Chain viper
| Chain viper | ||||||||||||
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Chain viper ( Daboia russelii ) |
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| Daboia russelii | ||||||||||||
| ( Shaw & Nodder , 1797) |
The chain viper ( Daboia russelii ) is a species of the Oriental Vipers ( Daboia ). It is distributed in two subspecies in Asia from India over parts of China to Southeast Asia and Indonesia. The chain viper is considered to be the most dangerous snake in Southeast Asia because of its extremely effective venom and its frequent occurrence in settlement areas; around 900 deaths are attributed to this species each year.
features
The length of the chain viper varies greatly from region to region. Island populations in Sri Lanka usually remain relatively small with average lengths of 0.90 m and maximum lengths of 1.5 m. In China, the mean length of the snakes is about 1.0 to 1.2 m with a maximum length of 1.67 m, and in India the mean length is 1.20 m and the maximum length is 1.85 m. The relatively short tail is about a sixth of the body length, the head of a 1.20 m long snake is about 5 centimeters long. The physique is a bit slimmer compared to other vipers. The head is flattened and almost triangular, it is clearly separated from the body.
The tip of the snout is arched and rounded at the front, the nostrils above are relatively large and covered with a single, large nasal shield . The nasorostral rests at the front end , which in turn lies above the almost square rostral at the front end of the snout, the supranasalia are strongly curved and shaped like a crescent moon. The skull itself is covered with small and uneven scales. The super-eye shields ( Supraocularia ) are very narrow and undivided, they are separated from each other by six to nine scales. The eyes are large and each bordered by 10 to 15 scales. The iris is golden yellow, the pupil is vertical. Below the eyes are three to four rows of under-eye shields (subocularia) and below the ten to twelve upper lip shields ( supralabials ), of which the fourth and fifth are significantly larger than the rest. On the underside of the head there are two pairs of chin shields, of which the front one is significantly enlarged.
The poisonous teeth in the front of the upper jaw, which are typical for vipers, can be folded out and are equipped with an internal venomous canal (solenoglyphic poisonous teeth). They are up to 16 millimeters long, with a minimum of two and a maximum of six pairs of teeth. The foremost teeth are particularly strong and contain the actual poison apparatus. If lost, they are replaced by the pairs of teeth behind them, which are also equipped with a venom canal. In addition, the species has 9 to 10 teeth on both sides on the wing bone ( pterygoid ), 12 to 13 on the mandible and 3 teeth on the palatine .
The body is built flat and is cylindrical in the middle. The back scales are strongly keeled, only the bottom row is smooth. The back is covered in the middle of the body from 27 to 33 rows of scales, the number of which varies from region to region. The abdomen shows 153–180 abdominal scales ( ventralia ), the adjoining anal shield is undivided. The short tail has 41 to 68 paired subcaudalia .
The color varies from dark yellow to light brown to earth brown. Three rows of bands of spots run down the back from head to tail, with the two rows on the side being broken up into individual spots. Each spot has a dark border, which in turn is bordered by a row of bright scales. On the head there are two darker spots above the eyes, from which a V- or X-shaped light brown to pink-colored pattern extends to the tip of the snout. On the sides of the head, behind the eyes, a brownish stripe of eyes extends backwards. The belly is white, yellowish, or pink in color and may be unevenly spotted with dark spots.
Overall, the coloring and especially the drawing of the animals can be very different from region to region, which is why five to seven subspecies have been described in the past. After a comprehensive investigation, this number was reduced to two currently recognized subspecies in 1992, the western D. russelii russelii and the southeastern D. russelii sublimitis .
distribution and habitat
The chain viper is distributed over a very large area in central and southern Asia. It occurs on the Indian subcontinent with India , Pakistan and Bangladesh , on Sri Lanka , in southern China and on Taiwan , in Myanmar , in Thailand and on some islands of Indonesia . There are both large, contiguous occurrence areas and regions with a rather patchy and isolated distribution. The chain vipers of the Indonesian islands of Komodo , Flores , Lembata and southern Java , which are more than 2000 kilometers from the nearest mainland populations in Thailand, are particularly isolated from other occurrences . Sumatra , Borneo , most of Java and also the Malay Peninsula have no chain vipers.
As a habitat, the species primarily prefers moderately moist habitats at lower altitudes. It is mainly found in grasslands and bush landscapes, often also in ruderal areas , peripheral vegetation on the banks of rivers and in agricultural areas and gardens. As a result, they are often found in the area of human settlement and agricultural areas, especially in India and some other countries. The species is also found in areas with dense shrubbery, but avoids closed forest areas with dense vegetation, as well as marshland and permanently humid areas. The maximum populated altitudes are around 2300 to 3000 meters above sea level , but mostly significantly lower.
