Spot-fin Porcupinefish

The spot-fin porcupinefish (Diodon hystrix), also referred to as the spotted porcupinefish, black-spotted porcupinefish, or simply porcupinefish, is a member of the Diodontidae family.

This species of porcupinefish is classified as medium-sized, reaching lengths of up to 91 cm, although the average observed size is typically around 40 cm. The body of the fish is elongated with a spherical head that features large, round protruding eyes and a notably large mouth that is rarely closed. Additionally, the pectoral fins are large, the pelvic fins are absent, and the anal and dorsal fins are positioned close to the caudal peduncle. During swimming, these fins move simultaneously.

The skin of the spot-fin porcupinefish is smooth and firm, with scales that have been modified into spines. The coloration of its body ranges from beige to sandy-yellow and is marbled with dark blotches, as well as dotted with numerous small black spots. In times of danger, the porcupinefish has the ability to inflate itself by swallowing water, thereby deterring potential predators with its increased volume. Furthermore, it is capable of raising its spines as an additional defense mechanism.

The porcupinefish accumulates tetrodotoxin in specific regions of its body, including the liver, skin, gonads, and viscera. This defensive system acts as a deterrent to potential predators.

The spot-fin porcupinefish can be found in tropical and subtropical waters worldwide. It has been observed on two occasions in the Mediterranean Sea, near southern Italy in 1963 and in the Balearic islands in 2016. While juveniles are typically pelagic until they reach a length of approximately 20 cm, adults tend to inhabit lagoons, top reefs, and seaward coral or rocky reefs at depths ranging from one to 50 meters. During the daytime, they seek shelter under ledges or in caves.

The porcupinefish's diet primarily consists of sea urchins, gastropods, clams, and crustaceans.

This fish is solitary, except during mating periods, and exhibits nocturnal activity, with peak activity occurring at sunset and sunrise.

Like most fish, the porcupinefish is susceptible to various parasites. Notably, cysts of the larvae of the trypanorhynch cestode Molicola horridus are often found in large quantities in its liver. However, these parasites pose no threat to humans.