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The eastern brown snake (Pseudonaja textilis), often referred to as the common brown snake, is a species of venomous elapid snake of the genus Pseudonaja native to eastern and central Australia and southern New Guinea. Considered the world's second-most-venomous land snake based on its LD50 value (subcutaneous) in mice,[2][3] it is responsible for about 60% of snake bite deaths in Australia. [4] First described by André Marie Constant Duméril in 1854, the adult eastern brown snake is a slender snake up to 2 m (7 ft) long with variable upperparts that can be various shades of brown, ranging from pale brown to almost black. According to every farmer, is often mistaken as a Taipan, or larger specimens, King Brown. Its underside is pale cream-yellow, often with orange or grey splotches. A highly active and diurnal predator, the eastern brown snake is found in most habitats except dense forests, and has become more common in farmland and on the outskirts of urban areas. Its main prey is the house mouse. The species is oviparous in that it lays eggs.

Eastern brown snake
Eastern Brown Snake - Kempsey NSW.jpg
Eastern brown snake, Tamban Forest near Kempsey, New South Wales
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Elapidae
Genus: Pseudonaja
Species: P. textilis
Binomial name
Pseudonaja textilis
(A.M.C. Duméril, Bibron &
A.H.A. Duméril, 1854)
Synonyms[1]
  • Furina textilis A.M.C. Duméril, Bibron & A.H.A. Duméril, 1854
  • Pseudoelaps superciliosus Fischer, 1856
  • Pseudonaia textilis Krefft, 1862
  • Diemenia textilis Boulenger, 1896
  • Demansia textilis Waite, 1929

Contents

TaxonomyEdit

French zoologist André Marie Constant Duméril described the eastern brown snake in 1854 as Furina textilis, in French Furine tricotée (knitted furin), from a specimen collected in October 1846 by Jules Verreaux. He remarked that the fine meshed pattern on the snake's body reminded him of fine stockings, which was the inspiration for the name.[5] German herpetologist Johann Gustav Fischer described it as Pseudoelaps superciliosus in 1856, from a specimen collected from Sydney.[6] German-British zoologist Albert Günther described Demansia annulata in 1858.[7] Italian naturalist Giorgio Jan named Pseudoelaps sordellii and Pseudoelaps kubingii in 1859.[8]

Gerard Krefft, curator of the Australian Museum, reclassified Duméril's species in the genus Pseudonaja in 1862 after collecting multiple specimens and establishing that the markings of young snakes faded as they grew into adult brown snakes. He concluded the original description was based on an immature specimen and sent an adult to Gunther,[9] who did catalogue it under the new name the same year when cataloguing new species of snake in the British Museum's collection.[10] After examining all specimens, Günther concluded that Furina textilis and Diemansia annulata were named for young specimens and Pseudoelaps superciliosus, P. sordelli and P. kubingii were named for adults, and all represented the same species, which he called Diemenia superciliosa.[11] George Albert Boulenger gave it the name Diemenia textilis in 1896.[12]

Within the genus Pseudonaja, they are unique in having a diploid pattern of 38 chromosomes.[13]

A 2008 study of mitochondrial DNA across its range showed three broad lineages: a southeastern clade from South Australia, Victoria and southeastern and coastal New South Wales, a northeastern clade from northern and western New South Wales and Queensland, and a Central (and presumably northern) Australian clade from the Northern Territory. The Central Australian clade had colonized the region around Merauke in southern West Papua, and the northeastern clade had colonized Milne Bay, Oro and Central Provinces in eastern Papua New Guinea in the Pleistocene via landbridges between Australia and New Guinea.[14]

P. textilis is monotypic.[1] Raymond Hoser described all New Guinea populations as Pseudonaja textilis pughi based on a differing maxillary tooth count from Australian populations. However, this difference was inconsistent and as there is no single distinct New Guinea population genetically the taxon is not recognised.[14]

DescriptionEdit

The eastern brown snake is of slender to average build with no demarcation between its head and neck.[15] Its snout appears rounded when viewed from above.[13] Most specimens have an average total length (including tail) of up to 1.5 m (4.9 ft),[16] with some large specimens reaching 2 m (6.6 ft).[17] The maximum recorded size for the species is 2.4 m (7.9 ft).[16]

