Wikipedia

Naja

This article is about a genus of venomous snakes. For other uses, see Naja (disambiguation).

Naja is a genus of venomous elapid snakes commonly known as cobras (or "true cobras"). Members of the genus Naja are the most widespread and the most widely recognized as "true" cobras. Various species occur in regions throughout Africa, Southwest Asia, South Asia, and Southeast Asia. Several other elapid species are also called "cobras", such as the king cobra and the rinkhals, but neither is a true cobra, in that they do not belong to the genus Naja, but instead each belong to monotypic genera Hemachatus (the rinkhals)[1] and Ophiophagus (the king cobra/hamadryad).[2][3]

Naja
Temporal range: Miocene–Holocene
Indian cobra (Naja naja), species typica of the genus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Elapidae
Genus: Naja
Laurenti, 1768
Type species
Coluber naja
Linnaeus, 1758

Until recently, the genus Naja had 20 to 22 species, but it has undergone several taxonomic revisions in recent years, so sources vary greatly.[4][5] Wide support exists, though, for a 2009 revision[6] that synonymised the genera Boulengerina and Paranaja with Naja. According to that revision, the genus Naja now includes 38 species.[7]

Indian cobra (Naja naja)
Dissected head of Naja melanoleuca showing (A) the fangs and (B) the venom gland

Etymology

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The origin of this genus name is from the Sanskrit nāga (with a hard "g") meaning "snake". Some[who?] hold that the Sanskrit word is cognate with English "snake", Germanic: *snēk-a-, Proto-IE: *(s)nēg-o-,[8] but Manfred Mayrhofer calls this etymology "not credible", and suggests a more plausible etymology connecting it with Sanskrit nagna, "hairless" or "naked".[9]

Description

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Naja species vary in length and most are relatively slender-bodied snakes. Most species are capable of attaining lengths of 1.84 m (6.0 ft). Maximum lengths for some of the larger species of cobras are around 3.1 m (10 ft), with the forest cobra arguably being the longest species.[10] All have a characteristic ability to raise the front quarters of their bodies off the ground and flatten their necks to appear larger to a potential predator. Fang structure is variable; all species except the Indian cobra (Naja naja) and Caspian cobra (Naja oxiana) have some degree of adaptation to spitting.[11]

Venom

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All species in the genus Naja are capable of delivering a fatal bite to a human. Most species have strongly neurotoxic venom, which attacks the nervous system, causing paralysis, but many also have cytotoxic features that cause swelling and necrosis, and have a significant anticoagulant effect. Some also have cardiotoxic components to their venom.

Several Naja species, referred to as spitting cobras, have a specialized venom delivery mechanism, in which their front fangs, instead of ejecting venom downward through an elongated discharge orifice (similar to a hypodermic needle), have a shortened, rounded opening in the front surface, which ejects the venom forward, out of the mouth. While typically referred to as "spitting", the action is more like squirting. The range and accuracy with which they can shoot their venom varies from species to species, but it is used primarily as a defense mechanism. The venom has little or no effect on unbroken skin, but if it enters the eyes, it can cause a severe burning sensation and temporary or even permanent blindness if not washed out immediately and thoroughly.

A recent study[12] showed that all three spitting cobra lineages have evolved higher pain-inducing activity through increased phospholipase A2 levels, which potentiate the algesic action of the cytotoxins present in most cobra venoms. The timing of the origin of spitting in African and Asian Naja species corresponds to the separation of the human and chimpanzee evolutionary lineages in Africa and the arrival of Homo erectus in Asia. The authors therefore hypothesise that the arrival of bipedal, tool-using primates may have triggered the evolution of spitting in cobras.

