Instruct: Given a question, retrieve passages that answer the question.
Query: What is the most venomous snake in the world?
The Inland taipan (Oxyuranus microlepidotus) is considered the most venomous snake in the world with a murine LD50 value of 0.025mg/kg SC.[6][90] Ernst and Zug et al. 1996 list a value of 0.01mg/kg SC, which makes it the most venomous snake in the world in their study too. They have an average venom yield of 44mg.[90] Bites from this species have a mortality rate of 80% if left untreated, although it is very rare for this species to bite. This species is known to be a very shy, reclusive and a laid-back snake that will nearly always slither away from disturbance. It is not an aggressive species and rarely strikes. No recorded incidents have been fatal since the advent of the monovalent (specific) antivenom therapy.
Ahaetulla is a genus of colubrid snakes commonly referred to as vine snakes, or whip snakes. They are considered by some scientists to be mildly venomous and are what is commonly termed as 'rear-fanged' or more appropriately, opisthoglyphous, meaning their enlarged teeth or fangs, intended to aid in venom delivery, are located in the back of the upper jaw, instead of in the front as they are in vipers or cobras. As colubrids, Ahaetulla do not possess a true venom gland or a sophisticated venom delivery system. The Duvernoy's gland of this genus, homologous to the venom gland of true venomous snakes, produces a secretion which, though not well studied, is considered not to be medically significant to humans.
Venom that is toxic only to a certain taxon, or strongly toxic only to a certain taxon, has been found in a number of snakes, suggesting that these venoms have evolved via natural selection to subdue preferred prey species. Examples of this phenomenon have been found in the Mangrove snake "Boiga dendrophila", which has a venom specifically toxic to birds, as well as in the genera "Echis" and "Sistrurus", and in sea snakes. However, while several snakes possess venom that is highly toxic to their preferred prey species, the reverse correlation is not necessarily true: the venoms of several snakes are toxic to taxa that they do not consume in high proportions. Most snake venom, for instance, is highly toxic to lizards, although the proportion of lizard prey varies among snake species. This has led researchers to suggest that toxicity to a certain taxon is nearly independent of toxicity to another distantly related taxon.
The venom produced by Collett's snake is similar to the Papuan black snake's and mulga snake's venom. The venom is cytotoxic and has haemolytic activity. Neurotoxins may also be found in its venom as well. "P. colletti" produces about 30 milligrams of venom in one strike. Black snake or tiger snake anti-venom can be administered. It is the world's nineteenth most venomous snake.
"Bitis nasicornis" is considered to be one of the most dangerous snakes in Africa. Small doses of the snake's primarily hemotoxic venom can be deadly. This is unlike the Gaboon viper, the largest of the vipers, which uses a considerably larger amount of venom. "Bitis nasicornis" has both neurotoxic, as well as hemotoxic venom, as do most other venomous snakes. The hemotoxic venom in rhinoceros vipers is much more dominant. This venom attacks the circulatory system of the snake's victim, destroying tissue and blood vessels. Internal bleeding also occurs. When not in use, the rhino viper's fangs are folded up into the roof of the snake's mouth. The snake has the ability to control the movement of its fangs. Simply because the rhino viper may open its mouth does not mean that the fangs will flip down into place. These fangs penetrate deep into the victim and the small doses of venom flow through the hollow fangs into the wound.
