Indian cobra

The Indian cobra (''Naja naja''), also known as the spectacled cobra, Asian cobra, or binocellate cobra, is a species of cobra found in India, Pakistan, Bangladesh, Sri Lanka, Nepal, and Bhutan, and a member of the "big four" species that are responsible for the most snakebite cases in India.

It is distinct from the king cobra which belongs to the monotypic genus ''Ophiophagus''. The Indian cobra is revered in Hindu mythology and culture, and is often seen with snake charmers. It is a protected species under the '' Indian Wildlife Protection Act'' (1972).

Taxonomy

The generic name and the specific epithet ''naja'' is a Latinisation of the Sanskrit word () meaning "cobra".

The Indian cobra is classified under the genus ''Naja'' of the family Elapidae. The genus was first described by Josephus Nicolaus Laurenti in 1768. The species ''Naja naja'' was first described by the Swedish physician, zoologist, and botanist Carl Linnaeus in 1758. 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 of Asiatic cobras, including ''Naja kaouthia'', ''Naja siamensis'', ''Naja sputatrix'', and the rest.

''Naja naja'' is considered to be the prototypical cobra species within the subgenus ''Naja'', and within the entire genus ''Naja''. All Asiatic species of ''Naja'' were considered conspecific with ''Naja naja'' until the 1990s, often as subspecies thereof. Many of the subspecies were later found to be artificial or composites. This causes much potential confusion when interpreting older literature.

Local names

The Indian cobra or spectacled cobra, being common in South Asia, is referred to by a number of local names deriving from the root of ''Naga.''

For Indo-Aryan and Dravidian languages:
* ''Phetigom'' (ফেতিগোম) in Assamese
* ''Gokhra ''(গোখরো) in Bengali
* ''Naag'' (नाग) in Hindi,
* ''Fetaar'' (फेटार) in Awadhi
* Gehuan (गेहुंअन)in Magahi
* ''Domi'' (डोमी) in Chhattisgarhi
* ''Naag'' (નાગ) in Gujarati
* ''Nagara Haavu'' (ನಾಗರ ಹಾವು) in Kannada
* ''Moorkkan'' (മൂര്‍ഖന്‍) in Malayalam
* ''Naag'' (नाग) in Marathi
* ''Gokhara Saapa'' (ଗୋଖର ସାପ) or ''Naaga Saapa'' (ନାଗ ସାପ) in Odia
* ''Naya'' (නයා) or ''Nagaya'' (නාගයා) in Sinhalese
* ''Nalla pambu'' (நல்ல பாம்பு) or ''Nagapambu'' (நாகப்பாம்பு) in Tamil
* నాగు పాము (Nagu Paamu) in Telugu
* Saanp (/sɑ̃ːp/) in Urdu, a local spice with a reputation for being effective against snakebite, has shown promise in experiments testing its activity against cobra venom.

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.

, an antivenom is currently being developed by the Costa Rican Clodomiro Picado Institute, and the clinical trial phase is in Sri Lanka.

Envenomation and Clinical Manifestation

Indian cobras (''N. naja'') earliest clinical manifestation of systemic envenoming was drowsiness, which occurred in 60% of cases starting at 30 minutes (severe bites) post-envenomation to 3 hours post bite. Difficulty in opening the eyes, speaking, opening the mouth, moving the lips and swallowing followed 1 – 4 hours later. Ptosis developed 1.6 – 6 hours post bite in all cases of systemic envenoming. General weakness was usually the last symptom to develop, followed by paralysis of the muscles in severe cases. Three patients developed respiratory paralysis and were given artificial respiration; 2 recovered and 1 died. The fatal case developed respiratory paralysis about 10 minutes before reaching hospital and patient became comatose; tracheostomy and artificial respiration were performed immediately and antivenom was administered intravenously. Patient survived for 8 days but finally died. The outstanding feature of systemic envenoming is paralysis of the muscles due to rapid action of neurotoxin at the myoneural junction. Respiratory paralysis may occur within 3 – 4 hours in severe cases.

Indian cobra bites are very common in many parts of India, Pakistan, Sri Lanka, and throughout their range in South Asia. Hundreds of individual case reports have been published in books and journals over the past century. It is astonishing, however, that no large prospective study of patients with proven bites by ''N. naja'' has been undertaken and reported. In a survey of snakebites in India, 91.4% of cases were bitten by an unidentified snake. Of the 6.1% of identified venomous snakes responsible for bites, 40% were ''N. naja''. As with bites by ''N. kaouthia'' and ''N. oxiana'', patients may show manifestations of systemic neurotoxic envenoming or local envenoming or both, although ''N. oxiana'' bites produce noticeable symptoms of envenomation more rapidly and prominent neurotoxicity (severe flaccid paralysis) is more common amongst patients bitten by ''N. oxiana''. A woman bitten by ''N. oxiana'' in northwestern Pakistan suffered prominent neurotoxicity and died while en route to the closest hospital nearly 50 minutes after envenomation (death occurred 45–50 minutes post envenomation). (''Naja naja oxiana'', Ladle Snake, p. 124).

