出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/11/29 06:49:42」(JST)
| Indian cobra | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Squamata |
| Suborder: | Serpentes |
| Family: | Elapidae |
| Genus: | Naja |
| Species: | N. naja |
| Binomial name | |
| Naja naja (Linnaeus, 1758)[1][2] |
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| Indian cobra distribution | |
| Synonyms[1][3] | |
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The Indian cobra (Naja naja) also known as the Spectacled cobra, Asian cobra or Binocellate cobra is a species of the genus Naja found in the Indian subcontinent (Pakistan, India) and a member of the "big four" species that inflict the most snakebites on humans in India.[4] This snake is revered in Indian mythology and culture, and is often seen with snake charmers. It is now protected in India under the Indian Wildlife Protection Act (1972).
Naja naja was first described by Swedish physician, zoologist, and botanist Carl Linnaeus in 1758.[2][5] The generic name and the specific epithet naja is a Latinisation of the Sanskrit word nāgá (नाग) meaning "cobra".[6]
The Indian cobra[7][8] or spectacled cobra,[4] being common in South Asia, is referred to by a number of local names deriving from the root of Nag (नाग) (Hindi, Oriya, Marathi), Moorkan, മൂര്ഖന് (Malayalam), Naya-නයා (Sinhalese), Nagu Pamu (Telugu),[8] Nagara Havu (Kannada),[8] Naga Pambu or Nalla pambu (நாகப் பாம்பு/நல்ல பாம்பு) (Tamil)[8] "Phetigom" (Assamese) and Gokhra (গোখরো) (Bengali).
The Indian cobra is classified under the genus Naja of the family Elapidae. The genus was first described by Josephus Nicolaus Laurenti in 1768.[9] The species Naja naja was first described by the Swedish physician, zoologist, and botanist Carl Linnaeus in 1758.[2][5] The genus Naja was split into several subgenera based on various factors, including morphology, diet, and habitat. Naja naja is part of the subgenus Naja, along with all the other species Asiatic cobras, including Naja kaouthia, Naja siamensis, Naja sputatrix, and the rest. Naja naja is considered to be the prototypical cobra species within the Naja subgenus, and within the entire Naja genus. The below cladogram illustrates the taxonomy and relationships among species of Naja:[10]
| Naja |
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The Oriental ratsnake Ptyas mucosus is often mistaken for the cobra; however this snake is much longer and can easily be distinguished by the more prominent ridged appearance of its body. Other snakes that resemble Naja naja are the banded racer Argyrogena fasciolata and the Indian smooth snake Coronella brachyura.[4]
The Indian cobra varies tremendously in colour and pattern throughout its range. The ventral scales or the underside colouration of this species can be grey, yellow, tan, brown, reddish or black. Dorsal scales of the Indian cobra may have a hood mark or colour patterns. The most common visible pattern is a posteriorly convex light band at the level of the 20th to 25th ventrals. Salt-and-pepper speckles, especially in adult specimens, are seen on the dorsal scales. Specimens, particularly those found in Sri Lanka may exhibit poorly defined banding on the dorsum. Ontogenetic colour change is frequently observed in specimens in the north-western parts of their geographic range (southern Pakistan and north-western India). In southern Pakistan, juvenile specimens may be grey in colour and may or may not have a hood mark. Adults on the other hand are typically uniformly black in colour on top (melanistic), while the underside, outside the throat region, is usually light. Patterns on the throat and ventral scales are also variable in this species. The majority of specimens exhibit a light throat area followed by dark banding, which can be 4-7 ventral scales wide. Adult specimens also often exhibit a significant amount of mottling on the throat and on the venter, which makes patterns on this species less clear relative to patterns seen in other species of cobra. With the exception of specimens from the north-west, there is often a pair of lateral spots on the throat where the ventral and dorsal scales meet. The positioning of these spots varies, with north-western specimens having the spots positioned more anterior, while specimens from elsewhere in their range are more posterior. Many specimens exhibit a hood mark. This hood mark is located at the rear of the Indian cobra's hood. When the hood mark is present, are two circular ocelli patterns connected by a curved line, evoking the image of spectacles.[11]
The Indian cobra is a moderately sized, heavy bodied species. This cobra species can easily be identified by its relatively large and quite impressive hood, which it expands when threatened. This species has a head, which is elliptical, depressed, and very slightly distinct from neck. The snout is short and rounded with large nostrils. The eyes are medium in size and the pupils are round.[12] The majority of adult specimens range from 1 to 1.5 metres (3.3 to 4.9 ft) in length. Some specimens, particularly those from Sri Lanka, may grow to lengths of 2.1 to 2.2 metres (6.9 to 7.2 ft), but this is relatively uncommon.[11]
Dorsal scales are smooth and strongly oblique. Midbody scales are in 23 rows (21-25), with 171-197 ventrals. There are 48-75 divided subcaudals and the anal shield is single. There are 7 upper labials (3rd the largest and in contact with nasal anteriorly, 3rd and 4th in contact with eye) and 9-10 lower labials (small angular cuneate scale present between 4th and 5th lower labial), as well as 1 preocular in contact with internasals, and 3 postoculars. Temporals are 2 + 3.[12]
