Daboia
| Russell's viper Daboia russelii | |
|---|---|
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| A Russell's viper in Pune, India. | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Subphylum: | Vertebrata |
| Class: | Reptilia |
| Order: | Squamata |
| Suborder: | Serpentes |
| Family: | Viperidae |
| Subfamily: | Viperinae |
| Genus: | Daboia Gray, 1842 |
| Species: | D. russelii |
| Binomial name | |
| Daboia russelii (Shaw & Nodder, 1797) | |
| Synonyms | |
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Daboia are commonly known as Russell's viper (Kannada : ಮಂಡಲದ ಹಾವು, Telugu : రక్త పింజరి, పొడ పాము,కాటుక రేకుల పొడ) and chain viper, among other names.[5][6]
Description
This snake can grow to a maximum length of 166 cm (5.5 ft) and averages about 120 cm (4 ft) on mainland Asian populations, although island populations do not attain this size.[5] It is more slenderly built than most other vipers.[7] Ditmars (1937) reported the following dimensions for a "fair sized adult specimen":[8]| Total length | 4 ft., 1 inch | 124 cm |
| Length of tail | 7 inches | 18 cm |
| Girth | 6 inches | 15 cm |
| Width of head | 2 inches | 5 cm |
| Length of head | 2 inches | 5 cm |
The head is flattened, triangular and distinct from the neck. The snout is blunt, rounded and raised. The nostrils are large, in the middle of a large, single nasal scale. The lower edge of the nasal touches the nasorostral. The supranasal has a strong crescent shape and separates the nasal from the nasorostral anteriorly. The rostral is as broad as it is high.[5]
The body is stout, the cross-section of which is rounded to cylindrical. The dorsal scales are strongly keeled; only the lower row is smooth. Mid-body, the dorsal scales number 27–33. The ventral scales number 153–180. The anal plate is not divided. The tail is short — about 14% of the total body length — with the paired subcaudals numbering 41–68.[5]
The color pattern consists of a deep yellow, tan or brown ground color, with three series of dark brown spots that run the length of its body. Each of these spots has a black ring around it, the outer border of which is intensified with a rim of white or yellow. The dorsal spots, which usually number 23–30, may grow together, while the side spots may break apart. The head has a pair of distinct dark patches, one on each temple, together with a pinkish, salmon or brownish V or X pattern that forms an apex towards the snout. Behind the eye, there is a dark streak, outlined in white, pink or buff. The venter is white, whitish, yellowish or pinkish, often with an irregular scattering of dark spots.[5]
Common names
Common names of Daboia include:- English – Russell's viper chain viper, Indian Russell's viper,common Russell's viper, seven pacer, chain snake, scissors snake. Previously, another common name was used to described a subspecies that is now part of the synonymy of this form: Sri Lankan Russell's viper for D. r. pulchella.
- Urdu, Hindi, Hindustani, Punjabi – daboia.
- Kashmiri – gunas.[9]
- Oriya – Chandan Boda
- Sindhi – koraile.[9]
- Bengali – bora, chandra bora, uloo bora.
- Gujarati – chitalo, khadchitalo.
- Marathi – ghonas.
- Telugu – katuka rekula paamu.or raktha penjara/penjari.
- Thai – ngu maew sao
- Kannada – mandaladha haav] or mandalata havu, kolakumandala.
- Tamil – retha aunali, kannadi virian or kannadi viriyan.
- Malayalam – mandali, raktamandali,chenathandan, manchatti, vattakoora, "Rakta Anali"
- Sinhala – tic polonga.
- Burmese – mwe lewe.
- Tulu – PILI kandhodi
Geographic range
Russell's viper from India
Brown (1973) mentions that it can also found in Vietnam, Laos and on the Indonesian island of Sumatra. Ditmars (1937) reportedly received a specimen from Sumatra as well.However, the distribution of this species in the Indonesian archipelago is still being elucidated.
Within its range it can be very common in some areas, but scarce in others. In India, is abundant in Punjab, very common along the West Coast and its hills, in southern India and up to Bengal. It is uncommon to rare in the Ganges valley, northern Bengal and Assam. It is prevalent in Myanmar.
