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Snakes are elongated limbless of the suborder Serpentes (). Cladistically Squamata, snakes are ectothermic, amniote covered in overlapping scales much like other members of the group. Many species of snakes have skulls with several more joints than their lizard ancestors and relatives, enabling them to swallow prey much larger than their heads (cranial kinesis). To accommodate their narrow bodies, snakes' paired organs (such as kidneys) appear one in front of the other instead of side by side, and most only have one functional lung. Some species retain a pelvic girdle with a pair of vestigial claws on either side of the cloaca. Lizards have independently evolved elongate bodies without limbs or with greatly reduced limbs at least twenty-five times via convergent evolution, leading to many lineages of . These resemble snakes, but several common groups of legless lizards have eyelids and external ears, which snakes lack, although this rule is not universal (see Amphisbaenia, Dibamidae, and Pygopodidae).
Living snakes are found on every continent except Antarctica, and on most smaller land masses; exceptions include some large islands, such as Ireland, Iceland, Greenland, and the islands of New Zealand, as well as many small islands of the Atlantic and central Pacific oceans. Additionally, are widespread throughout the Indian and Pacific oceans. Around thirty families are currently recognized, comprising about 520 Genus and about more than 4,170 species. They range in size from the tiny, Barbados threadsnake to the reticulated python of in length. The fossil species Titanoboa was long. Snakes are thought to have evolved from either burrowing or aquatic lizards, perhaps during the Jurassic period, with the earliest known fossils dating to between 143 and 167 Mega-annum ago. The diversity of modern snakes appeared during the Paleocene epoch ( 66 to 56 Ma ago, after the Cretaceous–Paleogene extinction event). The oldest preserved descriptions of snakes can be found in the Brooklyn Papyrus.
Most species of snake are nonvenomous and Venomous snake use it primarily to kill and subdue prey rather than for self-defense. Some possess venom that is potent enough to cause painful injury or death to humans. Nonvenomous snakes either swallow prey alive or kill by constriction.
The two of Serpentes are Alethinophidia and Scolecophidia. This separation is based on morphological characteristics and mitochondrial DNA sequence similarity. Alethinophidia is sometimes split into Henophidia and Caenophidia, with the latter consisting of "colubroid" snakes (colubrids, Viperidae, elapids, Hydrophiinae, and Atractaspidinae) and acrochordids, while the other alethinophidian families comprise Henophidia. While not extant today, the Madtsoiidae, a family of giant, primitive, python-like snakes, lived until 50,000 years ago in Australia, represented by genera such as Wonambi.
Recent molecular studies support the monophyly of the clades of modern snakes, scolecophidians, typhlopids + anomalepidids, alethinophidians, core alethinophidians, uropeltids ( Cylindrophis, Anomochilus, uropeltines), macrostomatans, booids, boids, pythonids and caenophidians.
| Infraorder Alethinophidia 25 families | |||||
| Acrochordidae | Bonaparte, 1831 | 1 | 3 | Wart snakes | Western India and Sri Lanka through tropical Southeast Asia to the Philippines, south through the Indonesian/Malaysian island group to Timor, east through New Guinea to the northern coast of Australia to Mussau Island, the Bismarck Archipelago and Guadalcanal Island in the Solomon Islands. |
| Aniliidae | Stejneger, 1907 | 1 | 1 | False coral snake | Tropical South America. |
| Anomochilidae | Cundall, Wallach, 1993 | 1 | 3 | Dwarf pipe snakes | West Malaysia and on the Indonesian island of Sumatra. |
| Atractaspididae | Günther, 1858 | 12 | 72 | Burrowing asps | Africa and the Middle East |
| Boidae | Gray, 1825 | 14 | 61 | Boas | Northern, Central and South America, the Caribbean, southeastern Europe and Asia Minor, Northern, Central and East Africa, Madagascar and Reunion Island, the Arabian Peninsula, Central and southwestern Asia, India and Sri Lanka, the Maluku Islands and New Guinea through to Melanesia and Samoa. |
| Bolyeriidae | Hoffstetter, 1946 | 2 | 2 | Splitjaw snakes | Mauritius. |
| Colubridae | Oppel, 1811 | 258 | 2055 | Typical snakes | Widespread on all continents, except Antarctica. (2025). 9780713668179, A & C Black Publishers Ltd. ISBN 9780713668179 |
| Cyclocoridae | Weinell & Brown, 2017 | 5 | 8 | Cyclocorids | The Philippines |
