Fish Capsule Report for Biology of Fishes
Order: Tetraodontiformes
Family: Diodontidae
Species: Diodon hystrix
Author and Year: Linnaeus, 1758
Common Names: Porcupinefish (USA, Australia, and S. Africa), o'pou
okala (Hawaii), atinga (W. Indies), puerco espino (Mexico), mojannur
(Marshall Islands), duto (Philippines), katu peyttheya (Sri Lanka),
yu hu (China), meshwaka (Egypt), pez erizo (Spain).
D. hystrix is a marine fish found in all tropical seas especially in the western boundary currents. This is the only member of the genus Diodon found in the Mediterranean. D. hystrix has been found as far north as Massachusetts. Although usually associated with coral reefs and mangrove areas, D. hystrix has been pulled from open ocean.
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Size: Adult Diodon hystrix average between 20 to 50 cm in length. However, adults have been reported exceeding 90 cm. There appears to be little or none sexual dimorphism in size.
Habitat: D. hystrix is a marine fish found primarily in coral reefs and mangroves. Larvae and juvenile are pelagic and are often found far from shore.
Diet: Examination of stomach contents of specimens collected in the Bahamas show that gastropod and bivalve molluscs and crabs account for about 80% of D. hystrix's diet. Specializations of the jaw allow D. hystrix to crush protective shells, however its relatively slow swimming speed limits its prey to stationary or slow-moving organisms. Juveniles have been found in plankton fields and presumably feed on the plankton.
Reproduction: There are no studies on D. hystrix in the field or laboratory. However, D. holacanthus breeding has been observed in aquaria. Breeding begins in May when water temperature reaches approximately 24.4ºc and continues until the end of August. In the late afternoon or early evening, one or two males approach a female which is lying motionless at the bottom. They slowly "encourage" her to the surface. Several other males join in the corralling process. If the female is not ready, she will return to the bottom. The female will release eggs just below the surface of the water. Four or five males simultaneously contribute their sperm for fertilization. The spawning always occurs between 20:52 and 23:25. Hatching occurs 103-118 hours after fertilization. The larvae live in pelagic waters until they reach about 16cm. There appears to be no nest building or protection provided by parents.
The picture
shows a juvenile D. holocantus which is nearly identical
to the juvenile D. hystrix.
Behavior: D. hystrix has been observed living in small groups of two or three. They are not known to migrate.
Diodon hystrix is abundant throughout the world. Destruction of coral reef habitat has impacted local populations of the species. Disease, especially the parasitic Peniculisa wilsoni, has infected substantial populations of D. hystrix leading to their localized demise.
The porcupine fish is popular in the marine aquarium trade. Due to its toxicity, it is not involved in commercial trade, although many local populations enjoy to eat this tasty fish.
D. hystrix is chock-full
of specilizations. Most noted is its ability to inflate itself
with water or air to 300% of its original volume and extend a
plethora of sharp spines. Inflation is achieved by pumping water
or air into the first 2/3rds of the stomach. The skin is reinforced
with a complex matrix of collagen fibers which allow stretching
and provide strength to the inflated fish. This usually is a good
deterrent from predation. If eaten D. hystrix has been
known to inflate in the throat of the predator, thereby killing
it. It has also been observed that the fish has gnawed its way
out of the stomachs of dolphins and sharks. The heron is a predator
which has some success against this defense. It can sometimes
pierce through the collagen-reinforced skin with its beak and
deflate the puffer. However, herons are only successful in capturing
D. hystrix in 10-20% of attempts. If caught, they often
loose the fish after it inflates. Inflation also changes the swimming
behavior of the fish. normally, D. hystrix swims by undulating
the rear portion of its body.
This video clip demonstrates normal swimming. When inflated, undulation is impossible. Swimming is accomplished by oscillating the caudal fin.
If your browser can't view inline MPEG movies <click here>.
D. hystrix also has a significantly developed mouth.
Its jaws have developed into a beak-like mouth with a flat, toothed
crushing plate on both biting surfaces. The adductor mandibulae
muscles are huge to provide plenty of force. The mechanical arrangement
of the mouth gives it an arrangement which produces great amounts
of crushing force but less speed. This configuration also produces
very little suction.
Diodon hystrix is also a tetrodotoxic and ichthyocrinotoxic fish. Tetrodotoxin is most famously associated by the spineless fugu puffer which is consumed in Japan. The toxin is quite potent acting primarily on the peripheral nervous system (so the victim can perceive the entire experience with a clear head). Symptoms include (in increasing order of severity): malaise, pallor, dizziness, parasthesias (prickling or tingling) of mouth or tongue (within 10-45 minutes), vomiting, diarrhea, numbness, floating sensation due to complete numbness, hypersalivation, profuse sweating, extreme weakness, subnormal temperature, hypotension, rapid weak pulse, respiratory distress/arrest, death. Click here for the FDA's notice on tetrodotoxin. It is believed that the toxin or its immediate precursors are obtained by D. hystrix's diet of hard-shelled marine organisms. The toxin is most concentrated in the liver, intestines, and ovaries. Toxicity and spawning are tightly correlated. D. hystrix is most toxic immediately before and during spawning. The ichthyocrinotoxic properties of the fish are less clearly understood. There are poisonous glands on the skin, but there is no delivery system for the toxin. Instead, the toxin is secreted outside of the fish. It is thought that this serves as a warning signal for predators. The toxin has not been identified although it is thought to be tetrodotoxin. Usually contact will cause skin irritation. If ingested, symptoms include: vomiting, nausea, loss of muscular control. Ingesting enough skin will produce symptoms similar to generalized tetrodotoxin poisoning.
Brained, E.E. (1994). Pufferfish Inflation: Functional Morphology of Postcranial Structures in Diodon holocanthus (Tetraodontiformes). Journal of Morphology, 220:243-261.
Chandran A. & Natarajan, P. (1994). Heavy infection of Diodon hystrix by the copepod Peniculisa wilsoni (Siphonostomatoida, Pennellidae). Journal of Fish Biology, 45:167-168.
Halstead, B.W. (1988). Poisonous and Venomous Marine Animals of the World. The Darwin Press, Inc., Princeton, NJ. pp. 525-644, 989-1028.
Leis, J.M. (1978). Systematics and zoogeography of the porcupinefishes (Diodon, Diodontidae, Tetraodontiformes), with comments on egg and larval development. Fishery Bulletin, 76(4):535-567.
Linnaeus, C. (1758). Systema Naturae, 10th ed. Holmiae, Impensis Direct Laurentii Salvi, Tomus 1. pp. 824.
Sakamoto, T. & Suzuki, K. (1978). Spawning behavior and early life history of the porcupine puffer, Diodon holacanthus, in aquaria. Japanese Journal of Ichthyology, 24(4):261-270.
Turingan, R.G. (1994). Ecomorphological relationships among Caribbean tetradontiform fishes. Journal of Zoology, Lond., 233:493-521.