Porcupinefishes or balloonfishes, are any of the various species of the genus ''Diodon'', the

type genus In biological taxonomy, the type genus is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearing type of a nominal f ...

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 Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill the ...

(

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

s and

mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

s). They differ from the

swelltoad ''Cyclicthys'' is a genus of fish in the porcupinefish family, Diodontidae. Species in the genus are often known as swelltoads. Distinguishing features Fish of the genus ''Cyclicthys'' have three-rooted, rigid spines (actually modified scales) ...

s and

burrfishes ''Chilomycterus'' is a genus of diodontid tetraodontiform fishes commonly called "burrfish." Species There are currently 5 recognized species in this genus:Matsuura, K. (2014): Taxonomy and systematics of tetraodontiform fishes: a review focusi ...

(genera ''

Cyclichthys ''Cyclicthys'' is a genus of fish in the porcupinefish family, Diodontidae. Species in the genus are often known as swelltoads. Distinguishing features Fish of the genus ''Cyclicthys'' have three-rooted, rigid spines (actually modified scales) ...

'' and ''

Chilomycterus ''Chilomycterus'' is a genus of diodontid tetraodontiform fishes commonly called "burrfish." Species There are currently 5 recognized species in this genus:Matsuura, K. (2014): Taxonomy and systematics of tetraodontiform fishes: a review focusi ...

'', 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 erected spines stand perpendicular to the skin, whereupon they then pose a major difficulty to their predators: a large porcupinefish that is fully inflated can choke a

shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimo ...

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 Tetrodotoxin (TTX) is a potent neurotoxin. Its name derives from Tetraodontiformes, an order that includes pufferfish, porcupinefish, ocean sunfish, and triggerfish; several of these species carry the toxin. Although tetrodotoxin was discovered ...

ciguatera Ciguatera fish poisoning (CFP), also known simply as ciguatera, is a foodborne illness caused by eating reef fish whose flesh is contaminated with certain toxins. Such individual fish are said to be ciguatoxic. Symptoms may include diarrhea, vomi ...

.Lieske, E. & Myers, R.F. (2004): ''Coral reef guide; Red Sea'' London, HarperCollins

Species

Extant

There are currently five recognized extant species in this genus:

Fossil

Fossils of porcupinefishes are known from

Tertiary Tertiary ( ) is a widely used but obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start ...

-aged marine strata. These species are similar to modern species. Fossil species include: * '' Diodon tenuispinus'', from the

Ypresian In the geologic timescale the Ypresian is the oldest age (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by th ...

-aged

Monte Bolca Monte Bolca is a lagerstätte near Verona, Italy that was one of the first fossil sites with high quality preservation known to Europeans, and is still an important source of fossils from the Eocene. Geology Monte Bolca was uplifted from the T ...

lagerstatte. * '' Diodon scyllai'', from middle

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

-aged Piemonte, Italy.

References

Diodontidae Extant Ypresian first appearances Marine fish genera Taxa named by Carl Linnaeus {{Tetraodontiformes-stub