| Cylindrophiidae | Fitzinger, 1843 | 1 | 14 | Asian pipe snakes | Sri Lanka east through Myanmar, Thailand, Cambodia, Vietnam and the Malay Archipelago to as far east as Aru Islands off the southwestern coast of New Guinea. Also found in southern China (Fujian, Hong Kong and on Hainan Island) and in Laos. |
| Elapidae | Friedrich Boie, 1827 | 55 | 389 | Elapids | On land, worldwide in tropical and subtropical regions, except in Europe. Sea snakes occur in the Indian Ocean and the Pacific. |
| Homalopsidae | Bonaparte, 1845 | 28 | 53 | Homalopsids | Southeastern Asia and northern Australia. |
| Lamprophiidae | Fitzinger, 1843 | 16 | 89 | Lamprophiids (formerly included Atracaspididae, Psammophiidae, and several other families) | Africa (including the Seychelles) |
| Loxocemidae | Cope, 1861 | 1 | 1 | Mexican burrowing snake | Along the Pacific versant from Mexico south to Costa Rica. |
| Micrelapidae | Sunandan Das et al., 2023 | 1 | 4 | Two-headed snakes | Eastern Africa and the Levant |
| Pareidae | Romer, 1956 | 3 | 20 | Snail-eating snakes | Southeast Asia and islands on the Sunda Shelf (Sumatra, Borneo, Java, and their surrounding smaller islands). |
| Prosymnidae | Kelly, Barker, Villet & Broadley, 2009 | 1 | 16 | Shovel-snout snakes | Subsaharan Africa |
| Psammodynastidae | Das et al., 2024 | 1 | 2 | Mock vipers | Tropical Asia |
| Psammophiidae | Bourgeois, 1968 | 8 | 55 | Psammophiids | Africa (including Madagascar), Asia and southern Europe |
| Pseudaspididae | Cope, 1893 | 2 | 2 | Pseudaspidids | Subsaharan Africa |
| Pseudoxyrhophiidae | Dowling, 1975 | 22 | 89 | Pseudoxyrhophiids | Mostly Madagascar and the Comoros; 5 species in subsaharan Africa, 1 in Socotra |
| Pythonidae | Fitzinger, 1826 | 8 | 40 | Pythons | Subsaharan Africa, India, Myanmar, southern China, Southeast Asia and from the Philippines southeast through Indonesia to New Guinea and Australia. |
| Tropidophiidae | Brongersma, 1951 | 2 | 34 | Dwarf boas | West Indies; also Panama and northwestern South America, as well as in northwestern and southeastern Brazil. |
| Uropeltidae | Müller, 1832 | 8 | 55 | Shield-tailed snakes | Southern India and Sri Lanka. |
| Viperidae | Oppel, 1811 | 35 | 341 | Vipers | The Americas, Africa, and Eurasia east to Wallace Line. |
| Xenodermidae | Cope, 1900 | 6 | 18 | Dragon and odd-scaled snakes | East Asia, Southern and southeastern Asia, and islands on the Sunda Shelf (Sumatra, Borneo, Java, and their surrounding smaller islands). |
| Xenopeltidae | Bonaparte, 1845 | 1 | 2 | Sunbeam snakes | Southeast Asia from the Andaman Islands and Nicobar Islands, east through Myanmar to southern China, Thailand, Laos, Cambodia, Vietnam, the Malay Peninsula and the East Indies to Sulawesi, as well as the Philippines. |
| Xenophidiidae | Wallach & Günther, 1998 | 1 | 2 | Spine-jawed snakes | Borneo and peninsular Malaysia. |
| Infraorder Scolecophidia 5 families | |||||
| Anomalepidae | Taylor, 1939 | 4 | 18 | Primitive blind snakes | From southern Central America to northwestern South America. Disjunct populations in northeastern and southeastern South America. |
| Gerrhopilidae | Vidal, Wynn, Donnellan and Hedges 2010 | 2 | 18 | Indo-Malayan blindsnakes | Southern and southeastern Asia, including Sri Lanka, the Philippines, and New Guinea. |
| Leptotyphlopidae | Stejneger, 1892 | 13 | 139 | Slender blind snakes | Africa, western Asia from Turkey to northwestern India, on Socotra Island, from the southwestern United States south through Mexico and Central to South America, though not in the high Andes. In Pacific South America they occur as far south as southern coastal Peru, and on the Atlantic side as far as Uruguay and Argentina. In the Caribbean they are found on the Bahamas, Hispaniola and the Lesser Antilles. |
| Typhlopidae | Blasius Merrem, 1820 | 18 | 266 | Typical blind snakes | Most tropical and many subtropical regions around the world, particularly in Africa, Madagascar, Asia, islands in the Pacific, tropical America and in southeastern Europe. |
| Xenotyphlopidae | Vidal, Vences, Branch and Hedges 2010 | 1 | 1 | Round-nosed blindsnake | Northern Madagascar. |
Based on genomic analysis it is certain that snakes descend from . This conclusion is also supported by comparative anatomy, and the fossil record.J. M. Mehrtens (1987). 080696460X, Sterling Publishers. 080696460X
Pythonidae and Boidae—primitive groups among modern snakes—have vestigial hind limbs: tiny, clawed digits known as , which are used to grasp during mating. The families Leptotyphlopidae and Typhlopidae also possess remnants of the pelvic girdle, appearing as horny projections when visible.