Some traditional hypotheses of snake venom evolution have supported the idea that most snakes inject far more venom into their prey than is required to kill them; thus, venom composition would not be subject to natural selection. This is known as the "overkill" hypothesis. However, recent studies of the molecular history of snake venom have contradicted this, instead finding evidence of rapid adaptive evolution in many different clades, including the carpet vipers, "Echis", the ground rattlesnakes, "Sistrurus", and the Malayan pit viper, as well as generally in the diversification of PLA2 proteins. There is phylogenetic evidence of positive selection and rapid rates of gene gain and loss in venom genes of "Sistrurus" taxa feeding on different prey. Several studies have found evidence that venom and resistance to venom in prey species have evolved in a coevolutionary arms race. For example, wood rats of the genus "Neotoma" have a high degree of resistance to the venom of rattlesnakes, suggesting that the rats have evolved in response to the snake venom, thus renewing selection pressure upon the snakes. The selection pressure on snake venom is thought to be selecting for functional diversity within the proteins in venom, both within a given species, and across species. The genes that code for venom proteins in some snake genera have a proportion of synonymous mutations that is lower than would be expected if venom were evolving through neutral evolutionary processes. In addition, snake venom is metabolically costly for a snake to produce, which scientists have suggested as further evidence that a selection pressure exists on snake venom (in this case, to minimize the volume of venom required). The use of model organisms, rather than snakes' natural prey, to study prey toxicity, has been suggested as a reason why the "overkill" hypothesis may have been overemphasized. However, the pitviper genus "Agkistrodon" has been found to be an exception to this; the composition of venom in "Agkistrodon" has been found to be related to the position of the species within the phylogeny, suggesting that those venoms have evolved mostly through neutral processes (mutation and genetic drift), and that there may be significant variation in the selection pressure upon various snake venoms.
Mortality (often determined by measured toxicity on mice) is a commonly used indicator to determine the danger of any given venomous snake, but important too are its efficiency of venom delivery, its venom yield and its behavior when it encounters humans.[19][20] Many snake experts have cited the black mamba and the coastal taipan as the world's most dangerous, albeit not the most venomous snakes.[21][22][23] Both species are elapids, and in several aspects of morphology, ecology and behaviour, the coastal taipan is strongly convergent with the black mamba.[24] Black mamba and coastal taipan bites require very rapid and vigorous antivenom therapy as without such intervention they are almost always fatal. The venoms of both species are exceptionally quick acting.
It is the most venomous sea snake, and one of the top three most venomous snakes in the world.
The eastern brown snake is considered to be the second-most venomous terrestrial snake in the world, behind only the inland taipan of central east Australia. It is the most commonly encountered dangerous snake in Adelaide, and is also found in Melbourne, Canberra, Sydney, and Brisbane. Clinically, the venom of the eastern brown snake is known to cause diarrhea, dizziness, collapse or convulsions, renal failure, paralysis, and cardiac arrest.
Without medical treatment, bites can be fatal. As this species tends to initiate its defence with nonfatal bites, the untreated mortality rate in most snakebite cases reported is 10–20%, a relatively low figure.
It has recently been suggested that all snakes may be venomous to a certain degree, with harmless snakes having weak venom and no fangs. Most snakes currently labelled "nonvenomous" would still be considered harmless according to this theory, as they either lack a venom delivery method or are incapable of delivering enough to endanger a human. This theory postulates that snakes may have evolved from a common lizard ancestor that was venomous—and that venomous lizards like the gila monster, beaded lizard, monitor lizards, and the now-extinct mosasaurs may also have derived from it. They share this venom clade with various other saurian species.
The coastal taipan ("Oxyuranus scutellatus"), or common taipan, is a species of large, extremely venomous snake in the family Elapidae. The species is native to the coastal regions of northern and eastern Australia and the island of New Guinea. According to most toxicological studies, this species is the third-most venomous land snake in the world after the Inland taipan and Eastern brown snake based on its murine .
Many species of snake, both venomous and non-venomous, make South Africa their home. The largest is the African rock python, a non-venomous snake that kills its prey, which includes creatures up to the size of an antelope, by constriction. A much smaller species that also kills by constriction is the mole snake; as its name suggests, this snake preys on small mammals, most often rodents such as mole-rats.
Many venomous snakes occur, some of which include famous examples such as the black mamba (one of the most deadly snakes in the world), eastern green mamba, boomslang, Cape cobra and rinkhals. Though human fatalities can occur, these snakes are normally timid and prefer to avoid humans. Snakes, both venomous and non-venomous, are important in controlling rodent populations.