The Caspian cobra (N. oxiana) of Central Asia is the most venomous Naja species. According to a 2019 study by Kazemi-Lomedasht et al, the murine LD50 via intravenous injection (IV) value for Naja oxiana (Iranian specimens) was estimated to be 0.14 mg/kg (0.067-0.21 mg/kg)[13] more potent than the sympatric Pakistani Naja naja karachiensis and Naja naja indusi found in far north and northwest India and adjacent Pakistani border areas (0.22 mg/kg), the Thai Naja kaouthia (0.2 mg/kg), and Naja philippinensis at 0.18 mg/kg (0.11-0.3 mg/kg).[14] Latifi (1984) listed a subcutaneous value of 0.2 mg/kg (0.16-0.47 mg/kg) for N. oxiana.[15] The crude venom of N. oxiana produced the lowest known lethal dose (LCLo) of 0.005 mg/kg, the lowest among all cobra species ever recorded, derived from an individual case of envenomation by intracerebroventricular injection.[16] The Banded water cobra's LD50 was estimated to be 0.17 mg/kg via IV according to Christensen (1968).[17][18] The Philippine cobra (N. philippinensis) has an average murine LD50 of 0.18 mg/kg IV (Tan et al, 2019).[14] Minton (1974) reported 0.14 mg/kg IV for the Philippine cobra.[19][20][21] The Samar cobra (Naja samarensis), another cobra species endemic to the southern islands of the Philippines, is reported to have a LD50 of 0.2 mg/kg,[22] similar in potency to the monocled cobras (Naja kaouthia) found only in Thailand and eastern Cambodia, which also have a LD50 of 0.2 mg/kg. The spectacled cobras that are sympatric with N. oxiana, in Pakistan and far northwest India, also have a high potency of 0.22 mg/kg.[14][23]

Other highly venomous species are the forest cobras and/or water cobras (Boulengerina subgenus). The murine intraperitoneal LD50 of Naja annulata and Naja christyi venoms were 0.143 mg/kg (range of 0.131 mg/kg to 0.156 mg/kg) and 0.120 mg/kg, respectively.[24] Christensen (1968) also listed an IV LD50 of 0.17 mg/kg for N. annulata.[17] The Chinese cobra (N. atra) is also highly venomous. Minton (1974) listed a value of LD50 0.3 mg/kg intravenous (IV),[19] while Lee and Tseng list a value of 0.67 mg/kg subcutaneous injection (SC).[25] The LD50 of the Cape cobra (N. nivea) according to Minton, 1974 was 0.35 mg/kg (IV) and 0.4 mg/kg (SC).[19][26] The Senegalese cobra (N. senegalensis) has a murine LD50 of 0.39 mg/kg (Tan et al, 2021) via IV.[27] The Egyptian cobra (N. haje) of Ugandan locality had an IV LD50 of 0.43 mg/kg (0.35–0.52 mg/kg).[28]

The Naja species are a medically important group of snakes due to the number of bites and fatalities they cause across their geographical range. They range throughout Africa (including some parts of the Sahara where Naja haje can be found), Southwest Asia, Central Asia, South Asia, East Asia, and Southeast Asia. Roughly 30% of bites by some cobra species are dry bites, thus do not cause envenomation (a dry bite is a bite by a venomous snake that does not inject venom).[29] Brown (1973) noted that cobras with a higher rates of 'sham strikes' tend to be more venomous, while those with a less toxic venom tend to envenomate more frequently when attempting to bite. This can vary even between specimens of the same species. This is unlike related elapids, such as those species belonging to Dendroaspis (mambas) and Bungarus (kraits), with mambas tending to almost always envenomate and kraits tending to envenomate more often than they attempt 'sham strikes'.[30]