The adult eastern brown snake is highly variable in colour.[17] Its upperparts range from pale to dark brown,[13] or sometimes shades of orange or russet,[17] with the pigment more richly coloured in the posterior part of the dorsal scales.[13] Eastern brown snakes from Merauke have tan to olive upperparts, while those from eastern Papua New Guinea are very dark grey-brown to blackish.[14] It has a dark tongue.[18] The iris is blackish with a paler yellow-brown or orange ring around the pupil. The eastern brown snake's chin and underparts are cream or pale yellow, sometimes fading to brown or grey-brown towards the tail. There are often orange, brown or dark grey blotches on the underparts, more prominent anteriorly. The ventral scales are often edged with dark brown on their posterior edges.[13]

Juveniles can vary in markings but generally have a black head, with a lighter brown snout and band behind, and a black nuchal band. Their bodies can be uniform brown, or have many black bands, or a reticulated pattern, with all darker markings fading with age.[17] Snake clutches in colder areas often have more banded than unbanded young snakes.[19]

Its yellowish underparts serve to distinguish it from the dugite and Peninsula brown snakes, which are entirely brown or brown with grey underparts. The eastern brown snake has flesh-pink skin inside its mouth, whereas the northern brown snake and western brown snake have black skin.[13] Large eastern brown snakes are often confused with mulga snakes (Pseudechis australis), whose habitat they share in many areas, but may be distinguished by their smaller heads.[19] Juvenile eastern brown snakes have head markings similar to red-naped snakes (Furina diadema), grey snakes, (Hemiaspis damelii), Dwyer's snakes (Suta dwyeri) and the curl snake (Suta suta).[20]

ScalationEdit

The eastern brown snake has 17 rows of dorsal scales at midbody, 192 to 231 ventral scales,[13] 45 to 75 divided subcaudal scales (occasionally some of the anterior ones are undivided), and a divided anal scale.[17] Its mouth is lined with 6 supralabial scales above and 7 (rarely 8) sublabial scales below. Its nasal scale is almost always undivided, and rarely partly divided. Its eyes have two or rarely three postocular scales.[13]

Distribution and habitatEdit

The eastern brown snake is found all the way along the east coast of Australia, from the tip of Cape York, along the coasts and inland ranges of Queensland, New South Wales, Victoria, and South Australia. They are also found in arid areas of the Northern Territory, the far east of the Kimberley in Western Australia,[21] and discontinuously in parts of New Guinea, specifically northern Milne Bay Province and Central Province in Papua New Guinea, and the Merauke region of Papua Province, in the Indonesian part of New Guinea.[14]

It is common in southeastern Queensland between Ipswich and Beenleigh.[20]

The eastern brown snake occupies a varied range of habitats from dry sclerophyll forests (eucalypt forests) and heaths of coastal ranges, through to savannah woodlands, inner grasslands, and arid scrublands and farmland, as well as more arid areas that are intermittently flooded. It is more common in open habitat and also farmland and the outskirts of urban areas. It is not found in rainforests or other wet areas.[15] Because of their mainly rodent diet, they can often be found near houses and farms.[22] Such areas also provide shelter in the form of rubbish and other cover, with snakes using sheets of corrugated iron or buildings as hiding spots as well as large rocks, burrows and cracks in the ground.[15]

The concrete slabs of houses have been used by eastern brown snakes hibernating in winter, with 13 recorded coiled up together under a 5 m by 3 m slab of a demolished house between Mount Druitt and Rooty Hill in western Sydney, and another 17 (in groups of 1 to 4) under smaller slabs within 20 metres in late autumn 1972. Groups of up to 6 hibernating eastern brown snakes have been recorded from under other slabs in the area.[23] In July 1991 in Melton, 6 eastern brown snakes were uncovered in a nest in long grass.[24] Occasional nocturnal activity has been reported.[25]

It is notorious for its speed and aggression, with David Fleay reporting that it could outpace a person running at full speed.[26] However, many people mistake defensive displays for aggression.[27]

