Каспий жыланының сипаттамасы

Species of snake

The Caspian cobra (Naja oxiana), also called the Central Asian cobra or Russian cobra, is a species of highly venomous snake in the family Elapidae. The species is endemic to Central Asia. First described by Karl Eichwald, a German physician, in 1831, it was for many years considered to be a subspecies of the Naja naja until genetic analysis revealed it to be a distinct species.

Karl Eichwald, a Baltic German, having been born modern day Saint Petersburg, Russia, who was a physician and naturalist first described the Caspian cobra originally as Tomyris oxiana in 1831. Russian naturalist Alexander Strauch placed it in the genus Naja in 1868. The generic name naja is a Latinisation of the Sanskrit word nāgá ([[wikt:नाग#Sanskrit) meaning "cobra". The specific epithet oxiana is derived from the word Ōxus in Latin or Ὦξος (Ôxos) in Greek, 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. 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.

Naja oxiana tends to avoid humans as much as it can, but it can become fiercely defensive when threatened or cornered, and even juveniles tend to be very aggressive. When cornered and provoked, it is liable to spread its hood, hiss, sway from side to side and strike repeatedly; however, it can not spit venom. This terrestrial species is mainly diurnal, but it may be crepuscular and nocturnal in some parts of its range during the hottest month (July). Caspian cobras are good climbers, and able swimmers. The Caspian cobra is often found in water and seldom found too far away from it. 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, similar to Naja naja. 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. which have been shown to cause cell death through damage to lysosomes. 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. 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. 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.

Naja oxiana is regarded as the most dangerous snake in Central Asia and is one of the venomous snakes with a high mortality rate. It is one of the most dangerous elapid species in the world. An older study by Zug et al listed a LD50 value of 0.2 mg/kg from Pakistani and Indian specimens. Average venom yield per bite for this species is between 75 and 125 mg (dry weight), and 784 mg (dry weight). 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 (an untreated mortality rate of 73%). 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 (Levant viper), 30,339 from E. carinatus (saw scaled viper), 51,657 from P. persicus (Persian horned viper) and 12,124 from N. oxiana (Caspian cobra). 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. Out of the 53,787 cases of snake bites which were reported to medical centers in Iran, 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 the 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%. In Pakistan, it is responsible for high rates of snakebites that result in mortality. 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). 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%).