Diodon

Porcupinefishes or balloonfishes are any of the various species of the genus Diodon, the type genus of Diodontidae.

Distinguishing features

Fish of the genus Diodon have:

• two-rooted, movable spines (which are derived from modified scales) distributed over their bodies.
• beak-like jaws, used to crush their hard-shelled prey (crustaceans and molluscs).

They differ from the swelltoads and burrfishes (genera Cyclichthys and Chilomycterus, respectively), which, in contrast, have fixed, rigid spines.

Defense mechanisms

• Like true pufferfishes of the related family Tetraodontidae, porcupinefishes can inflate themselves. Once inflated, a porcupinefish's erect spines stand perpendicular to the skin, so pose a major difficulty to their predators; a fully inflated, large porcupinefish can choke a shark to death. According to Charles Darwin in The Voyage Of the Beagle (1845), Darwin was told by a Doctor Allen of Forres, UK, that the Diodon actually had been found "floating alive and distended, in the stomach of the shark" and had been known to chew its way out of shark bodies after being swallowed, causing the death of its attacker.
• They may be poisonous, through the accumulation of tetrodotoxin or ciguatera.

Species

Extant species

Currently, five extant species are recognized in this genus:

Fossil species

Fossils of Diodon are known from Tertiary-aged marine strata. These species are similar to modern species. Fossil species include:

• †Diodon scillae <small>Agassiz, 1843</small> – Late Miocene of Cuba
• †Diodon serratus <small>Aguilera et al, 2017</small> – Middle Miocene of Venezuela
• †Diodon sigma <small>Martin, 1883</small> – Miocene of Java, Indonesia

References