Front limbs are nonexistent in all known snakes. This is caused by the evolution of their , controlling limb morphogenesis. The axial skeleton of the snakes' common ancestor, like most other tetrapods, had regional specializations consisting of cervical (neck), thoracic (chest), lumbar (lower back), sacral (pelvic), and caudal (tail) vertebrae. Early in snake evolution, the Hox gene expression in the axial skeleton responsible for the development of the thorax became dominant. As a result, the vertebrae anterior to the hindlimb buds (when present) all have the same thoracic-like identity (except from the atlas, axis, and 1–3 neck vertebrae). In other words, most of a snake's skeleton is an extremely extended thorax. Ribs are found exclusively on the thoracic vertebrae. Neck, lumbar and pelvic vertebrae are very reduced in number (only 2–10 lumbar and pelvic vertebrae are present), while only a short tail remains of the caudal vertebrae. However, the tail is still long enough to be of important use in many species, and is modified in some aquatic and tree-dwelling species.
Many modern snake groups originated during the Paleocene, alongside the adaptive radiation of mammals following the extinction of (non-avian) . The expansion of grasslands in North America also led to an explosive radiation among snakes. (2025). 9780253337214, Indiana University Press. ISBN 9780253337214 Previously, snakes were a minor component of the North American fauna, but during the Miocene, the number of species and their prevalence increased dramatically with the first appearances of and in North America and the significant diversification of Colubridae (including the origin of many modern genera such as Nerodia, Lampropeltis, Pituophis, and Pantherophis).
This hypothesis was strengthened in 2015 by the discovery of a 113-million-year-old fossil of a four-legged snake in Brazil that has been named Tetrapodophis. It has many snake-like features, is adapted for burrowing and its stomach indicates that it was preying on other animals. It is currently uncertain if Tetrapodophis is a snake or another species, in the Squamata order, as a snake-like body has independently evolved at least 26 times. Tetrapodophis does not have distinctive snake features in its spine and skull. A study in 2021 places the animal in a group of extinct marine lizards from the Cretaceous period known as Dolichosaurus and not directly related to snakes.
An alternative hypothesis, based on morphology, suggests the ancestors of snakes were related to —extinct aquatic animal reptiles from the Cretaceous—forming the clade Pythonomorpha. According to this hypothesis, the fused, transparent eyelids of snakes are thought to have evolved to combat marine conditions (corneal water loss through osmosis), and the external ears were lost through disuse in an aquatic environment. This ultimately led to an animal similar to today's . In the Late Cretaceous, snakes recolonized land, and continued to diversify into today's snakes. Fossilized snake remains are known from early Late Cretaceous marine sediments, which is consistent with this hypothesis; particularly so, as they are older than the terrestrial Najash rionegrina. Similar skull structure, reduced or absent limbs, and other anatomical features found in both mosasaurs and snakes lead to a positive Cladistics correlation, although some of these features are shared with varanids.
Genetic studies in recent years have indicated snakes are not as closely related to monitor lizards as was once believed—and therefore not to mosasaurs, the proposed ancestor in the aquatic scenario of their evolution. However, more evidence links mosasaurs to snakes than to varanids. Fragmented remains found from the Jurassic and Early Cretaceous indicate deeper fossil records for these groups, which may potentially refute either hypothesis.
In 2016, two studies reported that limb loss in snakes is associated with DNA mutations in the Zone of Polarizing Activity Regulatory Sequence (ZRS), a regulatory region of the sonic hedgehog gene which is critically required for limb development. More advanced snakes have no remnants of limbs, but basal snakes such as pythons and boas do have traces of highly reduced, vestigial hind limbs. Python embryos even have fully developed hind limb buds, but their later development is stopped by the DNA mutations in the ZRS.
At the other end of the scale, the smallest extant snake is Leptotyphlops carlae, with a length of about . Most snakes are fairly small animals, approximately in length.
Snakes rely heavily on their sense of smell to track prey. They collect particles from the air, ground, or water using their forked tongue, which are then transferred to the vomeronasal organ (also known as Jacobson's organ) in the mouth for analysis. The forked structure of the tongue provides directional information of smell which helps locate prey or predators. In aquatic species, such as the anaconda, the tongue functions efficiently underwater. When the tongue is retracted, the forked tips are pressed into the cavities of the Jacobson's organ, enabling a combined taste-smell analysis that provides the snake with detailed information about its environment.
