Russell's viper :The species you're referring to is actually known as the "Russell's viper" (Daboia russelii), not "Retake." Russell's viper is indeed a highly venomous snake in the family Viperidae, native to India, Pakistan, Sri Lanka, Nepal, and Bangladesh. It was first described by George Shaw and Frederick Polydore Nodder in 1797. The specific epithet "russelii" honors Patrick Russell, who was a Scottish herpetologist and is one of the "big four" venomous snakes in India, along with the Indian cobra, common krait, and saw-scaled viper.
Taxonomy
The passage provides a comprehensive overview of the taxonomic history, naming controversies, and subspecies diversity of Daboia russelii, also known as Russell's viper. Here are the key points highlighted:
1. **Taxonomic History**:
- George Shaw and Frederick Polydore Nodder formally described the species in 1797 as Coluber russelii, based on a specimen presented by Patrick Russell.
- Patrick Russell's earlier work from 1796, "An Account of Indian Serpents," confirmed the species' venomous nature through experiments on animals and noted its local name, "katuka retula poda."
2. **Subspecies Diversity**:
- Genetic studies suggest that the eastern subspecies of D. russelii should be classified as a distinct species, Daboia siamensis.
- Several other subspecies have been documented in literature, including D. s. formosensis (Thailand), D. s. limitis (Indonesia), D. r. pulchella (Sri Lanka), and D. r. nordicus (northern India).
3. **Spelling Controversy**:
- The correct spelling of the species epithet has been debated: "russelii" (as originally spelled by Shaw and Nodder) versus "russellii" (with an additional "L").
- Some argue that the original misspelling by Shaw and Nodder should be maintained under the rules of the International Code of Zoological Nomenclature, while others advocate for the corrected spelling.
4. **Etymology**:
- The species name, whether "russelii" or "russellii," honors Patrick Russell for his contributions to herpetology, despite the spelling discrepancy.
This passage underscores the complexities involved in scientific naming practices, historical context in taxonomy, and ongoing debates over species classification and nomenclature.
Etymology
The species Daboia russelii is named after Patrick Russell (1726–1805), a Scottish herpetologist renowned for his early descriptions of Indian snakes. The genus name "Daboia" is derived from a Hindi word meaning "that lies hid" or "the lurker."
In English, common names for D. russelii include Russell's viper, chain viper, Indian Russell's viper, common Russell's viper, seven pacer, chain snake, and scissors snake. These names reflect its distinctive appearance and behavior, such as the pattern resembling chains or its characteristic movement described as a "seven pacer."
Description
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The passage provides a detailed description of the morphology and physical characteristics of Russell's viper (Daboia russelii):
1. **Head and Facial Features**:
- The head is flattened, triangular, and distinct from the neck.
- Snout is blunt, rounded, and raised.
- Large nostrils positioned within a single large nasal scale.
- Supranasal scale crescent-shaped, separating nasal from nasorostral scale.
- Rostral scale broad and as high as it is wide.
2. **Head Scales**:
- Irregular, strongly fragmented scales on the crown.
- Narrow supraocular scales, six to nine across the head.
- Large eyes flecked with yellow or gold, surrounded by 10–15 circumorbital scales.
- 10–12 supralabials, fourth and fifth significantly larger.
- Eye separated from supralabials by three or four rows of suboculars.
- Enlarged front pair of chin shields.
3. **Fangs and Dentition**:
- Two maxillary bones supporting two to six pairs of fangs (active and replacements).
- Fangs can reach a length of 16.5 mm.
4. **Body**:
- Stout body with rounded to circular cross-section.
- Dorsal scales strongly keeled, except for lowest row which is smooth.
- 27–33 dorsal scales mid-body.
- 153–180 ventral scales.
- Undivided anal plate.
- Short tail (about 14% of total length) with 41–68 paired subcaudals.
5. **Coloration and Pattern**:
- Dorsal coloration deep yellow, tan, or brown.
- Three series of dark brown spots along the body, each with a black ring and sometimes rimmed with white or yellow.
- 23–30 dorsal spots that may merge; side spots may break apart.
- Head with distinct dark patches on temples and a V or X marking towards the snout.
- Dark streak behind the eye outlined in white, pink, or buff.
- Venter white, whitish, yellowish, or pinkish with irregular dark spots.
6. **Size**:
- Maximum length up to 166 cm (65 in), average around 120 cm (47 in) in mainland Asia.
- More slender compared to most vipers.
7. **Additional Dimensions** (reported from a specimen):
- Total length: 1.24 m (4 ft 1 in)
- Tail length: 430 mm (17 in)
- Girth: 150 mm (6 in)
- Head width and length: 51 mm (2 in)
This description provides a comprehensive overview of the physical attributes and dimensions of Russell's viper, detailing its morphology, coloration, and measurements typical of the species.
