Eastern gaboon viper
| Eastern gaboon viper | ||||||||||||
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Eastern gabon viper ( Bitis gabonica ) |
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| Bitis gabonica | ||||||||||||
| ( Duméril , Bibron & Duméril , 1854) |
The eastern gabon viper ( Bitis gabonica ) is a species of snake belonging to the puff adder genus ( Bitis Gray , 1842). With a maximum body length of over two meters, it is one of the longest vipers . With a maximum body weight of around ten kilograms, it is also one of the heaviest venomous snakes in the world. The fangs are with a length of around five centimeters with the longest of all snakes. Despite its size and its very effective venom, the species is of little medical relevance due to its low level of aggressiveness and mostly comparatively slow movements. Deaths from the snake's bite are extremely rare.
features
The Gaboon viper has an average body length of 1.20 to 1.50 meters, but can also get larger. Due to the very squat and heavy build, the species reaches a weight of eight to a maximum of ten kilograms, which is not reached even by significantly longer venomous snakes such as the king cobra ( Ophiophagus hannah ) with a maximum length of over five meters. The Gaboon viper is therefore considered to be the heaviest venomous snake in the world. The females are usually a little longer than the males, and the sexes can be differentiated based on the length of the tail. In males this is around twelve percent of the body length, in females only six percent.
The massive, triangular head of the snake is clearly separated from the body by a rather narrow neck directly behind the neck. The neck has a diameter that is about a third of the width of the head. The nasal scales ( nasalia ) are mainly found in the B. g. rhinoceros transformed into distinct horns. The eyes are very large and very agile compared to almost all other snake species. They are bordered by 15 to 21 circumocularia and below the subocularia with five rows of smaller scales separated from the shields of the upper lip ( supralabialia ). In total, the Gaboon viper has 13 to 18 supralabials and 16 to 22 lower lip shields ( sublabials ). The poison teeth in the upper jaw are up to five centimeters long, making them the longest known poison teeth. They are the poisonous teeth that stand in front and can be folded out, typical for vipers, with an internal venomous canal (solenoglyphic poisonous teeth), which are encased in a fleshy sheath that retracts when it is unfolded and then reveals the actual teeth. The fangs are connected by a canal to the very large poison glands behind the eyes. Other, much smaller teeth sit in two rows on the palatine bone and the wing bone (pterygoid).
At its thickest point, the body has 28 to 46 dorsal rows of scales per transverse row. With the exception of the outermost scales, the scales are very strongly keeled, the side scales are slightly curved. The ventral side is occupied by 124 to 140 abdominal scales ( ventralia ), with males seldom above and females rarely below 132 ventralia. The anal scale is undivided, 17 to 33 pairs of scales adjoin the underside of the tail ( subcaudalia ), males never have fewer than 25 and females never more than 23 pairs.
A basic color cannot be seen on the body of the snake, the color is rather composed of a mosaic of regularly shaped surfaces. The head is creamy white on top. The already mentioned dark triangles run down from the silvery-black eyes to the corner of the mouth. The cream-colored, almost pastel-colored area extends over the nape of the neck and merges into a series of rectangles, also in this color, that extend down the back to the tail. They are interrupted by olive-green and centrally constricted spots with a light border. In the constriction, the spots are complemented by brown triangles to form rectangles. Below this light drawing on the back, the flanks are mainly characterized by a row of large, light brown diamond spots ( diamonds ) alternating with dark triangles, which are delimited by a white zigzag line at the bottom. Below this are again brown triangles up to the belly. The drawing is individually slightly variable, although the colors in particular can be slightly different. Greenish, yellow, bluish or violet colors occur especially in freshly skinned animals, and between the main drawings there may be smaller spots of color in white, yellow or red.
Differences between Bitis gabonica and Bitis rhinoceros
Both Gabon vipers have a very colorful pattern and, lying on the ground, are very well camouflaged by the foliage pattern . Apart from the fact that they do not occur together in one region, the subspecies can mainly be distinguished by the fact that the head of B. gabonica, in contrast to B. rhinoceros, has no or only very small horn-like enlargements of the scales on the snout. B. gabonica has two dark triangular areas starting from the eye towards the mouth opening or one area divided by a light line of different strengths. B. rhinoceros has only one large or undivided triangle. In the other body shape and color, the two species hardly differ from each other.
Bitis gabonica
Bitis rhinoceros
distribution and habitat
The species was first described on a specimen from Gabon , which gave the snake both its scientific name " B. gabonica " and its common name "Gaboon viper" ( Terra typica ). The range of the species includes large parts of the rainforest area of Central Africa as well as several smaller, isolated areas in East and South Africa.