Many factors influence the differences in cases of fatality among different species within the same genus. Among cobras, the cases of fatal outcome of bites in both treated and untreated victims can be quite large. For example, mortality rates among untreated cases of envenomation by the cobras as a whole group ranges from 6.5–10% for N kaouthia.[30][31] to about 80% for N. oxiana.[32] Mortality rate for Naja atra is between 15 and 20%, 5–10% for N. nigricollis,[33] 50% for N. nivea,[30] 20–25% for N. naja,[34] In cases where victims of cobra bites are medically treated using normal treatment protocol for elapid type envenomation, differences in prognosis depend on the cobra species involved. The vast majority of envenomated patients treated make quick and complete recoveries, while other envenomated patients who receive similar treatment result in fatalities. The most important factors in the difference of mortality rates among victims envenomated by cobras is the severity of the bite and which cobra species caused the envenomation. The Caspian cobra (N. oxiana) and the Philippine cobra (N. philippinensis) are the two cobra species with the most toxic venom based on LD50 studies on mice. Both species cause prominent neurotoxicity and progression of life-threatening symptoms following envenomation. Death has been reported in as little as 30 minutes in cases of envenomation by both species. N. philippinensis purely neurotoxic venom causes prominent neurotoxicity with minimal local tissue damage and pain[35] and patients respond very well to antivenom therapy if treatment is administered rapidly after envenomation. Envenomation caused by N. oxiana is much more complicated. In addition to prominent neurotoxicity, very potent cytotoxic and cardiotoxic components are in this species' venom. Local effects are marked and manifest in all cases of envenomation: severe pain, severe swelling, bruising, blistering, and tissue necrosis. Renal damage and cardiotoxicity are also clinical manifestations of envenomation caused by N. oxiana, though they are rare and secondary.[36] The untreated mortality rate among those envenomed by N. oxiana approaches 80%, the highest among all species within the genus Naja.[32] Antivenom is not as effective for envenomation by this species as it is for other Asian 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%).[15]

Taxonomy

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Naja
(Naja)

The genus contains several species complexes of closely related and often similar-looking species, some of them only recently described or defined. Several recent taxonomic studies have revealed species not included in the current listing in ITIS:[5][37]

  • Naja anchietae (Bocage, 1879), Anchieta's cobra, is regarded as a subspecies of N. haje by Mertens (1937) and of N. annulifera by Broadley (1995). It is regarded as a full species by Broadley and Wüster (2004).[38][39]
  • Naja arabica Scortecci, 1932, the Arabian cobra, has long been considered a subspecies of N. haje, but was recently raised to the status of species.[40]
  • Naja ashei Broadley and Wüster, 2007, Ashe's spitting cobra, is a newly described species found in Africa and also a highly aggressive snake; it can spit a large amount of venom.[41][42]
  • Naja nigricincta Bogert, 1940, was long regarded as a subspecies of N. nigricollis, but was recently found to be a full species (with N. n. woodi as a subspecies).[43][44]
  • Naja senegalensis Trape et al., 2009, is a new species encompassing what were previously considered to be the West African savanna populations of N. haje.[40]
  • Naja peroescobari Ceríaco et al. 2017, is a new species encompassing what was previously considered the São Tomé population of N. melanoleuca.[45]
  • Naja guineensis Broadley et al., 2018, is a new species encompassing what were previously considered to be the West African forest populations of N. melanoleuca.[7]
  • Naja savannula Broadley et al., 2018, is a new species encompassing what were previously considered to be the West African savanna populations of N. melanoleuca.[7]
  • Naja subfulva Laurent, 1955, previously regarded as a subspecies of N. melanoleuca, was recently recognized as a full species.[7]

Two recent molecular phylogenetic studies have also supported the incorporation of the species previously assigned to the genera Boulengerina and Paranaja into Naja, as both are closely related to the forest cobra (Naja melanoleuca).[43][46] In the most comprehensive phylogenetic study to date, 5 putative new species were initially identified, of which 3 have since been named.[4]

The controversial amateur herpetologist Raymond Hoser proposed the genus Spracklandus for the African spitting cobras.[47] Wallach et al. suggested that this name was not published according to the Code and suggested instead the recognition of four subgenera within Naja: Naja for the Asiatic cobras, Boulengerina for the African forest, water and burrowing cobras, Uraeus for the Egyptian and Cape cobra group and Afronaja for the African spitting cobras.[6] International Commission on Zoological Nomenclature issued an opinion that it "finds no basis under the provisions of the Code for regarding the name Spracklandus as unavailable".[48]

Asiatic cobras are believed to further be split into two groups of southeastern Asian cobras (N. siamensis, N. sumatrana, N. philippinensis, N. samarensis, N. sputatrix, and N. mandalayensis) and western and northern Asian cobras (N. oxiana, N. kaouthia, N. sagittifera, and N. atra) with Naja naja serving as a basal lineage to all species.[49]

