Pit vipers
| Pit vipers | ||||||||||||
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Texas rattlesnake ( Crotalus atrox ), portrait with clearly visible pit organ between eye and nostril. |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Crotalinae | ||||||||||||
| Oppel , 1811 |
The pit vipers (Crotalinae) are a subfamily of vipers (Viperidae) in the subordination of the snakes (Serpentes). The German name refers to all species of the subfamily existing paired heat-sensitive pit organs on the front upper jaw, give the snakes a three-dimensional thermal image . This allows them to see warm-blooded prey even in the dark. Pit vipers are common in Eurasia and America.
features
Most pit vipers are strongly built. The largest pit vipers are the South American bushmasters ( Lachesis ), which can reach a total length of up to 3.0 m; however, most species remain well below 2.0 m in total length.
Pit vipers, like all vipers, have relatively long and erect poisonous fangs. Most pit vipers, unlike the other vipers, have a specialized muscle , the "Muscularis pterygoides glandulae", between a skull bone (the "ectopterygoid") and the venom glands. The contraction of this and another muscle pushes the poison out of the poison glands.
A common feature of all pit vipers are the paired pit organs that give them their name and are located in the loreal area on the front upper jaw between the nostrils and eyes. These are pit-like depressions that are divided into two floors by a membrane that is about 15 micrometers thick and has a very good blood supply. Numerous very fine ends of the trigeminal nerve serve as heat receptors in the membrane . These receptors are sensitive in the infrared range at wavelengths from about 1 and 3 micrometers to about 1 mm. They measure temperature changes; a temperature increase of only 0.003 ° C is sufficient for an excitation. The pit organs give the snake a three-dimensional thermal image of the environment so that it can perceive warm-blooded prey even in the dark.
Some species have horn-like or prickly scales above the eyes. The function of these scales is unclear, but a camouflage function through optical resolution of the eye area or protection of the eye when moving underground or through thick vegetation is suspected.
distribution
Pit vipers are common in Eurasia and America, but only one species occurs in Europe. In Asia, the distribution area of the Crotalinae extends from the north and east of the Caspian Sea and the Transcaucasus to the east to the Pacific and Japan and to the south-east to the Philippines . The distribution area of the Halysotter ( Gloydius halys ) extends from the Ural River to the middle reaches of the Huang Ho in China and thus also includes the far east of Europe.
Pit otters are also common in North and South America, where they are the only representatives of the vipers. The strongest adaptive radiations were found within the rattlesnakes in the USA and Mexico, the palm lance vipers in Central America, the American lance vipers in South America and within the bamboo vipers ( Trimeresurus ) in South Asia.
Genera and species (selection)
The generic list presented here essentially follows Campbell and Lamar as well as the Reptile Database , which has 216 species in the subfamily of pit vipers.
In 2004, based on a molecular genetic and morphological investigation, the division of the genus Trimeresurus into seven genera ( Trimeresurus , Parias , Cryptelytrops , Peltopelor , Viridovipera , Popeia , Himalayophis and Garthius) was proposed. David et al. however, do not follow this breakdown in a 2011 study. According to Orlov, the former genera Ermia and Triceratolepidophis are synonymous with Protobothrops . The exact systematics of pit vipers is still the subject of current research.
- Triangular-headed adder ( Agkistrodon )
- Leaping Lance Vipers ( Atropoides )
- Palm lance vipers ( bothriechis )
- Wood lance vipers ( Bothriopsis )
- Bothrocophias
- American lance vipers ( Bothrops )
- Malay moccasin viper ( Calloselasma )
- Mountain pit vipers ( Cerrophidion )
- Rattlesnakes ( Crotalus )
- Chinese nosed viper ( Deinagkistrodon )
- Garthius
- Halysother ( Gloydius )
-
Ceylon nasal vipers ( Hypnale )
- Indian nasal viper (
- Three-horned pit viper ( Protobothrops sieversorum )
- Wagler's lance viper ( Tropidolaemus wagleri )
Way of life
Some species are aquatic and a number of species and genera are arboreal, but the vast majority of pit vipers are ground-dwelling.
The food consists mainly of terrestrial vertebrates, as with other vipers, whereby in many genera a change in prey can be observed in the course of growth. While young animals predominantly prey on reptiles, amphibians and invertebrates , the proportion of warm-blooded vertebrates such as birds and especially mammals increases with age. The behavior when catching prey varies depending on the species and genus and is usually very constant within the individual taxa . The species of the genera Atropoides , Bothriechis and Lachesis hold rodents after being bitten . Large individuals of the genera Crotalus and Bothrops , on the other hand, immediately release the prey after the bite and then follow the trail of the bitten animal. Some species hold onto frogs or lizards after being bitten, but immediately release mammals. In other species, this change is age-dependent: young animals hold onto the bitten amphibians and reptiles, while adults let go of mammals after the bite.
As with many other groups of snakes, there are comment fights between males for females with pit otters . The vast majority of genera and species is viviparous ( viviparous ), in America only the Bushmaster are oviparous. The females of many species apparently look after or guard their young for a few days after birth.
Poison
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. A distinction is made between local and the whole body ( systemic ) symptoms.
Local effects
Typical local symptoms are especially severe pain, redness and swelling, which extend to the entire bitten limb and the adjacent fuselage, as well as small or large bubbles that clear or blutig- serous contain liquid. Severe necrosis often occurs , particularly of the muscle tissue.
Systemic effects
The poison of numerous types has a hemolytic effect and, due to metalloproteinases, hemorrhagic effects (destroys blood vessels). Often the poison contains thrombin-like enzymes ( TLEs ), which cause a change in the blood coagulation precursor fibrinogen and thereby a pathological activation of blood clotting . This leads to the rapid consumption of the coagulation factors via further steps and therefore has an anticoagulant effect ( consumption coagulopathy ).
In addition, species are known whose poison secretions contain neurotoxic components. However, these are often of no clinical relevance. A representative with potent neurotoxins is, for example, Crotalus durissus terrificus , a subspecies of the shower rattlesnake . A presynaptic blockade of the transmission of stimuli leads to paralysis .
swell
Individual evidence
- ↑ H. Penzlin: Textbook of animal physiology. 3. Edition. Stuttgart, New York 1981, ISBN 3-437-20241-3 , pp. 394-395.
- ^ Crotalinae in The Reptile Database
- ↑ A. Malhotra and RS Thorpe: A phylogeny of four mitochondrial gene regions suggests a revised taxonomy for Asian pitvipers (Trimeresurus and Ovophis). Molecular Phylogenetics and Evolution 32, 2004: pp. 83-100
- ↑ Patrick David, Gernot Vogel, Alain Dubois: On the need to follow rigorously the Rules of the Code for the subsequent designation of a nucleospecies (type species) for a nominal genus which lacked one: the case of the nominal genus Trimeresurus Lacépède, 1804 (Reptilia: Squamata: Viperidae) . In: Zootaxa . tape 2992 , 2011, ISSN 1175-5326 , pp. 1-51 .
- ^ Protobothrops mangshanensis in The Reptile Database
- ^ Protobothrops sieversorum in The Reptile Database
- ↑ WCH Clinical Toxinology Resources, University of Adelaide: Crotalus durissus , accessed on 18 February 2017.
literature
- Jonathan A. Campbell, William W. Lamar: The Venomous Reptiles of the Western Hemisphere. Comstock; Ithaca, London 2004, ISBN 0-8014-4141-2 .