'' by G. A. Boulenger (1890), illustrating the terminology of shields on the head of a snake]] Until the mid-20th century, it was widely believed that snakes were unable to hear. However, snakes possess two distinct auditory systems. One system, the somatic system, involves the transmission of vibrations through ventral skin receptors to the spine. The other system involves vibrations transmitted through the snake's elongated lung to the brain via cranial nerves. Snakes exhibit high sensitivity to vibrations, allowing them to detect even subtle sounds, such as soft speech, in quiet environments.
Snake vision varies significantly among species. While some snakes have keen eyesight, others can only distinguish light from dark. However, most snakes possess visual acuity sufficient to track movement. Arboreal snakes generally have better vision than burrowing species. Some snakes, such as the Ahaetulla, possess binocular vision, enabling both eyes to focus on the same point. Most snakes focus by moving the lens back and forth relative to the retina. Diurnal snakes typically have round pupils, while many nocturnal species have slit pupils. Most snakes possess three visual pigments, allowing them to perceive two primary colors in daylight. Certain species, such as the annulated sea snake and members of the genus Helicops, have regained significant color vision as an adaptation to their aquatic environments. Research suggests that the last common ancestor of all snakes had Ultraviolet-sensitive vision. However, many diurnal snakes have evolved lenses that filter out UV light, likely improving contrast and sharpening their vision.
For a snake, the skin has been modified to its specialized form of locomotion. Between the inner layer and the outer layer lies the dermis, which contains all the pigments and cells that make up the snake's distinguishing pattern and color. The epidermis, or outer layer, is formed of a substance called keratin, which in mammals is the same basic material that forms nails, claws, and hair. The snake's epidermis of keratin provides it with the armor it needs to protect its internal organs and reduce friction as it passes over rocks. Parts of this keratin armor are rougher than others. The less restricted portion overlaps the front of the scale beneath it. Between them lies a folded back connecting material, also of keratin, also part of the epidermis. This folded back material gives as the snake undulates or eats things bigger than the circumference of its body.
The shedding of scales is called ecdysis (or in normal usage, molting or sloughing). Snakes shed the complete outer layer of skin in one piece.Smith, Malcolm A. The Fauna of British India, Including Ceylon and Burma. Vol I, Loricata and Testudines. p. 30. Snake scales are not discrete, but extensions of the epidermis—hence they are not shed separately but as a complete outer layer during each molt, akin to a sock being turned inside out.
Snakes have a wide diversity of skin coloration patterns which are often related to behavior, such as the tendency to have to flee from predators. Snakes that are at a high risk of predation tend to be plain, or have longitudinal stripes, providing few reference points to predators, thus allowing the snake to escape without being noticed. Plain snakes usually adopt active hunting strategies, as their pattern allows them to send little information to prey about motion. Blotched snakes usually use ambush-based strategies, likely because it helps them blend into an environment with irregularly shaped objects, like sticks or rocks. Spotted patterning can similarly help snakes to blend into their environment.
The shape and number of scales on the head, back, and belly are often characteristic and used for taxonomic purposes. Scales are named mainly according to their positions on the body. In "advanced" () snakes, the broad belly scales and rows of correspond to the , allowing these to be counted without the need for dissection.
Snakes may shed four or five times a year, depending on the weather conditions, food supply, age of the snake, and other factors. It is theoretically possible to identify the snake from its cast skin if it is reasonably intact. Mythological associations of snakes with symbols of healing and medicine, as pictured in the Rod of Asclepius, are derivative of molting.
One can attempt to identify the sex of a snake when the species is not distinctly sexually dimorphic by counting scales. The cloaca is probed and measured against the subcaudal scales.Rosenfeld (1989), p. 11. Counting scales determines whether a snake is a male or female, as the Hemipenis of a male being probed is usually longer.
The skeleton of most snakes consists solely of the skull, hyoid, vertebral column, and ribs, though snakes retain vestiges of the pelvis and rear limbs. The hyoid is a small bone located posterior and ventral to the skull, in the 'neck' region, which serves as an attachment for the muscles of the snake's tongue, as it does in all other . The vertebral column consists of between 200 and 400 vertebrae, or sometimes more. The body vertebrae each have two ribs articulating with them. The tail vertebrae are comparatively few in number (often less than 20% of the total) and lack ribs. The vertebrae have projections that allow for strong muscle attachment, enabling locomotion without limbs.
