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Tetraodontidae is a family of primarily marine and estuarine fish of the Tetraodontiformes order. The family includes many familiar species which are variously called pufferfish, balloonfish, blowfish, bubblefish, globefish, swellfish, toadfish, toadies, honey toads, sugar toads, and sea squab. They are morphologically similar to the closely related porcupinefish, which have large external spines (unlike the thinner, hidden spines of Tetraodontidae, which are only visible when the fish has puffed up). The scientific name refers to the four large teeth, fused into an upper and lower plate, which are used for crushing the shells of crustaceans and mollusks, their natural prey.
Puffer fish are generally believed to be the second–most poisonous vertebrate in the world, after the Golden Poison Frog. Certain internal organs, such as liver, and sometimes their skin are highly toxic to most animals when eaten, but nevertheless the meat of some species is considered a delicacy in Japan (as 河豚, pronounced as fugu), Korea (as bok), and China (as 河豚 he2 tun2) when prepared by chefs who know which part is safe to eat and in what quantity.
The tetraodontidae contains at least 189 species of puffers in 19 genera.They are most diverse in the tropics and relatively uncommon in the temperate zone and completely absent from cold waters. They are typically small to medium in size, although a few species can reach lengths of greater than 100 centimetres (39 in).
Ecology and life history
Although most species live in inshore and estuarine waters, 29 species spend their entire life cycles in freshwater. These species are found in disjunct tropical regions of South America (1 species), Central Africa (3 species) and Southeast Asia (25 species).
The puffer’s unique and distinctive natural defenses help compensate for their slow locomotion. Puffers move by combining pectoral, dorsal, anal, and caudal fins. This makes them highly maneuverable but very slow, and therefore comparatively easy predation targets. Their tail fin is mainly used as a rudder, but it can be used for a sudden evasive burst of speed that shows none of the care and precision of their usual movements. The puffer’s excellent eyesight combined with this speed burst is the first and most important defense against predators. Their back up defense mechanism, used if they are successfully pursued, is to fill their extremely elastic stomachs with water (or air when outside the water) until they are much larger and almost spherical in shape. Even if they are not visible when the puffer is not inflated, all puffers have pointed spines, so a hungry predator may suddenly find itself facing an unpalatable pointy ball rather than a slow, tasty fish. Predators which don’t heed this warning (or who are “lucky” enough to catch the puffer suddenly, before or during inflation) may die from choking, and predators that do manage to swallow the puffer may find their stomachs full of tetrodotoxin, making puffers an unpleasant, possibly lethal, choice of prey. 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. It does not always have a lethal effect on large predators, such as sharks, but it can kill humans.
Not all puffers are necessarily poisonous; Takifugu oblongus, for example, is a fugu puffer that is not poisonous, and toxin level varies wildly even in fish that are. A puffer’s neurotoxin is not necessarily as toxic to other animals as it is to humans, and puffers are eaten routinely by some species of fish, such as lizardfishand tiger sharks.Also, Japanese fish farmers have grown nonpoisonous puffers by controlling their diet.
Puffers 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. Although most puffers are drab, many have bright colors and distinctive markings and make no attempt to hide from predators. This is likely an example of aposematism.
Many marine puffers have a pelagic, or open-ocean, life stage. Spawning occurs after males slowly push females to the water surface or join females already present. The eggs are spherical and buoyant. Hatching occurs after roughly four days. The fry are tiny, but under magnification have a shape that is usually reminiscent of a puffer fish. They have a functional mouth and eyes, and must eat within a few days. Brackish water puffers may breed in bays in a similar manner to marine species, or may breed more similarly to the fresh water species, in cases where they have moved far enough upriver.
Reproduction in fresh water species varies quite a bit. The dwarf puffers court with males following females, possibly displaying the crests and keels unique to this subgroup of species. After the female accepts his advances, the she will lead the male into plants, moss or another form of cover, where she can release eggs for fertilization. The male may help her by rubbing against her side. This has been observed in captivity, and they are the only commonly captive spawned puffer species.
Target-group puffers have also been spawned in aquariums, and follow a similar courting behavior, minus the crest/keel display. However, eggs are laid on a flat piece of slate or other smooth hard material, to which they adhere. The male will guard them until they hatch, carefully blowing water over them regularly to keep the eggs healthy. His parenting is finished when the young hatch, and the fry are on their own.
Information on breeding of specific species is very limited. T. Nigroviridis, the Green Spotted Puffer, has recently been artificially spawned under captive conditions. It is believed to spawn in bays in a similar manner to salt water species, as their sperm were found to be motile only at full marine salinities, but actual wild breeding has never been observed.
The Tetraodontids have been estimated to diverge from diodontids between 89 and 138 million years ago. There are four major clades and these diverged during the Cretaceous between 80 and 101 million years ago.
Puffer poisoning usually results from consumption of incorrectly prepared puffer soup, fugu chiri, or occasionally from raw puffer meat, sashimi fugu. While chiri is much more likely to cause death, sashimi fugu often causes intoxication, light-headedness, and numbness of the lips, and is often eaten for this reason. Puffer’s (tetrodotoxin) poisoning deadens the tongue and lips, and induces dizziness and vomiting, followed by numbness and prickling over the body, rapid heart rate, decreased blood pressure, and muscle paralysis. The toxin paralyzes diaphragm muscles and stops the person who has ingested it from breathing. People who live longer than 24 hours typically survive, although possibly after a coma lasting several days. Some people claim to have remained fully conscious throughout the coma, and can often recount events that occurred while they were supposedly unconscious. The paralysis reduces oxygen demands of the body dramatically, but because the toxin does not cross the blood-brain barrier, neural activity in the brain and from the eyes and ears are generally intact. In Voodoo, puffer’s poison must be part of the mixture given to the victim to make them a “zombie“, most likely because the paralysis and pseudo-comatose effect simulate the death portion of traditional zombie creation.
Pufferfish, called pakpao in Thailand, are usually consumed by mistake. They are often cheaper than other fish, and because they contain inconsistent levels of toxins between fish and season, there is little awareness or monitoring of the danger. Consumers are regularly hospitalized or die because cooks do not know which organs are not safe.
Saxitoxin, the cause of paralytic shellfish poisoning and red tide can also be found in certain puffers. Cases of neurological symptoms, including numbness and tingling of the lips and mouth, have been reported to rise after the consumption of puffers caught in the area of Titusville, Florida. The symptoms generally resolve within hours to days, although one affected individual required intubation for 72 hours. As a result, Florida banned the harvesting of puffers from certain bodies of water.
It is not believed that puffers produce toxins themselves, as puffer fish kept in tanks or fish farms are totally free of either toxin. The gastric contents of shellfish prey are believed to carry the toxins or their precursors, which are stored in the puffers organs.