NAJA
ناجا
| Indian cobra, N. naja | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Squamata |
| Suborder: | Serpentes |
| Family: | Elapidae |
| Genus: | Naja Laurenti, 1768 |
Naja is a genus of venomous elapid snakes. Although several other genera share the common name, Naja species are the most recognized and most widespread group of snakes commonly known as cobras. The genus Naja consists of 20 to 22 species, but has undergone several taxonomic revisions in recent years, so sources vary greatly. They range throughout Africa, Southwest Asia, South Asia and Southeast Asia.
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The origin of this genus name is from the Old Indic nāga, cognate with English 'snake', Germanic: *snēk-a-, Proto-IE: *(s)nēg-o-.
DescriptionDifferent 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 cobra are around 3.1 m (10 ft), with the forest cobra arguably being the longest species. 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.
VenomAll 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 which causes swelling and necrosis, and has 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 releasing venom through the tips (similar to a hypodermic needle), have a rifled opening in the front surface which allows the snake to propel the venom 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. Once sprayed onto a victim's skin, the venom acts as a severe irritant. If it is introduced to the eye, it can cause a severe burning sensation and temporary or even permanent blindness if not cleaned out immediately and thoroughly.
Murine subcutaneous LD50 values for some cobra species include 0.20 mg/kg for N. philippinensis (Philippine cobra), which is considered to be the most venomous species, 0.40 mg/kg for N. oxiana (Caspian cobra), 0.80 mg/kg for N. naja (Indian cobra), 1.15 mg/kg for N. haje (Egyptian cobra), 2.0 mg/kg for Naja nigricollis (black-necked spitting cobra), 0.72 mg/kg for N. nivea (Cape cobra), and 0.53 mg/kg for N. atra (Chinese cobra).
Some murine IV LD50 values include 0.29 mg/kg for N. melanoleuca (forest cobra), 0.345 mg/kg for N. atra (Chinese cobra), 0.373 mg/kg for N. kaouthia (monocled cobra), and 0.96 mg/kg for N. oxiana (Caspian cobra).
The murine IP LD50 of N. annulata (banded water cobra) and N. christyi (Congo water cobra) venoms were 0.143 and 0.120 mg/kg, respectively. Other IP LD50 values include N. haje (Egyptian cobra) at 0.185 mg/kg, N. kaouthia (monocled cobra) at 0.225 mg/kg, N. naja at 0.315 mg/kg, N. melanoleuca at 0.324 mg/kg, N. nivea (Cape cobra) at 0.4 mg/kg, N. nigricollis at 0.4 mg/kg, and N. pallida (red spitting cobra) at 2.0 mg/kg.
Species*) Not including the nominate subspecies. T) Type species.
TaxonomyThe genus contains several species complexes of closely related and often similar species, some of them only recently described or defined. Several recent taxonomic studies have revealed species not included in the current listing in ITIS:
- Naja anchietae (Bocage, 1879), or 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).
- 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.
- Naja ashei Broadley and Wüster, 2007, Ashe’s spitting cobra, is a newly described species found in Africa.
- 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).
- 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.
Two recent molecular phylogenetic studies have also supported the incorporation of the species normally assigned to the genera Boulengerina and Paranaja into Naja, as both are closely related to the forest cobra (Naja melanoleuca)
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