Tetraodontiformes
Encyclopedia
The Tetraodontiformes are an order
of highly derived ray-finned fish
, also called the Plectognathi. Sometimes these are classified as a suborder of the Perciformes
. The Tetraodontiformes are represented by ten families
and approximately 360 species
overall; most are marine and dwell in and around tropical coral reef
s, but a handful of species are found in freshwater streams and estuaries
. They have no close relatives, and descend from a line of coral
-dwelling species that emerged around 40 million years ago.
es), globose (pufferfish
es) to laterally compressed (filefish
es) and triggerfish
. They range in size from Rudarius excelsus, measuring just 2 centimetre (0.78740157480315 in) in length, to the ocean sunfish
, the largest of all bony fish at up to 3 metres (9.8 ft) in length and weighing over 2 tonnes.
Most members of this order, except for the Balistidae
family, are ostraciiforms, meaning the body is rigid and incapable of lateral flexure. Because of this, they are slow-moving and rely on their pectoral, dorsal, anal, and caudal fins for propulsion rather than by body undulation. However, movement is usually quite precise; dorsal and anal fins aid in manoeuvring and stabilizing. In most species, all fins are simple, small, and rounded, except for the pelvic fins which, if present, are fused and buried. Again, in most members, the gill plates are covered over with skin, the only gill opening a small slit above the pectoral fin.
The tetraodontiform strategy seems to be defense at the expense of speed, with all species fortified with scales modified into strong plates or spines — or with tough, leathery skin (the filefish
es and ocean sunfish
). Another striking defensive attribute found in the pufferfish
es and porcupinefish
es is the ability to inflate the body to greatly increase its normal diameter: this is accomplished by sucking water into a diverticulum
of the stomach
. Many species of the Tetraodontidae, Triodontidae and Diodontidae are further protected from predation by tetrodotoxin
, a powerful neurotoxin
concentrated in the animals' internal organs.
Tetraodontiforms have highly modified skeleton
s, with no nasal
, parietal
, infraorbital, or (usually) lower rib
bones. The bones of the jaw are modified and fused into a sort of "beak
"; there are visible sutures which divide the beaks into "teeth
". This is alluded to in their name, derived from the Greek
words tetra meaning "four" and odous meaning "tooth" and the Latin
forma meaning "shape". Counting these teeth-like bones is a way of distinguishing similar families. For example the Tetraodontidae ("four-toothed"), Triodontidae ("three-toothed"), and Diodontidae ("two-toothed").
The jaws are aided by powerful muscles and many species also have pharyngeal
teeth to further process prey items. This is because Tetraodontiformes prey mostly on hard-shelled invertebrate
s such as crustacean
s and shellfish
.
The Molidae
are conspicuous even within this oddball order: they lack swim bladders and spines, and are propelled by their very tall dorsal and anal fins. The caudal peduncle is absent and the caudal fin is reduced to a stiff rudder-like structure. Molids are pelagic
rather than reef-associated and feed on soft-bodied invertebrates, especially jellyfish
.
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
of highly derived ray-finned fish
Actinopterygii
The Actinopterygii or ray-finned fishes constitute a class or sub-class of the bony fishes.The ray-finned fishes are so called because they possess lepidotrichia or "fin rays", their fins being webs of skin supported by bony or horny spines , as opposed to the fleshy, lobed fins that characterize...
, also called the Plectognathi. Sometimes these are classified as a suborder of the Perciformes
Perciformes
The Perciformes, also called the Percomorphi or Acanthopteri, is one of the largest orders of vertebrates, containing about 40% of all bony fish. Perciformes means perch-like. They belong to the class of ray-finned fish and comprise over 7,000 species found in almost all aquatic environments...
. The Tetraodontiformes are represented by ten families
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
and approximately 360 species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
overall; most are marine and dwell in and around tropical coral reef
Coral reef
Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps...
s, but a handful of species are found in freshwater streams and estuaries
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
. They have no close relatives, and descend from a line of coral
Coral
Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...