Local necrosis was described after cobra bites in India in the 1860s and up to the 1920s but this was apparently forgotten until Reid's work in Malaysia. Severe local pain and swelling may begin almost immediately after the bite. The pain persists while swelling and tenderness extend up the bitten limb, sometimes spreading to the adjacent trunk. Darkening of the necrotic area of skin and blistering are apparent by about the third day with a characteristic putrid smell typical of necrotic cobra bites in Africa and Asia. Early systemic symptoms include headache, nausea, vomiting, dizziness and a feeling of lassitude, drowsiness and intoxication. "Many subjects describe their drowsiness as if they had imbibed large quantities of some potent intoxicant." Neurotoxic symptoms begin with ptosis (the patient puckers their brow, contracting the frontalis muscle, attempting to raise the eyelids or tilts the head back so as to see beneath the drooping upper lids), profuse viscid saliva, inability to clear secretions, sagging of the jaw or inability to open the mouth and progression to respiratory paralysis. It is not clear from the available literature whether the proportion of patients developing neurotoxicity and necrosis is different from that in patients bitten by ''N. kaouthia''.

Between 1968 - 1974, clinical observations were made on 20 cases of cobra bites in Thailand. Most of the patients came from the rural health centres and the cobra responsible for the bite was identified as ''Naja naja'' (Indian cobra). All 20 patients developed systemic envenoming. Antivenom for cobra bite was administered intravenously together with symptomatic and supportive treatment; 19 patients survived and 1 died from cerebral anoxia.

The outstanding feature of systemic envenoming is paralysis of the muscles due to rapid action of neurotoxin at the myoneural junction. Respiratory paralysis may occur within 3 – 4 hours in severe cases. Drowsiness is the first symptom, but it is difficult to assess because it is a subjective symptom. All of the cases developed ptosis 1.5 – 6 hours post bite. Since ptosis is easy to detect it is a valuable clinical sign for early diagnosis of systemic envenoming due to cobra bite. Restlessness, irregular breathing, and mental confusion usually developed before respiratory paralysis, indicating that they are significant early clinical signs of impending respiratory failure. It is important for clinicians to recognize the early signs of respiratory failure. Cases which show signs of systemic envenoming require antivenom. If some hours have elapsed since the bite the antivenom may be less successful. In general, 100 ml. of antivenom should be given in the first 30 minutes. If there is no distinct clinical improvement within 1 hour the dose should be repeated. Tracheostomy and artificial respiration are essential in cases of respiratory failure. Necrosis is the outstanding feature of local envenoming. Most patients were bitten on foot while working in rice fields. Authors recommended the wearing of shoes or boots while working, and that persons bitten by a snake apply a firm ligature above the bite and go to the nearest health centre or hospital.

Genome

Previous cytogenetic analysis revealed the Indian cobra has a diploid karyotype of 38 chromosomes, compromising seven pairs of macro-chromosomes, 11 pairs of micro-chromosomes and one pair of sexual chromosomes. Using next-generation sequencing and emerging genomic technologies, a de novo high-quality ''N. naja'' reference genome was published in 2020. Text was copied from this source, which is available under
Creative Commons Attribution 4.0 International License
The estimated size of this haploid genome is of 1.79 Gb, which has 43.22% of repetitive content and 40.46% of GC content. Specifically, macro-chromosomes, which represent 88% of the genome, have 39.8% of GC content, while micro-chromosomes, that represent only 12% of the genome, contain 43.5% of GC content.

Synteny analysis

Synteny analysis between the Indian cobra and the prairie rattlesnake genome revealed large syntenic blocks within macro, micro, and sexual chromosomes. This study allowed the observation of chromosomic fusion and fission events that are consistent with the difference in chromosome number between these species. For example, chromosome 4 of the Indian cobra shares syntenic regions with chromosomes 3 and 5 of the rattlesnake genome, indicating a possible fusion event. Besides, chromosomes 5 and 6 of the Indian cobra are syntenic to rattlesnake chromosome 4, indicating a possible fusion event between these chromosomes.

