Acute toxic effects of a novel cyanobacterial toxin on the crustaceans Artemia salina and Daphnia pulex

A strain of the cyanobacterium Oscillatoria agardhii non-toxic to mice was toxic to the crustaceans Daphnia pulex and Artemia salina. The 48 h EC(50)-value of a water extract to D. pulex corresponded to 0.26 mg/ml of freeze-dried cyanobacteria, and the 48 h EC(50)-value of a semi-purified, freeze-dried, water extract was 0.06 mg/ml. Whole cells were also toxic, but no clear dose-effect relationship could be established, probably because the feeding of the animals was inhibited. The toxic effect on D. pulex was reversible. Further purification of the toxin was achieved using gel filtration. A subsequent testing of the toxicity of the gel filtration fractions, using both species of crustaceans, suggests that a single compound caused the observed toxicity. The molecular weight of this toxin was around 2,000, as detected during gel filtration.