Species

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Image[5] Species[5] Authority[5] Subsp.*[5] Common name Geographic range
N. anchietae Bocage, 1879 0 Anchieta's cobra (Angolan Cobra) Angola, Botswana, Namibia, Zambia, eastern Zimbabwe
  N. annulata (Buchholz and Peters, 1876) 1 Banded water cobra Cameroon, the Central African Republic, the Democratic Republic of the Congo (Zaire), the Republic of Congo, Equatorial Guinea, Gabon, Rwanda, and the province of Cabinda in Angola
  N. annulifera Peters, 1854 0 Snouted cobra Botswana, Malawi, Mozambique, South Africa, Swaziland, Zambia, Zimbabwe
†N. antiqua Rage, 1976 0 Miocene-aged strata of Morocco
N. arabica Scortecci, 1932 0 Arabian cobra Oman, Saudi Arabia, Yemen
N. ashei Wüster and Broadley, 2007 0 Ashe's spitting cobra (giant spitting cobra) southern Ethiopia, Kenya, Somalia, eastern Uganda
  N. atra Cantor, 1842 0 Chinese cobra southern China, northern Laos, Taiwan, northern Vietnam
N. christyi (Boulenger, 1904) 0 Congo water cobra the Democratic Republic of the Congo (Zaire), the Republic of Congo, and the province of Cabinda in Angola
N. fuxi

