Puffer fish have many attempted predators, but only a few animals, such as tiger sharks and sea snakes, are unaffected by the tetrodotoxin that occurs naturally in most puffer fish. Puffer fish are sometimes eaten by humans as a Japanese delicacy called fugu, but consumption of this dish carries the risk of exposure to tetrodotoxin.
Puffer fish are found in salt, brackish and freshwater environments, and can be preyed upon by many different species of animals. Tiger sharks and sea snakes appear to be immune to the effects of tetrodotoxin found in puffer fish and to the spines found on all of the over 120 species of puffer fish.
However, other predators that attempt to eat puffer fish can succumb to the effects of tetrodotoxin, which is present in the skin, intestines, liver and sex organs of puffer fish. This toxin is approximately 1,200 times more potent than cyanide and is also known as fugu poison, maculotoxin and TTX. Alternatively, a predator can choke on the spines that protrude from the body of a puffer fish, especially after the puffer fish has drawn water into its expandable stomach.
Other animals besides puffer fish carry tetrodotoxin, including species of octopuses, newts and salamanders.