The Indian cobra is native to the Indian subcontinent and can be found throughout India, Pakistan, Sri Lanka, Bangladesh, and southern Nepal. In India, it may or may not occur in the state of Assam, some parts of Kashmir, and it does not occur in high altitudes of over 2,000 metres (6,600 ft) and extreme desert regions. In Pakistan, it is absent in most of Balochistan province, parts of North-West Frontier Province, desert areas elsewhere and Northern Areas. The most westerly record comes from Duki, Balochistan in Pakistan, while the most easterly record is from the Tangail District in Bangladesh. As this species has been observed in Drosh, in the Chitral Valley, it may also occur in the Kabul River Valley in extreme eastern Afghanistan.[11] There's been at least one report of this species occurring in Bhutan.[13]
The Indian Cobra inhabits a wide range of habitats throughout its geographical range. It can be found in dense or open forests, plains, agricultural lands (rice paddy fields, wheat crops), rocky terrain, wetlands, and it can even be found in heavily populated urban areas such as villages and city outskirts, ranging from sea-level to 2,000 metres (6,600 ft) in altitude. This species is absent from true desert regions. The Indian cobra is often found in the vicinity of water. Preferred hiding locations are holes in embankments, tree hollows, termite mounds, rock piles and small mammal dens.[12][14]
Indian cobras are oviparous and lay their eggs between the months of April and July. The female snake usually lays between 10 to 30 eggs in rat holes or termite mounds and the eggs hatch 48 to 69 days later. The hatchlings measure between 20 and 30 centimetres (7.9 and 11.8 in) in length. The hatchlings are independent from birth and have fully functional venom glands.
The Indian cobra's venom mainly contains a powerful post-synaptic neurotoxin[12] and cardiotoxin.[12][15] The venom acts on the synaptic gaps of the nerves, thereby paralyzing muscles, and in severe bites leading to respiratory failure or cardiac arrest. The venom components include enzymes such as hyaluronidase that cause lysis and increase the spread of the venom. Envenomation symptoms may manifest between 15 minutes and 2 hours following the bite.[16]
In mice, the SC LD50 range for this species is 0.45 mg/kg[17] – 0.80 mg/kg.[12][18] The average venom yield per bite is between 169 and 250 mg.[12] Though it is responsible for many bites, only a small percentage are fatal if proper medical treatment and anti-venom are given.[14] Mortality rate for untreated bite victims can vary from case to case, depending upon the quantity of venom delivered by the individual involved. According to one study, it is approximately 15–20%.[19] but in another study involving victims who were given prompt medical treatment, the mortality rate was only 7%.[18]
The Indian cobra is one of the Big four snakes of South Asia (mostly India) which are responsible for the majority of human deaths by snakebite in Asia. Polyvalent serum is available for treating snakebites caused by this species.[20] Zedoary, a local spice with a reputation for being effective against snakebite,[21] has shown promise in experiments testing its activity against cobra venom.[22]
The venom of young cobras has been used as a substance of abuse in India, with cases of snake charmers being paid for providing bites from their snakes. Though this practice is now seen as outdated, symptoms of such abuse include loss of consciousness, euphoria, and sedation.[23]
There are numerous myths about cobras in India, including the idea that they mate with ratsnakes.[24]
Rudyard Kipling's short story "Rikki-Tikki-Tavi" features a pair of Indian cobras named Nag and Nagaina, the Hindi words for male and female snake respectively.
The spectacled cobra is greatly respected and feared, and even has its own place in Hindu mythology as a powerful deity. The Hindu god Shiva is often depicted with a cobra coiled around his neck, symbolizing his mastery over "maya" or the world-illusion. Vishnu is usually portrayed as reclining on the coiled body of Adishesha, the Preeminent Serpent, a giant snake deity with multiple cobra heads. Cobras are also worshipped during the Hindu festival of Nag Panchami or Naagula Chavithi.
The Indian cobra's celebrity comes from its popularity as a Nipaie of choice for snake charmers. The cobra's dramatic threat posture makes for a unique spectacle as it appears to sway to the tune of a snake charmer's flute. Snake charmers with their cobras in a wicker basket are a common sight in many parts of India only during the Nag Panchami or Naagula Chavithi festival. The cobra is deaf to the snake charmer's pipe, but follows the visual cue of the moving pipe and it can sense the ground vibrations from the snake charmer's tapping. Sometimes, for the sake of safety, all the venom in cobra's teeth is removed. The snake-charmers sell the venom at a very high price. In the past Indian snake charmers also conducted cobra and mongoose fights. These gory fight shows, in which the snake was usually killed, are now illegal.[25]
Indian cobras were often a heraldic element in the official symbols of certain ancient princely states of India such as Gwalior, Kolhapur, Pal Lahara, Gondal, Khairagarh and Kalahandi, among others.[26]
Indian cobra displaying an impressive hood.
Binocellate cobra
Indian cobra outside a home in Yelandur, Karnataka, South India
The ocellation of the spectacled cobra
Common Cobra Vomiting in Patnagarh, Odisha, India
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| リンク元 | 「Micrurus」「インドコブラ」「Elapidae」「Naja haje」「mamba」 |
| 関連記事 | 「Naja」 |