Naja

Naja is a genus of venomous snakes belonging to the Elapidae family and ranging from Africa to the Middle East, Central Asia, South Asia (Indian subcontinent), Southeast Asia, and far East Asia. Although there are several other genera that share the common name, Naja are the most recognized and most widespread group of snakes commonly known as cobras. The genus Naja consists of 20 to 23 species, but has undergone several taxonomic revisions in recent years, so sources vary greatly.

Etymology
The generic name naja is a Latinisation of the Sanskrit word nāgá (नाग) meaning "cobra" or snake.

Description
Different Naja species range in length and most are relatively slender-bodied snakes. Most species are capable of attaining lengths of 1.84 m. Maximum lengths for some of the larger species of cobra is around 3.1 m, with the Forest cobra 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 form a hood to appear larger to a potential predator.

Venom
All species in the genus Naja are capable of delivering a fatal bite in 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 developed 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 Naja philippinensis (Philippine cobra) which is considered to be the most venomous species, 0.40 mg/kg for Naja oxiana (Caspian cobra), 0.80 mg/kg for Naja naja (Indian cobra), 1.15 mg/kg for Naja haje (Egyptian cobra), 2.0 mg/kg for Naja nigricollis (Black-necked spitting cobra), 0.72 mg/kg for Naja nivea (Cape cobra), and 0.53 mg/kg for Naja atra (Chinese cobra).

Some murine IV LD50 values include 0.29 mg/kg for Naja melanoleuca (Forest cobra), 0.345 mg/kg for Naja atra (Chinese cobra), 0.373 mg/kg for Naja kaouthia (Monocled cobra), and 0.96 mg/kg for Naja oxiana (Caspian cobra).

The murine IP LD50 of Naja annulata (Banded water cobra) and Naja christyi (Congo water cobra) venoms were 0.143 and 0.120 mg/kg, respectively. Other IP LD50 values include Naja haje (Egyptian cobra) at 0.185 mg/kg, for Naja kaouthia (Monocled cobra) it's 0.225 mg/kg, for Naja naja (Indian cobra) it's 0.315 mg/kg, for Naja melanoleuca (Forest cobra) it's 0.324 mg/kg, for Naja nivea (Cape cobra) it's 0.4 mg/kg, for Naja nigricollis (Black-necked spitting cobra) it's 0.4 mg/kg, and for Naja pallida (Red spitting cobra) it's 2.0 mg/kg.

Taxonomy
The 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). A.k.a. Anchieta's cobra. Regarded as a subspecies of N. haje by Mertens (1937) and of N. annulifera by Broadley (1995). Regarded as a full species by Broadley and Wüster (2004).
 * Naja arabica Scortecci, 1932. A.k.a. Arabian cobra. Long considered a subspecies of N. haje, this was recently raised to the status of a whole species
 * Naja ashei Broadley and Wüster, 2007. A.k.a. Ashe’s spitting cobra. This is a newly described species found in Africa.
 * Naja nigricincta Bogert, 1940. This was long regarded as a subspecies of Naja nigricollis, but was recently found to be a full species (with N. nigricincta woodi as a subspecies).
 * Naja senegalensis Trape et al., 2009. This new species, encompassing what were previously considered to be the West African savanna populations of N. haje, was recently described as a new species.

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)

Species
*) Not including the nominate subspecies. T ) Type species.