Caudal autotomy (self-amputation of the tail), a feature found in some lizards, is absent in most snakes.Cogger, H 1993 Fauna of Australia. Vol. 2A Amphibia and Reptilia. Australian Biological Resources Studies, Canberra. In the rare cases where it does exist in snakes, caudal autotomy is intervertebral (meaning the separation of adjacent vertebrae), unlike that in lizards, which is intravertebral, i.e. the break happens along a predefined fracture plane present on a vertebra.
In some snakes, most notably boas and pythons, there are vestiges of the hindlimbs in the form of a pair of . These small, claw-like protrusions on each side of the cloaca are the external portion of the vestigial hindlimb skeleton, which includes the remains of an ilium and femur.
Snakes are with teeth that are continuously replaced.
The snake's heart is encased in a sac, called the pericardium, located at the bifurcation of the bronchi. The heart is able to move around, owing to the lack of a diaphragm; this adjustment protects the heart from potential damage when large ingested prey is passed through the esophagus. The spleen is attached to the gall bladder and pancreas and filters the blood. The thymus, located in fatty tissue above the heart, is responsible for the generation of immune cells in the blood. The cardiovascular system of snakes is unique for the presence of a renal portal system in which the blood from the snake's tail passes through the kidneys before returning to the heart.
The circulatory system of a snake is basically like those of any other vertebrae. However, snakes do not regulate internally the temperature of their blood. Called Ectotherm, snakes actually have blood that is responsive to the varying temperature of the immediate environment. Snakes can regulate blood temperature by moving. Too long in direct sunlight, the snakes' blood is heated by beyond tolerance. Left in the ice or snow, the snake may freeze. In temperate zones with pronounced seasonal changes, snakes denning together have adapted to the onslaught of winter.
The vestige left lung is often small or sometimes even absent, as snakes' tubular bodies require all of their organs to be long and thin. In the majority of species, only one lung is functional. This lung contains a vascularized anterior portion and a posterior portion that does not function in gas exchange. This 'saccular lung' is used for hydrostatic purposes to adjust buoyancy in some aquatic snakes and its function remains unknown in terrestrial species. Many organs that are paired, such as kidneys or reproductive organs, are staggered within the body, one located ahead of the other.
The snake with its particular arrangement of organs may achieve a greater efficiency. For example, the lung encloses at the part nearest the head and throat an oxygen intake organ, while the other half is used for air reserve. The esophagus-stomach-intestine arrangement is a straight line. It ends where intestinal, urinary, and reproductive tracts open, in a chamber called the cloaca.
channel venom into the wound. Snake venoms are often prey-specific, and their role in self-defense is secondary.
Venom, like all salivary secretions, is a predigestant that initiates the breakdown of food into soluble compounds, facilitating proper digestion. Even nonvenomous snakebites (like any animal bite) cause tissue damage. Certain birds, mammals, and other snakes (such as ) that prey on venomous snakes have developed resistance and even immunity to certain venoms. Venomous snakes include three families of snakes, and do not constitute a formal taxonomic classification group.
The Colloquialism term "poisonous snake" is generally an incorrect label for snakes. A poison is inhaled or ingested, whereas venom produced by snakes is injected into its victim via fangs. There are, however, two exceptions: Rhabdophis sequesters toxins from the toads it eats, then secretes them from nuchal glands to ward off predators; and a small unusual population of in the US state of Oregon retains enough toxins in their livers from ingested to be effectively poisonous to small local predators (such as and ).
Snake venoms are complex mixtures of , and are stored in Venom gland at the back of the head. In all venomous snakes, these glands open through ducts into grooved or hollow teeth in the upper jaw. The proteins can potentially be a mix of (which attack the nervous system), (which attack the circulatory system), (which attack the cells directly), (related to neurotoxins, but also directly affect muscle tissue), and many other toxins that affect the body in different ways. Almost all snake venom contains hyaluronidase, an enzyme that ensures rapid diffusion of the venom.
Venomous snakes that use hemotoxins usually have fangs in the front of their mouths, making it easier for them to inject the venom into their victims. Some snakes that use neurotoxins (such as the mangrove snake) have fangs in the back of their mouths, with the fangs curled backwards. This makes it difficult both for the snake to use its venom and for scientists to milk them. Elapids, however, such as cobras and kraits are proteroglyphous—they possess hollow fangs that cannot be erected toward the front of their mouths, and cannot "stab" like a viper. They must actually bite the victim.
It has been suggested that all snakes may be venomous to a certain degree, with harmless snakes having weak venom and no fangs. According to this theory, most snakes that are labelled "nonvenomous" would be considered harmless because they either lack a venom delivery method or are incapable of delivering enough to endanger a human. The theory postulates that snakes may have evolved from a common lizard ancestor that was venomous, and also that venomous lizards like the gila monster, beaded lizard, , and the now-extinct mosasaurs, may have derived from this same common ancestor. They share this "venom clade" with various other species.
