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Lepisosteiformes (Gars)

Lepisosteiformes

(Gars)

Class Actinopterygii

Order Lepisosteiformes

Number of families 1


Evolution and systematics

Lepisosteiformes contains the extant family Lepisosteidae (the gars). Extinct families that may belong in the order include the Semionotidae. The order Lepisosteiformes is sometimes classified within the division Ginglymodi.

The family Lepisosteidae includes seven living species contained in two genera, Lepisosteus and Atractosteus. Fossil gars are known as far back as the early Cretaceous period. The earliest fossil gars are represented only by scale, teeth, or bone fragments, but there are complete skeletons known as far back as 110 million years.

The gars have sometimes been included within the order Semionotiformes because of a presumed close relationship with the Semionotidae. More recently, this relationship has come into question. Consequently, the ordinal name Lepisosteiformes as used in this chapter contains the gars, and the Semionotiformes includes Semionotidae, but excludes the gars.

The gars comprise one of only five living actinopterygian families not contained within Teleostei (a group containing over 25,000 living species). They have often been referred to as "living fossils," and understanding their morphology is important to deciphering the evolutionary relationships of rayfinned fishes. Some authors have placed the gars within Holostei (together with bowfins), but they are thought by most systematic ichthyologists to comprise the living sister group to Halecostomi (a group containing bowfins and teleosts, but excluding gars). Whether to recognize Holostei (grouping gars with bowfins) or Halecostomi (placing gars outside of a bowfin/teleost group) remains controversial. Morphological data supports Halecostomi, whereas molecular data supports Holostei. It has even been suggested that gars and teleosts form a monophyletic group that excludes bowfins, although this phylogenetic hypothesis has not been widely accepted.

Physical characteristics

Extant lepisosteids and many of the fossils have a similar appearance. They have a highly elongate snout or "bill," wellarmored elongate bodies covered with interlocking rhomboidshaped ganoid scales, posteriorly positioned median fins with a dorsal fin set above the anal fin, a "tongue" supported by a number of bony basihyal tooth plates, and a jaw articulation anterior to the orbit. They also have an "abbreviate heterocercal" caudal fin, in which the hypurals (caudal ray supports) attach proximally with the ventral surface of the upturned end of the vertebral column. Gars also have a number of extremely diagnostic small features that enable the identification of even fragmentary fossils as gars. These features include plicidentine teeth (a peculiar folded dentine structure surrounding the pulp cavity) and opisthocoelous vertebrae (vertebral centra that are convex anteriorly and concave posteriorly). The ganoid scales are also diagnostic among living fishes, although the scales of African polypterids are superficially similar.

Distribution

Extant gars are restricted to freshwaters of eastern North America, as far north as Montana, United States, and southern Quebec, Canada, and as far west as Montana; Central America; and Cuba. When fossil (extinct) species are included, gars comprise a much greater diversity and geographic range. Well-preserved fossil gar material extends the geographic range of the family into what are now parts of western North America, Europe, Africa, Madagascar, India, and South America. Fossil and living gars are notably absent from East Asia. The one report of a living gar from China (Lepisosteus sinensis Bleeker, 1873) was in error, and was a belonid (Teleostei) rather than a lepisosteid.

Habitat

Gars are primarily freshwater fishes, although some species are known to occasionally swim into brackish or nearshore marine environments. The alligator gar, Atractosteus spatula, in particular, is frequently caught by shrimp trawlers in the salt marshes of Louisiana, and has often been observed in waters of the Gulf Coast.

Gars can withstand aquatic environments of low oxygen content because their swim bladder is highly vascularized and

connected to the pharynx by an enlarged pneumatic duct, allowing them to breathe air.

Behavior

Gars are generally sluggish, but are capable of extremely quick movements for short periods of time. They often lie motionless near the surface until prey swims within reach. Then with a quick sideways thrust of its sharply toothed bill, the fish impales the food item and eventually swallows it. Although alligator gar reach a very large size (up to 9.8 ft/3 m total length) and have numerous, large, sharply pointed teeth and a head that superficially resembles that of a crocodilian, there are no authenticated records of any serious attacks on humans.

Feeding ecology and diet

Gars are primarily piscivorous, although most species supplement their diet with frogs, invertebrates, or even refuse that is dumped into the water. Gars are occasionally cannibalistic. The elongate, well-toothed jaws of gars facilitate the grasping of swimming prey with quick movements of the head. Large alligator gars also occasionally feed on water birds. Adult gars are well armored with their thick scales and dermal bones; consequently, they have few predators.

Reproductive biology

Gars spawn in freshwater generally in the spring (e.g., mid-May to mid-June in New York, United States). Fertilization is external, and large numbers of individuals concentrate in shoal areas and disperse quickly afterward. No parental care is given to the eggs or young. The eggs are black in color, adhesive, and stick to the substrate, rocks, or plants. After hatching, the larvae have adhesive suckers that enable them to stick to objects, even in moving water. The eggs are highly toxic.