Way of life
The chain viper is normally nocturnal and has its main activity time after sunset, but in particularly cold weather the activity can also be postponed into the day. It lives primarily on the ground and is mostly in bushes or tall grass, where it is well camouflaged by its drawing. Their locomotion is described as sluggish and gliding, with especially young animals being much more active.
When threatened, the snake curls up and lifts its upper body, it hisses loudly and clearly. From this position it pushes forward with great force when it bites, whereby almost the entire body can lose contact with the ground. As a rule, adult snakes are much calmer and less irritable than young snakes.
nutrition
The food of the chain viper consists mainly of small mammals such as various rats or mice as well as birds. A specialization in the Indian gerbil is described especially for South India . Otherwise, the very broad spectrum of potential prey animals ranges from the small mammals already mentioned to domestic cats , scorpions and other arthropods . Young animals mainly hunt lizards and also insects. Mainly due to the frequent occurrence of mice there, the snakes often live in fields and close to human dwellings, which means that humans and chain vipers meet comparatively often.
The snake stalks a potential prey and then strikes at an appropriate moment. After the bite, it withdraws immediately and waits for the prey to die. The prey is then devoured head first.
Reproduction and development
The mating of the chain viper usually takes place from April to July. The young are born from May to November, with most births occurring in June and July. The snake is viviparous ( ovoviviparous ) and gives birth to 20 to 40 juvenile snakes, the largest documented litters consisted of around 65 juvenile snakes. The young are between 215 and 260 millimeters long at birth. Sexual maturity is reached after two to three years with a body length of about one meter.
Systematics
→ Main article: Oriental vipers # systematics
The chain viper was first scientifically described by George Shaw and Frederick Polydore Nodder in 1797 as Coluber russelii and thus placed among the then known vipers . The namesake was the herpetologist Patrick Russell (1726-1805), who became known as the author of the books An Account of Indian Serpents (1796) and A Continuation of an Account of Indian Serpents (1801). In their first description, however, there was a spelling mistake, as they only spelled the name with an "l" instead of two. Shortly afterwards the corrected designation russelli was added , later also russellii - but both are invalid according to the priority rule of the International Code of Zoological Nomenclature (ICZN). In 1803, the species was first classified by François Marie Daudin as Vipera daboia in the genus of real otters and vipers and remained there under various synonyms until the 1990s, where it was also added to the genus Daboia several times by various authors .
In 1992, the genus Vipera was revised , in which it was finally assigned to the genus Daboia on the basis of biochemical characteristics , and the genus of large vipers ( Macroypena ) was also formed.
By Lenk et al. In 2001, however, this compilation was questioned. On a molecular biological basis, the assignment of the African Macroocket and the Palestine Aviper to the genus Daboia was proposed. This view is confirmed by Garrigues et al. 2004: As with Lenk et al. In 2001 the genus of large vipers is paraphyletic in the current compilation, the chain viper forms a taxon with the Palestine viper and the former African large viper species. Mallow et al. 2003 accordingly classified the Palestine otter in the genus, the Atlas otter was named by Wüster et al. based on the results of Lenk et al. put to Daboia .
Poison
Composition and effect
Like most viper venoms is above all the poison of the viper hemotoxic , so it mostly destroyed cells of the blood and the surrounding tissue by different proteases . Hemotoxins lead to extensive tissue destruction, internal bleeding and swelling as well as necrosis and are very painful. Among the most effective components of the poison in the chain viper, however, are proteins that suppress blood clotting and thus together with the tissue-destroying components cause internal bleeding. Bleeding occurs under the skin, in the nasal and oral cavities and, above all, in the victim's intestines and brain. In addition to cerebral hemorrhage, acute kidney failure from kidney hemorrhage is the main cause of death for victims.
The composition of the poison is very variable depending on the population of the chain viper and therefore the effect is sometimes very different depending on the location. The poison consists of about 57 to 70 percent of proteins , of which about 70 percent is phospholipase A 2 , of which seven different isoenzymes could be determined. According to various studies, the composition of the poison correlates neither with the location nor with the appearance of the animals. Investigations with antivenins have shown that they can be effective in populations of the two subspecies that live far apart; on the other hand, the antivenins can be effective in one population and ineffective in a closely neighboring population.
The effects of the chain viper venom are very strong. The lethal dose LD 50 in mice injected intravenously with the venom is only 0.08 to 0.31 micrograms per gram of body weight. If the poison is injected into the abdominal cavity (intraperitoneally), 0.4 micrograms per kilogram of body weight is sufficient as an LD 50 . For most people, amounts of poison of 40 to 70 mg are lethal, which makes the poison significantly more effective compared to almost all land-living snakes such as cobras , rattlesnakes , kraits , lance vipers or mambas . With an average first bite, the chain viper releases about 72 mg of venom, but with individual specimens, 150 to 250 mg of venom per bite could be found, this corresponds to the total content of the venomous glands of the animals.
