Porcupinefish

Description

The spot-fin porcupinefish is a medium-sized fish which grows up to 91 cm, but the typical size mostly observed is 40 cm. Its body is elongated with a spherical head with big round protruding eyes, and a large mouth that is rarely closed. The pectoral fins are large, the pelvic fins are absent, and the anal and dorsal fins are close to the caudal peduncle. The latter move simultaneously during swimming. The skin is smooth and firm; the scales are modified into spines. The body coloration is beige to sandy-yellow marbled with dark blotches and dotted with numerous small, black spots.

In case of danger, the porcupinefish can inflate itself by swallowing water to deter the potential predator with its larger volume, and it can raise its spines.

The porcupinefish concentrates tetrodotoxin in certain parts of its body such as the liver, skin, gonads, and the viscera. This defensive system constitutes an additional device to dissuade potential predators.

Genomics

A chromosome-level genome assembly of Diodon hystrix was published in 2026. The genome size is approximately 713.6 Mb, with 98.63% of the assembly anchored to 23 chromosomes. The assembly has a BUSCO completeness score of 97.7%, and 23,171 protein-coding genes were predicted.

Distribution and habitat

The porcupinefish is circumglobal, found in tropical and subtropical waters. It has been recorded twice in the Mediterranean Sea, off southern Italy (1963) and the Balearic islands (2016).

Juveniles are pelagic until they are about 20 cm in length. Adults favour lagoons, top reefs, and seaward coral or rocky reefs from one to 50 m depth, sheltering under ledges or in caves during the day.

Feeding

The porcupinefish's diet is based on sea urchins, gastropods, clams, and crustaceans.

Behavior

This fish is solitary, except during mating periods, and it has a nocturnal activity with a maximal activity at sunset and sunrise.

Parasites

As with most fish, the porcupinefish is infected by a variety of parasites. Spectacular parasites are the cysts of the larvae of the trypanorhynch cestode Molicola horridus, often found in great numbers in the liver. These parasites represent no danger to humans.

Additional field notes

A documented aquarium age provides a useful qualification to porcupinefish lifespan figures.

Sources: Diodon hystrix species summary

Recorded age and adult shelter

FishBase records an individual that reached ten years and 69 centimetres at the McGinty Aquarium. This is a captive observation, not an estimate of average survival in the wild. A lifespan quoted from that record should retain its aquarium context.

Adult fish commonly use reef holes and caves, while young fish up to about 20 centimetres can live in the open water. This is a change in habitat use as the fish grows, rather than evidence that the species is confined to either reefs or the offshore water column throughout its life.

Sources: Diodon hystrix species summary