Gar - WikiHQ

Gars are an ancient group of ray-finned fish in the family Lepisosteidae. They comprise seven living species of fish in two genera that inhabit fresh, brackish, and occasionally marine waters of eastern North America, Central America and Cuba in the Caribbean, though extinct members of the family were more widespread. They are the only surviving members of the Ginglymodi, a clade of fish which first appeared during the Triassic period, over 240 million years ago, and are one of only two surviving groups of holosteian fish, alongside the bowfins, which have a similar distribution. and fronted by similarly elongated jaws filled with long, sharp teeth. Gars are sometimes referred to as "garpike", but are not closely related to pike, which are in the fish family Esocidae. All of the gars are relatively large fish, but the alligator gar (Atractosteus spatula) is the largest; the alligator gar often grows to a length over and a weight over , and specimens of up to in length have been reported. Unusually, their vascularised swim bladders can function as lungs,

Etymology

The name "gar" was originally used for a species of needlefish (Belone belone) found in the North Atlantic and likely took its name from the Old English word for "spear". Belone belone is now more commonly referred to as the "garfish" or "gar fish" to avoid confusion with the North American gars of the family Lepisosteidae. Confusingly, the name "garfish" is also commonly used for a number of other species of the related genera Strongylura, Tylosurus, and Xenentodon of the family Belonidae.

The generic name Lepisosteus comes from the Greek lepis (λεπίς) meaning "scale" and osteon (ὀστέον) meaning "bone". Atractosteus is similarly derived from Greek, in this case from atraktos (ἀτρακτὀς), meaning spindle. They exhibit the slowest known rate of molecular evolution among all jawed vertebrates, with DNA evolving up to a thousand times more slowly than in other groups, which has consequently reduced their rate of speciation. The closest living relatives of gars are the bowfin, with the gars and bowfin together forming the clade Holostei; both lineages diverged during the Late Permian.

The closest extinct relatives of gar are the Obaichthyidae, an extinct group of gar-like fishes from the Early Cretaceous of Africa and South America, which likely diverged from the ancestors of true gars during the Late Jurassic. The oldest anatomically modern gar is Nhanulepisosteus from the Upper Jurassic (Kimmeridgian) of Mexico, around 157 million years old. Nhanulepisosteus inhabited a marine environment unlike modern gars, indicating that gars may have originally been marine fish prior to invading freshwater habitats before the Early Cretaceous. Although most succeeding gar fossils are known from freshwater environments, at least some marine gars are known to have persisted into the Late Cretaceous, with the likely marine Herreraichthys known from Mexico and the definitely marine Grandemarinus known from Morocco.

Gars diversified in western North America throughout the Early Cretaceous. Atractosteus and Lepisosteus had already diverged by the end of the Early Cretaceous, about 105 million years ago. From western North America, gars dispersed to regions as disparate as Africa, India, South America and Europe, and fossil remains of gars were widespread worldwide by the end of the Cretaceous. A few populations are also present in the Great Lakes region of the United States, living in similar shallow waters.

Anatomy

thumb|200px|right|Large gar in an aquarium

Scales

Gar bodies are elongated, heavily armored with ganoid scales, and fronted by similarly elongated jaws filled with long, sharp teeth. Their tails are heterocercal, and the dorsal fins are close to the tail.

Jaw

Gar jaws are elongated and extend from the front of the head, with the jaw joints located anterior to the eye sockets. The primary bones involved in the elongation of the snout are the premaxilla and vomer of the upper jaw, and the dentary of the lower jaw, which grow throughout development and provide the foundational shape of the jaw. Due to their ambush predator hunting style, early establishment of snout shape is necessary for young gars to feed. Meckel’s cartilage is present throughout development, though reduced—initially spanning the entire lower jaw, by adulthood it spans less than half the jaw and has reduced connection points at both ends.

Swim bladder

As their vascularised swim bladders can function as lungs, This adaptation can be the result of environmental pressures and behavioral factors. As a result of this organ, they are extremely resilient and able to tolerate conditions that most other fish could not survive.

Pectoral girdle

thumb|Medial and lateral view of Lepisosteidae pectoral girdle

The gar has paired pectoral fins and pelvic fins, as well as an anal fin, a caudal fin, and a dorsal fin. The bone structures within the fins are important to study as they can show homology throughout the fossil record. Specifically, the pelvic girdle resembles that of other actinopterygians while still having some of its own characteristics. Gars have a postcleithrum—which is a bone that is lateral to the scapula, but do not have postpectorals. Proximally to the postcleithrum, the supracleithrum is important as it plays a critical role in opening the gar's jaws. This structure has a unique internal coracoid lamina only present in the gar species. Near the supracleithrum is the posttemporal bone, which is significantly smaller than other actinopterygians. Gars also have no clavicle bone, although elongated plates have been observed within the area.