Conservation status

No species of gars are included on the IUCN Red List. Most species are quite abundant, although the alligator gar is becoming very rare in some areas of its former range. Sport fishing for alligator gars is popular in some areas of the southeastern United States. Because the species are widely perceived by sport fishermen as being detrimental to game fishes, these fishes have received little sympathy. There have been efforts to manage alligator gars, and they have been declared an endangered species in some of the southeastern states.

Significance to humans

Gars are often thought of as a nuisance fish detrimental to game fishes, and they often break up the nets of commercial fishermen in the southeastern states; but alligator gars are important predators in most aquatic ecosystems where they occur. The flesh of gars is extremely bony and not generally used for food. Exceptions include New Orleans and some other regions of the southeastern United States where alligator gar meat is sold, and the Pacific side of southern Mexico and Guatemala where the tropical gar is an important food item. The eggs of gars are toxic.

The ganoid scales of gars have historically been used for jewelry, arrowheads, and ornaments.

Alligator gars are popular sport fishes in the southern United States, and have inspired "fishing rodeos" and other tournaments. The Florida gar, Lepisosteus platyrhincus, has an attractive color pattern which makes it a popular aquarium fish. The longnose, Lepisosteus osseus, spotted, Lepisosteus oculatus, and alligator gars occasionally turn up in the pet trade as well.

Species accounts

List of Species

Alligator gar
Cuban gar
Tropical gar
Spotted gar
Longnose gar
Shortnose gar
Florida gar

Alligator gar

Atractosteus spatula

family

Lepisosteidae

taxonomy

Atractosteus spatula Lacépède, 1803 type locality not specified. "Lepisosteus ferox" Rafinesque, 1820. The type species for the genus Atractosteus, is a subjective junior synonym of A. spatula, making this species the effective species type of the genus Atractosteus.

other common names

French: Garpique alligateur; Spanish: Catán, gaspar baba, pejelagarto.

physical characteristics

Attains the largest size of any living gar, up to 9.8 ft (3 m) total length. One specimen has been reported at "9 feet 8.5 inches long and [weighing] 302 pounds" (2.8 m/137 kg). Adults usually have heavy ornamentation on exposed surfaces of the scales.

distribution

North America from Vera Cruz, Mexico, north through the Mississippi River drainage into southern Illinois, Indiana and Ohio, United States, and along much of the Gulf Coast. There is also a disjunct population reported from Lake Nicaragua and Rio Sapoá, Nicaragua. There are records of exotic introductions by humans as far west as California. Reported as a fossil from Pliocene deposits of Kansas and Pleistocene deposits of Texas

and Florida, but fossils assigned to this species are isolated fragments (mostly scales) and somewhat tenuous in their assignment.

habitat

Freshwater river and swamp habitats, but also enters brackish and even marine waters. Of gar species, the most tolerant of salinity.

behavior

Little is known besides feeding behavior.

feeding ecology and diet

Often portrayed as a voracious predator, although many reports are largely poorly documented sensationalism. As the largest, most solidly toothed gar, it is anatomically equipped to take a large variety of large prey, but this species is also a scavenger, and has been reported to compete with sharks for garbage at the wharves in Pensacola, Florida. The diet includes other fishes, blue crabs and other invertebrates, small mammals, and water birds such as ducks and water turkeys. Will prey opportunistically on alligator and crocodile hatchlings.

reproductive biology

Very little is known about the reproductive habits. As in other gar species, the eggs are toxic to other animals.

conservation status

Not threatened, although large individuals are taken in fish rodeos, spear fishing, and numerous annual contests.

significance to humans

Used for food and in sport fishing in the southern United States. Sometimes turns up in the pet trade.


Cuban gar

Atractosteus tristoechus

family

Lepisosteidae

taxonomy

Atractosteus tristoechus Bloch and Schneider, 1801, Cuba. Sometimes confused with the alligator gar. It is distinguishable as a separate species, but in the late nineteenth and early twentieth centuries, several authors considered the Cuban gar (A. tristoechus) and the alligator (A. spatula) to be synonyms. Consequently, some authors referred to the alligator gar as "A. tristoechus" or "L. tristoechus," and museum specimens of alligator gars are sometimes labeled as "tristoechus." In the author's experience, museum specimens collected in North America labeled "L. tristoechus" or "A. tristoechus" are actually A. spatula.

other common names

French: Garpique cubain; German: Alligatorhecht, Kaimanfisch; Spanish: Manjuari.

physical characteristics

Not as large as the alligator gar; largest known specimen is 36.6 in (93 cm) total length. Caudal fin has a distinctive color pattern, with the fin outlined with a thin line of dark pigment.

distribution

Western Cuba and the nearby Isle of Pines.

habitat

Very little is known.

behavior

Similar to that for entire order.

feeding ecology and diet

Based on stomach-content analysis, evidently feeds on other fishes, but further studies are still needed.

reproductive biology

Very little is known.

conservation status

Not listed by the IUCN.

significance to humans

None known.