Venomous snakes are classified in two taxonomic families:
There is a third family containing the opistoglyphous (rear-fanged) snakes (as well as the majority of other snake species):
Most species of snakes lay eggs which they abandon shortly after laying. However, a few species (such as the king cobra) construct nests and stay in the vicinity of the hatchlings after incubation. Most pythons coil around their egg-clutches and remain with them until they hatch. A female python will not leave the eggs, except to occasionally bask in the sun or drink water. She will even "shiver" to generate heat to incubate the eggs.
Some species of snake are Ovoviviparity and retain the eggs within their bodies until they are almost ready to hatch.Capula (1989), p. 118. Several species of snake, such as the boa constrictor and green anaconda, are fully Viviparity, nourishing their young through a placenta as well as a yolk sac; this is highly unusual among reptiles, and normally found in requiem sharks or placental mammals. Retention of eggs and live birth are most often associated with colder environments.
Sexual selection in snakes is demonstrated by the 3,000 species that each use different tactics in acquiring mates. Ritual combat between males for the females they want to mating with includes topping, a behavior exhibited by most viperids in which one male will twist around the vertically elevated fore body of its opponent and force it downward. It is common for neck-biting to occur while the snakes are entwined.
Reproduction in Squamata reptiles is almost exclusively sexual. Males ordinarily have a ZZ pair of sex-determining chromosomes, and females a ZW pair. However, the Colombian Rainbow boa ( Epicrates maurus) can also reproduce by facultative parthenogenesis, resulting in production of WW female progeny. The WW females are likely produced by terminal automixis.
There is ample literature focusing on the limb development/lack of development in snake embryos and the gene expression associated with the different stages. In Henophidia, such as the python, embryos in early development exhibit a hind limb bud that develops with some cartilage and a cartilaginous pelvic element, however this degenerates before hatching. This presence of vestigial development suggests that some snakes are still undergoing hind limb reduction before they are eliminated. There is no evidence in basal snakes of forelimb rudiments and no examples of snake forelimb bud initiation in embryo, so little is known regarding the loss of this trait. Recent studies suggest that hind limb reduction could be due to mutations in enhancers for the Sonic hedgehog gene, however other studies suggested that mutations within the Hox gene or their enhancers could contribute to snake limblessness. Since multiple studies have found evidence suggesting different genes played a role in the loss of limbs in snakes, it is likely that multiple gene mutations had an additive effect leading to limb loss in snakes
The snake's jaw is a complex structure. Contrary to the popular belief that snakes can dislocate their jaws, they have an extremely flexible mandible, the two halves of which are not rigidly attached, and numerous other joints in the skull, which allow the snake to open its mouth wide enough to swallow prey whole, even if it is larger in diameter than the snake itself. For example, the Dasypeltis has flexible jaws adapted for eating eggs much larger than the diameter of its head. This snake has no teeth, but does have bony protrusions on the inside edge of its Vertebral column, which it uses to break the shell when eating eggs.
The majority of snakes eat a variety of prey animals, but there is some specialization in certain species. and the Australian bandy-bandy consume other snakes. Species of the family Pareidae have more teeth on the right side of their mouths than on the left, as they mostly prey on snails and the shells usually spiral clockwise.
Some snakes have a venomous bite, which they use to kill their prey before eating it. Other snakes kill their prey by constriction, while some swallow their prey when it is still alive.
After eating, snakes become dormant to allow the process of digestion to take place; this is an intense activity, especially after consumption of large prey. In species that feed only sporadically, the entire intestine enters a reduced state between meals to conserve energy. The digestive system is then 'up-regulated' to full capacity within 48 hours of prey consumption. Being ectothermic ("cold-blooded"), the surrounding temperature plays an important role in the digestion process. The ideal temperature for snakes to digest food is . There is a huge amount of metabolism energy involved in a snake's digestion, for example the surface body temperature of the South American rattlesnake ( Crotalus durissus) increases by as much as during the digestive process. If a snake is disturbed after having eaten recently, it will often vomiting its prey to be able to escape the perceived threat. When undisturbed, the digestive process is highly efficient; the snake's digestive enzymes dissolve and absorb everything but the prey's hair (or feathers) and claws, which are excreted along with uric acid.
Terrestrial lateral undulation is the most common mode of terrestrial locomotion for most snake species. In this mode, the posteriorly moving waves push against contact points in the environment, such as rocks, twigs, irregularities in the soil, etc. Each of these environmental objects, in turn, generates a reaction force directed forward and towards the midline of the snake, resulting in forward thrust while the lateral components cancel out. The speed of this movement depends upon the density of push-points in the environment, with a medium density of about 8 along the snake's length being ideal. The wave speed is precisely the same as the snake speed, and as a result, every point on the snake's body follows the path of the point ahead of it, allowing snakes to move through very dense vegetation and small openings.
