Tetraodontiformes

(vertebrate zoology) An order of specialized teleost fishes that includes the triggerfishes, puffers, trunkfishes, and ocean sunfishes.

(Pufferfishes, triggerfishes, and relatives)

Class: Actinopterygii

Order: Tetraodontiformes

Number of families: 9

Evolution and systematics

Although it is remarkably derived, this order of fishes dates from the early Eocene epoch or, possibly, the late Cretaceous period. There are nine families, including the spikefishes (Triacanthodidae, 11 genera and 21 species), the triplespines (Triacanthidae, four genera and seven spp.), the boxfishes (Ostraciidae, 11 genera and 37 spp.), the filefishes and leatherjackets (Monacanthidae, 25 genera and at least 104 spp.), the triggerfishes (Balistidae, 12 genera and at least 37 spp.), the threetooth puffer (Triodontidae, one genus and one species), the pufferfishes (Tetraodontidae, 26 genera and at least 170 species, with one species that has two subspecies), the porcupinefishes (Diodontidae, seven genera and 20 spp.), and the molas or ocean sunfishes (Molidae, three genera and four spp.).

Physical characteristics

There is some variability within this order, but all are distinguished by fused teeth within their jaws. Spikefishes are compressed, high bodied (great in depth), or elongate; some have concave foreheads and others elongated, tubelike snouts. The caudal fin is rounded to truncated, and there are 12–18 soft rays in the dorsal fin and 11–16 rays in the anal fin. Coloring is orange, yellow, or pink. Triplespines are compressed and elongate, with steeply sloping foreheads, narrow caudal peduncles, and forked tails. The first dorsal spine is large. The coloring is silvery, with hints of yellow or pale olive. The boxfishes are indeed boxlike, with bodies covered in bony-like plates. They have large rounded or truncated caudal fins and the ability, in numerous species, to secrete ostracitoxin (a poison that makes the creature unpalatable) as an anti-predatation mechanism. Some species have horns that protrude from their heads. A few species are brightly colored, but most are dull or cryptic.

Filefishes and leatherjackets also vary in shape and appearance. Generally, they are compressed and somewhat elongate, and they may have steeply sloped foreheads. Others are rhomboid in shape. At least one species, Anacanthus barbatus, is long and slender and resembles superficially a pipefish (Sygnathidae). The first dorsal spine usually is tall and strong. The caudal fin is truncated or slightly rounded. Color patterns vary, ranging from bright colors to cryptic or nondescript shades. Triggerfishes are compressed, rhomboid, or slightly elongate, with pelvic fins that are fused into a single spine. The first dorsal spine is capable of locking by using the second spine as a trigger that locks it into place. It is used as an anti-predation mechanism. The eyes can rotate independently of each other. Color patterns also vary and may be spectacular and bright or quite dull or cryptic.

The threetooth puffer has a beak consisting of three fused teeth, with a median suture in the upper jaw. The body is elongate, compressed, and inflatable. The caudal penduncle is long, and the caudal fin forked. Pufferfishes have four teeth fused together to form a beak, but there are medial sutures in both the upper and lower jaws. Their bodies are elongate, usually compressed or rhomboid in shape, and inflatable. There are seven to 18 soft rays in both the dorsal and anal fins, respectively. Many species have small prickles on the skin of their bellies. Their skin, entrails, and sometimes their flesh may contain tetraodotoxin, an anti-predation poison that is highly toxic. Porcupinefishes are large, elongate, robust, and somewhat boxlike, and they are capable of inflation. They have numerous spines along the body. The two teeth on their jaws are fused into a beak. Molas are large, compressed, and typically high-bodied fishes, with jaws that support two fused teeth. The caudal fin may be replaced by a clavus, which is used to stablize the fish when swimming. The dorsal and anal fins are set high. Both the lateral line and swimbladder are missing from adults.

