Chemical Ecology (Session I 2001)
Home Units Defensive Mechanisms Tetrodotoxin: The Neurotoxin
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Tetrodotoxin - The Neurotoxin
 
 
Tetrodotoxin

The toxin that has been demostrated to be the active agent in "puffer poisoning" is tetrodotoxin.Tetrodotoxin is at least one order of magnitude more lethal than the venom of the black widow spider. It has toxicity similar to saxitoxin, a toxin from a marine dinoflaggelate that causes paralytic shellfish poisoning. It is noteworthy that tetrodotoxin and saxitoxin are relatively unusual in that there are few potent non-protein toxins. They are similar in that each contains the positively charged guanidinium moiety.

The Nobel Prize was awarded, in part, in recognition of R.B. Woodward's synthesis of tetrodotoxin


 
 
guanidinium moiety

 
      Saxitoxin

 
 
 

The California newt (Taricha torosa) was found to contain a potent toxin in the 1930ís and several related species of Taricha in California were subsequently found to contain the same toxin. Stanford chemists Brown and Mosher isolated the toxin and named it tarichatoxin. (Note. The garter snake has adapted to the toxin)Later the toxin of the blue ringed octopus (H. maculosa), was isolated and named maculotoxin. Both aculotoxin and tarichatoxin were subsequently shown to be identical to tetrodotoxin. Many species of the family Salamandridae and a group of Central American toads, the harlequin frogs, also possess the toxin. But tetrodotoxin is even more widely distributed. It appears in triggerfishes, ocean sunfishes, globefishes, the porcupinefishes, some parrotfishes, a goby, xanthid crabs, seastars, an angelfish, a horseshoe crab, a number of marine snails, a flatworm, a South Atlantic "sea squirt, ribbon worms and a marine red alga. Read more about the blue ringed octopus
And: First Aid

It is clear that tetrodotoxin provides a clear advantage to the animals that possess it. Although the blue ringed octopus uses tetrodotoxin to capture prey (as do several worm species) it also uses it as a protective measure. Other animals such as the pufferfish employ the toxin as a defensive measure which, in the pufferfish for example, makes up for its lack of mobility and inability to avoid predators. (Pity the predator that attacks the pufferfish, a little nip can mean death!)

How does one explain the wide distribution of tetrodotoxin, a single complex molecule that appears to have no critical metabolic role. One of the first clues was obtained when Matsui found that captivity-raised pufferfish contained no tetrodotoxin. Daly recently reported similar findings with respect to the harlequin frog. The Japanese investigator Yasumoto detected tetrodotoxin in the algae and in bacteria associated with the algae that some of the tetrodotoxin containing crabs and fish fed on.. This suggested that these animals were obtaining the tetrodotoxin from the environment and that bacteria were the source of the toxin. Bacteria have subsequently been found to synthesize tetrodotoxin in many other creatures.


 

General information on puffer fish and tetrodotoxin see: Molecule of the Month: Tetrodotoxin

See: Eye of NEWT, Skin of TOAD, Bile of PUFFERFISH

See the diversity and complexity of marine toxins:

For fun read how to create a zombie