Agkistrodon is a genus of commonly known as American moccasins.[Crother, B. I. (ed.). 2017. Scientific and Standard English Names of Amphibians and Reptiles of North America North of Mexico, with Comments Regarding Confidence in Our Understanding. SSAR Herpetological Circular 43, 1–102 pp. (page 59)][Liner, E. A. and G. Casas-Andreu. 2008. Standard Spanish, English and scientific names of the amphibians and reptiles of Mexico. Society for the Study Amphibians and Reptiles. Herpetological Circular 38: i-iv, 1-162. (pages 95-96)] The genus is endemic to North America, ranging from the Southern United States to northern Costa Rica.[Porras, Louis W., Larry David Wilson, Gordon W. Schuett, and Randall S. Reiserer 2013. A taxonomic reevaluation and conservation assessment of the common cantil, Agkistrodon bilineatus (Squamata: Viperidae): a race against time. Amphibian & Reptile Conservation 7(1): 48–73.][Frank T. Burbrink, Timothy J. Guiher (2014). Considering gene flow when using coalescent methods to delimit lineages of North American pitvipers of the genus Agkistrodon. Zoological Journal of the Linnean Society, December 2014. ] all of them Monotypic taxon and closely related.[Gloyd HK, Conant R. 1990. Snakes of the Agkistrodon Complex: A Monographic Review. Society for the Study of Amphibians and Reptiles. 614 pp. 52 plates. LCCN 89-50342. .] Common names include: cottonmouths, copperheads, and cantils.[Campbell JA, Lamar WW. 2004. The Venomous Reptiles of the Western Hemisphere. Comstock Publishing Associates, Ithaca and London. 870 pp. 1500 plates. .]
Name origin
The name
Agkistrodon comes from the
Greek language words ankistron (ἄγκιστρον, 'fishhook', with the irregular transliteration
gk rather than the usual
nk) and odon (ὀδών)
[A variant form of odous (ὀδούς)); stem: odont- (ὀδόντ-).] 'tooth'
[, , .] 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 "moccasin". 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.
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.
The Phylogenetics of the species has long been controversial. Studies based on morphological[Knight A, Densmore III LD, Real ED (1992). "Molecular systematics of the Agkistrodon complex". pp. 49-70. In : Campbell JA, Brodie Jr ED (1992). Biology of the Pitvipers . Texas: Selva. 467 pp. 17 plates. ] as well as more recent molecular studies,[Parkinson CL, Moody SM, Ahlquist JE (1997). "Phylogenetic relationships of the "Agkistrodon complex" based on mitochondrial DNS data". pp. 63-78. In: Thorpe RS, Wüster W, Malhotra A (1997). Venomous Snakes: Ecology, Evolution, and Snakebite. Oxford: Clarendon Press] have concluded that A. bilineatus and A. piscivorus are sister taxa, with A. contortrix being a sister species to them both.
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
Ovoviviparity.
A 2012 study found that they are not only capable of parthenogenesis (asexual reproduction), but that litters created without a male may account for up to 5% of litters in the wild, even in areas that have males present. This phenomenon had previously only been observed in captive populations. [1]
Venom
Pit vipers of the genus
Agkistrodon rely on a potent
venom they produce for their survival. Used to immobilize
prey and fend off
Predation, 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.
["Agkistrodon acutus pit vipers." Medical-Explorer.com; accessed April 2010. [2]]
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 Electrophoresis 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.