Shi, Vogel, Chen, & Ding, 2022

0 Brown banded cobra China, Myanmar, Laos, Thailand, Vietnam
N. guineensis Broadley, Trape, Chirio, Ineich &Wüster, 2018 0 Black forest cobra Ghana, Guinea, Guinea-Bissau, the Ivory Coast, Liberia, Sierra Leone, Togo
  N. haje Linnaeus, 1758 0 Egyptian cobra Tanzania, Kenya, Somalia, Ethiopia, Uganda, South Sudan, Sudan, Cameroon, Nigeria, Niger, Burkina Faso, Mali, Senegal, Mauritania, Morocco, Algeria, Tunisia, Libya, and Egypt
†N. iberica Szyndlar, 1985 Miocene-aged strata of Spain
  N. kaouthia Lesson, 1831 0 Monocled cobra Bangladesh, Bhutan, Burma, Cambodia, southern China, eastern India, Laos, northwestern Malaysia, Nepal, Thailand, southeastern Tibet, Vietnam
  N. katiensis Angel, 1922 0 Mali cobra (Katian spitting cobra) Benin, Burkina Faso, Cameroon, Ghana, Guinea, the Ivory Coast, Mali, Gambia, Mauritania, Niger, Nigeria, Senegal, Togo
  N. mandalayensis Slowinski & Wüster, 2000 0 Mandalay spitting cobra (Burmese spitting cobra) Myanmar (Burma)
  N. melanoleuca Hallowell, 1857 0 Central African forest cobra Angola, Benin, Cameroon, the Central African Republic, the Republic of Congo, the Democratic Republic of the Congo (Zaire), Equatorial Guinea, Gabon, Nigeria
  N. mossambica Peters, 1854 0 Mozambique spitting cobra extreme southeastern Angola, Botswana, Malawi, Mozambique, Somalia, northeastern Namibia, South Africa, Swaziland, Tanzania (including Pemba Island), Zambia, Zimbabwe
N. multifasciata Werner, 1902 0 Many-banded cobra Cameroon, Congo, the Democratic Republic of the Congo (Zaire), Gabon
  N. naja (Linnaeus, 1758) 0 Indian cobra (spectacled cobra) Bangladesh, Bhutan, India, Nepal, Pakistan, Sri Lanka
  N. nana Collet & Trape, 2020 0 Dwarf water cobra Democratic Republic of Congo
  N. nigricincta Bogert, 1940 1 Zebra spitting cobra Angola, Namibia, South Africa
  N. nigricollis Reinhardt, 1843 0 Black-necked spitting cobra Angola, Benin, Burkina Faso, Burundi, Cameroon, the Central African Republic, Chad, the Democratic Republic of the Congo (Zaire) (except in the central region), Congo, Ethiopia, Gabon, Gambia, Ghana, Guinea-Bissau, Guinea, the Ivory Coast, Kenya, Liberia, Mali, Mauritania, Namibia, Niger, Nigeria, Rwanda, Senegal, Sierra Leone, Sudan, Tanzania, Somalia, Togo, Uganda, Zambia
  N. nivea (Linnaeus, 1758) 0 Cape cobra (yellow cobra) Botswana, Lesotho, Namibia, South Africa
  N. nubiae Wüster & Broadley, 2003 0 Nubian spitting cobra Chad, Egypt, Eritrea, Niger, Sudan
N. obscura Saleh & Trape, 2023 0 Obscure cobra Egypt
  N. oxiana (Eichwald, 1831) 0 Caspian cobra Afghanistan, northwestern India, Iran, Kyrgyzstan, Pakistan, Tajikistan, Turkmenistan, Uzbekistan
  N. pallida Boulenger, 1896 0 Red spitting cobra Djibouti, Ethiopia, Kenya, Somalia, Tanzania
N. peroescobari Ceríaco, Marques, Schmitz & Bauer, 2017 0 São Tomé forest cobra, cobra preta São Tomé and Príncipe (São Tomé)
  N. philippinensis Taylor, 1922 0 Philippine cobra the Philippines (Luzon, Mindoro)
†N. romani (Hofstetter, 1939) 0 † Miocene-aged strata of France, Germany, Austria, Russia, Hungary, Greece and Ukraine.[50]
  N. sagittifera Wall, 1913 0 Andaman cobra India (the Andaman Islands)
  N. samarensis Peters, 1861 0 Samar cobra the Philippines (Mindanao, Bohol, Leyte, Samar, Camiguin)
  N. savannula Broadley, Trape, Chirio & Wüster, 2018 0 West African banded cobra Benin, Burkina Faso, Cameroon, Chad, Gambia, Ghana, Guinea, the Ivory Coast, Mali, Niger, Nigeria, Senegal, Togo
N. senegalensis Trape, Chirio & Wüster, 2009 0 Senegalese cobra Benin, Burkina Faso, Ghana, Guinea, Mali, Niger, Nigeria, Senegal
  N. siamensis Laurenti, 1768 0 Indochinese spitting cobra Cambodia, Laos, Thailand, Vietnam
  N. sputatrix F. Boie, 1827 0 Javan spitting cobra Indonesia (Java, the Lesser Sunda Islands, East Timor)
  N. subfulva Laurent, 1955 0 Brown forest cobra Angola, Burundi, Cameroon, the Central African Republic, Chad, the Republic of Congo, the Democratic Republic of the Congo (Zaire), Ethiopia, Kenya, Malawi, Mozambique, Nigeria, Rwanda, Somalia, South Africa, South Sudan, Tanzania, Uganda, Zambia, Zimbabwe
  N. sumatrana Müller, 1887 0 Equatorial spitting cobra Brunei, Indonesia (Sumatra, Borneo, Bangka, Belitung), Malaysia, the Philippines (Palawan), southern Thailand, Singapore
  • Not including the nominate subspecies

† Extinct
T Type species[2]

References

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  48. ^ "Opinion 2468 (Case 3601) – Spracklandus Hoser, 2009 (Reptilia, Serpentes, Elapidae) and Australasian Journal of Herpetology issues 1–24: confirmation of availability declined; Appendix A (Code of Ethics): not adopted as a formal criterion for ruling on Cases". The Bulletin of Zoological Nomenclature. 78 (1): 42–45. 2021. doi:10.21805/bzn.v78.a012. ISSN 0007-5167. S2CID 233448875.
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  50. ^ Syromyatnikova, E.; Tesakov, A.; Titov, V. (2021). "Naja romani (Hoffstetter, 1939)(Serpentes: Elapidae) from the late Miocene of the Northern Caucasus: the last East European large cobra". Geodiversitas. 43 (19): 683–689. doi:10.5252/geodiversitas2021v43a19. S2CID 238231298.
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