Distribution and habitat
Russell's viper (Daboia russelii) is distributed across several countries in South Asia, including India, Sri Lanka, Bangladesh, Nepal, and Pakistan. Formerly, populations from Southeast Asia were included under this species, but they are now classified as a separate species, Daboia siamensis.
**Habitat and Distribution**:
- Within its range, Russell's viper can vary in abundance, being common in some areas while scarce in others. In India, it is particularly abundant in Punjab, common along the West Coast and its hills, and in southern regions like Karnataka extending northward to Bengal.
- It is less commonly found in the Ganges valley, northern Bengal, and Assam.
- Russell's viper is adaptable to a variety of habitats but tends to avoid dense forests. It is typically found in open, grassy or bushy areas, second growth forests (scrub jungles), forested plantations, and farmland.
- The viper prefers plains, coastal lowlands, and hills with suitable vegetation. It generally avoids high-altitude regions but has been reported as high as 2300–3000 m (7,500–9,800 ft).
- Humid environments such as marshes, swamps, and rainforests are not preferred habitats.
**Behavior and Interaction with Humans**:
- Russell's viper is known to inhabit highly urbanized areas and settlements in rural settings due to the presence of rodents, which are attracted to human habitation.
- This proximity increases the risk of encounters with humans, particularly those engaged in outdoor activities in these areas.
- However, unlike cobras (Naja species) and kraits (Bungarus species), Russell's viper does not closely associate with human habitation as a primary habitat.
In summary, Russell's viper demonstrates a broad distribution across South Asia, adapting to a range of habitats but typically avoiding dense forests and high-altitude regions. Its presence near human settlements increases the potential for bites, primarily due to the abundance of rodent prey in these areas.
Behaviour and ecology
Russell's viper (Daboia russelii) exhibits distinctive behaviors and characteristics related to its hunting, defense, and sensory capabilities:
1. **Activity and Behavior**:
- The viper is primarily terrestrial and active predominantly at night (nocturnal). However, in cooler weather conditions, it may also be active during the day.
- Adults are generally slow-moving and sluggish, typically not aggressive unless provoked. They are capable of striking with incredible speed when threatened.
- Juveniles, on the other hand, are more nervous and may exhibit quicker responses to threats.
2. **Defensive Behavior**:
- When threatened, Russell's vipers adopt a defensive posture by forming a series of S-loops and raising the front part of their body.
- They produce a hiss described as louder than that of other snakes, which serves as a warning signal.
- If provoked further, they can strike aggressively, capable of lifting their body off the ground due to the force exerted.
- This defensive behavior sometimes leads to misconceptions that the vipers actively chase and attack humans, though they typically prefer to avoid confrontation.
3. **Sensory Capabilities**:
- Unlike pit vipers (Crotalinae) that possess heat-sensitive pit organs, Russell's viper belongs to a group lacking such specialized organs.
- Despite this, they demonstrate the ability to react to thermal cues, suggesting they may possess a form of heat sensitivity through other mechanisms.
- The specific organ responsible for this sensitivity is not conclusively identified, but nerve endings in the supranasal sac resemble those found in heat-sensitive organs of other snakes.
In summary, Russell's viper displays behaviors adapted for both nocturnal hunting and defense against threats. While typically avoiding conflict, they can react swiftly and forcefully if provoked, relying on defensive posturing, hissing, and striking to deter perceived threats. Their sensory capabilities, including potential thermal sensitivity, contribute to their effectiveness as predators in diverse habitats across their range.]
Reproduction
Russell's viper (Daboia russelii) exhibits unique reproductive characteristics typical of ovoviviparous snakes:
1. **Reproductive Behavior**:
- The species is ovoviviparous, meaning the embryos develop inside eggs within the female's body, and live young are born.
- Mating generally occurs early in the year, although pregnant females may be found throughout the year.
- The gestation period lasts more than six months.
2. **Breeding Season and Birth**:
- Young are typically born from May to November, with peak births occurring in June and July.
- Russell's viper is considered a prolific breeder, with litters commonly ranging from 20 to 40 offspring.
- However, litter sizes can vary widely, with reports ranging from as few as one offspring to a maximum of 75 in a single litter.
3. **Juvenile Characteristics**:
- At birth, juveniles measure between 215–260 mm (8.5–10.2 inches) in total length.
- Gravid (pregnant) females have a minimum total length of about 100 cm (39 inches).
4. **Maturity and Birth Process**:
- Sexual maturity is typically reached in 2–3 years.
- The birthing process can be prolonged, with one recorded instance where it took nearly 4.5 hours for a female to give birth to 11 young.