Habitat
It is not restricted to any particular habitat, but does tend to avoid dense forests. The snake is mostly found in open, grassy or bushy areas, but may also be found in second growth forests (scrub jungles), on forested plantations and farmland. They are most common in plains, coastal lowlands and hills of suitable habitat. Generally not found at altitude, but has been reported as far up as 2300–3000 m. Humid environments, such as marshes, swamps and rain forests, are avoided.This species is often found in highly urbanized areas and settlements in the countryside, the attraction being the rodents commensal with man. As a result, those working outside in these areas are most at risk of being bitten. It should be noted, however, that D. russelii does not associate as closely with human habitation as Naja and Bungarus (cobras and kraits).
Behavior
This snake is terrestrial and active primarily as a nocturnal forager. However, during cool weather it will alter its behavior and become more active during the day.Adults are reported to be persistently slow and sluggish unless pushed beyond a certain limit, after which they become aggressive. Juveniles, on the other hand, are generally more nervous.
When threatened they form a series of S-loops, raise the first third of the body and produce a hiss that is supposedly louder than that of any other snake. When striking from this position, they can exert so much force that even a large individual can lift most of its body off the ground in the process. These snakes are strong and may react violently to being picked up. The bite may be a snap, or they may hang on for many seconds.
Although this genus does not have the heat-sensitive pit organs common to the Crotalinae, it is one of a number of viperines that are apparently able to react to thermal cues, further supporting the notion that they too possess a heat-sensitive organ. 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.
Reproduction
This species is ovoviviparous. Mating generally occurs early in the year, although gravid females may be found at any time. The gestation period is more than six months. Young are produced from May to November, but mostly in June and July. It is a prolific breeder. Litters of 20–40 are common,although there may be fewer offspring and as little as one. The reported maximum is 65 in a single litter. At birth, juveniles are 215–260 mm in length. The minimum length for a gravid female is about 100 cm. It seems that sexual maturity is achieved in 2–3 years. In one case, it took a specimen nearly 4.5 hours to produce 11 young.Prey
Juveniles are known to be cannibalistic.
Mimicry
Venom
The quantity of venom produced by individual specimens is considerable. Reported venom yields for adult specimens range from 130–250 mg to 150–250 mg to 21–268 mg. For 13 juveniles with an average length of 79 cm, the average venom yield was 8–79 mg (mean 45 mg).The LD50 in mice, which is used as a possible indicator of snake venom toxicity, is as follows: 0.133 mg/kg intravenous, 0.40 mg/kg intraperitoneal, about 0.75 mg/kg subcutaneous.For most humans, a lethal dose is approximately 40–70 mg. 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 post-bite. There is a drop in blood pressure, 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. Kidney failure (renal failure) also occurs in approximately 25-30 percent of untreated bites. Severe disseminated intravascular coagulation also can occur in severe envenomations. Early medical treatment and early access to antivenom can prevent and drastically reduce the chance of developing the severe/potentially lethal complications.
Severe pain may last for 2–4 weeks. Locally, it may persist depending on the level of tissue damage. Often, local swelling peaks within 48–72 hours, involving both the affected limb and the trunk. If swelling up to the trunk occurs within 1–2 hours, massive envenomation is likely. Discoloration may occur throughout the swollen area as red blood cells and plasma leak into muscle tissue. Death from septicaemia, kidney, respiratory or cardiac failure may occur 1 to 14 days post-bite or even later.
A study in The Lancet journal showed that out of a sample of people bitten by Daboia russelii who survived, 29% of them suffered severe damage to their pituitary glands, which later resulted in hypopituitarism. Other scientific studies support the hypothesis that D. russelii bites can cause hypopituitarism.
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.
In India, the Haffkine Institute prepares a polyvalent antivenin that is used to treat bites from this species.
Subspecies
| Subspecies | Taxon author[ | Common name | Geographic range |
|---|---|---|---|
| D. r. russelii | (Shaw, 1797) | Indian Russell's viper[33] | Across the Indian subcontinent through Pakistan and Bangladesh to Sri Lanka. |
| D. r. siamensis | (M.A. Smith, 1917) | Eastern Russell's viper[34] | From Myanmar through Thailand, Cambodia, Indonesia and southern China. Also found in Taiwan. |
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