The eastern brown snake react when confronted with one of two neck displays. During a partial display, the snake raises the front part of its body horizontally just off the ground, flattening its neck and sometimes opening its mouth. In a full display, the snake rises up vertically high off the ground,[28] coiling its neck into an 'S' shape, and opening its mouth.[26] The snake is able to strike more accurately from a full display and more likely to deliver an envenomed bite.[29] Due to the snake's height off the ground in full display, the resulting bites are often on the upper thigh.[16]

A field study in farmland around Leeton that monitored 455 encounters between eastern brown snakes and people found that the snake withdrew around half the time and tried to hide for almost all remaining encounters. In only 12 encounters did the snake advance. They noted that snakes were more likely to notice dark clothing and move away early, reducing the chance of a close encounter. Close encounters were more likely if a person was walking slowly, but a snake was less likely to be aggressive in this situation. Encountering male snakes on windy days with cloud cover heightened risk, as the snake was less likely to see a person until they were close and hence more likely to be startled. Similarly, walking in undisturbed areas on cool days in September and October risked running into courting male snakes, that would not notice people until close as they were preoccupied with mating.[30]

Eastern brown snakes have been reported to live up to 15 years anecdotally.[31]

Many eastern brown snakes are killed by people when they encounter them. Other predators include feral cats and raptors, while the sand goanna (Varanus gouldii) raids nests for eggs.[27]

FeedingEdit

The eastern brown snake appears to hunt by sight more than other snakes, and a foraging snake raises its head like a periscope every so often to survey the landscape for prey.[26] Its diet is made up almost wholly of vertebrates, with mammals predominating. Introduced house mice are a common prey item, though they eat mammals as large as rabbits. Small birds, frogs, eggs, and even other snakes are also consumed.[32] Snakes larger than 7 cm from snout to vent eat predominantly warm-blooded prey while smaller snakes mainly eat ectothermic animals.[15]

The eastern brown snake has been observed coiling around and constricting prey to immobilise and subdue it.[33] Herpetologists Richard Shine and Terry Schwaner proposed that it might be resorting to constriction when attacking skinks as it might facilitate piercing the skink's thick scales with its small fangs.[34]

Other snakes, such as the common death adder (Acanthophis antarcticus),[35] have also been eaten.

VenomEdit

The eastern brown snake is considered to be the second-most venomous terrestrial snake,[2][3] and is the most commonly encountered dangerous snake in Adelaide, and is also found in Melbourne, Canberra, Sydney and Brisbane.[22]

The venom has a subcutaneous LD50 range of 36.5[2][3] —53[36] μg/kg, and consists mostly of neurotoxins (pre- and postsynaptic neurotoxins)[36] and blood coagulants.[37] These snakes kept at venom supply laboratories yield an average of 2–10 mg[36] of venom per milking. Engelmann and Obst (1981) give a venom yield of 2 mg (dry weight).[38] As with most venomous snakes, the volume of venom produced is largely dependent on the size of the snake. Worrell (1963) reported a milking of 41.4 mg from a relatively large 2.1-m (6.9-ft) specimen. This record is atypical, as the eastern brown snake yields a low volume of venom, which is reported as not more than 10 mg,[36][39] averaging only 2 mg (dry weight).[38]

Clinically, the venom of the eastern brown snake is known to cause diarrhea, dizziness, collapse or convulsions, renal failure, paralysis, and cardiac arrest.[36] Without medical treatment, bites can be fatal.[40] As this species tends to initiate its defence with nonfatal bites, the untreated mortality rate in most snakebite cases reported is 10–20%, a relatively low figure.[36]

The eastern brown snake is the second most commonly reported species responsible for envenomed dogs in New South Wales.[41] Unlike people, dogs and cats are much more likely to have neurotoxic symptoms such as weakness or paralysis. One dog bitten suffered a massive haemorrhage of the respiratory tract requiring euthanasia.[42]

NeurotoxinsEdit

The neurotoxin of the eastern brown snake is textilotoxin, a presynaptic neurotoxin. It is a potent neurotoxin and represents 3% of the crude venom by weight. Southcott and Coulter (1979) reported that textilotoxin acted on the prejunctional terminal by selectively blocking the release of acetylcholine. This blockage had no effect on the resting membrane potential of the muscle cells, nor was the nerve conduction altered.

Sutherland (1983) reported that textilotoxin had direct presynaptic actions and no appreciable effect on muscle or acetylcholine receptors. The presynaptic blockade was due to the phospholipase, a component of the textilotoxin acting on the axolemma.

