See the wikipedia article on tetrodotoxin, TTX.
Scientists have found that toxic fugu have unique exocrine glands for the secretion of tetrodotoxin. The fish appear to actively produce the toxin, rather than passively acquire it from the environment.
neurotoxins, like tetrodotoxin
Tetrodotoxin blocks action potentials by binding with the voltage-gated, fast sodium (Na+) channels in neural membranes. This prevents the influx of sodium ions required to propagate an action potential.
A Blue ring Ooctopus does have toxic called tetrodotoxin.
Tetrodotoxin is a poison. It begins with the letter t.
Puffer fish have a very strong toxin in their bodies that is called tetrodotoxin.
Tetrodotoxin is a potent neurotoxin with no known antidote. It gets its name from "Tetraodontiforme", the name of the order of fish that carry the toxin. Tetraodontiforme includes animals such as the pufferfish, procupinefish, and ocean sunfish.
Tetrodotoxin binds to voltage gated sodium channels and blocks them from passing sodium into cells. These channels are a critical part of the functioning of nerve cells and blocking the movement of sodium effectively blocks the transmission of information along the nerve cells. This in turns leads to paralysis in the animal or person that was exposed to tetrodotoxin.
Tetrodotoxin from the blow fish (puffer fish), Spherodinides Tetrodontus.
It blocks the sodium channels that are required to create action potential in the muscles to make them contract.
It's a type of tetrodotoxin, a neurotoxic venom similar to the kind found in fugu (Japanese blowfish).