Distribution

Members of this order occur in marine, brackish, and freshwater of the tropics, subtropics, and temperate zones. The spikefishes are tropical and subtropical deepwater residents of the western Atlantic and Indo-Pacific regions. Triplespines occur in shallow marine and brackish waters of the Indo-Pacific region. Boxfishes, triggerfishes, filefishes, and leatherjackets are distributed widely, mainly in coastal waters of the tropical, subtropical, and temperate or warm temperate Atlantic, Indian, and Pacific Oceans. The monotypic threetooth puffer is a deep-slope species of the Indo-Pacific region. Marine pufferfishes occur in tropical and subtropical waters of the Atlantic, Indian, and Pacific Oceans; numerous species enter brackish water or even freshwater. Some strictly freshwater species are found in river systems of Africa, Asia, or South America. Porcupinefishes occur in tropical, subtropical, and warm temperate waters of the Atlantic and Indo-Pacific regions; at least one species is circumglobal in its distribution. Molas also are found in tropical, subtropical, and warm temperate waters of the Atlantic, Indian, and Pacific Oceans but are largely pelagic and venture inshore only occasionally.

Habitat

Habitat preferences and utilization vary widely within this order. Most species are marine, but at least 20 occur in freshwater systems. Spikefishes are bottom dwelling in relatively deep waters. Triplespines also live on the bottom but on shallow marine and brackish water sand flats and mudflats. Boxfishes frequent coral or rocky reefs in relatively shallow water; others occur on sea grass flats and algae beds. Large post-larvae or young juveniles of some species are pelagic and are part of the diet of tunas and billfishes; others enter estuaries. Triggerfishes also are associated with coral or rocky reefs but may be found on rubble and sand flats. Some species are pelagic or semipelagic, the latter dwelling in the water column but seeking shelter in holes on the bottom or along walls. Filefishes and leatherjackets are quite wide ranging in their habitat use. Many species are associated with coral or rocky reefs; others with sponge reefs, sea grass flats, algae beds, or rubble and sand flats; and still others dwell in the water column. The threetooth puffer is a benthic, deep-slope-dwelling fish. Marine and brackish water pufferfishes occur on coral and rocky reefs, on rubble, sand, mud, or sea grass flats; on algae beds; or in the water column. Freshwater species tend to be benthic. Porcupinefishes occur on coral and rocky reefs, usually to seaward, and also utilize caves and holes in relatively shallow water. They also frequent reefs dominated by sponges. The molas are pelagic fishes that prefer the upper depths of the open ocean but also venture inshore, especially near deep-slope habitats that experience upwelling of deeper, cooler water.

Behavior

To some extent, tetraodontiform fishes incorporate their unique body structure and abilities into their patterns of behavior. For defense, feeding, social interaction, or reproduction, they rely variously on body armament; their fused beaks or ability to inflate with water; or their color patterns, which may advertise toxicity. Adult boxfishes utilize their body armor and ability to secrete ostracitoxin, a compound poisonous to predators (and other fishes, including themselves, if they are kept in a confined space), as defensive mechanisms. Thus, predation risk is minimized as they swim along the bottom or up into the water column. Despite reduction in risk, however, numerous species are quite cryptic as they move about in algae or corals. Boxfishes also are territorial. A majority of triggerfishes are colorful, solitary, and quite aggressive in the defense of their territories. Those species that dwell in the water column often assemble in loose aggregations of up to hundreds of individuals as they forage off walls or along deep slopes. These species quickly retreat to individual shelters when threatened, however.

Filefishes and leatherjackets are solitary or gather in small groups, but some form monogamous pairs that patrol a home range or territory. Others, such as Aluterus monoceros, form large schools. Many species are cryptic as well and take advantage of structure to mask their movements. A few species, such as juvenile Aluterus scriptus, swim on their sides and mimic floating leaves or other vegetation. Some swim openly in the water column, however. The color pattern of some filefishes and leatherjackets may be put to a surprising advantage. For example, the mimic filefish, Paraluteres prionurus, mimics the toxic saddled puffer, Canthigaster valentini, and thus avoids predation. Another species, the diamond filefish (Rudarius excelsius) mimics benthic algae.