Species
|
| | A. bilineatus
(Günther 1863)[Günther. A. 1863. Third account of new species of snakes in the collection of the British Museum. Ann. Mag. Nat. Hist. (3) 12: 348 - 365] | Cantil
| Mexico and Central America, from southern Sonora, Mexico south to Guatemala, El Salvador, and Honduras. |
| | A. contortrixT
(Linnaeus 1766)[Linné, C. von = 1766. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio duodecima, reformata. Laurentii Salvii, Stockholm, Holmiae. 1-532 pp.] | Eastern copperhead | The United States (East Texas, Oklahoma, and Kansas, eastward to the Atlantic coast, including Missouri, Arkansas, Louisiana, Mississippi, Alabama, Georgia, northern Florida, South Carolina, North Carolina, Tennessee, Kentucky, Virginia, West Virginia, Illinois, Indiana, Ohio, Iowa, Pennsylvania, Maryland, New Jersey, Delaware, New York, Connecticut, Massachusetts). |
| | A. laticinctus
Howard Gloyd & Conant, 1934[Gloyd H. and Conant R. 1934. The broad-banded copperhead: a new spubspecies of Agkistrodon mokasen. Occasional Papers of the Museum of Zoology University of Michigan, No. 283, p. 2] | Broad-banded copperhead | Eastern Kansas, central Oklahoma, central and Trans-Pecos Texas, and adjacent areas of northern Chihuahua and Coahuila, Mexico. |
| | A. howardgloydi
Conant 1984[Conant, R. 1984. A new subspecies of the pit viper Agkistrodon bilineatus (Reptilia: Viperidae) from Central America. Proc. Biol. Soc. Washington 97: 135-141] | Gloyd's moccasin | Northwestern Costa Rica, western Nicaragua, southern Honduras. |
| | A. piscivorus
(Lacépède 1798)[Lacepède, B. G. E. 1789. Histoire Naturelle des Quadrupèdes Ovipares et de Serpens. Vol.2. lmprimerie du Roi, Hôtel de Thou, Paris, 671 pp.] | Northern cottonmouth | 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. conanti
Howard Gloyd 1969[Gloyd, H. K. 1969. Two additional subspecies of North American crotalid snakes, genus Agkistrodon. Proc. Biol. Soc. Washington 82: 219-232] | Florida cottonmouth | Southernmost Georgia through Florida. |
| | A. russeolus
Howard Gloyd, 1972[Gloyd, H. K. 1972. A subspecies of Agkistrodon bilineatus (Serpentes: Crotalidae) on the Yucatán Peninsula, México. Proc. Biol. Soc. Washington 84: 327-334.] | Yucatecan cantil | Yucatan, Mexico, northern Guatemala, northern Belize. |
| | A. taylori
Burger & Robertson, 1951[Burger, W.L. & Robertson,W.B. 1951. A new subspecies of the Mexican moccasin, Agkistrodon bilineatus. Univ. Kansas Sci. Bull. 34 (5): 213-218] | Taylor's cantil | Gulf Coast lowlands of northeast Mexico, primarily southern Tamaulipas, with a few records from adjacent areas of Nuevo Leon, San Luis Potosi, Veracruz, and Hidalgo. |
T Type species.
Taxonomy
This genus was previously much larger and also included the following genera:
Further reading
-
Daudin FM (1801-1803). Histoire naturelle, générale et particulière des reptiles: ouvrage faisant suit à l'histoire naturelle générale et particulière, composée par Leclerc de Buffon; et rédigée par C.S. Sonnini, miembre de plusieurs sociétés savantes. 8 vols. Paris: F. Dufart. (in French). For.
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Fischer JG (1813). Zoognosia tabulis synopticus illustrata, in usum praelectionum Academiae Imperialis medico-chirurgicae Mosquensis edita. 3d ed. vol. 1, pt. 3 (Reptiles, Poissons): 57–117. Moscow: Nicolai Sergeidis Vsevolozsky. (in Latin).
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Fitzinger LJ (1826). Neue Classification der Reptilien nach ihren natürlichen Verwandtschaften: nebst einer Verwandtschafts-Tafel und einem Verzeichnisse der Reptilien-Sammlung des K. K. Zoologischen Museums zu Wien. Vienna: J.G. Heubner. five unnumbered + 67 pp. + one plate. (in German and Latin).
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Hubbs B, O'Connor B (2012). A Guide to the Rattlesnakes and other Venomous Serpents of the United States. Tempe, Arizona: Tricolor Books. 129 pp. .
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Link HF (1807). Beschreibung der naturalien-sammlung der Universität zu Rostock. Zweite abtheilung, pp. 51–100. Rostock: Gebruckt bei Adlers Erben. (in German).
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Sonnini CS, Latreille PA (1801). Histoire naturelle des reptiles, avec figures dissinees dápres nature. 4 Vols. Paris: Deterville. (in French). For.
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Wagler JG (1830). Natürliches System der Amphibien, mit vorangehender Classification der Säugthiere und Vögel. Ein Beitrag zur vergleichenden Zoologie. Munich, Stuttgart and Tübingen: J.G. Cotta. vi + 354 pp. + one plate. (in German and Latin).
External links
