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Caspian cobra

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Caspian cobra
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Elapidae
Genus: Naja
Species:
N. oxiana
Binomial name
Naja oxiana
(Eichwald, 1831)[2]
Naja oxiana distribution

The Caspian cobra (Naja oxiana), also called the Central Asian cobra, ladle snake,[3] Oxus cobra, or Russian cobra is a species of venomous snake in the family Elapidae. The species is endemic to Central Asia. Described by Karl Eichwald in 1831, it was for many years considered a subspecies of the Indian cobra until genetic analysis revealed it to be a distinct species.

Taxonomy

Baltic German naturalist Karl Eichwald described the Caspian cobra originally as Tomyris oxiana in 1831.[4] Russian naturalist Alexander Strauch placed it in the genus Naja in 1868. The generic name Naja is a Latinisation of the Sanskrit word nāgá (नाग), meaning "cobra". The specific epithet oxiana is derived from the word Ōxus in Latin or Ὦξος (Ôxos) in Greek,[5] and refers to the ancient name of the river Amu Darya which flows along Afghanistan`s northern border separating it from Tajikistan and Uzbekistan before turning northwest into Turkmenistan and flows from there into the southern remnants of the Aral Sea in Central Asia (Transoxiana), where this species occurs. For most of the twentieth century, all Asiatic cobras were considered to be subspecies of the Indian cobra (Naja naja); during this period, the subspecific names N. naja oxiana and N. naja caeca were applied to plain-scaled populations of N. naja from the north of India as well as populations corresponding to the Caspian cobra. Highly variable coloration and size within individual species made classification difficult until the advent of genetic analysis.[6]

A mitochondrial DNA study of Asiatic cobras in the subgenus Naja showed the Caspian cobra diverged from a lineage that gave rise to the monocled cobra (Naja kaouthia) and the Andaman cobra (Naja sagittifera) around 3.21 million years ago. The species itself appears to be genetically homogeneous despite population separation caused by the Hindu Kush mountains; this suggests a recent rapid range expansion.[7]

Naja
(Naja)

Description

A Caspian cobra

Naja oxiana is medium in length, a heavy-bodied snake with long cervical ribs capable of expansion to form a hood. Anteriorly, the body is depressed dorsoventrally, and posteriorly it is subcylindrical. This species averages about 1 m (3.3 ft)[8] in total length (including tail) and rarely reaches lengths over 1.5 m (4.9 ft).[9] The head is elliptical, depressed, and slightly distinct from the neck, with a short, rounded snout and large nostrils. The eye is medium in size with a round pupil. The dorsal scales are smooth and strongly oblique, with the outer two or three scale rows larger than the remainder.[8] Juveniles tend to be pale, with a faded appearance. Juveniles have noticeable dark and light cross-bands of approximately equal width around the body. Adults of this species are completely light to chocolate brown or yellowish, with some specimens retaining traces of juvenile banding, especially the first few dark ventral bands. This species has no hood mark and no lateral throat spots.[9]

Confusions may exist with the Indian cobra (Naja naja), as specimens without a hood mark are usually confused with this species, and these two species coexist in Pakistan and northern India. They're also both the only true non-spitting cobras in Asia.[10] The Caspian cobra (Naja oxiana) is never fully black, although some specimens may be quite dark. The Caspian cobra (N. oxiana) normally has several dark bands under the throat, whereas in the black phase of the Indian cobra (N. naja) from Pakistan, almost the entire throat is black.[11]

Scalation

See also: Snake scale § Nomenclature of scales

The number and pattern of scales on a snake's body are a key element of identification to species level.[12] Naja oxiana has 23 to 27 (usually 25) dorsal scale rows at the hood, 19-23 (usually 21) just ahead of midbody, 191-210 ventrals, and 57-71 paired subcaudals; cuneate scales (small angular scales between the labials) are often absent.[9]

Distribution and habitat

Naja oxiana occurs in the Transcaspian region. It is found throughout Turkmenistan, Uzbekistan, Kyrgyzstan, southwestern Tajikistan, the Fergana Valley, north and east Afghanistan, northeastern Iran (from East Azerbaijan Province, southern half of Ardabil Province to the Provinces of Zanjan and Tehran all the way to the eastern half of both Isfahan and Yazd Provinces, as well the northeastern parts of Kerman Province, northern part of Sistan and Baluchestan Province, and throughout throughout the Provinces of Semnan, Mazandaran, and Golestan the entire former Province of Khorasan, which was split into three separate provinces post-2004), the northern half of Pakistan, from Balochistan to Gilgit-Baltistanand Azad Kashmir. This species has also been observed in northwest India in Jammu and Kashmir (union territory) and the state of Himachal Pradesh. It's also suspected to occur in Ladakh.[8][9] There is also some anecdotal evidence of it ranging as far north as the Aral Sea on the Uzbekistan/Kazakhstan border.[13]