When swimming, the waves become larger as they move down the snake's body, and the wave travels backwards faster than the snake moves forwards. Thrust is generated by pushing their body against the water, resulting in the observed slip. In spite of overall similarities, studies show that the pattern of muscle activation is different in aquatic versus terrestrial lateral undulation, which justifies calling them separate modes. All snakes can laterally undulate forward (with backward-moving waves), but only sea snakes have been observed reversing the motion (moving backwards with forward-moving waves).
Gliding snakes ( Chrysopelea) of Southeast Asia launch themselves from branch tips, spreading their ribs and laterally undulating as they glide between trees. These snakes can perform a controlled glide for hundreds of feet depending upon launch altitude and can even turn in midair.
Documented deaths resulting from snake bites are uncommon. Nonfatal bites from venomous snakes may result in the need for amputation of a limb or part thereof. Of the roughly 725 species of venomous snakes worldwide, only 250 are able to kill a human with one bite. Australia averages only one fatal snake bite per year. In India, 250,000 snakebites are recorded in a single year, with as many as 50,000 recorded initial deaths. The WHO estimates that on the order of 100,000 people die each year as a result of snake bites, and around three times as many amputations and other permanent disabilities are caused by snakebites annually.
The health of people is seriously threatened by snakebites, especially in areas where there is a great diversity of snakes and little access to medical care such as the Amazon Rainforest region in South America. Snakebite is classified by the World Health Organization (WHO) as "other neglected conditions". Although there aren't many recorded snakebite deaths, the bites can cause serious complications and permanent impairments. The most successful treatment for snakebites is still antivenom, which is made from snake venom. However, access to antivenom differs greatly by location, with rural areas frequently experiencing difficulties with both cost and availability. Clinical studies, serum preparation, and venom extraction are among the intricate procedures involved in the manufacturing of antivenom. The development of alternative treatments and increased accessibility and affordability of antivenom are essential for reducing the global impact of snake bites on human populations.
The Wildlife Protection Act of 1972 in India technically prohibits snake charming on the grounds of reducing animal cruelty. Other types of snake charmers use a snake and mongoose show, where the two animals have a mock fight; however, this is not very common, as the animals may be seriously injured or killed. Snake charming as a profession is dying out in India because of competition from modern forms of entertainment and environment laws proscribing the practice. Many Indians have never seen snake charming and it is becoming a folktale of the past.
Despite the existence of snake charmers, there have also been professional snake catchers or wranglers. Modern-day snake trapping involves a herpetologist using a long stick with a V-shaped end. Some television show hosts, like Bill Haast, Austin Stevens, Steve Irwin, and Jeff Corwin, prefer to catch them using bare hands.
In Egyptian history, the snake occupies a primary role with the Nile cobra adorning the crown of the pharaoh in ancient times. It was snake worship as one of the gods and was also used for sinister purposes: murder of an adversary and ritual suicide (Cleopatra). The ouroboros was a well-known symbol of a serpent swallowing its own tail. The precursor to the ouroboros was the "Many-Faced", a serpent with five heads, who, according to the Amduat, the oldest surviving Book of the Afterlife, was said to coil around the corpse of the sun god Ra protectively. The earliest surviving depiction of a "true" ouroboros comes from the gilded shrines in the tomb of Tutankhamun. In the early centuries AD, the ouroboros was adopted as a symbol by Gnosticism Christians and chapter 136 of the Pistis Sophia, an early Gnostic text, describes "a great dragon whose tail is in its mouth". In medieval alchemy, the ouroboros became a typical western dragon with wings, legs, and a tail.
In the Bible, King Nahash of Ammon, whose name means "Snake", is depicted very negatively, as a particularly cruel and despicable enemy of the ancient Hebrews.
The ancient Greeks used the Gorgoneion, a depiction of a hideous face with serpents for hair, as an Apotropaic magic to ward off evil. In a Greek mythology described by Pseudo-Apollodorus in his Bibliotheca, Medusa was a Gorgon with serpents for hair whose gaze turned all those who looked at her to stone and was slain by the hero Perseus.Pseudo-Apollodorus, Bibliotheca 2.37, 38, 39 In the Roman poet Ovid's Metamorphoses, Medusa is said to have once been a beautiful priestess of Athena, whom Athena turned into a serpent-haired monster after she was raped by the god Poseidon in Athena's temple. In another myth referenced by the poet Hesiod and described in detail by Pseudo-Apollodorus, the hero Heracles is said to have slain the Lernaean Hydra, a multiple-headed serpent which dwelt in the swamps of Lerna.
