Friday Fellow: Toxic gambierdisc

by Piter Kehoma Boll

Last week I introduced a coral reef fish, the porkfish, and mentioned that sometimes eating it may lead to ciguatera, a kind of food poisoning. So today I decided to introduce one of the main responsibles for ciguatera, the dinoflagellate Gambierdiscus toxicus, or toxic gambierdisc.

Gambierdiscus toxicus was discovered in 1975 in material collected around the Gambier Islands, where ciguatera often occurs, and described in 1979. As most dinoflagellates, it is unicellular and covered with hardened plates forming a structure called theca.

Living on the surface of seaweeds, especially brown algae, the toxic gambierdisc is ingested by fish who feed on the algae. Its toxins may therefore bioaccumulate in the fish’s tissues and be transfered to larger fish that feed on the smaller ones. If those fish are eaten by humans, it leads to ciguatera.

The symptoms of ciguatera poisoning include nausea, vomiting, diarrhea, headeaches, muscle aches, numbness, vertigo, hallucinations, etc. They may last from weeks to several years, sometimes up to two decades.

Among the main toxins produced by Gambierdiscus toxicus are ciguatoxins an maitotoxin. Ciguatoxins are lipophilic polyethers that act by lowering the threshold for opening sodium channels in synapses of the nervous system, which causes depolarization, leading to paralysis. On the other hand, maitotoxin is a hydrophilic molecule that activates extracellular calcium channels and may cause cell lysis and subsequent necrosis. There is no known antidote or effective treatment against ciguatera.

So, our lesson is: don’t mess with dinoflagellates!

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References:

Adachi, R.; Fukuyo, Y. 1979. The thecal structure of a marine toxic dinoflagellate Gambierdiscus toxicus gen. et sp. nov. collected in a ciguatera-endemic area. Bulletin of the Japanese Society of Scientific Fisheries, 45(1): 67-71.

Bagnis, R.; Chanteau, S.; Chungue, E.; Hurtel, J. M.; Yasumoto, T.; Inoue, A. 1980. Origins of ciguatera fish poisoning: a new dinoflagellate, Gambierdiscus toxicus Adachi and Fukuyo, definetely involved as a causal agent. Toxicon, 18: 199-209.

Wikipedia. Ciguatera. Availabe at: <https://en.wikipedia.org/wiki/Ciguatera >. Access on February 29, 2016.

Wikipedia. Ciguatoxin. Available at: <https://en.wikipedia.org/wiki/Ciguatoxin&gt;. Access on February 29, 2016.

Wikipedia. Maitotoxin. Available at: <https://en.wikipedia.org/wiki/Maitotoxin >. Access on February 29, 2016.

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