Cells are attached to form unbranched filaments (like a string of beads) that may appear randomly twisted and coiled, sometimes regularly coiled like springs, or entangled with numerous other filaments. Vegetative cells may be spherical to oblong (4-14 mm diameter, 6-12 mm long) with granular contents and conspicuous, refractive pseudovacuoles. Two types of specialized cells may be present in various numbers within a filament of vegetative cells (Fig. 2). Akinetes are larger than vegetative cells and may appear spherical to sausage-shaped (6-13 mm diameter, 20-50 mm long). Heterocysts, which appear "empty," are somewhat spherical (7-9 mm diameter, 6-10 mm long).
Anabaena sp. can produce several kinds of toxins. Two different neurotoxins have been described. Anatoxin-a is a potent postsynaptic cholinergic nicotinic agonist, which causes a depolarizing neuromuscular blockade. Anatoxin-a(s), chemically unrelated to the first, acts as an inhibitor of cholinesterase leading to a neuromuscular blockade. Both cause a "tetanus- like" muscle paralysis.
Members of this genus also produce Microcystins (hepatotoxins). Named for the genus in which they were originally discovered, they alter the cytoskeletal components of hepatocytes leading to intercellular dissociation 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. Researchers suspect these toxins may be possible liver carcinogens. This could prove significant to humans following continuous, low level exposure.
Neurotoxins are notoriously rapid-acting poisons. Onset of symptoms and death to the animal may occur within a few minutes to a few hours, depending upon size of animal and amount of toxic bloom consumed. Anatoxin-a toxicosis may exhibit staggering, paralysis, fasciculations (muscle twitching), gasping, convulsions, backward arching of neck in birds, and death. Anatoxin-a(s) induced toxicosis in experimental animals may exhibit hypersalivation, tremors, fasciculations, involuntary muscle movement, diarrhea, cyanosis (tongue and mouth lining appear bluish). and death.
Poisoning from microcystins 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 exhibit jaundice, shock, abdominal pain/distention, weakness, nausea/vomiting, severe thirst, rapid/weak pulse, and death. Anabaena sp. can produce several kinds of toxins. Two different neurotoxins have been described.
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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