When animals attack #2 Puffer Fish

The latest in the series is the Puffer Fish...

The puffer fish's unique and distinctive natural defenses are necessary due to their particular form of locomotion. Puffer fish use a combination of pectoral, dorsal, anal, and caudal fins for propulsion that make them highly maneuverable but very slow, and therefore comparatively easy targets for predators. As a defense mechanism, puffer fish have the ability to inflate rapidly, filling their extremely elastic stomachs with water (or air when outside the water) until they are almost spherical in shape. Thus, a hungry predator stalking the puffer fish may suddenly find itself facing what seems to be a much larger fish and pause, giving the puffer fish an opportunity to retreat to safety.

Some puffer fish also produce a powerful neurotoxin in their internal organs, making them an unpleasant, possibly lethal, meal for any predatory fish that eats one. This neurotoxin is found primarily in the ovaries and liver, although smaller amounts exist in the intestines and skin, as well as trace amounts in muscle tissue and in its blood. Many puffer fish have bright colors and distinctive markings and make no attempt to hide from predators. This is likely an example of aposematism, where the puffer fish advertises to potential predators that it is not safe to eat. Obviously being poisonous does not help the puffer fish once it has been eaten, so the evolutionary mechanism at work benefits the species, with predators learning that puffer fish are at least distasteful and probably sickening, and so avoided next time that predator encounters that species of puffer fish.

It should be noted that puffer fish toxin is not necessarily as toxic to other animals as it is to humans, and some species of fish routinely eat puffer fish, such as lizardfish [1] and tiger sharks [2]. Puffer fish toxin evolved as a response to aquatic predators such as larger fish, rather than for use against humans.