Porcupinefish

Porcupinefish are medium-to-large fish belonging to the family Diodontidae from the order Tetraodontiformes which are also commonly called blowfish and, sometimes, balloonfish and globefish. The family includes about 18 species. They are sometimes collectively called pufferfish, not to be confused with the morphologically similar and closely related Tetraodontidae, which are more commonly given this name.

They are found in shallow, temperate, and tropical seas worldwide. A few species are found much farther out from shore, wherein large schools of thousands of individuals can occur.

Characteristics
Porcupinefish are generally slow-moving.

They have the ability to inflate their bodies by swallowing water or air, thereby becoming rounder. This increase in size (almost double vertically) reduces the range of potential predators to those with much bigger mouths. A second defense mechanism is provided by the sharp spines, which radiate outwards when the fish is inflated.

They have upper and lower teeth that fuse into a shape of a parrot's beak; they use this beak to eat molluscs and sea urchins.

Some species are poisonous, having tetrodotoxin in their internal organs, such as the ovaries and liver. This neurotoxin is at least 1200 times more potent than cyanide. The poison is produced by several types of bacteria obtained from the fish's diet. As a result of these three defenses, porcupinefish have few predators, although adults are sometimes preyed upon by sharks and orcas. Juveniles are also preyed on by Lysiosquillina maculata, tuna, and dolphins.

Consumption
Porcupinefish are eaten as food fish and are an exotic delicacy in Cebu, Philippines, where they are called tagotongan. However, pufferfish can be dangerous to consume since they can cause tetrodotoxin poisoning.

In popular culture
The porcupine fish (as Diodon antennatus) is mentioned in Charles Darwin's famous account of his trip around the world, The Voyage of the Beagle. He noted how the fish can swim quite well when inflated, though the altered buoyancy requires them to do so upside down. Darwin also mentioned hearing that a fellow naturalist, Dr. Allen of Forres, had "frequently found a Diodon, floating alive and distended, in the stomach of the shark; and that on several occasions he has known it eat its way, not only through the coats of the stomach, but through the sides of the monster".