The legendary account of the foundation of Thebes mentioned a monster snake guarding the spring from which the new settlement was to draw its water. In fighting and killing the snake, the companions of the founder Cadmus all perished—leading to the term "Cadmean victory" (i.e. a victory involving one's own ruin).
Three medical symbols involving snakes that are still used today are Bowl of Hygieia, symbolizing pharmacy, and the Caduceus and Rod of Asclepius, which are symbols denoting medicine in general.
One of the etymologies proposed for the common female first name Linda is that it might derive from Old German Lindi or Linda, meaning a serpent.
India is often called the land of snakes and is steeped in tradition regarding snakes. Snakes are worshipped as gods even today with many women pouring milk on snake pits (despite snakes' aversion for milk). The cobra is seen on the neck of Shiva and Vishnu is depicted often as sleeping on a seven-headed snake or within the coils of a serpent. There are also several temples in India solely for cobras sometimes called Nagraj (King of Snakes) and it is believed that snakes are symbols of fertility. There is a Hindu festival called Nag Panchami each year on which day snakes are venerated and prayed to. See also Nāga.
The snake is one of the 12 celestial animals of Chinese zodiac, in the Chinese calendar.
Many ancient Peruvian cultures worshipped nature. They emphasized animals and often depicted snakes in their art.
Snakes have been widely revered in many cultures, such as in ancient Greece where the serpent was seen as a healer.
In religious terms, the snake and jaguar were arguably the most important animals in ancient Mesoamerica. "In states of ecstasy, lords dance a serpent dance; great descending snakes adorn and support buildings from Chichen Itza to Tenochtitlan, and the Nahuatl word coatl meaning serpent or twin, forms part of primary deities such as Mixcoatl, Quetzalcoatl, and Coatlicue." In the Maya calendar and , the fifth day of the week was known as Snake Day.
In some parts of Christianity, the redemptive work of Jesus is compared to saving one's life through beholding the Nehushtan (serpent of brass). Snake handlers use snakes as an integral part of church worship, to demonstrate their faith in divine protection. However, more commonly in Christianity, the serpent has been depicted as a representative of evil and sly plotting, as seen in the description in Genesis of a snake tempting Eve in the Garden of Eden. Saint Patrick is purported to have expelled all snakes from Ireland while converting the country to Christianity in the 5th century, thus explaining the absence of snakes there.
In Christianity and Judaism, the snake makes its infamous appearance in the first book of the Bible when a serpent appears before Adam and Eve and tempts them with the forbidden fruit from the Tree of Knowledge. The snake returns in the Book of Exodus when Moses turns his staff into a snake as a sign of God's power, and later when he makes the Nehushtan, a bronze snake on a pole that when looked at cured the people of bites from the snakes that plagued them in the desert. The serpent makes its final appearance symbolizing Satan in the Book of Revelation: "And he laid hold on the dragon the old serpent, which is the devil and Satan, and bound him for a thousand years."
In Neo-Paganism and Wicca, the snake is seen as a symbol of wisdom and knowledge. Additionally, snakes are sometimes associated with Hecate, the Greek goddess of witchcraft.
(1997). 9780500018026, Thames & Hudson. ISBN 9780500018026
Religion
Snakes are used in Hinduism as a part of ritual worship. In the annual Nag Panchami festival, participants worship either live cobras or images of Nāgas. Lord Shiva is depicted in most images with a snake coiled around his neck. Puranas literature includes various stories associated with snakes, for example Shesha is said to hold all the planets of the Universe on his hoods and to constantly sing the glories of Vishnu from all his mouths. Other notable snakes in Hinduism are Vasuki, Takshaka, Karkotaka, and Pingala. The term Nāga is used to refer to entities that take the form of large snakes in Hinduism and Buddhism.
(2025). 9780128153390 ISBN 9780128153390 Asclepius carried a serpent wound around his wand, a symbol seen today on many ambulances. In Judaism, the snake of brass is also a symbol of healing, of one's life being saved from imminent death.
Medicine
Several compounds from snake venoms are being researched as potential treatments or preventatives for pain, cancers, arthritis, stroke, heart disease, hemophilia, and hypertension, as well as to control bleeding (e.g., during surgery).
See also
Bibliography
(1974). 9780394488820, Alfred A. Knopf. ISBN 9780394488820
Further reading
(1999). 9781893777002, Herpetologists' League. ISBN 9781893777002
(2025). 9780691240664, Princeton University Press. ISBN 9780691240664
(1995). 9780883590294, Ralph Curtis Publishing. ISBN 9780883590294
External links
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