Жұлынды жылан – Расселдің уыты

Species of venomous snake

Russell's viper (Daboia russelii) is a highly venomous snake in the family Viperidae native to the Indian subcontinent and one of the big four snakes in India. It was described in 1797 by George Shaw and Frederick Polydore Nodder, and named after Patrick Russell, who wrote about it in his 1796 work An account of Indian serpents, collected on the coast of Coromandel.

English naturalist George Shaw—with illustrator Frederick Polydore Nodder—in The Naturalist's Miscellany: Or, Coloured Figures Of Natural Objects; Drawn and Described Immediately From Nature formally described the species in 1797 as Coluber russelii, from a specimen presented to the British Museum by Scottish herpetologist Patrick Russell. Russell had written of the species in his 1796 work An account of Indian serpents, collected on the coast of Coromandel, confirming its highly venomous nature by experimenting on chickens and dogs. He added the native people called it katuka retula poda. Analysis of morphological and mitochondrial DNA data shows that the eastern subspecies of D. russelii should be considered a separate species, Daboia siamensis. a Scottish herpetologist who first described many of India's snakes, and the name of the genus is from the Hindi word meaning "that lies hid", or "the lurker". In English, common names of D. russelii include Russell's viper, chain viper, common Russell's viper, seven pacer, chain snake, and scissors snake.

Russell's viper is found in India, Sri Lanka, Bangladesh, Nepal, and Pakistan. Populations from South East Asia previously assigned to this species are now considered to be part of a different species, Daboia siamensis. The type locality is listed as "India". More specifically, this would be the Coromandel Coast, by inference of Russell (1796). Within its range, it can be common in some areas, but scarce in others. The bite may be a snap, or they may hang on for many seconds. The identity of this sensor is not certain, but the nerve endings in the supranasal sac of these snakes resemble those found in other heat sensitive organs.

Russell's viper is ovoviviparous. in a single litter. At birth, juveniles are in total length. The minimum total length for a gravid female is about It seems that sexual maturity is achieved in 2–3 years. In one case, it took a specimen nearly 4.5 hours to give birth to 11 young. The quantity of venom produced by individual specimens of D. russelii is considerable. Venom yields for adult specimens have been reported as 130–250 mg, 150–250 mg, and 21–268 mg. For 13 juveniles with an average total length of , the venom yield ranged from 8 to 79 mg (mean 45 mg). 0.40 mg/kg intraperitoneal, about 0.75 mg/kg subcutaneous. For most humans, a lethal dose is about 40–70 mg, well within the amount that can be delivered in one bite. In general, the toxicity depends on a combination of five different venom fractions, each of which is less toxic when tested separately. Venom toxicity and bite symptoms in humans vary within different populations and over time.

Envenomation symptoms begin with pain at the site of the bite, immediately followed by swelling of the affected extremity. Bleeding is a common symptom, especially from the gums and in the urine, and sputum may show signs of blood within 20 minutes after the bite. The blood pressure drops, and the heart rate falls. Blistering occurs at the site of the bite, developing along the affected limb in severe cases. Necrosis is usually superficial and limited to the muscles near the bite, but may be severe in extreme cases. Vomiting and facial swelling occur in about one third of all cases. Other scientific studies support the hypothesis that D. russelii bites can cause hypopituitarism.

In India, the Haffkine Institute prepares a polyvalent antivenom that is used to treat bites from this species.

Because this venom is so effective at inducing thrombosis, it has been incorporated into an in vitro diagnostic test for blood clotting that is widely used in hospital laboratories. This test is often referred to as dilute Russell's viper venom time (dRVVT). The coagulant in the venom directly activates factor X, which turns prothrombin into thrombin in the presence of factor V and phospholipid. The venom is diluted to give a clotting time of 23 to 27 seconds and the phospholipid is reduced to make the test extremely sensitive to phospholipid. The dRVVT test is more sensitive than the aPTT test for the detection of lupus anticoagulant (an autoimmune disorder), because it is not influenced by deficiencies in clotting factors VIII, IX or XI.