Naja oxiana is often found in arid and semiarid, rocky or stony, shrub or scrub covered foothills[8] at elevations up to about 3,000 m (9,800 ft) above sea level. This is also the westernmost species of Asiatic cobra.[14]

Behavior and ecology

Naja oxiana is generally aggressive and bad-tempered; although it will avoid humans as much as it can, it will become fiercely aggressive when threatened or cornered, and even juveniles tend to be very aggressive. When cornered and provoked, N. oxiana is liable to spread its hood, hiss, sway from side to side and strike repeatedly; however, it is not a spitter. This terrestrial species is mainly diurnal, but it may be crepuscular and nocturnal in some parts of its range during the hottest months (July and August). Caspian cobras are good climbers, and able swimmers. The Caspian cobra is often found in water and seldom found too far away from it, where it feeds on small mammals, amphibians, and birds, both during the evening, and early morning. The Caspian cobra preys mainly on rodents, toads and frogs, occasionally fish, and birds and their eggs.[8] Quick-moving and agile, this species lives in holes in embankments or trees.[14]

Venom

Composition

The Caspian cobra is considered to be the most venomous species of cobra in the world. Several different toxinological studies suggest this, including one particular study reported in the Indian Journal of Experimental Biology in 1992.[15] A study analyzing the toxic fractions of Naja oxiana venom from Iran indicated that toxic fractions constituted 78% by weight of crude venom of this species,[16][17] similar to Naja naja.[18] The toxic fractions were composed of three protein families, among which the 3FTs was dominant, similar to all other Naja species. The venom of N. oxiana was rich in short neurotoxins, which make up the majority of crude venom.[17] A number of small nonenzymatic proteins are found in the venom, including neurotoxins and members of the cytotoxin family,[19] which have been shown to cause cell death through damage to lysosomes.[20]

In addition to nonenzymatic proteins, the venom also contains nucleases, which cause tissue damage at the site of the bite and may also potentiate systemic toxicity by releasing free purines in situ.[21] A ribonuclease isolated and purified from Caspian cobra venom, ribonuclease V1, is commonly used as a laboratory reagent in molecular biology experiments due to its unusual ability to break down structured RNA.[22]

N. oxiana is one of the most dangerous snakes belonging to the elapidae family. Two main toxins as well as a number of minor components and three basic polypeptides similar to cardiotoxins (CTXs) and cytotoxins were isolated from the crude venom of this species, with acute effects on cardiac system during the first few hours post-envenomation. There are a few case reports of acute myocardial infarction (MI) following bites from elapids. At least one case of myocardial infarction following a bite from a Caspian cobra is recorded.[23]

Toxic effects

Naja oxiana is regarded as the most dangerous snake in Central Asia and is one of the venomous snakes with a high mortality rate.[24] It is one of the most dangerous elapid species in the world.[23] A bite from this species will cause severe pain and swelling at the site of the bite, along with rapid onset of prominent neurotoxicity. Weakness, drowsiness, ataxia, hypotension, and paralysis of throat and limbs may appear in less than one hour after the bite. In a study, the first signs and symptoms of envenomation appeared within 15 minutes post-envenomation. Without medical treatment, symptoms rapidly worsen and death can occur soon after a bite due to respiratory failure.[14] As with all species of cobra, there is great variation in venom toxicity and composition based on diet and geographical location. Venom toxicty is lowest among specimens in the eastern parts of their geographical range (Indian and Pakistani specimens). Specimens from Iran, Uzbekistan, northeastern Afghanistan, and Turkmenistan can have considerably more potent venoms. Onset of symptoms are rapid and are extremely painful. Without treatment, death is likely and depending on the nature of the bite, the potency of the venom and the amount, death can occur in as little as 45 minutes or may be prolonged for up to 24 hours.[23]

