Phycotoxins from blue-green algae

Unpredictable poisonings of livestock and wildlife by waterblooms or scums of freshwater cyanophytes (cyanobacteria) occur when toxic strains of the common spe.cies dominate composition sufficiently to provide above-threshold levels of phycótoxins by susceptible animals.Known phycotoxins from freshwater cyanophytes are alkaloids, polypeptides or pteridines.New toxins produced by new strains have been described recently.Freshwater cyanophyte waterblooms can cause allergic reactions and, in water supplies, are suspected of causing outbreaks of human gastroenteritis.The structures of dermatitis-producing and non-dermatitis-producing phycotoxins from species of marine cyanophytes have been reported recently.I NTRODUCTION Species of marine algae have been gathered and used for food in Japan and China for centuries.To a lesser extent they have been gathered and used in Europe, North America, and other parts of the world as well.In recent times much research has been done to develop methods for culturing, harvesting and drying both seaweeds and freshwater micro-algae.These methods are being utilized more and more in different countries to supply food for man or for livestock.The chief micro-algae that are being grown for human or animal consumption are eukaryotic chlorophytes, such as Chlorella and Scenedesmus.The coccoid bloom-forming cyanophyte Microcystis is the principal species which has long been grown on human and animal wastes as a food source for fish in manmade ponds and lagoons in India, Pakistan and other countries in south-east Asia.Another cyanophyte, Spirulina, traditionally eaten by people in central Africa and Mexico is now being cultured, or being considered for culture, as a food in Belgium, Mexico, Peru, California, Israel, South Africa and Thailand (16).Freshwater cyanophytes are potentially excellent sources of food because they have a high protein content and good digestibility.They also grow quite rapidly and can be cultured relatively easily on by-product or waste sources of nutrients.However, one of the serious drawbacks to using bloom-forming cyanophytes as food for livestock or man is the fact that toxic strains of several species of cyanophytes are now known to exist which are usually morphologically indistinguishable from non-toxic strains.Poisonings of livestock and other animals attributed to toxic blooms of freshwater cyanophytes occur with considerable frequency but unpredictably in western Canada and mid-western United States, and in similar climatic and geographic regions of South America, Europe, Asia, South Africa and Australia.These poisonings can cause considerable economic loss and hence are of