-dwelling species that emerged around 40 million years ago.
Physical characteristics
Various bizarre forms are included here, all radical departures from the streamlined body plan typical of most fishes. These forms range from nearly square or triangular (boxfishBoxfish
Ostraciidae is a family of squared, bony fish belonging to the order Tetraodontiformes, closely related to the pufferfishes and filefishes. Fish in the family are known variously as boxfishes, cofferfishes, cowfishes and trunkfishes...
es), globose (pufferfish
Pufferfish
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...
es) to laterally compressed (filefish
Filefish
Filefish are tropical to subtropical tetraodontiform marine fish of the diverse family Monacanthidae. Found in the Atlantic, Pacific and Indian Oceans, the filefish family contains approximately 107 species in 26 genera...
es) and triggerfish
Triggerfish
Triggerfishes are about 40 species of often brightly colored fishes of the family Balistidae. Often marked by lines and spots, they inhabit tropical and subtropical oceans throughout the world, with the greatest species richness in the Indo-Pacific...
. They range in size from Rudarius excelsus, measuring just 2 centimetre (0.78740157480315 in) in length, to the ocean sunfish
Ocean sunfish
The ocean sunfish, Mola mola, or common mola, is the heaviest known bony fish in the world. It has an average adult weight of . The species is native to tropical and temperate waters around the globe. It resembles a fish head with a tail, and its main body is flattened laterally...
, the largest of all bony fish at up to 3 metres (9.8 ft) in length and weighing over 2 tonnes.
Most members of this order, except for the Balistidae
Triggerfish
Triggerfishes are about 40 species of often brightly colored fishes of the family Balistidae. Often marked by lines and spots, they inhabit tropical and subtropical oceans throughout the world, with the greatest species richness in the Indo-Pacific...
family, are ostraciiforms, meaning the body is rigid and incapable of lateral flexure. Because of this, they are slow-moving and rely on their pectoral, dorsal, anal, and caudal fins for propulsion rather than by body undulation. However, movement is usually quite precise; dorsal and anal fins aid in manoeuvring and stabilizing. In most species, all fins are simple, small, and rounded, except for the pelvic fins which, if present, are fused and buried. Again, in most members, the gill plates are covered over with skin, the only gill opening a small slit above the pectoral fin.
The tetraodontiform strategy seems to be defense at the expense of speed, with all species fortified with scales modified into strong plates or spines — or with tough, leathery skin (the filefish
Filefish
Filefish are tropical to subtropical tetraodontiform marine fish of the diverse family Monacanthidae. Found in the Atlantic, Pacific and Indian Oceans, the filefish family contains approximately 107 species in 26 genera...
es and ocean sunfish
Ocean sunfish
The ocean sunfish, Mola mola, or common mola, is the heaviest known bony fish in the world. It has an average adult weight of . The species is native to tropical and temperate waters around the globe. It resembles a fish head with a tail, and its main body is flattened laterally...
). Another striking defensive attribute found in the pufferfish
Pufferfish
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...
es and porcupinefish
Porcupinefish
Porcupinefish are fish of the family Diodontidae, , also commonly called blowfish ....
es is the ability to inflate the body to greatly increase its normal diameter: this is accomplished by sucking water into a diverticulum
Diverticulum
A diverticulum is medical or biological term for an outpouching of a hollow structure in the body. Depending upon which layers of the structure are involved, they are described as being either true or false....
of the stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
. Many species of the Tetraodontidae, Triodontidae and Diodontidae are further protected from predation by tetrodotoxin
Tetrodotoxin
Tetrodotoxin, also known as "tetrodox" and frequently abbreviated as TTX, sometimes colloquially referred to as "zombie powder" by those who practice Vodou, is a potent neurotoxin with no known antidote. There have been successful tests of a possible antidote in mice, but further tests must be...
