Agkistrodon

Agkistrodon is a genus of pit vipers found in Americas from the United States south to northern Costa Rica.[1] Eight species are currently recognized,[2][3] all of them monotypic and closely related.[4] Like all pit vipers, it is venomous. Common names include: cottonmouths, copperheads, and cantils.[5] Some varieties are known as "moccasins" or "moccasin snakes", such as Agkistrodon piscivorus, the water moccasin.

Not to be confused with the proterosuchid archosauriform Ankistrodon.

Agkistrodon
Copperhead, A. contortrix
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Viperidae
Subfamily: Crotalinae
Genus: Agkistrodon
Palisot de Beauvois, 1799
Synonyms

Name origin

The name Agkistrodon comes from the Greek words ankistron (ἄγκιστρον, 'fishhook', with the irregular transliteration gk rather than the usual nk) and odon (ὀδών)[6] 'tooth'[7] and is likely a reference to the fangs.[5]

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.[8] Another source for this name may be the Native American word "mokesoji" of unknown origin and meaning.[9]

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.[5]

The phylogeny of the three species has long been controversial. Studies based on morphological[4] and venom characteristics[10] support the idea that A. bilineatus and A. contortrix are more closely related. However, an analysis of mitochondrial DNA,[11] as well as more recent molecular studies,[12][13] have concluded that A. bilineatus and A. piscivorus are sister taxa, with A. contortrix being a sister species to them both.[5]

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.[1]

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.[5]

Reproduction

The members of this genus are all ovoviviparous.[5]

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.[14]

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,[10] and no reason exists to believe that these differences do not correspond with variations in toxicity.[5]

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.[15] 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.[15]

Species
Image Species[16] Taxon author[16] Subsp.*[16] Common name Geographic range[1][4][5][17]
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. contortrixT (Linnaeus, 1766) 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 (Gloyd & Conant, 1934) Broad-banded copperhead

Texas copperhead

 Eastern Kansas, southward through central Oklahoma, central and Trans-Pecos Texas, and adjacent areas of northern Chihuahua and Coahuila, Mexico.
A. howardgloydi Conant, 1984 Gloyd's cantil

Gloyd's moccasin
southern cantil

 Northwestern Costa Rica, western Nicaragua, southern Honduras.
A. piscivorus (Lacépède, 1789) 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. conanti (Gloyd, 1969[18]) Florida cottonmouth

Green-tailed moccasin

 Southernmost Georgia through Florida.
A. russeolus Gloyd, 1972 Yucatecan cantil Yucatan, Mexico, northern Guatemala, northern Belize.
A. taylori Burger & Robertson, 1951 Taylor's cantil

ornate cantil

 Gulf Coast lowlands of northeast Mexico, primarily in central and southern Tamaulipas, neighboring areas of Nuevo Leon, and northern Veracruz, with a few records from adjacent areas of San Luis Potosi, and Hidalgo.

Not including the nominate subspecies. T Type species.[1]

Taxonomy

This genus was previously much larger and also included the following genera:[1]

References
  1. McDiarmid RW, Campbell JA, Touré T. 1999. Snake Species of the World: A Taxonomic and Geographic Reference, vol. 1. Herpetologists' League. 511 pp. ISBN 1-893777-00-6 (series). ISBN 1-893777-01-4 (volume).
  2. 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.
  3. 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. doi:10.1111/zoj.12211
  4. 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. ISBN 0-916984-20-6.
  5. Campbell JA, Lamar WW. 2004. The Venomous Reptiles of the Western Hemisphere. Comstock Publishing Associates, Ithaca and London. 870 pp. 1500 plates. ISBN 0-8014-4141-2.
  6. A variant form of odοus (ὀδούς)); stem: odont- (ὀδόντ-).
  7. ἄγκιστρον, ὀδών, ὀδούς. Liddell, Henry George; Scott, Robert; A Greek–English Lexicon at the Perseus Project.
  8. "Moccasin". The Word Detective. January 2014. Retrieved November 21, 2016.
  9. Catherine C. Hopley (1882). Snakes: curiosities and wonders of serpent life. London, Griffith & Farran; New York, E.P. Dutton & co. Besides that 'deadly moccasin' and frequent 'black snakes,' there were 'whip snakes,' 'milk snakes,' and many others which the negroes would bring home as trophies of their courageous slaughter; but by no scientific names were they known there. Except this name moccasin or mokesoji, which probably conveyed some especial meaning to the aborigines, few of the Indian vernaculars have been preserved in the United States, as we find them in other parts of America, which latter are treated of in chapters xxii. and xxiii. of this work ; but common English names prevail.
  10. Jones JM (1976). "Variation of venom proteins in Agkistrodon snakes from North America". Copeia. 1976 (3): 558–562. doi:10.2307/1443375. JSTOR 1443375.
  11. 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. ISBN 0-9630537-0-1
  12. Parkinson CL (1999). "Molecular systematics and biogeographical history of pitvipers as determined by mitochondrial ribosomal DNA sequences". Copeia. 1999 (3): 576–586. doi:10.2307/1447591. JSTOR 1447591.
  13. 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
  14. "Agkistrodon acutus pit vipers." Medical-Explorer.com; accessed April 2010.
  15. Gennaro JF, Hall HP, Casey ER, Hayes WK (September 2007). "Neurotropic effects of venoms and other factors that promote prey acquisition". Journal of Experimental Zoology Part A. 307 (9): 488–99. doi:10.1002/jez.405. PMID 17620305.
  16. "Agkistrodon". Integrated Taxonomic Information System. Retrieved 2 November 2006.
  17. Savage, JM. The Amphibians and Reptiles of Costa Rica. The University of Chicago Press, 2002, p. 719. ISBN 0-226-73537-0.
  18. McDiarmid RW, Campbell JA, Touré T (1999). Snake Species of the World: A Taxonomic and Geographic Reference, Volume 1. Washington, District of Columbia: Herpetologists' League. 511 pp. ISBN 1-893777-00-6 (series). ISBN 1-893777-01-4 (volume).

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 a discussion of the publication date, see Harper F (1940). American Midland Nataturalist 23: 693].
  • 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).
  • 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).
  • 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. ISBN 978-0-9754641-3-7.
  • Link HF (1807). Beschreibung der naturalien-sammlung der Universität zu Rostock. Zweite abtheilung, pp. 51–100. Rostock: Gebruckt bei Adlers Erben. (in German).
  • Palisot de Beauvois AMFJ (1799). "Memoir on Amphibia. Serpentes". Transactions of the American Philosophical Society. 4: 362–381. doi:10.2307/1005115. JSTOR 1005115.
  • Sonnini CS, Latreille PA (1801). Histoire naturelle des reptiles, avec figures dissinees dápres nature. 4 Vols. Paris: Deterville. (in French). [For a discussion of the publication date, see Harper F (1940). American Midland Naturalist 23: 692-723].
  • Troost G (1836). "On a new genus of serpents, and two new species of the genus Heterodon, inhabiting Tennessee". Ann. Lyc. Nat. Hist. New York. 3: 174–190.
  • 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).
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.