According to a 2019 study by Kazemi-Lomedasht et al, the murine LD50 via subcutaneous injection value for Naja oxiana (Iranian specimens) was estimated to be 0.14 mg/kg,[24] more potent than the sympatric Pakistani Naja naja karachiensis (0.22 mg/kg), the Thai Naja kaouthia (0.2 mg/kg), and Naja philippinensis (0.18 mg/kg).[25] An older study by Zug et al listed a LD50 value of 0.2 mg/kg from Pakistani and Indian specimens.[26] Average venom yield per bite for this species is between 75 and 125 mg (dry weight),[8] but can reach up to 590 mg.[27] The crude venom of N. oxiana has a lowest published lethal dose (LCLo) of 0.005 mg/kg, the lowest among all cobra species, derived from an individual case of poisoning by intracerebroventricular injection.[28]

Between 1979 and 1987, 136 confirmed bites were attributed to this species in the former Soviet Union. Of the 136, 121 received antivenom, and only 8 died (6.6%). Of the 15 who did not receive antivenom, 11 died (untreated mortality rate of 73%).[29][30] In Iran, where the Caspian cobra is widespread, it is responsible for the highest number of deaths due to snakebite in the country. The Levant viper, Saw-scaled viper, and the Persian horned viper are responsible for more snakebite incidents, but they have a lower mortality rate compared to N. oxiana. Multiplying habitat suitability models of the four snakes showed that the northeast of Iran (west of Khorasan-e-Razavi province) has the highest snakebite risk in the country. In addition, villages that were at risk of envenoming from the four snakes were identified. Results revealed that 51,112 villages are at risk of envenoming from M. lebetinus, 30,339 from E. carinatus, 51,657 from P. persicus and 12,124 from N. oxiana. A study reported 53,787 cases of bites by venomous snakes between 2002 and 2011 in Iran, with the highest rate of snakebite incidents being found in provinces in the south and southwest of Iran.[31] In another study, from 2002 to 2011, 53,787 cases of snake bites were reported by medical centers in Iran. Out of 53,787 cases only 118 were correctly identified as bites by this species. In total there were 67 deaths, 51 of which were due to N. oxiana. Out of 51 bites, 46 didn't receive medical treatment. One 10 year old male died en route to the closest hospital ~35 minutes post-envenomation. Five were treated with antivenom, but succumbed to the venom regardless of the fact (~7% mortality despite treatment). Untreated mortality rates seem to be particularly high for a species within the genus Naja, at around ~80%.[32][3] In Pakistan, it is responsible for high rates of snakebites that result in mortality.[14] Reliable figures on incidence, morbidity and mortality are limited but almost 40,000 biting cases are reported annually which result up to 8,200 fatalities in one study. An estimates of annual mortality rate in Pakistan is around 1.9 per 100,000 population. In one survey, it was reported that out of 5,337 envenomed patients, 57% were cobra victims and the remaining rest of 35% were bitten by kraits and vipers. Of the 5,337 envenomed patients, there were 3,064 cobra (N. naja and N. oxiana) victims. Out of the 3,064 bitten by cobras (841 correctly identified as N. naja, and 384 were correctly identified as N. oxiana). There were 78 untreated case, of which 64 were fatal (82%), much higher than untreated cases for N. naja (33.6%).[27] [33] A woman bitten by this species 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).[32] Antivenom is not as effective for envenomation by this species as it is for other Asiatic cobras within the same region, like the Indian cobra (N. naja), and due to the dangerous toxicity of this species' venom, massive amounts of antivenom are often required for patients. As a result, a monovalent antivenom serum is being developed by the Razi Vaccine and Serum Research Institute in Iran. Response to treatment with antivenom is generally poor among patients, so mechanical ventilation and endotracheal intubation is required. As a result, mortality among those treated for N. oxiana envenomation is still relatively high (up to 30%) compared to all other species of cobra (<1%).[27]

