Tetraodontidae: Difference between revisions

Pufferfish
White-spotted Puffer, Arothron hispidus
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Subphylum:	Vertebrata
Class:	Actinopterygii
Order:	Tetraodontiformes
Family:	Tetraodontidae
Genera
Amblyrhynchotes Arothron Auriglobus Canthigaster Carinotetraodon Chelonodon Colomesus Contusus Ephippion Feroxodon Fugu Gastrophysus Javichthys Lagocephalus Liosaccus Marilyna Monotretus Omegaphora Pelagocephalus Polyspina Reicheltia Sphoeroides Takifugu Tetractenos Tetraodon Torquigener Tylerius Xenopterus For species see Genera articles.

The 'pufferfish', also called blowfish, swellfish, globefish, balloonfish are fish making up the family Tetraodontidae, within the order Tetraodontiformes. They are named for their ability to inflate themselves to several times their normal size by swallowing water or air when threatened; the same adaptation is found in the closely related porcupinefish, which have large conspicuous spines (unlike the small, almost sandpaper-like spines of pufferfish). The scientific name, Tetraodon, refers to the fact that they have four large teeth, fused into an upper and lower plate, which are used for crushing the shells of crustaceans and mollusks, their natural prey.

The eyes and internal organs of most pufferfish are highly toxic, but nevertheless the meat is considered a delicacy in Japan and Korea. The name "fugu" is used both for the fish that are eaten and for their meat (for more details see Fugu). The Korean term for this fish is "boh-guh" fish.

There are 185 known species of the family Tetraodontidae, of which 38 can be found in Japan. They can be found worldwide from about 45° latitude north to 45° latitude south, mostly in salt water near coral reefs or the shore, but some species also live in fresh water and brackish water.

The pufferfish's unique and distinctive natural defenses are necessary due to its slow speed. Pufferfish use a combination of pectoral, dorsal, anal, and caudal fins for propulsion, making it unmaneuverable and an easy target for predators. As a defense mechanism, pufferfish have the ability to inflate rapidly, filling their extremely elastic stomachs with water (or air when outside the water) until they are almost spherical in shape. Thus, a hungry predator stalking the pufferfish may suddenly find itself facing what seems to be a much larger fish and pause, giving the pufferfish an opportunity to retreat to safety.

Pufferfish also produce a powerful neurotoxin in their internal organs, making them a lethal meal for most predators including humans. This neurotoxin is found primarily in the ovaries and liver, although smaller amounts exist in the intestines and skin, as well as trace amounts in muscle tissue and in its blood. This last line of defense may induce an evolutionary aversion to pufferfish in other creatures, as those organisms which are predisposed to hunt pufferfish quickly perish after eating their prey.

Pufferfish toxin is called tetrodotoxin, or more precisely anhydrotetrodotoxin 4-epitetrodotoxin. It is also found within other animals such as the Blue-Ringed Octopus and in certain varieties of newt. Tetrodotoxin is produced within the pufferfish by bacteria, which are acquired through food. This means that pufferfish raised in captivity do not contain tetrodotoxin, and therefore are not poisonous until they come into contact with the bacteria. The pufferfish itself has immunity to the poison due to a mutation in the protein sequence of the sodium channel pump on the cell membranes.

Tetrodotoxin is an exceptionally lethal poison. Tetrodotoxin is approximately 1200 times deadlier than the neurotoxin cyanide. In animal studies with mice, 8 µg tetrodotoxin per kilogram of body weight killed 50% of the mice (see also LD50). It is estimated that a single pufferfish has enough poison to kill 30 adult humans. Some also believe that there is also enough poison to kill up to a dozen elephants.

Pufferfish poisoning usually occurs as a result of accidental consumption of fish or meat tainted with pufferfish. Treatment consists of supportive care and intestinal decontamination with gastric lavage and activated charcoal. Case reports suggest that anticholinesterases such as edrophonium may be effective.

Saxitoxin, the cause of PSP (paralytic shellfish poisoning, red tide), can also be found in pufferfish. Cases of neurologic symptoms, including numbness and tingling of the lips and mouth, have been reported to arise rapidly after the consumption of pufferfish caught in the area of Titusville, Florida. These symptoms are generally resolved within hours to days, although one affected individual required intubation for 72 hours. As a result of such cases, Florida banned the harvesting of pufferfish from certain bodies of water.

A drug called Tectin that is derived from tetrodotoxin is being developed as a potent pain reliever. Administered in very small quantities it can bring relief to those suffering from intense chronic pain, such as that experienced by some cancer patients. Other uses, such as helping opiate addicts through withdrawal, are also being studied.

Coming from all over the world, it can sometimes be difficult to find the blowfish’s origin. It is found in the Pacific and Atlantic Oceans; certain species can also be found in freshwater streams and rivers.

Due to some unknown selection pressure, intronic and extragenic sequences have been drastically reduced within this family. As a result, they have the smallest-known genomes yet found amongst the vertebrate animals, while containing a genetic repertoire very similar to other fishes and thus comparable to vertebrates generally. Since these genomes are relatively compact it is relatively fast and inexpensive to compile their complete sequences, as has been done for two species (Takifugu rubripes and Tetraodon nigroviridis).

Pufferfish are also one of few kinds of fish that can blink or close their eyes. (Some claim they are the only fish that can close its eyes, but certain attacking sharks close their eyes to protect themselves from struggling prey.)

Pufferfish are able to move their eyes independently, and many species can change the color or intensity of their patterns in response to environmental changes. In these respects they are somewhat similar to the terrestrial Chameleon.

• Puffy the pufferfish has been chosen as the mascot of the OpenBSD project.
• Bloat, voiced by Brad Garrett, is a pufferfish in Finding Nemo.
• Dolphins have been observed using pufferfish as a sort of toy in the wild. They tease the pufferfish with their teeth, causing the small fish to become alarmed and then inflate. After a while the fish calms down and deflates, thus starting the cycle over again. It is speculated that dolphins may also enjoy the mild numbing effect from small amounts of the pufferfish toxin.
• The covers of the books "Understanding Japanese Information Processing" and "Understanding CJKV Information processing" by Ken Lunde, published by O'Reilly, feature an engraving of a pufferfish.
• When lifted out of water, pufferfish can inflate with air, but they may have problems deflating again afterwards. When this happens with aquarium specimens, fishkeepers hold the puffer underwater by the tail, head upwards, and shake the fish gently until the air escapes out of the mouth.

Arreola, V.I., and M.W. Westneat. 1996. Mechanics of propulsion by multiple fins: kinematics of aquatic locomotion in the burrfish (Chilomycterus schoepfi). Proceedings of the Royal Society of London B 263: 1689-1696.

Ebert, Klaus (2001): The Puffers of Fresh and Brackish Water, Aqualog, ISBN 3-031702-60-X

Gordon, M.S., Plaut, I., and D. Kim. 1996. How puffers (Teleostei: Tetraodontidae) swim. Journal of Fish Biology 49: 319-328.

Plaut, I. and T. Chen. 2003. How small puffers (Teleostei: Tetraodontidae) swim. Ichthyological Research 50: 149-153.

• Fugu sequencing project
• Tetraodon sequencing project
• EMedicine Article about the Toxicity of Tetrodotoxin
• Half Japanese half English page with Information about the species and their toxicity
• Extensive List of all Genus and Species for the family Tetraodontidae
• FishBase listing for Tetraodontidae
• Article regarding Tectin's use in pain relief
• Comprehensive database of freshwater and brackish pufferfish