The distribution areas of Bitis gabonica and Bitis rhinoceros are completely separated by the Dahomey-Gap , an almost forest-free and dry corridor between the Upper Guinean and Congolese rainforests . In eastern and southern Africa, the occurrences are also locally very limited and isolated from the main distribution area in the Congo Basin .
The Gaboon viper is a distinct forest species that lives mainly in the tropical rainforest and its marginal forests. It also lives in marshland, both in the area of still waters and in the vicinity of rivers or other flowing waters. In West Africa in particular, the snake is found in cocoa and in East Africa in coffee plantations in former rainforest areas, and occurrences of the viper in secondary forests , cashew plantations and bushy cultivated land as well as thickets are described for Tanzania . They are mainly found in the flatlands, less often at heights of up to 1,500 or even 2,100 m above sea level .
Way of life
The Gaboon viper is a solitary, ground-living and mostly nocturnal snake, which is mainly active at dusk . She is commonly described as very sedate or lethargic and often barely moves for hours. It moves crawling, pulling itself forward on its belly scales , and very slowly. If it is disturbed, it can meander for a short time; however, in most cases it remains motionless or takes a defensive position.
If the snake is very irritated and feels threatened by it, it comes to the threatening behavior typical of puff adders, in which it inflates itself several times and releases the air it has taken in with a hiss or loud popping noises. This excitement can go on for a very long time; Hans-Günter Petzold , former deputy director and curator for lower vertebrates at Tierpark Berlin , reported, for example, about a captive Gaboon viper whose terrarium was covered with mats for days until the animal had calmed down again. When the snake bites, the front body shoots forward with such force that the animal is raised up to halfway off the ground.
nutrition
The Gaboon viper is an unspecialized ambulance hunter . Lying in the foliage and well camouflaged, it waits for potential prey to come within range, and then quickly snaps forward. It reacts to vibrations in the ground or to the smell of the prey. When impacting, a speed of 23.6 meters per second was measured, which corresponds to approx. 85 km / h.
The bulk of their prey can according benthic small mammals from, in particular rodents such as cane rats , giant pouched rat , mastomys and porcupines , but even small monkeys , bats or royal antelope ( Neotragus pygmaeus ). In addition, birds such as francolin or pigeons as well as frogs and lizards belong to their range of prey . The poison is brought very far into the body through the long fangs and has a correspondingly strong effect.
Unlike many other large vipers, it usually holds its prey until it has died from the poisonous effect. Only rarely and with particularly defensive prey does the snake let go of the prey and actively search for it after about one to two minutes by following the scent trail. The prey is then swallowed completely, alternately being pushed into the throat by the movements of the lower jaw and the teeth of the palate. This is usually done head first, but smaller prey can be swallowed in almost any position due to the very flexible jaws.
Predators and parasites
There are no known predators of the Gaboon viper. Since the animals are very well camouflaged in the foliage and also very defensive, the range of potential enemies should be rather small.
However, like most other snakes, Gabon vipers are colonized by a variety of parasites . Most of the captured Gabonese vipers contain tongue worms (Pentastomida) of the species Armillifer armillatus and tapeworms of the species Proteocephalus gabonica , which have specialized in these vipers. In addition, there are Proglottiden , more tapeworms and eggs of the roundworms belonging roundworms (Ascaridae) and Strongylidae in the faeces of the animals.
Reproduction and development
The courtship and mating season of the Gabon vipers is in the rainy season and can vary from region to region. The main activity is in spring and early summer from March to June. How the sexual partners find each other is still unclear. It is assumed, however, that the females emit odorous substances ( pheromones ), which the males can follow. The males carry out comment fights during this time when several animals meet at the same female. They embrace each other to push the respective opponent to the ground. These "dances" are accompanied by a continuous loud hissing hiss from both animals, and very often the animals separate without a winner - in this case neither male mates with the female.
The male begins the mating itself, as does the fights, by stroking his head over the back of the potential partner. When the female allows mating and signals this by lifting the tail, the male wraps his front body around the female and introduces one of the two hemipenes into the female's cloaca to release his sperm . The sperm can be stored in the female's genital tract before the actual fertilization , which means that the gestation period can be from seven months to a year. During this time, the mother snakes increase significantly in weight and girth. Around 2.15 kilograms of weight gain was observed in captive snakes.
The Gaboon viper is ovoviviparous , which means that it gives birth to live young animals that are only surrounded by a thin embryonic shell. The young snakes hatching directly from it have a body length of about 24.5 to 27 centimeters and a weight of 32 to 39 grams. The litter of a snake consists of 16 to over 40 individuals, the sexes are evenly distributed. After just one day, the young snakes instinctively snap for prey of the right size, for example baby mice in the terrarium. The poison glands and teeth are already fully developed and functional.