Tropical gar

Atractosteus tropicus

family

Lepisosteidae

taxonomy

Atractosteus tropicus Gill, 1863.

other common names

Spanish: Catán, gaspar, pejelagarto.

physical characteristics

Small species; largest specimen known to the author is 49.2 in (125 cm) total length. Trunk is more pigmented than in other Atractosteus species.

distribution

Southern Mexico and Central America, with disjunct populations on both Atlantic and Pacific drainages

habitat

Freshwater rivers, streams, and near-shore lacustrine environments, but will occasionally enter brackish water.

behavior

Visible on the surface and resemble floating logs.

feeding ecology and diet

Feeds mainly on fishes, but also may take copepods, insects, and plant material.

reproductive biology

Reaches sexual maturity at about 14 in (36 cm) total length. Enters shallow lakes at beginning of dry season, spawning as rains cause flooding. Large schools form to lay eggs in a large gelatinous mass.

conservation status

Not listed by the IUCN.

significance to humans

None known.


Spotted gar

Lepisosteus oculatus

family

Lepisosteidae

taxonomy

Lepisosteus oculatus Winchell, 1864, Duch Lake, Calhoun Co., Michigan, United States.

other common names

French: Garpique tachetée; German: Gefleckter Knochenhecht; Spanish: Gaspar pintado.

physical characteristics

Maximum total length (known to the author) is 32.9 in (83.5 cm), although reported up to 44 in (112 cm). Has a profusion of dark spots on the body, head, and fins (although these spots are not generally as large and strong as in the Florida gar). Adults have a series of small bony plates on the ventral surface of the isthmus. Females have been reported to have proportionately longer snouts than males.

distribution

Great Lakes south to the gulf coast of Texas, United States, and northern Mexico, east to northwestern Florida, United States. Reported as a fossil from Pleistocene deposits of Texas, but the material is too fragmentary to be reliably included in the species.

habitat

Quiet, clear waters with abundant vegetation, also brackish waters along the Gulf of Mexico.

behavior

Little is known.

feeding ecology and diet

Feeds mainly on fishes, but may also take crabs and crayfishes.

reproductive biology

Spawns in shallow freshwater. Like L. osseus, newly hatched larvae have adhesive pad on the head that allows them to adhere to the substrate or objects on the substrate. This organ is lost early in development. Sometimes hybridizes with L. platyrhincus.

conservation status

Not threatened.

significance to humans

Turns up frequently in the pet trade.


Longnose gar

Lepisosteus osseus

family

Lepisosteidae

taxonomy

Lepisosteus osseus Linnaeus, 1758, eastern United States.

other common names

English: Billfish, common gar pike, needlenose gar; French: Garpique longnez; German: Gemeiner Knochenhecht, Gemeiner Langschnäuziger, Langnasen-Knochenhecht; Spanish: Catán, gaspar picudo, pejelagarto.

physical characteristics

Maximum total length about 6 ft (183.4 cm), weight of about 50 lb (22.7 kg). Has the longest snout and most elongate body shape of any gar species. Color pattern variable. As a juvenile, it has a lateral stripe that disappears in the adult.

distribution

Southern Quebec, Canada, south to Florida, United States, westward from the Great Lakes region to Montana, United States, and from Florida to northern Mexico. Reported as a fossil from Pleistocene deposits of Kansas and North Carolina, United States, although species identification of this fragmentary material is tenuous.

habitat

Normally inhabits quiet, weedy, shallow-water lake environments or large rivers. Typically freshwater, but occasionally enters brackish water along its coastal distribution, particularly in the southern United States. Can also survive for weeks in oxygen-poor stagnant ponds and canals by breathing air at the surface with its functional lung (vascularized swim bladder).

behavior

Often lies motionless near the surface until prey swim within reach. With a quick sideways thrust of its sharply toothed bill, it impales the prey.

feeding ecology and diet

Voracious predators; by the time they reach about 1 in (2.6 cm) total length, feed primarily on other fishes. Also feed on decapods, insects, and other invertebrates. Young are cannibalistic, sometimes feeding on siblings 70% of their own length.

reproductive biology

Lake-dwelling; often migrates up streams and rivers to spawn. Some also spawn in nearshore lake shallows. Eggs in a female 40 in (102 cm) long can number more than 36,000. Males mature at three or four years, females at six. Longevity appears to be sexually dimorphic.

conservation status

Not threatened.

significance to humans

Occasionally turns up in the pet trade.