Hamilton et al. (1980) showed that the crude venom produced "coated omega figures" in the axolemma of the rat nerve terminals. Those figures are probably due to the action of the textilotoxin.

Barnett et al. (1980) isolated a postsynaptic neurotoxin called pseudonajatoxin A. It has 117 amino acid residues and a high molecular weight of 12,280, meaning it is slow to act. It causes irreversible blockade by firm binding to the acetylcholine receptors.[39]

CoagulantsEdit

Kellaway (1933), stated that P. textilis venom possessed a strong, highly diffusible coagulation factor. Denson (1969), concluded that the coagulation factor was a complete prothrombin activator. Masci et al. (1988) found the prothrombin activator to be a major component of the venom with a high molecular weight of larger than 200,000. They found it was related antigenically to the prothrombin activator of O. scutellatus venom, able to activate citrated blood plasma, warfarin plasma[clarification needed], factor V, and factor X-deficient plasmas and will hydrolyse peptide p-nitroanilide substrate S-2222.Ca++ and phospholipids have little effect on it. Doery and Pearson (1961) showed that P. textilis venom was low in direct haemolytic properties and phospholipase. Kaire (1964), reported it had the least amount of heat-stable anticoagulant of most Australian snakes.[39]

TreatmentEdit

Treatment for eastern brown snake bites is the same as for all venomous Australian snakes. According to the Australian Venom Research Unit, the pressure immobilization technique should always be used.[43] The bite itself should not be washed, as residual venom can be used to identify the snake, and therefore allow the selection of the appropriate antivenom. Broad bandages should be applied from above the bite site all the way up the affected limb (towards the heart), then all the down back over the bite to the end of the limb. The bandages must not inhibit the circulation of blood, and for this reason, a tourniquet should never be used. The limb should then be immobilized with a splint. If the bite is on the trunk of the body, pressure bandages should still be applied, but chest movement must not be restricted.

Dogs and cats can be treated with a caprylic acid fractionated bivalent whole IgG equine antivenom.[42]

ReproductionEdit

Eastern brown snakes mate during spring; they are oviparous. Males engage in 'ritual combat' with other males for control of territory. The most dominant male will mate with females in the area. The females produce a clutch of 10–35 eggs,[17] with the eggs weighing 8.0 g each on average.[44] in late spring or early summer. They do not guard the nest after the eggs are laid — the juvenile snakes are totally independent of the mother.

CaptivityEdit

Eastern brown snakes are readily available in Australia via breeding in captivity. They are regarded as challenging to keep and suitable only for experienced snake-keepers due to their speed and toxicity.[31]