, a powerful neurotoxin
Neurotoxin
A neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels. Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...
concentrated in the animals' internal organs.
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...
s, with no nasal
Nasal bone
The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face, and form, by their junction, "the bridge" of the nose.Each has two surfaces and four borders....
, parietal
Parietal bone
The parietal bones are bones in the human skull which, when joined together, form the sides and roof of the cranium. Each bone is roughly quadrilateral in form, and has two surfaces, four borders, and four angles. It is named from the Latin pariet-, wall....
, infraorbital, or (usually) lower rib
Rib
In vertebrate anatomy, ribs are the long curved bones which form the rib cage. In most vertebrates, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the chest cavity. They serve to protect the lungs, heart, and other internal organs of the thorax...
bones. The bones of the jaw are modified and fused into a sort of "beak
Beak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
"; there are visible sutures which divide the beaks into "teeth
Tooth
Teeth are small, calcified, whitish structures found in the jaws of many vertebrates that are used to break down food. Some animals, particularly carnivores, also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the Mandible bone or the Maxillary bone and are...
". This is alluded to in their name, derived from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
words tetra meaning "four" and odous meaning "tooth" and the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
forma meaning "shape". Counting these teeth-like bones is a way of distinguishing similar families. For example the Tetraodontidae ("four-toothed"), Triodontidae ("three-toothed"), and Diodontidae ("two-toothed").
The jaws are aided by powerful muscles and many species also have pharyngeal
Pharynx
The human pharynx is the part of the throat situated immediately posterior to the mouth and nasal cavity, and anterior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx , the oropharynx , and the laryngopharynx...
teeth to further process prey items. This is because Tetraodontiformes prey mostly on hard-shelled invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s such as crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s and shellfish
Shellfish
Shellfish is a culinary and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater environments, some kinds are found only in freshwater...
.
The Molidae
Molidae
Molidae is the family of the molas or ocean sunfishes, unique fish whose bodies come to an end just behind the dorsal and anal fins, giving them a "half-a-fish" appearance...
are conspicuous even within this oddball order: they lack swim bladders and spines, and are propelled by their very tall dorsal and anal fins. The caudal peduncle is absent and the caudal fin is reduced to a stiff rudder-like structure. Molids are pelagic
Pelagic zone
Any water in a sea or lake that is not close to the bottom or near to the shore can be said to be in the pelagic zone. The word pelagic comes from the Greek πέλαγος or pélagos, which means "open sea". The pelagic zone can be thought of in terms of an imaginary cylinder or water column that goes...
rather than reef-associated and feed on soft-bodied invertebrates, especially jellyfish
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...
.
Families
- AracanidaeAracanidaeThe Aracanidae are a family of bony fishes related to the boxfishes. They are somewhat more primitive than the true boxfishes, but have a similar protective covering of thickened scale plates. They are found in the Indian Ocean and the west Pacific...
- deepwater boxfishes - Balistidae — triggerfishes
- Diodontidae — porcupinefishes
- MolidaeMolidaeMolidae is the family of the molas or ocean sunfishes, unique fish whose bodies come to an end just behind the dorsal and anal fins, giving them a "half-a-fish" appearance...
— ocean sunfishes - Monacanthidae — filefishes
- Ostraciidae — boxfishes
- Tetraodontidae — pufferfishes
- TriacanthidaeTriacanthidaeTriacanthidae, commonly known as triplespines or tripodfishes, is a family of Indo-Pacific fishes. It is classified in the order Tetraodontiformes, along with the pufferfishes and the ocean sunfish...
— triplespines - Triacanthodidae — spikefishes
- Triodontidae — the Three-toothed puffer
Fossil families
- †Bolcabalistidae
- †Cretatriacanthidae
- †Eoplectidae
- †Eospinidae
- †Moclaybalistidae
- †Plectocretacicidae
- †Protobalistidae
- †Protriacanthidae
- †Spinacanthidae