Pit viper
Texas Rattlesnake ( Crotalus atrox ), portrait with clearly visible pit organ between the eye and nostril.
The pit vipers ( Crotalinae ) are a subfamily of vipers ( Viperidae ) in the suborder of snakes ( Serpentes ) dar. The German name refers to the present in all species of the subfamily paired heat-sensitive pit organs on the front upper jaw which give the snakes a three-dimensional thermal image. This allows them to perceive even in the dark warm-blooded prey. Pit vipers are common in Eurasia and America.
- 6.1 Notes and references
- 6.2 Literature
Features
Most pit vipers are strongly built. The largest pit vipers are the South American Bushmaster ( Lachesis ), which can reach up to 3.0 m total length; However, most species remain well below 2.0 m total length.
Pit vipers like all vipers relatively long and erectile fangs. Most pit vipers, in contrast to the other vipers a specialized muscle, the " muscularis pterygoides glandulae " between a cranial bone ( the " Ektopterygoid ") and the venom glands. Due to the contraction of this muscle and another the poison from the venom gland is pressed.
A common feature of all pit vipers are the eponymous, paired pit organs that are located in the area of Loreale the front upper jaw between nostrils and eyes. These are pit-like depressions, which are divided by an approximately 15 microns thick and very well supplied with blood membrane into two floors. The heat receptors are trigeminal numerous very fine ends of the nerve in the membrane. These receptors are sensitive in the infrared range at wavelengths of about 1 and 3 microns to about 1 mm. They measure temperature changes, it goes a temperature increase of only 0.003 ° C for a thrill from. The pit organs give the snake a three-dimensional thermal image of the environment so that they can perceive warm-blooded prey, even in darkness.
Some species have the eyes of horn- or spike- like scales. The function of these scales is unknown, suspected a Tarnfunktion is by optical resolution of the eyes or eye protection when moving under the ground or through thick vegetation.
Dissemination
Pit vipers are common in Eurasia and America, but in Europe only happens one way. In Asia, the distribution area of the Crotalinae from the north and the eastern edge of the Caspian Sea and the Trans- Caucasus east to the Pacific and Japan and south-east to the Philippines last. The distribution of Halysotter ( Gloydius halys ) extends from the Ural River to the middle reaches of the Huang Ho in China and also includes with it the extreme east of Europe.
In addition, pit vipers are common in North and South America, where they are the only representatives of the vipers. The largest adaptive radiations that have occurred in the rattlesnakes in the U.S. and Mexico, the Palm Terciopelos in Central America, the American Terciopelos in South America as well as within the bamboo viper ( Trimeresurus ) in South Asia.
Genera
The genus list illustrated here essentially follows Campbell and Lamar and the Reptile Database, which leads 216 species in the subfamily of pit vipers.
In 2004, the division of the genus Trimeresurus in seven genera ( Trimeresurus, pariahs, Cryptelytrops, Peltopelor, Viridovipera, Popeia, Himalayophis and Garthius ) was proposed on the basis of a molecular genetic and morphological investigation. David et al. do not follow this division in a study of 2011, however. The former genera Ermia and Triceratolepidophis are according to Orlov synonymous with Protobothrops. The exact classification of pit vipers is still the subject of current research.
- Triangle head vipers ( Agkistrodon )
- Jumping Terciopelos ( Atropoides )
- Palm Terciopelos ( Bothriechis )
- Forest Terciopelos ( Bothriopsis )
- Bothrocophias
- American Terciopelos ( Bothrops )
- Malaysian Mokassinotter ( Calloselasma )
- Mountain pit viper ( Cerrophidion )
- Rattlesnakes (Crotalus )
- Chinese nose viper ( Deinagkistrodon )
- Garthius
- Halysottern ( Gloydius )
- Ceylon nose vipers ( Hypnale )
- Bushmaster ( Lachesis )
- Mixcoatlus
- Mexican Horn Terciopelos ( Ophryacus )
- Mountain pit viper ( Ovophis )
- Hook nose Terciopelos ( Porthidium )
- Protobothrops
- Rhinocerophis
- Dwarf rattlesnakes ( Sistrurus )
- Bamboo viper ( Trimeresurus )
- Tropidolaemus
Way of life
Some species are aquatic and a number of genera and species is arboreal, the vast majority of pit vipers, however, soil inhabiting.
The diet consists mainly of vipers like other terrestrial vertebrates, while in many genera, a change of prey during growth is observed. While young animals mainly prey on reptiles and amphibians and invertebrates, the proportion of warm-blooded vertebrates such as birds and mammals in particular is increasing with age. The behavior during the prey capture, depending on the species and genus different and within each taxa usually very consistent. The species of the genera Atropoides, Bothriechis and Lachesis keep rodents fixed after the bite. Large individuals of the genera Crotalus and Bothrops, however, let the loot after the bite immediately go again, and then follow the trail of the bitten animal. Some species keep frogs or lizards fixed after the bite, but leave mammalian again immediately. In other species, this change is related to age and young animals keep the bitten amphibians and reptiles found during adult animals mammal release after the bite.
As with many other snake groups also exist in the pit vipers Comment fights between males for females. The majority of genera and species is viviparous ( viviparous ), in America only the bushmaster are oviparous. The females of many species care or apparently guarding their young for several days after birth.
Poison
Venoms of pit vipers are by far the most complex natural toxins. They contain a mixture of enzymes, low molecular weight polypeptides, metal ions and other, in their function so far poorly understood components. Just as diverse are the effects of these toxins. A distinction is made between local and the whole body in question ( systemic ) symptoms.
Local effects
Typical local symptoms are especially severe pain, redness and swelling, which extend to the entire bitten limb and adjacent trunk, as well as small or large blisters that contain clear or bloody, serous fluid. Frequently cause severe necrosis, especially of the muscle tissue.
Systemic effects
The poison works by hemolytic and hemorrhagic metalloproteinases (blood vessels destructive). Often contains the venom thrombin-like enzymes ( TLEs ), resulting in a change of the coagulation precursor fibrinogen and thereby a pathological activation of clotting. This leads on further steps to rapid consumption of coagulation factors and therefore has anti-coagulant.