Pufferfishes are solitary or paired or form small groups or schools. Many species utilize color pattern to advertise their toxic nature and thus avoid predation. Others are remarkably cryptic and even bury themselves in the sand. Some frequent the water column but return to the bottom for shelter or to feed. All are capable of inflating as a defensive mechanism. When they are not sheltering in holes or caves, porcupinefishes swim openly in the water column and depend on both their large spines and ability to inflate themselves to defend against predation. They reportedly have toxic flesh or organs that may contribute toward their defense as well. Some species have been observed to bury themselves in the sand. Although they are seen swimming during daylight hours, numerous species also are nocturnal. Molas swim about sideways or upright at or near the surface in the open ocean and, despite their ungainly appearance, are relatively strong and fast swimmers when necessary. They also drift on their sides in the current. When they are inshore near kelp beds, they allow themselves to be cleaned by resident cleanerfish species. The behavior of deep-dwelling spikefishes and threetooth puffers is largely unknown. Presumably, these fishes are largely solitary and move about the bottom or in the water column. The threetooth puffer is able to defend itself by inflation.

Feeding ecology and diet

Feeding patterns and dietary preferences of tetraodontiform fishes also vary. Little is known about spikefish feeding. Those species with long, slender, and highly specialized snouts likely pluck microinvertebrates from the bottom or possibly the water column. Species with relatively larger mouths probably feed on benthic invertebrates. At least one species, Macrorhamphosodes uradoi, feeds on the scales of other fishes. Triplespines also eat benthic invertebrates unearthed from sand or mud. Boxfishes are mainly omnivorous and feed upon small invertebrates, especially sessile species, as well as benthic algae. Triggerfishes are more wide ranging in their diet and feed upon benthic invertebrates that include gastropods, bivalves, crustaceans, and various echinoderms. Some species also eat algae, and those that dwell in the water column eat zooplankton. Similarly, filefishes and leatherjackets favor various benthic invertebrates, but some species are specialized to feed upon live corals or zooplankton. The threetooth puffer probably limits its diet to benthic invertebrates. Pufferfishes are remarkable opportunists and feed upon various invertebrates as well as algae. Larger species are quite capable of breaking open hard-shelled organisms, such as gastropods, bivalves, and crustaceans. Some species are specialized for certain invertebrates, however. Porcupinefishes prefer hard-shelled invertebrates, which they crush with their beaks. The molas utilize their parrot-like beaks to feed upon zooplankton and jellyfishes in the water column but also take fishes, mollusks, crustaceans, and brittlestars when they are inshore or near the bottom in deep-slope areas.

Most members of this order are preyed upon while in the larva or post-larva stage. As adults, relatively few have predators. Successful predators would have to be tolerant of spines, bony plates, and ossicles formed from fused bones, and, in some families, toxins. Some toxic puffers (Tetraodontidae), however, are preyed upon by sea snakes.

Reproductive biology

Depending upon the species, tetraodontiform fishes have diverse mating systems and spawn demersal or pelagic eggs. Seasonality may be pronounced at higher latitudes or in colder, deeper waters. Reproduction also may be linked to lunar or semilunar cycles. Little is known of the reproductive biology of the deep-dwelling spikefishes, threetooth puffers, and shallow-dwelling triplespines, but their eggs are likely demersal and their larvae pelagic. Boxfishes have mainly male-dominated mating groups, court and spawn at dusk, and produce pelagic eggs and larvae. Triggerfishes have varying mating systems, including monogamy, bigamy, and polygyny. They usually spawn demersal eggs in nests that are guarded quite aggressively by females or, to a lesser extent, by males. Larvae are pelagic. The filefishes and leatherjackets studied thus far have mating systems that include monogamy, facultative monogamy, polygyny, female visiting within male territories, or promiscuity. They all appear to lay demersal eggs in nests or on algae. There may be male parental care, female parental care, biparental care. or no care of eggs. The larvae are pelagic and may be adapted for an extended pelagic existence.