Although Australian snakes can be very venomous, comparatively little is known about the protein compositions of venoms from Australian snakes, compared to those of Asia and America. Wide access to antivenom and adequate medical care has made deaths exceedingly rare with only a few fatalities each year. Australian snakes possess potent venom: 5 of the world's top 10 most venomous snakes live in Australia.
The Eastern brown snake (Pseudonaja textilis) has a venom LD50 value of 0.053mg SC according to (Brown, 1973) and a value of 0.0365mg SC according to (Ernst and Zug et al. 1996).[5] According to both studies, it is the second most venomous snake in the world. Average venom yield is 2–6mg according to (Meier and White, 1995). According to (Minton, 1974) average venom yield (dry weight) is between 5–10mg.[91] Maximum venom yield for this species is 155mg.[8] This species is legendary for its bad temper, aggression, and for its speed. This species is responsible for more deaths every year in Australia than any other group of snakes> It must be noted that Australia reports on average well under 10 snake bite deaths per year.[92]
The two other described species of "Oxyuranus" are among the most venomous land snakes in the world - "Oxyuranus microlepidotus" ranked the most venomous land snake and "Oxyuranus scutellatus" the third most venomous after "Pseudonaja textilis". The new species, "O. temporalis", is likely to be extremely venomous given its close relationship to the other two species. As the new species is known from the single specimen, very little is known of its natural history, and nothing of its venom.
It has been suggested that snakes evolved the mechanisms necessary for venom formation and delivery sometime during the Miocene epoch. During the mid-Tertiary, most snakes were large ambush predators belonging to the superfamily Henophidia, which use constriction to kill their prey. As open grasslands replaced forested areas in parts of the world, some snake families evolved to become smaller and thus more agile. However, subduing and killing prey became more difficult for the smaller snakes, leading to the evolution of snake venom. Other research on Toxicofera, a hypothetical clade thought to be ancestral to most living reptiles, suggests an earlier time frame for the evolution of snake venom, possibly to the order of tens of millions of years, during the Late Cretaceous.
Collett's snake ("Pseudechis colletti" ), also commonly known as Collett's black snake, Collett's cobra, or Down's tiger snake, is a species of venomous snake in the family Elapidae. The species is native to Australia. Although Collett's snake is not as venomous as other Australian snakes, it is capable of delivering a fatal bite, ranking nineteenth in the world's most venomous snakes.
Belcher's sea snake ("Hydrophis belcheri"), which many times is mistakenly called the hook-nosed sea snake ("Enhydrina schistosa"), has been erroneously popularized as the most venomous snake in the world, due to the first edition of Ernst and book, "Snakes in Question: The Smithsonian Answer Book", published in 1996.
Prominent venom expert Associate Professor Bryan Grieg Fry has clarified the error: "The hook nosed myth was due to a fundamental error in a book called "Snakes in Question". In there, all the toxicity testing results were lumped in together, regardless of the mode of testing (e.g., subcutaneous vs. intramuscular vs. intravenous vs. intraperitoneal). As the mode can influence the relative number, venoms can only be compared within a mode. Otherwise, it's apples and rocks." Belcher's sea snake's actual LD (recorded only intramuscularly) is 0.24 mg/kg and 0.155 mg/kg. Studies on mice and human cardiac cell culture show that venom of the inland taipan, drop by drop, is the most toxic among all snakes.
The eastern brown snake ("Pseudonaja textilis") is the most toxic member of the genus and is considered by some to be the second-most toxic land snake in the world, after the inland taipan (which is also found in Australia). The western brown snake is the tenth-most venomous snake in the world.
