Gar
Gar Temporal range:
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Spotted gar (Lepisosteus oculatus) | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Actinopterygii |
Clade: | Ginglymodi |
Order: | Lepisosteiformes |
Superfamily: | Lepisosteoidea
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Family: | Lepisosteidae G. Cuvier, 1825 |
Genera | |
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Gars are an ancient group of
Gars have elongated bodies that are heavily armored with
Etymology
The name "gar" was originally used for a species of
The generic name Lepisosteus comes from the Greek lepis meaning "scale" and osteon meaning "bone".[12] Atractosteus is similarly derived from Greek, in this case from atraktos, meaning arrow.[13]
Evolution
Evolutionary history
Gars are considered to be the only surviving members of the
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.[14][16] 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.[17][18]
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.[16]
Several different gar genera survived the
Phylogeny
The following phylogeny of extant and fossil gar genera was found by Brownstein et al. (2022):[16]
Lepisosteoidea |
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A slightly different phylogeny was found by Cooper et al (2023):[18]
Lepisosteoidea |
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Distribution
Fossils indicate that gars formerly had a wider distribution, having been found on every continent except Australia and Antarctica.[14] Living gars are confined to North America. The distribution of the gars in North America lies mainly in the shallow, brackish waters off of Texas, Louisiana, and the eastern coast of Mexico, as well as in some of the rivers and lakes that flow into them.[19][20] A few populations are also present in the Great Lakes region of the United States, living in similar shallow waters.[21]
Anatomy
Scales
Gar bodies are elongated, heavily armored with
Swim bladder
As their vascularised swim bladders can function as lungs,[7] most gars surface periodically to take a gulp of air, doing so more frequently in stagnant or warm water when the concentration of oxygen in the water is low. Experiments on the swim bladder has shown that the temperature of the water affects which respiration method the gar will use - aerial or aquatic. They increase the aerial breathing rate (breathing air) as the temperature of the water is increased. Gars can live completely submerged in oxygenated water without access to air and remain healthy while also being able to survive in deoxygenated water if allowed access to air.[23] This adaptation can be the result of environmental pressures and behavioral factors.[24] As a result of this organ, they are extremely resilient and able to tolerate conditions that most other fish could not survive.
Pectoral girdle
The gar has paired pectoral fins and pelvic fins, as well as an anal fin, a caudal fin, and a dorsal fin.
Morphology
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 8 ft 5 in (2.6 m) long, weighed 327 lb (148 kg), and was 47 in (120 cm) around the girth.[27] Even the smaller species, such as Lepisosteus oculatus, are large, commonly reaching lengths of over 60 cm (2.0 ft), and sometimes much longer.[28]
Ecology
Gars tend to be slow-moving fish except when striking at their prey. They prefer the shallow and weedy areas of rivers, lakes, and
Species and identification
The gar family contains seven extant species, in two genera:[7]
Cladogram of living gars[30] |
Family Lepisosteidae
- Genus †Nhanulepisosteus Brito, Alvarado-Ortega & Meunier, 2017
- Genus †Masillosteus Micklich & Kappert, 2001
- Genus †Cuneatus Grande, 2010
- 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" africanus (Arambourg & Joleaud, 1943) [31] (nomen dubium)
- †Atractosteus grandei (Brownstein, Lyson, 2022)[32]
- Atractosteus spatula (Lacépède, 1803) (alligator gar)
- J. G. Schneider, 1801) (Cuban gar)
- Atractosteus tropicus Gill, 1863 (tropical gar)
- Genus Lepisosteus Linnaeus, 1758
- †Lepisosteus bemisi Grande, 2010
- †Lepisosteus cominatoi Santos, 1984
- †Lepisosteus fimbriatus (Wood 1846)
- †Lepisosteus indicus (Woodward, 1908)
- †Lepisosteus opertus Estes, 1964
- 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