Within about a year, the young snakes reach a body length of about 60 centimeters, whereby the proportional increase in length decreases with age. After two years the snakes are about one meter long, after three years about 1.3 meters. At that age they weigh about 3 kilograms. Terrarium experiments have shown that an average daily amount of food of 2.1 g / kg body weight is required to achieve growth and weight gain, below an amount of 1.7 g / kg body weight the animals lose weight. After about six years, the Gaboon viper is fully grown or growing only minimally, and the body weight remains largely constant.
The maximum age of the snakes is unknown, but the literature gives life spans for kept snakes from 10 to 30 years. If these numbers are correct, the Gaboon viper is one of the longest-lived venomous snakes for which relevant life data is available, together with the forest cobra ( Pseudohaje goldii ), the South African spitting cobra ( Hemachatus haemachatus ) and the forest rattlesnake ( Crotalus horridus ). However, there is no corresponding data for most species, so it is quite possible that this maximum age can be reached by many other species.
Taxonomy
Research history
The Gaboon viper was first described in 1854 by André Marie Constant Duméril , Gabriel Bibron and Auguste Duméril as Echidna Gabonica . Gabriel Bibron was assistant to André Duméril, director of the Muséum national d'histoire naturelle in Paris , and died while working on the publication of the Erpétologie générale in 1848. André Duméril's son Auguste took over his position and carried out the work together with his father to an end before he became a professor at the museum himself in 1857. At the time of the first description of the Gaboon viper in Erpétologie générale in 1854, Bibron had already died, but was named posthumously as the author of the work, while Auguste Duméril was not.
In 1896, George Albert Boulenger classified the species in the genus Bitis , created by John Edward Gray in 1842, under the name Bitis gabonica , which is still valid today . By Robert Mertens from Forschungsinstitut- and Senckenberg Museum in Frankfurt until 1937, a new classification as Cobra gabonica and 1951, a return assignment to the genus Bitis .
Current system
The Gaboon viper is one of fourteen species of puff adder ( Bitis ). Within this, it is classified in the subgenus Macrocerastes together with the rhinoceros viper ( B. nasicornis ) and the Ethiopian puff adder ( B. parviocula ) . These species are larger puffers, which are mainly characterized by the formation of the head shields. The nasals are with them at least four scales from the first Supralabiale from and through three or five shed rostral separated. In addition, all these species have a triangular head and at least a pair of horn-like enlarged scales at the tip of the snout. The rhinoceros viper is the closest relative or sister species of the Gaboon viper.
According to studies by Peter Lenk et al. from the year 1999 in molecular biology based on the analysis of the cytochrome b - gene of the mitochondrial detected DNA, the long time recognized subtypes of Bitis gabonica that differ greatly. They identified major differences between B. g. gabonica and B. g. rhinoceros , which correspond to those of each one of the closest related rhinoceros viper. On this basis it was proposed to use the western subspecies B. g. rhinoceros to be regarded as a separate species Bitis rhinoceros and as a sister species to the rhinoceros viper. This view has meanwhile become established within the system and both Gabon vipers are to be regarded as separate species.
Snake venom
When the Gaboon viper bites, a powerful poison is injected through the canals of its teeth, which has both neurotoxic and hemolytic components. The amount of poison secreted by a bite of this type is also quite high, and the very long poison fangs bring the poison deep into the bite site.
composition
Like most snake poisons, the poison of the Gaboon viper is a mixture of different protein components, which have different effects in the body of the prey or a bitten person. The first substantial work to identify the individual components of the poison dates back to 1969, but it has not yet been conclusively clarified which components have which effects. A work from 2007 identified 38 different proteins with molecular masses from 7 to 160 kDa in the proteome of the poison glands with the help of various analysis methods , which can be assigned to 12 different poison groups.
Most of the components of the poison go back evolutionarily, as is typical for vipers, to components of the blood coagulation system and act accordingly. The main part is made up of serine proteinases , which are very similar in structure and function to the coagulation enzyme thrombin . There are also under other Zn 2+ - metalloproteases , lectin-like proteins, phospholipase A 2 , bradykinin -verstärkende proteins and generic typical Bitiscystatine . Some poisons are typical of the species, including gabonin -1 and -2 and the disintegrins bitisgabonin -1 and -2. The composition of the serine proteases is also unique to the Gabon viper and the gabonase in particular is typical of the Gabon viper. In its structure, it is similar to other serine proteases from snake venom, such as the crotalase in the venom of rattlesnakes ( Crotalus ).
