(21-01-10) This is the alligator gar, an outrageous and fascinating creature of prehistoric appearance that lives in rivers and estuaries in Center and North America. It becomes very big and is characterised by an enormous jaw full with teeth and a body covered with hard scales, which makes it look like a crocodile.

         Lacepede first described the alligator gar in 1803. The original name was Lepisosteus spatula and later changed by Wiley in 1976 to Atractosteus spatula in order to recognize two distinct extant genera of gars. The name spatula is the Latin derivative of the Greek word spathe meaning "any tool with a broad, flat blade."

    The genus Atractosteus is derived from the Greek word atractus, meaning "spindle" and osteus (Greek osteos) which means "bony." Synonyms of Atractosteus spatula include Lesisosteus [sic] ferox (Rafinesque 1820), and Lepisosteus spatula (Lacepede 1803).

    Fossils from the order Lepisosteiformes have been collected in Europe from the Cretaceous to Oligocene periods, in Africa and India from the Cretaceous, and in North America from the Cretaceous to recent. There is only one extant family of gar, Lepisosteidae, which has seven species all located in North and Central America.

    The English common names for Atractosteus spatula are alligator gar, gator, greater gar, garpike, longnose gar, garfish, and Mississippi alligator gar. Other common names are pejelagarto, manjuari, espátula (Spanish), garpigue alligator (French), alligatorpansergedde (Danish), alligatorbengadda (Swedish), keihasluuhauki (Finnish), and kostlin obrovsky (Czech).

    Although fossils of gars have been found in North America, Central America, Europe, and Asia, the living members of the family are restricted to seven species living in North and Central America. Five of this seven species live in the United States.

    The range of the alligator gar extends from the Florida Panhandle, through the Gulf Coastal Plain and the Mississippi River Basin extending north to the lower portions of the Ohio and the Missouri River, and ranges southwest through Texas down to Veracruz, Mexico.

    There is a population in Mississippi Sound and the brackish water of the Gulf Coast and Mobile-Tensaw Delta that seldom stray far inland. There are also reports of a disjunctive isolated population living in Nicaragua. The alligator gar is disappearing from many parts of the range, and declining in population everywhere due to over-fishing and the construction of dikes, dams, and other flood control devices, resulting in loss of key breeding habitat.

    The alligator gar was once reported as common and even numerous in much of its northern range. Now it is rare in the Northern parts of its range with reports of valid sightings coming in only every few years.

OCCASIONALLY STRAYS INTO SALT WATER

    The alligator gar inhabits large, slow moving rivers, reservoirs, oxbow lakes, bayous and bays, in fresh and brackish water. The alligator gar is the most tolerant gar species of high salinity and occasionally strays into salt water. Young may be seen at the surface in debris such as leaves and twigs. Alligator gar prefer large rivers that have a large overflow floodplain, but these rivers have all but disappeared in North America due to the use of dredging, dams, dikes, and levees.

    All gars have an elongated, torpedo-shaped body. The caudal fin of the alligator gar is abbreviate-heterocerical, meaning the tail is not symmetrical. The dorsal and anal fins are located very far back on the body. Gars bodies are covered by ganoids scales, which are thick overlapping scales that create a protective covering similar to medieval chain mail.

    Gars have retained the spiral valve intestine a primitive feature of the digestive system commonly associated with sharks. Gars also have a highly vascularised swim bladder connected to the pharynx by a pneumatic duct. This enables them to gulp air, which aids in facultative air breathing. This allows gar to breathe when there are very low oxygen levels in the water.

    The alligator gar is distinguished from other gars in the United States by its relatively short, broad snout which has two rows of fang-like teeth in the upper jaw. The inner row of teeth in the upper jaw is palatine and larger than the outer row of teeth.

    The alligator gar is dark olive-green dorsally, fading to yellowish white ventrally. Young alligator gars possess a light mid-dorsal stripe bordered by thin dark lines from the tip of snout to the dorsal fin, and a dark lateral band extends along the sides with irregular borders. The dorsal, anal, and caudal fins of the Alligator gar often have oval-shaped black spots. Adult specimens lack spots on the body.

    Alligator gars have two rows of teeth. The inner row of teeth is palatine and is longer than the outer row of teeth. The teeth of the alligator gar are long, slander, and fang like, enabling these fish to pierce and hold their prey.

    This is one of the largest freshwater fishes in North America and is the largest of the gar species. Young gars have an adhesive disc on the underside of the snout that they use to attach to objects on the bottom until the yolk sac is absorbed. Young gars also have a dorsal caudal filament at the posterior end of the upturned vertebral column, which atrophies and disappears in adults.

THE LARGEST SPECIMEN RECORDED WEIGHED 350 lbs.

    Gars are slow growing fish, with female alligator gars reaching sexual maturity around age 11 and living to age 50. Male alligator gars mature around age 6 and live at least 26 years. Alligator gars commonly grow to a size of 6 1/2ft (2 m) and over 100 lbs. (45kg). But have been reported to grow up to 350 lbs and around 10 ft (3m) in length. The largest recorded alligator gar comes from the St. Francis River, Arkansas in the 1930's, and weighed 350 lbs (159 kg).

    Food Habits Alligator gars appear sluggish, however they are voracious predators. Gars are ambush predators, primarily piscivores, they lay still in the water until an unsuspecting fish swims by, and then lunging forward and lashing the head from side to side in order to capture prey. Many times gars will lie still at the top of the water for long periods of time, appearing to be merely a log.

Texto: Nathaniel Goddard y M. Montoya