User:Chrisf1020/sandbox/Agkistrodon

Not to be confused with the proterosuchid archosauriform Ankistrodon.

Agkistrodon
Copperhead, A. contortrix
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Suborder:	Serpentes
Family:	Viperidae
Subfamily:	Crotalinae
Genus:	Agkistrodon Palisot de Beauvois, 1799
Synonyms
Agkistrodon Palisot de Beauvois, 1799 Agkishodon Palisot de Beauvois, 1799 Scytale Latreille In Sonnini & Latreille, 1801 Cenchris Daudin, 1803 Cenchrus Link, 1807 Scytalus Fischer, 1813 Tisiphone Fitzinger, 1826 Ancistrodon Wagler, 1830 Acontias Troost, 1836 Toxicophis Troost, 1836

Agkistrodon is a genus of venomous pit vipers found in North America from the United States south to northern Costa Rica. Eight species are currently recognized, all of them monotypic and closely related. Common names include: cottonmouths, copperheads, cantils, and moccasins.

Name origin

The name Agkistrodon comes from the Greek words agkistron (ἄγκιστρον, 'fishhook', with the irregular transliteration gk rather than the usual nk) and odous (ὁδοὐς, 'tooth,' from the stem ὁδόντ-) and is likely a reference to the fangs.

Some varieties of the genus are given the common name "moccasin" or "moccasin snake" in the United States, which is the Algonquian word for "shoe". The origin of this nickname is unknown. The first known use of "moccasin" to refer to a deadly venomous snake was in a 1765 publication. The nickname is used to refer to both cottonmouths and copperheads. According to the Word Detective, this use may be related to their color and appearance or the silence with which they move. Another source for this name may be the Native American word "mokesoji" of unknown origin and meaning.

Description

Members of this genus have a number of features in common. All species have a relatively broad head with short fangs. A loreal scale is present, except in A. piscivorus. Usually, nine large symmetrical platelike scales are on the crown of the head, but in all species, these are often irregularly fragmented or have sutures, especially in A. bilineatus. All have a sharply defined canthus rostralis and a vertically elliptical pupil. Usually eight (6-10) supralabial scales and usually 10-11 (8-13) sublabials are present. The dorsal scales are mostly keeled and at midbody number 21-25 (usually 23), while A. piscivorus has 23-27 (usually 25). The snake has 127-157 ventral scales and 36-71 subcaudals. Of the latter, some may be divided. The anal scale is single. All have a color pattern of 10-20 dark crossbands on a lighter ground color, although sometimes the crossbands are staggered as half bands on either side of the body.

Geographic range

They are found in North America from the northeastern and central United States southward through peninsular Florida and southwestern Texas, and in Central America on the Atlantic versant from Tamaulipas and Nuevo León southward to the Yucatan Peninsula, Belize, and Guatemala. They are seen along the Pacific coastal plain and lower foothills from Sonora south through Guatemala, El Salvador, Honduras, and Nicaragua to northwestern Costa Rica.

Behavior

All are semiaquatic to terrestrial and are often found near sources of water. However, A. contortrix and A. bilineatus are also found in dry habitats, often far from permanent streams or ponds.

Reproduction

The members of this genus are all ovoviviparous.

Venom

Pit vipers of the genus Agkistrodon rely on a potent venom they produce for their survival. Used to immobilize prey and fend off predators, one bite can inject enough venom into a human to cause severe pain, swelling, weakness, difficulty breathing, hemorrhaging, gangrene, fever, vomiting, and in rare instances, even death.

The venom of all three species is assumed to be not unlike that of A. contortrix, which contains thrombin-like enzymes that act upon the coagulant activity of the blood. A study of electrophoretic patterns of proteins in venoms among and within populations of A. contortrix and A. piscivorus showed that substantial variation exists, and no reason exists to believe that these differences do not correspond with variations in toxicity.

Research

In a study conducted at the College of Medicine at the University of Florida, venom from A. piscivorous was injected into the lymph fluid of a frog. The frog immediately suffocated because of the collapse of its lung sacs. The venom even resulted in lung constriction when directly applied to the surface of the frog's lungs. To test this, trace amounts of venom were dropped onto a single pulmonary sac in a frog's lung after it was anesthetized and its chest cavity dissected open. A drop of solution containing a venom concentration of 1 mg/ml was enough to cause contraction of the pulmonary artery adventitia after 5-8 sec in a frog weighing 40 g. The study found, however, that this toxic effect is simply a tool the snake can choose to employ from an accessory venom gland it has. In most instances, the viper injects a venom that tends to immobilize, not kill, its prey before ingestion. In this case, the main venom glands secrete a toxin that inhibits the prey’s sympathetic response to flee or fend off its predator. This essentially stuns the animal so that the predator can easily attack.

Species

Image	Species	Taxon author	Subsp.	Common name	Geographic range
	A. bilineatus	(Günther, 1863)	0	cantil Mexican cantil Mexican ground pit viper Mexican yellow-lipped viper cantil viper Mexican moccasin black moccasin neotropical moccasin	Mexico and Central America. It is found from southern Sonora in Mexico south through Guatemala, El Salvador, and Honduras.
	A. conanti	Conant, 1984	0	Gloyd's cantil Gloyd's moccasin southern cantil	Northwestern Costa Rica, western Nicaragua, southern Honduras.
	A. contortrixT	(Linnaeus, 1766)	0	copperhead	The United States (Texas, Oklahoma, Kansas, Missouri, Arkansas, Louisiana, Mississippi, Alabama, Georgia, Florida, South Carolina, North Carolina, Tennessee, Kentucky, Virginia, West Virginia, Illinois, Indiana, Ohio, Iowa, Pennsylvania, Maryland, New Jersey, Delaware, New York, Connecticut, Massachusetts), Mexico (Chihuahua, Coahuila).
	A. howardgloydi	Conant, 1984	0	Gloyd's cantil Gloyd's moccasin southern cantil	Northwestern Costa Rica, western Nicaragua, southern Honduras.
	A. laticinctus	Conant, 1984	0	Gloyd's cantil Gloyd's moccasin southern cantil	Northwestern Costa Rica, western Nicaragua, southern Honduras.
	A. piscivorus	(Lacépède, 1789)	0	cottonmouth water moccasin worm-tailed pit viper	The eastern United States from extreme southeastern Virginia, south through peninsular Florida and west to Arkansas, southeastern Kansas, eastern and southern Oklahoma and eastern and central Texas. A few records exist from along the Rio Grande in Texas, but these are thought to represent isolated populations that possibly no longer exist.
	A. russeolus	Gloyd, 1972	0	Yucatecan cantil	Mexico, northern Guatemala, northern Belize.
	A. taylori	Burger & Robertson, 1951	0	Taylor's cantil ornate cantil	Mexico.

Taxonomy

The phylogeny of the species in this genus has long been controversial. Studies based on morphological and venom characteristics support the idea that the A. bilineatus species complex (including former subspecies A. howardgloydi, A. russeolus, and A. taylori) and A. contortrix species complex (including former subspecies A. laticinctus) are more closely related. However, an analysis of mitochondrial DNA, as well as more recent molecular studies, have concluded that the A. bilineatus species complex and the A. piscivorus species complex (including A. conanti) are sister taxa, with A. contortrix being a sister species to them both.

This genus was previously much larger and also included the following genera:

• Calloselasma - Ground pit viper found in Southeast Asia (Malaya).
• Deinagkistrodon - The Hundred-pace viper found mostly in southern China.
• Gloydius - Ground pit vipers found in Asia.
• Hypnale - Hump-nosed vipers found in India and Sri Lanka.