On the other hand, by performing whole-genome synteny comparison between the Indian cobra and other reptilian and avian genomes, it was revealed the presence of large syntenic regions between macro, micro, and sexual chromosomes across species from these classes, which indicates changes in chromosome organization between reptile and avian genomes and is consistent with their evolutionary trajectories.

Gene organization

Using protein homology information and expression data from different tissues of the cobra, 23,248 protein-coding genes, 31,447 transcripts, and 31,036 proteins, which included alternatively spliced products, where predicted from this genome. 85% of these predicted proteins contained start and stop codon, and 12% contained an N-terminal secretion signal sequence, which is an important feature in terms of toxins secretion from venom glands.

Venom gland genes

Further studies on gene prediction and annotation of the Indian cobra genome identified 139 toxin genes from 33 protein families. These included families like three-finger toxins (3FTxs), snake venom metalloproteinases (SVMP), cysteine-rich secretory venom proteins and other toxins including natriuretic peptide, C-type lectin, snake venom serine proteinase (SVSP), Kunitz and venom complement-activating gene families, group I phospholipase A2 (PLA2) and one cobra venom factor (CVF) gene. These major toxin gene families in the Indian cobra are mostly found in the snake's macro-chromosomes, which differs from '' Crotalus virides'' (rattlesnake) that presents them in its micro-chromosomes, and is indicative of the differences in their venom evolution. Besides, comparison of venom gland genes between the Indian cobra and '' C. virides'', identified 15 toxin gene families that are unique to the Indian cobra, which included cathelicidins and phospholipase B-like toxins.

Venom gland transcriptome and toxin gene identification

Analysis of transcriptomic data from 14 different tissues of the Indian cobra identified 19,426 expressed genes. Out of these genes, 12,346 belonged to the venom gland transcriptome, which included 139 genes from 33 toxin gene families. Additionally, differential expression analysis revealed that 109 genes from 15 different toxin gene families were significantly up-regulated (fold change > 2) in the venom gland and this included 19 genes that were exclusively expressed in this gland.

These 19 venom specific toxins (VSTs) encode the core effector toxin proteins and include 9 three-finger toxins (out of which six are neurotoxins, one cytotoxin, one cardiotoxin and one muscarinic toxin), six snake venom metalloproteinases, one nerve growth factor, two venom Kunitz serine proteases and a cysteine-rich secretory venom protein. Additionally to these VSTs, other accessory venom proteins (AVPs) were also found to be highly expressed in the venom gland such as: cobra venom factor (CVF), coagulation factors, protein disulfide isomerases, natriuretic peptides, hyaluronidases, phospholipases, L-amino acid oxidase (LAAO), vascular endothelial growth factor (VEGF) and 5' nucleotidases.

This transcriptomic data together with the information provided by the high quality Indian cobra genome generated by Susyamohan et al., 2020 suggest that these VSTs together with AVPs form the core toxic effector components of this venomous snake, which induce muscular paralysis, cardiovascular dysfunction, nausea, blurred vision and hemorrhage after snake bite.

The identification of these genes coding for core toxic effector components from the Indian cobra venom may allow the development of recombinant antivenoms based in neutralizing antibodies for VST proteins.

Popular culture

There are numerous myths about cobras in India, including the idea that they mate with rat snakes.

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.

Hinduism

The Indian 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 called Vasuki, 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'' and ''Nagula Chavithi''. When killed by humans, it is usually cremated with milk and ghee along with a cloth by Hindus.

Snake charming

The Indian cobra's celebrity comes from its popularity with 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, the cobra will either be venomoid or the venom will have been milked prior to the snake charmer's act. The snake charmer may then sell this 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.

Heraldry

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.Heraldry of Madhya Pradesh
hubert-herald.nl

Gallery

Image:Indiancobra.jpg, Indian cobra displaying an impressive hood
Image:Albino specticled cobra.jpg, Albino spectacled cobra
Image:Indian Binocellate Cobra.JPG, Binocellate cobra
Image:Cobra home.JPG, Indian cobra outside a home in Yelandur, Karnataka, South India
File:Common Cobra Vomiting.JPG, Cobra regurgitating bones and hair

References

External links

Serpents in Indian culture
An article o
Biodiversity of India
website.

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Naja
Snakes of Asia
Reptiles of Bangladesh
Reptiles of Bhutan
Reptiles of India
Reptiles of Nepal
Reptiles of Pakistan
Reptiles of Sri Lanka
Fauna of South Asia
Reptiles described in 1758
Taxa named by Carl Linnaeus
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