Compared to the poison of the puff adder ( Bitis arietans ), which is the only one in the genus that has also been examined in detail, the composition of the Gaboon viper venom is significantly more complex. On the other hand, the puff adder venom is described as more effective. The difference can probably be explained mainly by an evolutionary adaptation of the poisons to the specific prey animals; However, no data are available on the effect on these.
effect
The Gaboon viper venom has a very strong hemorrhagic and cytotoxic effect , and it also contains neurotoxic components. The lethal dose LD 50 in mice and rabbits injected intravenously with the poison is 0.55 to 0.71 and 0.86 to 2.76 milligrams (dry weight) per kilogram of body weight, respectively. In monkeys, the LD 50 is 0.2 to 0.6 mg / kg, on this basis it was extrapolated for humans that an untreated bite with a venom injection of more than 35 milligrams can be considered fatal.
With an average bite, however, the Gaboon viper releases significantly larger amounts, which are in the range between 200 and 600 milligrams; the maximum amount determined to date with a poison extraction was even 2.4 grams of dry poison or 9.7 milliliters of wet poison. These are the largest amounts of poison that have ever been documented for poisonous snakes.
The consequences of a snakebite in humans are diverse and can vary depending on the amount and speed of poison uptake. Often there is a sharp drop in blood pressure up to shock , bleeding in the area of the bite wound and in other parts of the body and organs, and a disorder of blood coagulation that is very similar to disseminated intravascular coagulation (DIC) .
The coagulation disorder is triggered by the high amount of thrombin-like components of the poison, which lead to an incomplete formation of fibrin from the existing fibrinogen and a subsequent breakdown of the same. The effect is reinforced by the bitisgabonins, which bind the fibronectin required for coagulation and thus withdraw it from the blood. The blood becomes incoagulable due to the snake venom. Cytotoxic effects of two hemorrhagic proteins, which lead to a separation of endothelial cells of the blood vessels and thus an escape of blood into the surrounding tissue, are held responsible for the diffuse bleeding. Metabolic changes lead to decreased oxygen uptake in tissue and metabolic acidosis with increased blood concentrations of glucose and lactate . At the heart disturbances are the conduction and changes in the action potential by decreased membrane permeability to calcium ions observed that too at an increasing heart failure leads.
Epidemiology
Bite accidents caused by the Gaboon viper in humans are relatively rare and usually result from the victim stepping on a hidden snake. Even with relatively strong irritation, most Gabonese vipers hardly react or only react with a brief hissing sound. Exact numbers of bite accidents are not available and deaths that can be traced back to the Gaboon viper are not documented. So far, only one case in the US state of California has been traced back to the bite of a Gaboon viper: On December 17, 1999, Anita Finch, the owner of a Gaboon viper, was found dead in her trailer in the Van Nuys district of Los Angeles after being caught by the Gaboon viper was bitten in the hand.
Humans and the gaboon viper
No figures are available on the population of the individual Gaboon viper populations , but it is assumed that these animals are present in relatively large numbers in the rainforests of Africa. Entries in the Red List of Endangered Species and in the Species List of the Washington Convention on the Protection of Species (CITES) do not exist.
In some parts of its range, the Gaboon viper is a welcome prey as a meat supplier. It is usually caught with bare hands and carried while hanging from the tail, as it seldom defends itself. The Gaboon viper is a delicacy, especially in Uganda , where it is mainly eaten in a soup. A medical use of the snake venom is not yet known.
The cultural-historical significance of the Gaboon viper cannot be separated from that of other snakes in its range. Although snakes appear very often in African fairy tales and stories, it is hardly possible to assign these individual species.
The English African explorer Henry Hamilton Johnston described the Gaboon viper living in Uganda in 1902 in his two-volume work The Uganda Protectorate :
“The cruel viper is very common in Uganda, and its bites are believed to be faster and more inevitable than those of any other venomous snake. However, as far as I have learned, it is not an aggressively vicious creature, and it is so clumsy that I kept the animal in captivity for some time with little concern. Occasionally she managed to escape, but then allowed herself to be picked up and brought back by a black servant without attempting to bite him. The coloring of this puff adder is probably more vivid and beautiful than any other snake. It is like a carpet pattern of alternating black, greenish-yellow, mauve, and sand-yellow, while the white borders of the scales are shown with the regular enlargement of the body.
Soon after death, these colors completely fade, and the dried skin does not reveal the blooming colors of the living animal. I write "blooming" because the beauty of these colors is enhanced by the fine sheen that appears on the scales, which softens the colors, as if the entire pattern were painted on velvet. "
supporting documents
Evidence cited
Most of the information in this article has been taken from the sources given under literature; the following sources are also cited:
- ↑ a b c Unless otherwise indicated, all numerical values come from Mallow et al.
