For many years a strange type of poisoning occurring after eating a
number of different species of edible fish, including moray eel and
barracuda, has been known as ciguatera poisoning. It can be a serious
problem in tropical and subtropical parts of the world. Nausea, vomiting
and diarrhoea may be accompanied by neurosensory disturbances, con-
vulsions, muscular paralysis and even death.
After many years research it has been shown that the toxins respon-
sible for these symptoms, which include ciguatoxin C 60 H 86 O 19 , a poly-
unsaturated polycyclic ether, are produced by a benthic or epiphytic
species of dinoflagellate known asGambierdiscus toxicus. The toxins are
concentrated along a food chain starting with the consumption of algae
by herbivorous and detritus-feeding reef fish which themselves are con-
sumed by the larger carnivorous fish caught for human consumption.
8.3.2 Cyanobacterial Toxins
Although the blue–green algae are prokaryotes, their photosynthesis,
during which oxygen is liberated from water, is characteristic of that
shown by the eukaryotic algae and higher plants. Several genera of
freshwater cyanobacteria, especially species ofMicrocystis, Anabaena
andAphanizomenon, can form extensive blooms in lakes, ponds and
reservoirs and may cause deaths of animals drinking the contaminated
water. The presence of such cyanobacteria in public water supplies has
also been implicated in outbreaks of human gastroenteritis.
The cyanoginosins, toxic metabolites ofMicrocystis aeruginosa, are
cyclic polypeptides containing some very unusual amino acids (Figure
8.6) and are essentially hepatotoxins.
8.3.3 Toxic Diatoms
An outbreak of food poisoning, known as amnesic shellfish poisoning
(ASP) or domoic acid poisoning, following consumption of cultivated
mussels from farms in Canada, which involved more than 100 cases and
three deaths, was shown to be due to a glutamate antagonist in the
Figure 8.5 Dinophysistoxin
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