In summary, Russell's viper demonstrates a reproductive strategy adapted to its environment, producing large litters of live young after an extended gestation period. This strategy ensures the survival of offspring in varied habitats across its range in South Asia.
Prey
Russell's viper (Daboia russelii) exhibits a varied diet and feeding behavior throughout its life stages:
1. **Diet**:
- The primary diet of Russell's viper consists of rodents, which are its preferred prey.
- It also consumes other small animals such as reptiles (especially lizards), land crabs, scorpions, and various arthropods.
- This diverse diet allows the viper to adapt to different prey availability in its habitat.
2. **Feeding Behavior Across Life Stages**:
- **Juveniles**: When young, Russell's vipers are crepuscular (active at dawn and dusk) and feed on lizards primarily. They are also known to actively forage for food.
- **Adults**: As they mature into adults, Russell's vipers increasingly specialize in hunting rodents. The presence of rodents around human settlements attracts them to these areas.
- The availability of rodents and lizards near human habitats is a significant factor in why Russell's vipers are frequently found in urbanized or rural areas.
3. **Cannibalism**:
- Juvenile Russell's vipers have been observed exhibiting cannibalistic behavior, where they may prey upon smaller individuals of their own species.
In summary, Russell's vipers play a crucial ecological role by controlling rodent populations, which are abundant in agricultural and rural landscapes. Their ability to switch diets as they mature—from lizards to rodents—helps them adapt to changing food availability and ensure their survival in diverse habitats across South Asia.
Mimicry
Some herpetologists speculate that due to the success and fearsome reputation of Russell's viper (Daboia russelii) within its natural environment, another snake species has evolved to mimic its appearance. Specifically, the rough-scaled sand boa (Eryx conicus) is cited as a non-venomous snake that superficially resembles Russell's viper:
1. **Appearance**:
- The rough-scaled sand boa, Eryx conicus, often displays a color pattern that resembles that of Russell's viper.
- This mimicry includes similar markings and coloration, potentially serving as a protective adaptation against predators that avoid or fear Russell's viper due to its venomous nature.
2. **Behavior and Harmlessness**:
- Despite its visual resemblance, the rough-scaled sand boa is completely harmless to humans and other animals.
- It does not possess venom or any other defensive mechanisms beyond its mimicry of Russell's viper's appearance.
3. **Ecological Role**:
- Mimicry in snakes like Eryx conicus illustrates an evolutionary strategy where harmless species benefit from resembling dangerous or intimidating species.
- This mimicry can enhance their survival by reducing predation or intimidation from potential threats that mistake them for a more dangerous species.
In summary, the rough-scaled sand boa (Eryx conicus) mimics the appearance of Russell's viper (Daboia russelii), possibly as a protective adaptation in response to the viper's formidable reputation and ecological success. This phenomenon highlights the diversity of survival strategies in nature, where harmless species can gain an advantage by resembling more threatening counterparts.]
Venom
Russell's viper (Daboia russelii) is equipped with solenoglyphous dentition, specialized for delivering venom effectively. Here are some key points regarding its venom and toxicity:
1. **Venom Production**:
- Adult specimens of Russell's viper can produce significant amounts of venom. Reported venom yields vary, with ranges such as 130–250 mg, 150–250 mg, and 21–268 mg per milking.
- Juveniles, with an average total length of 79 cm (31 in), have been reported to yield venom ranging from 8 to 79 mg, with a mean of 45 mg.
2. **Toxicity**:
- The LD50 (median lethal dose) in mice serves as a measure of venom toxicity:
- Intravenous (IV): Approximately 0.133 mg/kg
- Intraperitoneal (IP): About 0.40 mg/kg
- Subcutaneous (SC): Around 0.75 mg/kg
- For humans, a lethal dose is estimated to be between 40–70 mg, which is well within the amount that can be delivered in a single bite.
- Russell's viper venom is composed of multiple fractions, each contributing to its overall toxicity. These fractions are less toxic individually than when combined in the venom mixture.
3. **Variability and Impact**:
- Venom toxicity and the symptoms of envenomation in humans can vary among different populations and over time.
- Factors influencing the severity of envenomation include the size of the snake, the amount of venom injected, and the location and depth of the bite.
4. **Research Insights**:
- Studies, such as those by Meier and Theakston, highlight that the lethality of Russell's viper venom can vary depending on the route of injection (IV, IP, SC), emphasizing the importance of understanding venom delivery mechanisms and their effects.
In summary, Russell's viper possesses potent venom capable of causing severe envenomation in humans. Understanding the composition, yield, and toxicity of its venom is crucial for effective medical management of snakebite cases and for developing appropriate antivenoms.