- ↑ Map after S. Spawls, B. Branch: The Dangerous Snakes of Africa , Ralph Curtis Books Oriental Press, Dubai 1995, pages 192ff., ISBN 0-88359-029-8
- ^ HG Petzold; H. Saint Girons: Vipers and Pit Vipers in Grzimek's Animal Life , Volume 6: Kriechtiere, Kindler Verlag, Zurich 1971
- ^ DG Broadley, EV Cock: Snakes of Rhodesia , Longman, Salisbury 1975. Quoted in: Marsh & Whaler 1984
- ↑ All numerical values according to Marsh & Whaler 1984
- ↑ The full title of the work was: AM Duméril, CG Bibron: Erpétologie générale ou histoire naturelle complète des reptiles. Tome Septième. Deuxième Partie, comprenant des serpents venimeux , Libraire Encyclopedique de Roret, Paris 1854; Full text, online .
- ↑ according to ITIS
- ↑ Peter Lenk, Hans-Werner Herrmann, Ulrich Joger, Michael Wink: Phylogeny and Taxonomic Subdivision of Bitis (Reptilia: Viperidae) Based on Molecular Evidence , Kaupia - Darmstädter Contributions to Natural History 8, 1999, pages 31 to 38. ( full text ; PDF ; 1.2 MB)
- ↑ Bitis gabonica in the Integrated Taxonomic Information System (ITIS)
- ^ Juan J. Calvete, Cezary Marcinkiewicz, Libia Sanz: Snake venomics of Bitis gabonica gabonica. Protein family composition, subunit organization of venom toxins, and characterization of dimeric disintegrins bitisgabonin-1 and bitisgabonin-2 . In: Journal of Proteome Research . tape 6 , no. 1 , 2007, p. 326-336 , doi : 10.1021 / pr060494k , PMID 17203976 .
- ↑ Hubert Pirkle, Ida Theodor, Don Miyada, Greg Simmons: Thrombin-like Enzyme from the Venom of Bitis gabonica , Journal of Biological Chemistry 261 (19), 1986, pages 8830 to 8835 full text (PDF; 2.7 MB)
- ↑ Values come from specimens between 1.25 and 1.55 m in length; according to Mallow et al. 2003
- ↑ All numerical values according to Mallow et al. 2003
- ↑ SM Wildi, A. Gämperli, G. Beer, K. Markwalder: Severe envenoming by a Gaboon viper (Bitis gabonica) , Swiss Med Wkly (2001) 131: 54-55, PMID 11219193 full text ( Memento from August 14, 2009 in Internet Archive )
- ↑ N. Marsh, D. Gattullo, P. Pagliaro, G. Losano: The Gaboon viper, Bitis gabonica: hemorrhagic, metabolic, cardiovascular and clinical effects of the venom , Life Sci (1997) 61: 763-769, PMID 9275005
- ↑ Woman Who Kept Poisonous Snakes in Home Found Dead. Los Angeles Times, December 17, 1999; Retrieved July 6, 2015.
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↑ Original text: “ The dreadful viper is very common in Uganda, and its bite is perhaps more rapidly and surely fatal than that of any other venomous snake. Nevertheless, it is not, as far as I can learn, a creature of aggressive malice, and is so far sluggish that the specimen was kept by me in captivity for some time with very little objection on its part. It used occasionally to escape, and would then allow itself to be picked up and brought back by the negro servants without any attempt at biting. The coloration of this puff-adder is perhaps more vivid and beautiful than in any other snake. It is like a carpet pattern of alternate black, greenish yellow, mauve, and buff, while by the inflation of the body white edges to the scales are often shown.
Soon after death these colors fade away completely and dry skin gives no idea of the blooming tints of the live animal. I write “blooming”, because the beauty of these colors is enhanced by a delicate bloom which appears on the scales, and which softens the tints so that the whole design might have been painted on velvet. From Henry Hamilton Johnston : The Uganda Protectorate , quoted in Marsh & Whaler 1984; Page 690.
literature
- David Mallow, David Ludwig, Göran Nilson: True Vipers. Natural History and Toxicology of Old World Vipers , Krieger Publishing Company, Malabar (Florida) 2003, pp. 150-159, ISBN 0-89464-877-2
- NE Marsh, BC Whaler: The Gaboon viper (Bitis gabonica): its biology, venom components and toxinology , Toxicon 22 (5), 1984, pp. 669-694