The largest member of the gar family, the alligator gar (Atractosteus spatula), can measure up to 10 feet long and weigh over 300 pounds.[33][34] Its body and snout are wide and stocky, and it was named "alligator gar" because locals often mistook it for an alligator.[33][35] The species can be found in Texas, Oklahoma, Louisiana, the Mississippi River, Ohio, the Missouri river, and the southern drainages into Mexico.[34][35] Its habitat consists of lakes and bays with slow currents.[34] The gars grow rapidly when young and continue to grow at a slower rate after reaching adulthood.[36] They are deep green or yellow in color.[34][35] Recreational fishing of the alligator gar became popular due to its massive size and its meat is sold for food.[37] Over five decades of overfishing have brought it close to extinction,[35][36] and man-made dams have contributed to this loss by restricting the gar's access to the flood plain areas in which it spawns.[37] Some U.S. states have enacted laws to combat overfishing, and reintroduction programs are being carried out in some states, such as Illinois, where human activity has extirpated the gar.[35][36] Before being released, each gar must meet a length requirement to ensure that it has the best chance of survival in the wild.[38] 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.[39] 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.[40]
Florida gar
The Florida gar (Lepisosteus platyrhincus) can be found in the Ocklockonee river, Florida, and Georgia,[41][42] and prefers muddy or sandy bottoms with bountiful vegetation.[41][43] It is commonly confused with its cousin, the spotted gar.[41] Uneven black spots cover its head, body, and fins.[41][42] Green-brown scales run along the back of its body, and the scales on its underbelly are white or yellow.[41][44] This coloration, which blends well with the gar's surroundings, allows it to ambush its prey.[41][44] The Florida gar has no ganoid scales on its throat.[41] Female Florida gars grow to lengths between 13 and 34 inches, bigger than their male counterparts.[41][44]
Spotted gar
The spotted gar (Lepisosteus oculatus) is a smaller species of gar,[33] measuring just under four feet long and weighing 15 pounds on average.[33] Like Florida gars, female spotted gars are typically larger than male spotted gars.[45] This gar has dark spots covering its head, body, and fins.[33] Its body is compact, and it has a shorter snout.[33] It prefers to live in clearer shallow water with a depth of 3–5 meters,[40] and to surround itself in foliage.[43][45] Its habitat ranges from the waters of Lake Michigan, the Lake Erie Basin, the Mississippi River System, and river drainages along the northern coast of the Gulf of Mexico from the Nueces River in Texas east to the lower Apalachicola River in Florida.[45][46] It shares its habitat with the alligator gar, its main predator. These smaller gar live an average of 18 years.[45]
Shortnose gar
The shortnose gar (Lepisosteus platostomus) is found in the Mississippi River Basin, Indiana, Wisconsin, Montana, Alabama, and Louisiana.[47] It prefers to live in lakes, swamps, and calm pools.[43][47] The shortnose gar takes its name from its snout, which is shorter and broader than that of other gar species.[33][47] Like the longnose gar, it has one row of teeth. The upper jaw is longer than the rest of its head.[47] The shortnose gar is deep green or brown in color, similar to the alligator gar.[33][47] Depending on the clarity of water, spots can be present on the caudal, dorsal, and anal fins.[47] The shortnose gar has a lifespan of 20 years, reaches up to 5 pounds in weight,[48] and grows to lengths of 24–35 inches.[46][48] It consumes more invertebrates than any other gar,[47] and their stomachs have been found to contain higher Asian carp content than any other native North American fish.[40]
Longnose gar
The Longnose gar (Lepisosteus osseus) has a longer, narrower, more cylindrical body,[33][49] 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.[50][51] It can reach up to 6 feet and 8 inches in length and weigh up to 35–80 pounds.[33][50] Like the shortnose gar, it has only a single row of teeth.[50][51] Unlike its relatives, it enters brackish water from time to time.[43][50] Females are larger and live longer than the male longnose gar.[49][50] Females live 22 years, and males about half as long.[50] There are spots on the head, dorsal, anal, and caudal fins.[33][50][52] Depending on the water clarity, the longnose gar comes in two colors.[50] In clear water, they're a dark deep green color. In muddy waters, it is more brown in color.[50] Edges of the ganoid scales and in between are black.[50][52] These types of gar are occasionally fished by locals, and blamed for eating other fish in the rivers.[49][50] The longnose gar has a large range of territory in North America, into the Gulf of Mexico.[50][52] Located in Florida, Quebec, all Great Lakes except Lake Superior, Missouri, Mississippi, Texas, and northern Mexico.[50][53]
Roe
The flesh of gar is edible, but its eggs contain an ichthyotoxin, a type of protein toxin which is highly toxic to humans.[54][55] The protein can be denatured when brought to a temperature of 120 degrees Celsius,[56] 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, however, and not the result of explicit natural selection.[54]
Significance to humans
Several species are traded as aquarium fish.