Symptoms
Envenomation by Russell's viper (Daboia russelii) can lead to a range of severe symptoms and complications, highlighting the urgency of medical intervention and access to antivenom:
1. **Initial Symptoms**:
- Envenomation typically begins with immediate pain at the site of the bite, followed rapidly by swelling of the affected limb or area.
- Bleeding is common, often seen from the gums, urine (hematuria), and sometimes in sputum, occurring within about 20 minutes post-bite.
- Blood pressure drops (hypotension) and heart rate decreases (bradycardia).
2. **Progression of Symptoms**:
- Blistering may develop at the bite site and can spread along the affected limb in severe cases.
- Necrosis (tissue death) is generally superficial, primarily affecting muscles near the bite site, but in extreme cases, it can be severe.
- Vomiting and facial swelling are observed in approximately one-third of cases.
3. **Complications**:
- Kidney failure (renal failure) occurs in about 25–30% of untreated bites, emphasizing the systemic impact of the venom.
- Severe cases may lead to disseminated intravascular coagulation (DIC), a condition where blood clotting mechanisms are disrupted, potentially leading to widespread bleeding.
4. **Long-Term Effects**:
- Survivors of Russell's viper bites may experience prolonged severe pain lasting 2–4 weeks, depending on the extent of tissue damage.
- Local swelling typically peaks within 48–72 hours and can involve both the affected limb and the trunk, indicating the severity of envenomation.
- Rapid swelling extending up to the trunk within 1–2 hours suggests massive envenomation.
5. **Hypopituitarism**:
- Studies, including research published in The Lancet, have indicated that a significant percentage (29%) of survivors of D. russelii bites suffer severe damage to their pituitary glands.
- This damage can lead to hypopituitarism, a condition where the pituitary gland fails to produce adequate amounts of hormones, impacting various bodily functions.
In conclusion, timely administration of antivenom and comprehensive medical care are crucial in managing Russell's viper bites to mitigate severe complications and improve outcomes. The diverse range of symptoms and potential long-term effects underscore the importance of immediate medical attention following a snakebite incident.]
Antivenom treatment
In India, the Haffkine Institute manufactures a polyvalent antivenom specifically designed to treat bites from Russell's viper (Daboia russelii). This antivenom is crucial for neutralizing the venom's effects and saving lives following snakebite incidents.
Additionally, in late 2016, a new antivenom was developed by the Clodomiro Picado Institute in Costa Rica. This development marked a significant advancement in antivenom technology, particularly tailored for treating Russell's viper bites. Clinical trials for this new antivenom were initiated in Sri Lanka, aiming to validate its efficacy and safety in local populations exposed to the viper's venom.
The introduction of new antivenoms reflects ongoing efforts to improve treatment options for snakebite envenomation worldwide, addressing regional variations in venom composition and enhancing the accessibility of effective medical interventions. These developments are crucial in combating the serious health threats posed by venomous snakebites, particularly in regions where Russell's viper is prevalent.
Clinical use
The venom of Russell's viper (Daboia russelii) is notable for its ability to induce thrombosis, which has led to its use in an in vitro diagnostic test for blood clotting known as dilute Russell's viper venom time (dRVVT). This test is widely utilized in hospital laboratories for specific purposes:
1. **Mechanism and Function**:
- The coagulant in Russell's viper venom directly activates factor X in the coagulation cascade.
- Activated factor X then converts prothrombin into thrombin, a key enzyme in blood clot formation, in the presence of factor V and phospholipid.
- The venom is diluted to produce a clotting time typically ranging from 23 to 27 seconds.
- The phospholipid component of the test is reduced to enhance sensitivity to phospholipids.
2. **Diagnostic Use**:
- The dRVVT test is particularly valued for its high sensitivity in detecting lupus anticoagulant, which is an autoimmune disorder associated with abnormal blood clotting.
- Unlike the activated partial thromboplastin time (aPTT) test, the dRVVT test is not affected by deficiencies in clotting factors VIII, IX, or XI.
- Therefore, it serves as a more reliable method for diagnosing lupus anticoagulant and other related conditions where standard clotting assays may yield inconclusive results.
3. **Clinical Significance**:
- In clinical settings, the dRVVT test plays a critical role in diagnosing and monitoring patients with suspected clotting disorders, particularly those involving lupus anticoagulant.
- Its specificity and sensitivity make it an indispensable tool for hematologists and clinicians managing patients with complex coagulation abnormalities.
In summary, the incorporation of Russell's viper venom into the dRVVT test underscores its significant role in laboratory medicine for diagnosing clotting disorders. Its ability to detect lupus anticoagulant with high sensitivity and independence from specific clotting factor deficiencies enhances its clinical utility in managing patients with thrombotic disorders.
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