Shortnose gar

Lepisosteus platostomus

family

Lepisosteidae

taxonomy

Lepisosteus platostomus Rafinesque, 1820, type locality not specified but probably Mississippi River basin, United States.

other common names

English: Duckbill garfish; Finnish: Pikkuluuhauki.

physical characteristics

Maximum total length 34.6 in (88 cm). Has a reduced color pattern on the trunk region (i.e., spots are few and not as strong as in other Lepisosteus species) and two complete rows of premaxillary teeth.

distribution

Primarily within the low gradient regions of the Mississippi River basin in the United States, running from northeastern Texas north to Montana, east to Ohio, and south to Mississippi. It is absent from the Ozark plateau. Has been reported as a fossil from Kansas, but the material is too fragmentary to be reliably included in the species.

habitat

Quiet, sparsely planted backwater areas of rivers, lakes, and oxbows. Appears to be more tolerant of turbidity than most other gar species.

behavior

Little is known.

feeding ecology and diet

Feeds mainly on crayfishes, fishes, and aquatic insects.

reproductive biology

Reaches sexual maturity at about three years of age. Spawning takes place in spring. Eggs are scattered in quiet, shallow, freshwater and hatch in about eight days. Young become active (and feed) about seven days after hatching.

conservation status

Not threatened.

significance to humans

None known.


Florida gar

Lepisosteus platyrhincus

family

Lepisosteidae

taxonomy

Lepisosteus platyrhincus DeKay, 1842, Florida, United States.

other common names

English: Florida spotted gar; Finnish: Floridanluuhauki.

physical characteristics

Maximum total length 52.4 in (133 cm). Has numerous dark brown spots covering the anterior body and head; spots similar to those of L. oculatus, but more prominent and darker on the dorsal surface of the head and body. Also distinguished from L. oculatus by the lack of plates on the ventral surface of the isthmus.

distribution

Florida and the lowlands of southern Georgia, United States. Reported from Pleistocene deposits of Florida based on fragmentary material, but material is too fragmentary to be reliably included in the species.

habitat

Quiet lowland streams and lakes with heavy vegetation and a mud-sand bottom. The rarity of records of this species in brackish or salt water may reflect a very limited tolerance to salinity.

behavior

Little is known.

feeding ecology and diet

Feeds primarily on fishes, but also on crustaceans and insects.

reproductive biology

Little is known about the reproductive habits; may interbreed with L. oculatus in the Apalachicola River drainage.

conservation status

Not threatened.

significance to humans

Turns up frequently in the pet trade.


Resources

Books

Breeder, C. M., and D. E. Rosen. Modes of Reproduction in Fishes. New York: Natural History Press, 1966.

Bussing, W. A. Peces de las aguas continentales de Costa Rica. San José, Costa Rica: Universidad de Costa Rica, Trejos Hermanos Sucesores, S.A., 1987.

Jordan, D. S. A Guide to the Study of Fishes. New York: Henry Holt and Co., 1905.

Lee, D. S., C. R. Gilbert, C. H. Hocutt, R. E. Jenkins, D. E. McAllister, and J. R. Stauffer, Jr. Atlas of North American Freshwater Fishes. Raleigh: North Carolina State Museum of Natural History, 1980.

Scott, W. B., and E. J. Crossman. Freshwater Fishes of Canada. Ottawa: Fisheries Resource Board of Canada, 1973.

Periodicals

Agassiz, A. "Embryology of the Gar-Pike (Lepidosteus)." Science News 1 (1879): 19–20.

Bleeker, P. "Mémoire sur la faune ichthyologique de Chine." Nederlandsch Tijdschrift voor de Dierkunde 4 (1873): 113–154.

Dugas, C. N., M. Konikoff, and M. F. Trahan. "Stomach Contents of Bowfin (Amia calva) and Spotted Gar (Lepisosteus oculatus) Taken in Henderson Lake, Louisiana." Proceedings of the Louisiana Academy of Sciences 39 (1976): 28–34.

Reséndez Medina, A., and M. L. Salvadores–Baledón. "Contribución al conocimiento de la biología del pejelagarto Lepisosteus tropicus (Gill) y la tenguayaca Petenia splendida Günther, del estado de Tabasco." Biotica 8, no. 4 (1983): 413–426.

Suttkus, R. D. "Order Lepisostei: Fishes of the Western North Atlantic." 3. Memoirs of the Sears Foundation for Marine Research 1 (1963): 61–88.

Uyeno, T. and R. R. Miller. "Summary of Late Cenozoic Freshwater Fish Records for North America." Occasional Papers of the Museum of Zoology, University of Michigan, Ann Arbor 631 (1963): 1–34.

Wiley, E. O. "The Phylogeny and Biogeography of Fossil and Recent Gars (Actinopterygii: Lepisosteidae)." University of Kansas Museum of Natural History Miscellaneous Publication 64 (1976): 1–111.

Lance Grande, PhD

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