Triangular head adder
| Triangular head adder | ||||||||||||
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North American copper head ( Agkistrodon contortrix ) |
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| Agkistrodon | ||||||||||||
| Palisot de Beauvois , 1799 |
The triangular-headed caterpillars ( Agkistrodon ) are a species of snake from the subfamily of the pit vipers (Crotalinae) distributed in North and Central America with four species . They are also known in German as moccasin otters or moccasin snakes .
description
Triangular-headed snakes are stocky and well-built, medium-sized to large snakes. The body length of the smallest species, the North American copper head, is 50 to 95 cm, a maximum of 135 cm; in the largest species, the water moccasin otter at 75 to 155 cm, maximum 185 cm. As far as is known, males of all species are on average significantly larger and heavier than females.
The head is relatively broad, and the poisonous teeth that are present in all pit otters are relatively short. The upper side of the snake is cross-banded or, especially with the water moccasin otter, more or less monochrome. They have a lacunolabiale (dimple lip), the top of the head usually has nine large signs, sometimes also a few smaller scales. The dorsal scales are arranged in the middle in 23, only in A. piscivorus in 25 longitudinal rows. In all species, the tail end of the young is light yellow to green.
distribution and habitat
The four types of triangular-headed admirers inhabit North and Central America . Two species ( Agkistrodon contortrix and A. piscivorus ) inhabit the temperate and subtropical zones in eastern and southern North America, the other two species ( A. bilineatus and A. taylori ) live in the tropical regions of Mexico and Central America. They are ground-dwelling (terrestrial) to semi-aquatic and mainly occur in forests. All species show a certain attachment to stagnant water and like to swim, although three of the four species can also be found in dry habitats far away from such water.
Way of life
nutrition
Like all pit otters , the triangular-headed adder has special pit organs on the sides of the head between the nostril and eyes, with which they perceive thermal radiation ( infrared radiation ) so that they can also hunt at night. Foraging for food is also done visually and with the sense of smell. Small mammals and other terrestrial vertebrates are bitten at lightning speed and immediately released. If they do not succumb to the poison immediately, the snake follows the scent of the prey that has fled until it has found it.
Unusual hunting behavior can be observed in young animals of all four species: they move their bright tails back and forth as bait to lure prey close to them. With age, the behavior fades, as does the light color of the tail.
The food spectrum of all species seems to be very broad and includes practically all small vertebrates of the respective habitat, including amphibians , small turtles , young alligators , lizards , snakes , birds and small mammals . The water moccasin otter also often eats fish, which is rarely the case with the other species. It is also apparently the only species in the genus that regularly eats carrion (small vertebrate animals). Young animals of all species in particular also eat invertebrates ; spiders , cicadas , grasshoppers , dragonflies , caterpillars and land snails have been identified .
Reproduction
Triangular-headed cubs are sexually mature at two to three years of age. They are viviparous ( ovoviviparous ) and have 2 to 20, usually between 5 and 12, relatively large young. The two more northerly widespread species ( A. contortrix and A. piscivorus ) mate in autumn, or in spring immediately after leaving their winter quarters; the cubs are born between August and early October. The two more southerly species ( A. bilineatus and A. taylori ) have less limited breeding times. The mating takes place from November to April, the young are born in the rainy season from May to September.
Life expectancy
There is no information on the average and maximum age of free-living individuals of any kind. The maximum ages reached in captivity were 29 years and 10 months for A. contortrix , 24 years and 6 months for A. piscivorus , at least 24 years for A. bilineatus , and A taylori 15 years and 7 months.
Systematics
Fossil lore
The earliest finds of fossil snakes that can be assigned to the genus Agkistrodon come from the late Miocene (10–12 million years ago) in America.
External system
Which species belong to the genus Agkistrodon has long been disputed. Until the beginning of the 1990s, depending on the author, a number of Asian and European species were added to this genus, combined in a taxon "Agkistrodontini" or referred to as the "Agkistrodon complex". The great difficulties in the systematic classification of the species were probably essentially due to the lack of differentiation between original ( symplesiomorphic ) and derived ( apomorphic ) morphological features in this evolutionarily relatively original snake group.
Molecular genetic studies of the mitochondrial DNA have since proven the common ancestry ( monophyly ) of the American representatives of the genus. Furthermore, it was found that these are much more closely related to the rattlesnakes (genera Crotalus and Sistrurus ) than to the Eurasian species that were previously assigned to Agkistrodon . These Eurasian species have since been included under the previously proposed genus Gloydius ( Halysotters ); the genus Agkistrodon therefore only includes the four American species. The taxon "Agkistrodontini" was rejected as obviously paraphyletic .
