This porcupinefish has its spiny scales laid flat against its body. They show up as light areas on its body. By Eliaped via Wikimedia Commons
Porcupinefish grow up to three feet long. They live in warm ocean waters all over the world. They spend most of their time in shallow areas, especially around coral reefs where they can find cracks and caves in which they hide.
Porcupinefish are nocturnal, which means they usually rest during the day and are active at night. During the night, porcupinefish hunt for snails, small crabs, and sea urchins on the ocean floor. The teeth in a porcupinefish’s mouth are fused together to make a hard beak. The porcupinefish uses its beak to crack open the shells of snails and crabs so it can eat them.
Porcupinefish have a special adaptation that helps protect them from predators. Some of the scales on a porcupinefish’s body are actually hard spines. Most of the time the spiny scales lie flat against the porcupinefish’s body and it looks like a normal fish. When a porcupinefish feels threatened by a predator it swallows lots of water until it puffs up into a big balloon shape and the spiny scales stick out in all directions from its body. Most predators leave the porcupinefish alone when it does this, and after the predator leaves the porcupinefish lets the water out of its body and continues swimming.
A drawing from a book published in the late 1700s in France shows what a porcupinefish looks like when it is puffed up with water. From “Illustrations de Ichtyologie ou histoire naturelle générale et particulière des Poissons” via Wikimedia Commons
Porcupinefish often live near coral reefs. They find shelter in cracks in the reefs and food sources near the reefs. By Albert Kok
For references, see the above links and the following book:
Kells, Val and Kent Carpenter. A Field Guide to Coastal Fishes: From Maine to Texas. Baltimore, MD: John Hopkins University Press, 2011. Pp. 426-427.