Marine Animal Encyclopedia
Porcupinefish Diodon histrix
When a porcupinefish is frightened, it pumps water into its body until it looks like a prickly soccer ball. Few predators are large enough or brave enough to swallow a fish in this state.
Left to itself, the porcupinefish deflates and its long spines lie flat against its body. During the day, it hides in caves and reef crevices, emerging at night to feed on hard-shelled invertebrates such as gastropod mollusks.
Porcupinefish are nocturnal, carnivorous predators specialized in eating hard-shelled prey. Their strong beak-like mouth is used to seize and crush prey such as urchins, crabs, snails and clams. Like many animals that eat hard or prickly prey, porcupinefish also posess thick, rubbery lips to protect them from being injured by the spines and broken shells of the prey they eat. At night, porcupinefish can be observed actively combing the reef for food and investigating sandy areas, crevices and caves where their prey might be found.
Attack & Defense Behavior
Porcupinefish are generally shy, do not defend territories, and will attempt to escape to shelter at the first sign of a threat. Their relatively large size and toxicity make them difficult to stomach for most reef predators.
Occasionally, porcupinefish become aggressive and chase other members of their species - perhaps to defend mates or food resources. When chased, a porcupinefish displays a series of large, dark blotches on its back to show that it is submissive and does not want to fight.
Porcupinefish also possess the amazing ability to inflate up to three times their normal size by rapidly swallowing a large volume of water. Inflation also causes the body spines to stand on end, making this species a much less appetizing snack.
These fish are wary of divers and snorkelers, and often retreat to shelters if they approach too closely, stay at a distance to observe these fish without disturbing their normal behaviour. Although porcupinefish spawning behaviour is not well described, it is likely to be similar to that of its close relative the balloonfish (Diodon holocanthus), which has been well studied.
Soon after dusk, males search for ripe females and court them by nuzzling and nudging their belly. The female is pushed towards the surface by the male where both sexes release their eggs and sperm simultaneously before returning to the reef. Spawning is thought to occur year round in porcupinefish, but activity peaks between the months of February and March.