Pufferfishes have diverse mating systems and patterns of courtship and spawning. The eggs generally are demersal and are laid in nests on algae or scattered on the bottom. The eggs of some species are poisonous. Porcupinefish reproductive behavior appears to vary within as well as between species. Both pair and group (single female and multiple males) spawning has been reported for Diodon holacanthus. Courtship begins at dusk, and spawning is pelagic in shallow water and may involve splashing at the surface as eggs and milt are released. Alternately, the eggs may sink to the bottom. The larvae are pelagic as well. Eggs of the genus Chilomycterus reportedly are demersal, although their larvae are pelagic. Details of courtship and spawning of molas are not well known. They are highly fecund and produce hundreds of millions of pelagic eggs. The larvae are also pelagic.

Conservation status

A few species are cited on the IUCN Red List. The queen triggerfish, Balistes vetula (Balistidae), the Rapa Island toby, Canthigaster rapaensis (Tetraodontidae), and the blunthead puffer, Liosaccus (= Sphoeroides) pachygaster (Tetraodontidae), are listed as Vulnerable. Five additional species in the family Tetradontidae are listed as Data Deficient. Various species may be at risk from overfishing (as a target species or as bycatch) or habitat destruction. The European Community prohibits the trade of pufferfish products.

Significance to humans

Numerous species of triggerfishes, filefishes and leatherjackets, pufferfishes, and molas are taken in subsistence and artisinal fisheries. Commercial fisheries exist for certain triplespines, triggerfishes, filefishes and leatherjackets, and pufferfishes. The latter group includes the famous fugu (Takifugu spp.), which is esteemed as a delicacy in Japan but poses a serious health risk from tetraodotoxin poisoning if it is not prepared properly. Boxfishes and molas also are or may be poisonous. Various species are used in Chinese medicine. Many species of boxfishes, porcupinefishes, and puffers are taken for use as decorations in the ornamental trade; for example, diodontids are often used to make lamp shades. Some triggerfishes and filefishes and leatherjackets are considered game fishes. Many species of triggerfishes, filefishes and leatherjackets, and pufferfishes (both marine and freshwater) are collected for the aquarium trade, and some are highly valued.

Species accounts

Resources

Eschmeyer, William N., ed. Catalog of Fishes, 3 vols. San Francisco: California Academy of Sciences, 1998.

Helfman, G. S., B. B. Collette, and D. E. Facey. The Diversity of Fishes. Malden, MA: Blackwell Science, 1997.

Leis, J. M., and B. M. Carson-Ewart, eds. The Larvae of Indo-Pacific Coastal Fishes: An Identification Guide to Marine Fish Larvae. Boston: Brill, 2000.

Masuda, H., K. Amaoka, C. Araga, T. Uyeno, and T. Yoshino, eds. The Fishes of the Japanese Archipelago. Tokyo: Tokai University Press, 1984.

Myers, R. F. Micronesian Reef Fishes. 3rd edition. Barrigada, Guam: Coral Graphics, 1999.

Nelson, J. S. Fishes of the World. 3rd edition. New York: John Wiley and Sons, 1994.

Randall, John E., Gerald R. Allen, and Roger C. Steene. Fishes of the Great Barrier Reef and Coral Sea. Honolulu: University of Hawaii Press, 1996.

Smith, M. M., and P. C. Heemstra, eds. Smiths' Sea Fishes. Berlin: Springer-Verlag, 1986.

Thresher, R. E. Reproduction in Reef Fishes. Neptune City, NJ: T.F.H. Publications, 1984.

Ishihara, M., and T. Kuwamura. "Bigamy or Monogamy with Maternal Egg Care in the Triggerfish, Sufflamen chrysopterus." Ichthyological Research 43 (1996): 307–313.

Kawase, H., and A. Nakazono. "Two Alternative Female Tactics in the Polygynous Mating System of the Threadsail Filefish, Stephanolepis cirrhifer (Monacanthidae)." Ichthyological Research 43, no. 3 (1996): 315–323.