References

  1. ^ Wuster, W. (1996). "Naja oxiana". IUCN Red List of Threatened Species. 1996: e.T164642A5915160. doi:10.2305/IUCN.UK.1996.RLTS.T164642A5915160.en. Retrieved 19 November 2021.
  2. ^ "Naja oxiana (Eichwald, 1831)". ITIS Standard Report Page. ITIS.gov. Retrieved 13 January 2012.
  3. ^ a b Latifi, Mahmoud (1991). Snakes of Iran. Oxford, Ohio: Society for the Study of Amphibians and Reptiles. ISBN 978-0-916984-22-9. (Naja naja oxiana, Ladle Snake, p. 124).
  4. ^ Eichwald, Karl (1931). Zoologia specialis, quam expositis animalibus tum vivis, tum fossilibus potissimuni rossiae in universum, et poloniae in specie, in usum lectionum publicarum in Universitate Caesarea Vilnensi (in Latin). Vilnius: Zawadski. p. 171.
  5. ^ Lewis, CT. "Oxos". Clarendon Press. Retrieved 13 December 2021.
  6. ^ Wüster, Wolfgang (1996). "Taxonomic changes and toxinology: Systematic revisions of the asiatic cobras (Naja naja species complex)". Toxicon. 34 (4): 399–406. doi:10.1016/0041-0101(95)00139-5. ISSN 0041-0101. PMID 8735239.
  7. ^ Kazemi, Elmira; Nazarizadeh, Masoud; Fatemizadeh, Faezeh; Khani, Ali; Kaboli, Mohammad (2021). "The phylogeny, phylogeography, and diversification history of the westernmost Asian cobra (Serpentes: Elapidae: Naja oxiana) in the Trans-Caspian region". Ecology and Evolution. 11 (5): 2024–2039. doi:10.1002/ece3.7144. ISSN 2045-7758. PMC 7920780. PMID 33717439.
  8. ^ a b c d e f "Naja oxiana - General Details, Taxonomy and Biology, Venom, Clinical Effects, Treatment, First Aid, Antivenoms". WCH Clinical Toxinology Resource. University of Adelaide. Retrieved 13 January 2012.
  9. ^ a b c d "Species of Asiatic Naja". The Asiatic Cobra Systematics Page. Bangor University. Retrieved 13 January 2012.
  10. ^ Wüster, W; Thorpe, RS (December 1992). "Dentitional Phenomena in Cobras Revisited: Spitting and Fang Structure in the Asiatic Species of Naja (Serpentes: Elapidae)". Herpetologica. 48 (4): 424–434. JSTOR 3892862. Retrieved 14 July 2021.
  11. ^ "Naja oxiana". Venom Street. Collector and Breeder of Asian Cobras. Venom Street. Archived from the original on 21 October 2014. Retrieved 3 February 2012.
  12. ^ Hutchinson, Mark; Williams, Ian (2018). "Key to the Snakes of South Australia" (PDF). South Australian Museum. Government of South Australia. Retrieved 8 February 2019.
  13. ^ Frerichs, Ralph R. "Anthrax buried for good". www.ph.ucla.edu.
  14. ^ a b c d "Naja oxiana". Armed Forces Pest Management Board. United States Department of Defense. Archived from the original on 11 January 2012. Retrieved 14 January 2012.
  15. ^ Khare AD, Khole V, Gade PR (December 1992). "Toxicities, LD50 prediction and in vivo neutralisation of some elapid and viperid venoms". Indian Journal of Experimental Biology. 30 (12): 1158–62. PMID 1294479.
  16. ^ Akbari, A; Rabiei, H; Hedayat, A; Mohammadpour, N; Zolfagharian, H; Teimorzadeh, SH (June 2010). "Production of effective antivenin to treat cobra snake (Naja naja oxiana) envenoming". Archives of Razi Institute. 65 (1): 33–37. Retrieved 28 December 2021.
  17. ^ a b Samianifard, M; Nazari, A; Tahoori, F; Mohammadpour Dounighi, N (1 March 2021). "Proteome Analysis of Toxic Fractions of Iranian Cobra (Naja naja Oxiana) Snake Venom Using Two-Dimensional Electrophoresis and Mass Spectrometry". Archives of Razi Institute. 76 (1): 127–138. doi:10.22092/ari.2020.128766.1428. PMC 8410206. PMID 33818965.
  18. ^ Dutta, S; Chanda, A; Kalita, B; Islam, T; Patra, A; Mukherjee, AK (6 March 2017). "Proteomic analysis to unravel the complex venom proteome of eastern India Naja naja: Correlation of venom composition with its biochemical and pharmacological properties". Journal of Proteomics. 156: 29–39. doi:10.1016/j.jprot.2016.12.018. PMID 28062377. Retrieved 28 December 2021.
  19. ^ Dementieva, Daria V.; Bocharov, Eduard V.; Arseniev, Alexander S. (1999). "Two forms of cytotoxin II (cardiotoxin) from Naja naja oxiana in aqueous solution. Spatial structures with tightly bound water molecules". European Journal of Biochemistry. 263 (1): 152–162. doi:10.1046/j.1432-1327.1999.00478.x. PMID 10429199.