Epidemiology
According to the effect of the poison and the frequent encounters between humans and chain viper, especially in the vicinity of settlements or on agricultural areas, the chain viper is rated as the most dangerous venomous snake in India and Southeast Asia. About 2000 bites and about 900 deaths are attributed to the chain viper annually.
In India, the species is included in the Big Four together with the spectacled snake ( Naja naja ), the sand rattle otter ( Echis carinatus ) and the Indian krait ( Bungarus caeruleus ) , the four species of snake that alone cause almost 100 percent of deaths in India from snake bites. This is where about 34 percent of all snakebites come from the chain viper, and about 30 percent of these encounters are fatal. In southern China, on the other hand, only one bite less than 640 on average comes from the chain viper.
Threat and protection
The chain viper is only threatened by active hunting in parts of its range, and for the most part it can be found regularly or frequently. The hunt mainly takes place in the areas where their skin is made into snakeskin or where they are eaten like other snakes. By contrast, the chain viper is hardly affected by habitat destruction, as it also settles in agricultural areas or gardens and only finds no habitat in more densely populated urban areas.
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Sources cited
Most of the information in this article has been taken from the sources given under literature; the following sources are also cited:
- ↑ Anslem de Silva: Venomous Snakes, their Bites and Treatment in Sri Lanka. In: P. Gopalakrishnakone, LM Chou: Snakes of Medical Importance. Venom and Toxin Research Group, National University of Singapore, 1990, ISBN 9971-62-217-3 , p. 529.
- ^ E. Zhao: Venomous Snakes of China. In: P. Gopalakrishnakone, LM Chou: Snakes of Medical Importance. Venom and Toxin Research Group, National University of Singapore, 1990, ISBN 9971-62-217-3 , p. 247.
- ↑ TSN Murthy: Venomous Snakes of Medical Importance in India (Part A). In: P. Gopalakrishnakone, LM Chou: Snakes of Medical Importance. Venom and Toxin Research Group, National University of Singapore, 1990, ISBN 9971-62-217-3 , p. 290.
- ↑ W. Wüster, S. Otsuka, A. Malhotra, RS Thorpe: Population Systematics of Russell's Viper: A Multivariate Study. In: Biological Journal of the Linnean Society 47 (1), 1992, pp. 97-113.
- ↑ a b c Paul J. Belt, Anita Malhotra, Roger S. Thorpe, David A. Warrell, Wolfgang Wüster: Russel's viper in Indonesia: snakebite and systematics. Symp zool. Soc. London 70, 1997, pp. 219-234.
- ↑ H.-W. Herrmann, U. Joger, G. Nilson: Phylogeny and systematics of viperine snakes. III: resurrection of the genus Macroektivena (Reuss, 1927) as suggested by biochemical evidence. Amphibia-Reptilia, 13, 1992, pp. 375-392.
- ↑ P. Lenk, S. Kalayabina, M. Wink, U. Joger: Evolutionary relationships among the true vipers (Reptilia: Viperidae) inferred from mitochondrial DNA sequences . In: Molecular Phylogenetics and Evolution 19, 2001, pp. 94-104 ( PDF; 140 kB ).
- ↑ Thomas Garrigues, Catherine Dauga, Elisabeth Ferquel, Valérie Choumet and Anna-Bella Failloux: Molecular phylogeny of Vipera Laurenti, 1768 and the related genera Macroypena (Reuss, 1927) and Daboia (Gray, 1842), with comments about neurotoxic Vipera aspis aspis populations. In: Molecular Phylogenetics and Evolution 35 (1), 2005, pp. 35-47.
- ↑ David Mallow, David Ludwig, Göran Nilson: True Vipers. Natural History and Toxinology of Old World Vipers . Krieger Publishing Company Malabar, Florida 2003, ISBN 0-89464-877-2 , pp. 141-159.
- ↑ Wolfgang Wüster, Lindsay Peppin, Catharine E. Pook, Daniel E. Walker: A nesting of vipers: Phylogeny and historical biogeography of the Viperidae (Squamata: Serpentes). In: Molecular Phylogenetics and Evolution 49, 2008, pp. 445-459.
- ↑ a b All numerical values according to Mallow et al. 2003
literature
- David Mallow, David Ludwig, Göran Nilson: True Vipers. Natural History and Toxicology of Old World Vipers. Krieger Publishing Company Malabar, Florida 2003, ISBN 0-89464-877-2 , pp. 150-159.
- JC Daniels: Book of Indian Reptiles and Amphibians. Oxford University Press, 2002, ISBN 0-19-566099-4 , pp. 148-151.
- Muhammad Sharif Khan: The Snakes of Pakistan. Frankfurt Contributions to Natural History, Volume 15, Edition Chimaira. Frankfurt am Main 2002, ISBN 3-930612-43-7 , pp. 182-183.