Internal system
The genus Agkistrodon today consists of four species:
- North American copper head ( A. contortrix )
- Water moccasin otter ( A. piscivorus )
- Mexican moccasin viper ( A. bilineatus )
- Agkistrodon taylori
Agkistrodon taylori was only granted species status in 2000; it was previously considered a subspecies of the Mexican moccasin viper ( A. bilineatus ). The copper head ( A. contortrix ) is the earliest branch of a common ancestor ; A. piscivorus and A. bilineatus / A. taylori form sister taxa.
| Triangular head adder |
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Origin of name
The generic name is composed of the Greek words άγκιστρον agkistron = "hook, fishhook" and όδών odon = "tooth, incisor". Literally translated, “Agkistrodon” (pronounced [ aŋˈkɪstrodɔn ]) means something like “ hook tooth ”, which obviously refers to the poisonous teeth. There has been some confusion and scientific controversy over the spelling of the name. The reason for this was a typographical error in the original description by Palisot de Beauvois , followed by an error in the transmission by later authors. In the original description, the misspelled name "Agkishodon" can be found in a footnote; in the further text, however, it is clear that the author wanted to name the genus "Agkistrodon". In the following period it was pointed out several times that if the Latinization of the Greek words were correct, the spelling “Ancistrodon” would be preferred; however, a corresponding application to the International Commission on Zoological Nomenclature (ICZN) to change the name was rejected.
Behavior towards people
The two northern species A. contortrix and A. piscivorus are not very aggressive and try to avoid humans. They often fail to bite even when provoked or cornered. A. bilineatus and A. taylori are considered to be significantly more excitable and more aggressive.
Poisonous effect
The toxin mixtures of pit vipers are by far komplexesten natural poisons. They contain a mixture of enzymes , low molecular weight polypeptides , metal ions and other components whose function has so far hardly been understood. The effects of these poisons are correspondingly diverse.
The poison of the triangular head adder has a strong protein-degrading effect and therefore leads to the destruction of tissue . It causes severe pain, redness, swelling, and necrosis around the bite site. The poison has a hemolytic and anticoagulant effect ; in severe cases it can stop the blood from clotting completely. It also causes the release of the peptide bradykinin , which among other things causes a drop in blood pressure, nausea, nausea, diarrhea and an increase in pain. It also contains the enzyme phospholipase A 2 , which has a toxic effect on muscle fibers.
There is no systematic record, but it is estimated that around 8,000 people are bitten by poisonous snakes each year in the USA. About 20% of the bites, i.e. around 1600, are caused by copper heads, another 9% (i.e. around 700) by water moccasin otters. With improved medical treatment, copperhead deaths are now rare exceptions; The number of deaths from water moccasin otters is also estimated to average less than one per year.
In the two southern, more aggressive species ( A. bilineatus and A. taylori ) the poisonous effect is apparently considerably stronger. They are therefore considered to be significantly more dangerous and caused a number of deaths at least until the mid-1980s; There are no reliable current figures on the annual number of bites or deaths. If antiserum is given in good time , deaths can be avoided. However, the tissue damage is irreversible and often associated with a permanent loss of function of the affected limb. Since A. bilineatus is endangered today and the area of A. taylori is very small, both species probably only play a subordinate role in Central America in poisoning by snakes.
Overall, the toxic effects and the number of deaths are significantly lower than with rattlesnakes or American lanceolers in the same area of distribution. Like other pit vipers, triangular-headed adlers do not necessarily inject venom into the wound with every bite, but every bite event should be taken seriously and medical help sought, even if there is no immediate toxic effect.
swell
Individual evidence
- ↑ Christopher L. Parkinson, Scott M. Moody, Jon E. Ahlquist: Phylogenetic relationships of the 'Agkistrodon complex' based on mitochondrial DNA sequence data. Symp zool. Soc. London 70, 1997; Pp. 63-78
- ↑ Christopher L. Parkinson, Kelly R. Zamudio and Harry W. Greene: Phylogeography of the pitocket clade Agkistrodon: historical ecology, species status, and conservation of cantils . Molecular Ecology 9, 2000: pp. 411-420
- ↑ For photos of the effects of A. piscivorus bites see http://www.gifte.de/Gifttiere/agkistrodon_piscivorus_biss01.htm
- ^ Robert Norris: Venom Poisoning by North American Reptiles . In: Jonathan A. Campbell and William W. Lamar: The Venomous Reptiles of the Northern Hemisphere . Comstock; Ithaca, London. 2004: p. 692
- ^ Robert Norris: Venom Poisoning by North American Reptils . In: Jonathan A. Campbell and William W. Lamar: The Venomous Reptiles of the Northern Hemisphere . Comstock; Ithaca, London. 2004: pp. 705-706
literature
- Jonathan A. Campbell, William W. Lamar: The Venomous Reptiles of the Western Hemisphere. Comstock; Ithaca, London. 2004. ISBN 0-8014-4141-2
- Ronald L. Gutberlet and Michael B. Harvey: The Evolution of New World Venomous Snakes . In: Jonathan A. Campbell, William W. Lamar: The Venomous Reptiles of the Western Hemisphere. Comstock; Ithaca, London. 2004. ISBN 0-8014-4141-2 : pp. 634-682.