Species of this genus possess highly neurotoxic venom with some other toxic constituents that have multiple effects on victims. The venom is known to paralyse the victim's nervous system and clot the blood, which then blocks blood vessels and uses up clotting factors. Members of this genus are considered to be among the most venomous land snakes based on their murine , an indicator of the toxicity on mice. The inland taipan is considered to be the most venomous land snake and the coastal taipan, which is arguably the largest Australian venomous snake, is the third-most venomous land snake. The central ranges taipan has been less researched than other species of this genus, so the exact toxicity of its venom is still not clear, but it may be even more venomous than the other taipan species. Apart from venom toxicity, quantities of venom delivered should also be taken into account for the danger posed. The coastal taipan is capable of injecting a large quantity of venom due to its large size.
The boomslang's venom is the most potent of all rear-fanged snakes in the world based on LD50. Although its venom may be more potent than some vipers and elapids, it causes fewer fatalities owing to various factors (for example, the fangs' effectiveness is not high compared with many other snakes: the venom dose delivered is low, and boomslangs are generally less aggressive in comparison to other venomous snakes such as cobras and mambas).
Snake antivenom is a medication made up of antibodies used to treat snake bites by venomous snakes. It is a type of antivenom.
It is a biological product that typically consists of venom neutralizing antibodies derived from a host animal, such as a horse or sheep. The host animal is hyperimmunized to one or more snake venoms, a process which creates an immunological response that produces large numbers of neutralizing antibodies against various components (toxins) of the venom. The antibodies are then collected from the host animal, and further processed into snake antivenom for the treatment of envenomation. 
They are on the World Health Organization's List of Essential Medicines, the most important medications needed in a basic health system.
Belcher's sea snake ("Hydrophis belcheri"), which many times is mistakenly called the hook-nosed sea snake ("Enhydrina schistosa"), has been erroneously popularized as the most venomous snake in the world, due to Ernst and Zug's published book "Snakes in Question: The Smithsonian Answer Book" from 1996. Bryan Grieg Fry, a prominent venom expert, has clarified the error: "The hook-nosed myth was due to a fundamental error in a book called "Snakes in Question". In there, all the toxicity testing results were lumped in together, regardless of the mode of testing (e.g. subcutaneous vs. intramuscular vs intravenous vs intraperitoneal). As the mode can influence the relative number, venoms can only be compared within a mode. Otherwise, it's apples and rocks." Belcher's sea snake's actual LD (recorded only intramuscularly) is 0.24 mg/kg and 0.155 mg/kg, less lethal than other sea snakes such as the olive sea snake ("Aipysurus laevis") 0.09 mg/kg and the most toxic intramuscularly, recorded of the sea snakes – the black-banded robust sea snake ("Hydrophis melanosoma") 0.082 mg/kg. The black-banded robust sea snake has also been tested subcutaneously registering at 0.111 mg/kg. more than four times less toxic than the inland taipan's venom. In the LD subcutaneous test, it is actually Dubois' sea snake ("Aipysurus duboisii") which has the most toxic venom of any of the sea snakes tested, registering at 0.044 mg/kg. This is still nearly half as lethal as the inland taipan's venom.
The acute toxicity of snake venom is conventionally tested on laboratory animals and is evaluated in terms of the median lethal dose (LD), that is, the dose required to kill half the members of a tested population divided by the weight of the tested animal. The LD depends on the animal. Rabbits are about twice as sensitive to sea snake venom as mice, and fish and frogs are even more susceptible. The LD for subcutaneous injection of "A. duboisii" venom into mice is 0.044 mg/kg of body weight. This makes "A. duboisii" the most venomous sea snake tested, and one of the top three most venomous snakes in the world, together with the inland taipan ("Oxyuranus microlepidotus", LD=0.025 mg/kg) and the eastern brown snake ("Pseudonaja textilis", LD=0.0365 mg/kg).
Frederick McCoy is the taxon author of three species of Australian venomous snakes, including "Oxyuranus microlepidotus", commonly known as the inland taipan or fierce snake, which is considered to be the world's most venomous snake.