Kokita, T., and A. Nakazono. "Pair Territoriality in the Longnose Filefish, Oxymonacanthus longirostris." Ichthyological Research 46 (1999): 297–302. ——. "Spawning Substrate Selection by Female Longnose Filefish, Oxymonacanthus longirostris." Ichthyological Research 46, no. 4 (1999): 429–432.

Nakae, M., and K. Sasaki. "A Scale-Eating Triacanthodid, Macrorhamphosodes uradoi: Prey Fishes and Mouth 'Handedness' (Tetradontiformes, Triacanthoidei)." Ichthyological Research 49, no. 1 (2002): 7–14.

IUCN/SSC Coral Reef Fishes Specialist Group. International Marinelife Alliance-University of Guam Marine Laboratory, UOG Station, Mangilao, Guam 96913 USA. Phone: (671) 735-2187. Fax: (671) 734-6767. E-mail: donaldsn@uog9.uog.edu Web site:

[Article by: Terry J. Donaldson, PhD]

An order of specialized teleost fishes, also called Plectognathi, that includes the triggerfishes (see illustration), puffers, trunkfishes, ocean sunfishes, and their allies. It is a group of diverse structure. The body is variably armored with bony plates or spines, encased in bone, prickly, thorny, or naked. Fin spines and some fins are variably well developed or wanting. Some species can inflate the body.

Gray triggerfish (Batistes capriscus). (After G. B. Goode, Fishery Industries of the United States, sect. 1, 1884)

Tetraodontiforms may be classified conservatively into 7 families, nearly 60 genera, and about 320 Recent species, but some specialists recognize more families and genera. Tetraodontiforms are largely reef and shore fishes of tropical or subtropical seas, but a few are pelagic, enter temperate waters, or ascend tropical rivers. Many are colorful inhabitants of coral reefs. Some are valued as food, but a few have a neurotoxic poison, tetrodotoxin, in the viscera that is sometimes fatal when eaten. See also Actinopterygii.

Tetraodontiformes Fossil range: Eocene–Recent PreЄ Є O S D C P T J K Pg N [1]
American whitespotted filefish, Cantherhines macrocerus
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Actinopterygii Order: Tetraodontiformes
Families
See text.

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 reefs, 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.

Contents 1 Physical characteristics 2 Families 3 Fossil families 4 References

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 (boxfishes), globose (pufferfishes) to laterally compressed (filefishes) and Triggerfish. They range in size from Rudarius excelsus, measuring just 2 centimetres (0.79 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.^[1]

Most members of this order, except for the [[Ballistidie ]]family, are ostraciiforms, meaning the body is inflexible. 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 witht 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 filefishes and ocean sunfish). Another striking defensive attribute found in the pufferfishes and porcupinefishes 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.

Long-spine porcupinefish, Diodon holocanthus. On the right is a blue-spotted grouper, Cephalopholis argus.

Tetraodontiforms have highly modified skeletons, 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 invertebrates such as crustaceans 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.

Families

Ocean sunfish.

The Honeycomb cowfish is part of the Ostraciidae family.

• Aracanidae
• Balistidae — triggerfishes
• Diodontidae — porcupinefishes
• Molidae — ocean sunfish and relatives
• Monacanthidae — filefishes
• Ostraciidae — boxfishes
• Tetraodontidae — pufferfishes
• Triacanthidae — triplespines
• Triacanthodidae — spikefishes
• Triodontidae — three-toothed puffer

Fossil families

• †Bolcabalistidae
• †Cretatriacanthidae
• †Eoplectidae
• †Eospinidae
• †Moclaybalistidae
• †Plectocretacicidae
• †Protobalistidae
• †Protriacanthidae
• †Spinacanthidae

References

1. ^ ^{a b} Keiichi, Matsura & Tyler, James C. (1998). Paxton, J.R. & Eschmeyer, W.N.. ed. Encyclopedia of Fishes. San Diego: Academic Press. pp. 230. ISBN 0-12-547665-5. 

• "Tetraodontiformes". FishBase. Ed. Ranier Froese and Daniel Pauly. January 2006 version. N.p.: FishBase, 2006.
• Tree of Life: Tetraodontiformes

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