Morphology

thumb|Fin chart for shortnose gar

All the gars are relatively large fish, but the alligator gar (Atractosteus spatula) is the largest. The largest alligator gar ever caught and officially recorded was long, weighed , and was around the girth. Even the smaller species, such as Lepisosteus oculatus, are large, commonly reaching lengths of over , and sometimes much longer.

Ecology

thumb|right|A gar leaps out of the water.

Gars tend to be slow-moving fish except when striking at their prey. They prefer the shallow and weedy areas of rivers, lakes, and bayous, often congregating in small groups.

Species and identification

The gar family contains seven extant species, in two genera. This list also includes definitively known fossil taxa, common names for which are based on Grande (2010):

Family Lepisosteidae

Genus †Nhanulepisosteus Brito, Alvarado-Ortega & Meunier, 2017
Genus †Britosteus Martinelli et al 2025
Genus †Masillosteus Micklich & Kappert, 2001
Genus †Cuneatus Grande, 2010 (cuneatus gar)
Tribe Lepisosteini
Genus †Herreraichthys Alvarado-Ortega et al 2016
Genus †Grandemarinus Cooper et al 2023
Genus †Oniichthys Cavin & Brito, 2001
Genus Atractosteus Rafinesque, 1820
†Atractosteus atrox (Leidy, 1873) (Green River atrox gar)
†Atractosteus grandei Brownstein & Lyson, 2022
†Atractosteus messelensis Grande, 2010
†Atractosteus simplex (Leidy, 1873) (simplex gar)
Atractosteus spatula (Lacépède, 1803) (alligator gar)
Atractosteus tristoechus (Bloch & J. G. Schneider, 1801) (Cuban gar)
Atractosteus tropicus Gill, 1863 (tropical gar)
Genus Lepisosteus Linnaeus, 1758
†Lepisosteus bemisi Grande, 2010 (Green River longnose gar)
†Lepisosteus indicus (Woodward, 1890) (Indian gar)
Lepisosteus oculatus Winchell, 1864 (spotted gar)
Lepisosteus osseus (Linnaeus, 1758) (longnose gar)
Lepisosteus platostomus Rafinesque, 1820 (shortnose gar)
Lepisosteus platyrhincus DeKay, 1842 (Florida gar)

Alligator gar

alt=|thumb|Alligator gar (Atractosteus spatula)

The largest member of the gar family, the alligator gar (Atractosteus spatula), can reach over (although 10-foot individuals are possible, and likely exist) and weigh over . Its body and snout are wide and stocky, and it was named "alligator gar" because locals often mistook it for an alligator. The species can be found in Texas, Oklahoma, Louisiana, the Mississippi River, Ohio, the Missouri river, and the southern drainages into Mexico. They are deep green or yellow in color. Over five decades of overfishing have brought it close to extinction, Some states, such as Texas, restrict the number of gar that may be caught in a day, the season in which they may be caught, and the equipment anglers may use to catch them. Some states also impose a minimum length requirement to prevent gar from being caught at too early an age. Scientists have found that the alligator gar can help maintain ecosystem balance by eating invasive species such as the Asian carp, and their success in a particular area can show scientists that area may also make a suitable habitat for other migratory species. and prefers muddy or sandy bottoms with bountiful vegetation. It is commonly confused with its cousin, the spotted gar. This coloration, which blends well with the gar's surroundings, allows it to ambush its prey. This gar has dark spots covering its head, body, and fins. and to surround itself in foliage. It shares its habitat with the alligator gar, its main predator. These smaller gar live an average of 18 years. It prefers to live in lakes, swamps, and calm pools. and grows to lengths of . and can be distinguished from other species of gar by its snout, which is more than twice the length of the rest of its head. It can reach up to 6 feet and 8 inches in length and weigh up to . Depending on the water clarity, the longnose gar comes in two colors.

Roe

The flesh of gar is edible, but its eggs contain an ichthyotoxin, a type of protein toxin which is highly toxic to humans. The protein can be denatured when brought to a temperature of 120 degrees Celsius, but as the roe's temperature does not typically reach that level when it is cooked, even cooked roe causes severe symptoms. It was once thought that the production of the toxin in gar roe was an evolutionary adaptation to provide protection for the eggs, but bluegills and channel catfish fed gar eggs in experiments remained healthy, even though they are the natural predators of the gar eggs. Crayfish fed the roe were not immune to the toxin, and most died. The roe's toxicities to humans and crayfish may be coincidences, and not the result of explicit natural selection. It is suspected that gars have an unusually strong DNA repair apparatus. If confirmed by further studies, it could be used in medical treatments against human diseases like cancer.

Not much is known about the precise function of the gar in Native American religion and culture other than the ritual "garfish dances" that have been performed by Creek and Chickasaw tribes.

References

External links

Family Lepisosteidae