References
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- ^ "Atractosteus spatula". Florida Museum of Natural History. Retrieved 2016-04-21.
- ^ a b "Atractosteus spatula - Alligator gar". Retrieved 2007-07-19.
- ^ a b c Froese, Rainer, and Daniel Pauly, eds. (2009). "Lepisosteidae" in FishBase. January 2009 version.
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- ^ "Alligator Gar (Atractosteus spatula)". Texas Parks & Wildlife Department. Retrieved March 8, 2016.
- ^ ISBN 0-7938-0086-2[page needed]
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- ^ Jeremy J. Wright, Solomon R. David, Thomas J. Near: Gene trees, species trees, and morphology converge on a similar phylogeny of living gars (Actinopterygii: Holostei: Lepisosteidae), an ancient clade of ray-finned fishes. Molecular Phylogenetics and Evolution 63 (2012) 848–856 PDF
- ^ Cavin, Lionel; Martin, Michel; Valentin, Xavier (1996). "Occurrence of Atractosteus africanus (actinopterygii, lepisosteidae) in the early Campanien of Ventabren (Bouches-du-Rhône, France). Paleobiogeographical implications". Revue de Paléobiologie. 15 (1): 1–7.
- ^ Prostak, Sergio (2022-08-16). "Newly-Discovered Giant Gar Species Survived Dinosaur Extinction | Sci.News". Sci.News: Breaking Science News. Retrieved 2022-08-16.
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- ^ a b c d e "Alligator Gars, Alligator Gar Pictures, Alligator Gar Facts". National Geographic. 2009-12-15. Archived from the original on October 3, 2018. Retrieved 2019-07-24.
- ^ a b c "Alligator Gar (Atractosteus spatula)". tpwd.texas.gov. Retrieved 2019-07-26.
- ^ a b "Alligator Gar". U.S. Fish and Wildlife Service.
- ^ "Fishing in Illinois". www.ifishillinois.org. Retrieved 2019-08-03.
- ^ "Who Fishes for Alligator Gar?". tpwd.texas.gov. Retrieved 2019-08-03.
- ^ a b c "Conservation of Ancient Fishes: Reintroducing the Alligator Gar; and What About Those Carp?". National Geographic Society Newsroom. 2016-08-08. Archived from the original on January 8, 2018. Retrieved 2019-08-03.
- ^ a b c d e f g h "Lepisosteus platyrhincus". Florida Museum. 2017-05-10. Retrieved 2019-07-24.
- ^ a b "Florida Gar". Florida Fish And Wildlife Conservation Commission. Retrieved 2019-08-03.
- ^ a b c d "FAMILY Details for Lepisosteidae - Gars". www.fishbase.in. Retrieved 2019-07-26.
- ^ a b c "Toronto Zoo | Florida gar". www.torontozoo.com. Retrieved 2019-08-03.
- ^ a b c d Givinsky, Lana Hall; Thomas Meade; Drew Paulette; Josh Albert; Stephanie. "Lepisosteus oculatus (Spotted gar)". Animal Diversity Web. Retrieved 2019-07-24.
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- ^ a b c d e f g Bradburn, Mark. "Lepisosteus platostomus (Shortnose gar)". Animal Diversity Web. Retrieved 2019-07-24.
- ^ a b "Lepisosteus platostomus summary page". FishBase. Retrieved 2019-07-24.
- ^ a b c "Longnose Gar | Chesapeake Bay Program". www.chesapeakebay.net. Retrieved 2019-07-26.
- ^ a b c d e f g h i j k l m "Lepisosteus osseus". Florida Museum. 2017-05-10. Retrieved 2019-07-24.
- ^ a b "Gar - NYS Dept. of Environmental Conservation". www.dec.ny.gov. Retrieved 2019-08-03.
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