Lepisosteus (from Greek lepis, 'scale' and osteos, 'bone')[1] is a genus of gars in the family Lepisosteidae. It contains four extant species, found throughout eastern and central North America. It is one of two extant gar genera alongside Atractosteus.
Lepisosteus is known to be a freshwater fish. However, they do have the ability to survive in high salinity, and low oxygen water after gulping air.[2] Lepisosteus prefers to reside in brackish and shallow slow-moving waters, living usually in schools. The habitat range of this genus ranges on the Eastern coast from the Gulf of Mexico in Florida north to Quebec. Habitats can be found in the Missouri River Basin and Mississippi River drainage area, westward in the Rio Grande River basin of Southern Texas and Northern Mexico. There are also populations in the Great Lakes except for Lake Superior. Their range can occasionally reach out towards the Mobile Bay, Perdido Bay, and Mississippi Sound.
Lepisosteus appears to have a wider distribution in the past, as the extinct species L. bemisi inhabited intermountain lakes in the Green River Formation of what is now Wyoming, significantly west of the genus's modern range. The oldest record of the genus, a well-preserved skull from the Campanian, is known from the Oldman Formation of Canada. Even more removed from the genus's present distribution was L. indicus from the Maastrichtian-aged Lameta Formation and Intertrappean Beds of India. This species' inclusion in Lepisosteus is uncertain, as it was classified based on characteristics of the skull that were later found to be shared among many different gar taxa. However, phylogenies include it as more closely related to Lepisosteus than to Atractosteus or fossil gars.[3] [4] [5] Indeterminate gar remains, most likely of Lepisosteus, from the Palana Formation of India suggest that the genus may have persisted in India up to the Late Paleocene.[6]
These fish have ganoid scales on their elongated bodies with a single dorsal fin on the posterior side approximately one inch from their caudal fin.[7] Depending on the clarity of the water, Lepisosteus colors will change. In clear water they can have bright colors of green and silvery-white; alternatively if the water is brackish and cloudy, their colors will be more of a brown hue.[8] Hatchlings are approximately 8–10 mm in size. The average full-grown length of Lepisosteus varies from 34 to 78 inches depending on the species. In comparison to their long snouts, Lepisosteus have relatively small heads; however, their mouths full of sharp teeth.
Lepisosteus is a slow-growing genus generally living a long time. Female gars take 6 years to reach sexual maturity, grow larger, and live up to 22 years. Male gars reach maturity around 3 or 4 years after hatching. The males do not often live longer than 11 years.[9] The longnose gar will migrate upstream to smaller streams with faster-moving water to spawn and lay eggs. Fish of this genus that are newly hatched will attach themselves vertically to submerged objects by an adhesive disc on their snout. The youth stay attached to the objects until the yolk sac is absorbed which usually takes about 9 days. After the yolk sac of an egg is absorbed, the roe hatches. Hatchlings stabilize to a horizontal position, take their first aerial breath, and begin feeding.
Because Lepisosteus has evolved to be a top predator, they are voracious eaters that eat a variety of other freshwater fish and crustaceans such as Ictiobus and blue crabs. Adults will float toward the surface of streams to scout prey that are below them while younger fish in this genus will hide in submersed vegetation to ambush hunt.[10] Studies have found this native North American species is a predator of invasive Asian carp, whose habitat they share.[11] This genus is not generally used for recreational hunting because their roe is toxic to humans. There are no significant threats to these top predators other than habitat loss.[12] On the IUCN Red List of Threatened Species, this genus is listed as Least Concern.[13]
Phylogenetic evidence suggests that Lepisosteus is ancient genus that diverged from its only extant relative, Atractosteus, during the Early Cretaceous. As with Atractosteus, fossil evidence suggests that the ancestral range of the genus was likely centered around western North America during the Cretaceous and early Paleogene, until major climatic changes led to a shift in range to eastern North America by the late Paleogene.
The currently recognized species are: Lepisosteus oculatus, Lepisosteus osseus, Lepisosteus platostomus, and Lepisosteus platyrhincus. Three species formerly classified in Lepisosteus (tropical gar, Cuban gar, and alligator gar) are now assigned to the genus Atractosteus.
| Image | Scientific name | Common name | Distribution |
|---|---|---|---|
| Lepisosteus oculatus Winchell, 1864 | Spotted gar | North America | |
| Lepisosteus osseus Linnaeus, 1758 | Longnose gar | east coast of North and Central America in freshwater lakes and as far west as Kansas and Texas and southern New Mexico | |
| Lepisosteus platostomus Rafinesque, 1820 | Shortnose gar | Montana to the west and the Ohio River to the east, southwards to the Gulf Coast. | |
| Lepisosteus platyrhincus DeKay, 1842 | Florida gar | USA from the Savannah River and Ochlockonee River watersheds of Georgia and throughout peninsular Florida | |
According to Grande, 2010. In addition, an indeterminate record (known as "Lepisosteus sp. A") is known from Campanian-aged Oldman Formation of Canada, and represents the oldest record of the genus.[14]