muscle paralysis, and death. Humans may
also exhibit tingling
around the mouth and fingertips, as well as slurred speech.
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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