  20. ^ Sharonov, George V.; Feofanov, Alexei V.; Astapova, Maria V.; Rodionov, Dmitriy I.; Utkin, Yuriy N.; Arseniev, Alexander S. (2005). "Cancer cell injury by cytotoxins from cobra venom is mediated through lysosomal damage". Biochemical Journal. 390 (1): 11–18. doi:10.1042/BJ20041892. PMC 1184559. PMID 15847607.
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  22. ^ Ying, Shao Yao, ed. (2006). MicroRNA Protocols. Humana Press. p. 23. ISBN 9781597451239. Retrieved 28 January 2015.
  23. ^ a b c Angaji, SA; Houshmandi, A; Zare Mirakabadi, A (December 2016). "Acute Effects of the Iranian Snake (Naja Naja Oxiana) Venom on Heart" (PDF). Biomacromolecular Journal. 2 (2): 97–101.
  24. ^ a b Kazemi-Lomedasht, F; Yamabhai, M; Sabatier, J; Behdani, M; Zareinejad, MR; Shahbazzadeh, D (5 December 2019). "Development of a human scFv antibody targeting the lethal Iranian cobra (Naja oxiana) snake venom". Toxicon. 171: 78–85. doi:10.1016/j.toxicon.2019.10.006. PMID 31622638. S2CID 204772656. Retrieved 28 December 2021.
  25. ^ Wong, KY; Tan, CH; Tan, NH (3 January 2019). "Venom and Purified Toxins of the Spectacled Cobra (Naja naja) from Pakistan: Insights into Toxicity and Antivenom Neutralization". The American Journal of Tropical Medicine and Hygeine. 94 (6): 1392–1399. doi:10.4269/ajtmh.15-0871. PMC 4889763. PMID 27022154.
  26. ^ Zug, George R. [in German] (1996). Snakes in Question: The Smithsonian Answer Book. Washington, District of Columbia: Smithsonian Institution Scholarly Press. ISBN 978-1-56098-648-5.
  27. ^ a b c Latifi, M (1984). "Variation in yield and lethality of venoms from Iranian snakes". Toxicon. 22 (3): 373–380. doi:10.1016/0041-0101(84)90081-3. PMID 6474490.
  28. ^ Lysz, Thomas W.; Rosenberg, Philip (May 1974). "Convulsant activity of Naja naja oxiana venom and its phospholipase A component". Toxicon. 12 (3): 253–265. doi:10.1016/0041-0101(74)90067-1. PMID 4458108.
  29. ^ Gopalakrishnakone, P; Chou, LM (1990). Snakebite: a medical and public health problem in Pakistan (Snakes of medical importance (Asia Pacific region) ed.). Singapore: National University Singapore. pp. 447–461.
  30. ^ Wüster, W; Thorpe, RS (March 1992). "Asiatic Cobras: Population Systematics of the Naja naja Species Complex (Serpentes: Elapidae) in India and Central Asia". Herpetologica. 48 (1): 69–85. JSTOR 3892921. Retrieved 9 May 2021.
  31. ^ Yousefi, M; Kafash, A; Khani, A; Nabati, N (22 October 2020). "Applying species distribution models in public health research by predicting snakebite risk using venomous snakes' habitat suitability as an indicating factor". Sci Rep. 10 (18073): 18073. Bibcode:2020NatSR..1018073Y. doi:10.1038/s41598-020-74682-w. PMC 7582189. PMID 33093515.
  32. ^ a b Gopalkrishnakone P, Chou LM (editors) (1990). Snakes of Medical Importance (Asia-Pacific Region). Singapore: National University of Singapore. ISBN 978-9971-62-217-6. {{cite book}}: |author= has generic name (help)[page needed]
  33. ^ Kasturiratne, A; Wickremasinghe, AR; de Silva, N; Gunawardena, NK; Pathmeswaran, A (November 2008). "The global burden of snakebite: a literature analysis and modelling based on regional estimates of envenoming and deaths". PLOS Medicine. 5 (11): e218. doi:10.1371/journal.pmed.0050218. PMC 2577696. PMID 18986210.

Further reading

  • Wüster, Wolfgang (1993). "A century of confusion: Asiatic cobras revisited". Vivarium. 4 (4): 14–18.
  • Wüster, Wolfgang; Thorpe, Roger S. (1991). "Asiatic cobras: Systematics and snakebite". Experientia. 47 (2): 205–209. doi:10.1007/BF01945429. PMID 2001726. S2CID 26579314.
  • Wüster W, Thorpe RS (1992). "Asiatic Cobras: Population Systematics of the Naja naja Species Complex (Serpentes: Elapidae) in India and Central Asia". Herpetologica. 48 (1): 69–85. JSTOR 3892921.
  • Wüster W (1998). "The cobras of the genus Naja in India". Hamadryad. 23 (1): 15–32.
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