Chemical structure of the ciguatoxin CTX1B, Showing multiple ether bridges

Ciguatoxins are a class of toxic polycyclic polyethers found in fish that cause ciguatera.

There are several different chemicals in this class. "CTX" is often used as an abbreviation.

Toxic effect

Some ciguatoxins lower the threshold for opening voltage-gated sodium channels in synapses of the nervous system. Opening a sodium channel causes depolarization, which could sequentially cause paralysis, heart contraction, and changing the senses of heat and cold. The condition is known as ciguatera.

Ciguatoxins are lipophillic, able to cross the blood brain barrier, and can cause both central and peripheral neurologic symptoms.

The major symptoms will develop within 1-3 hours of toxin ingestion: vomiting, diarrhea, numbness of extremities, mouth and lips, reversal of hot and cold sensation, muscle and joint aches. The symptoms may last from days to weeks or even months depending on each individual situation. There is no known antidote.


Ciguatoxin is produced by Gambierdiscus toxicus, a type of dinoflagellate. The toxin usually accumulates in the skin, head, viscera, and roe of big reef fish like grouper, wrasse, triggerfish, lionfish, and amberjack.

Ciguatoxin cannot be destroyed by cooking.[1] Rapid testing for this toxin in food is not standard.


  1. Swift A, Swift T (1993). "Ciguatera". J. Toxicol. Clin. Toxicol. 31 (1): 1–29. doi:10.3109/15563659309000371. PMID 8433404.

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