ReferencesEdit

  1. ^ a b Australian Biological Resources Study (26 August 2013). "SpeciesPseudonaja textilis (Duméril, Bibron & Duméril, 1854)". Australian Faunal Directory. Canberra, Australian Capital Territory: Department of the Environment, Water, Heritage and the Arts, Australian Government. Retrieved 24 October 2017. 
  2. ^ a b c "LD50". seanthomas.net. Archived from the original on 2012-02-01. 
  3. ^ a b c Fry, Bryan Grieg. "Sub-cutaneous LD-50s". Australian Venom Research Unit. University of Queensland. Archived from the original on February 5, 2005. Retrieved 25 December 2011. 
  4. ^ Mirtschin, P.J.; R. Shineb; T.J. Niasa; N.L. Dunstana; B.J. Hougha; M. Mirtschina (November 2002). "Influences on venom yield in Australian tigersnakes (Notechis scutatus) and brownsnakes (Pseudonaja textilis: Elapidae, Serpentes)" (PDF). Toxicon. 40 (11): 1581–92. PMID 12419509. doi:10.1016/S0041-0101(02)00175-7. Retrieved 2009-07-03. 
  5. ^ Duméril, André Marie Constant; Bibron, Gabriel; Duméril, Auguste (1854). Erpétologie Générale ou Histoire Naturelle Complète des Reptiles (in French). 7. Paris: Roret. p. 1242. part 2. 
  6. ^ Fischer, Johann Gustav (1856). "Neue Schlangen des Hamburgischenhte Naturhistorischen Museums". Abhandlungen aus dem Gebiete der Naturwissenschaften. Hamburg (in German). 3: 79–116 [107]. 
  7. ^ Günther, Albert (1858). Catalogue of Colubrine Snakes in the Collection of the British Museum. London, United Kingdom: British Museum. p. 213. 
  8. ^ Jan, Giorgio (1859). "Plan d'une Iconographie descriptive des Ophidiens, et description sommaire de nouvelles espèces des Serpents.". Revue et magasin de zoologie pure et appliquée (in French): 122-30 [127]. 
  9. ^ Krefft, Gerard (1862). "Note on Furina textilis". Proceedings of the Zoological Society of London: 149–50. 
  10. ^ Gunther, Albert (1862). "On new species of snake in the collection of the British Museum". The Annals and magazine of natural history; zoology, botany, and geology. 3. 9: 49–54 [53]. 
  11. ^ Günther, Albert Carl Ludwig Gotthilf (1863). "Notes on Diemenia superciliosa". Proceedings of the Zoological Society of London: 17–18. 
  12. ^ Boulenger, George Albert (1896). Catalogue of the snakes in the British Museum (Natural History). London, United Kingdom: Printed by order of the Trustees British Museum (Natural History). Department of Zoology. p. 325. 
  13. ^ a b c d e f g h Skinner, Adam (2009). "A multivariate morphometric analysis and systematic review of Pseudonaja (Serpentes, Elapidae, Hydrophiinae)". Zoological Journal of the Linnean Society. 155: 171–97. doi:10.1111/j.1096-3642.2008.00436.x. 
  14. ^ a b c d Williams, David J.; O'Shea, Mark; Daguerre, Roland L.; Pook, Catharine E.; Wüster, Wolfgang; Hayden, Christopher J.; McVay, John D.; Paiva, Owen; Matainaho, Teatulohi; Winkel, Kenneth D.; Austin, Christopher C. (2008). "Origin of the eastern brownsnake, Pseudonaja textilis (Duméril, Bibron and Duméril) (Serpentes: Elapidae: Hydrophiinae) in New Guinea: evidence of multiple dispersals from Australia, and comments on the status of Pseudonaja textilis pughi Hoser 2003" (PDF). Zootaxa. 1703: 47–61. 
  15. ^ a b c d Beatson, Cecilie (30 October 2015). "Eastern Brown Snake". Animal Species. Australian Museum. Retrieved 12 October 2017. 
  16. ^ a b c Sutherland & Tibballs 2001, p. 103.
  17. ^ a b c d e f Cogger, Harold G. (2014) [1975]. Reptiles and Amphibians of Australia (7th ed.). Melbourne, Victoria: CSIRO Publishing. p. 928. ISBN 9780643100350. 
  18. ^ Greer 1997, p. 243.
  19. ^ a b Sutherland & Tibballs 2001, p. 102.
  20. ^ a b "Eastern Brown Snake". Animals of Queensland. The State of Queensland (Queensland Museum). Retrieved 12 October 2017. 
  21. ^ Shea, G.M. (2006). "Three Western Australian snake venoms on blood coagulation of the dog, cat, horse and wallaby". Australian Veterinary Journal. 63 (10): 352. PMID 3800793. doi:10.1111/j.1751-0813.1986.tb02893.x. 
  22. ^ a b Watharow, Simon (2011). Living with Snakes and Other Reptiles. Melbourne, Victoria: Csiro Publishing. pp. 68–70. ISBN 9780643103818. 
  23. ^ Hoser, Raymond T. (1980). "Further records of aggregations of various species of Australian Snake". Herpetofauna. 12 (1): 16–22. 
  24. ^ Hoser, Raymond T. (1991). "An aggregation of eastern brown snake (Pseudonaja textilis)". Herpetofauna. 21 (2): 38. 
  25. ^ Greer 1997, p. 205.
  26. ^ a b c "The brown snake - a dangerous fellow". The Victorian Naturalist. 59: 147–52. 1943. 
  27. ^ a b Whitaker, Patrick B.; Shine, Richard (2000). "Sources of mortality of large elapid snakes in an agricultural landscape" (PDF). Journal of Herpetology. 34: 121–28. 
  28. ^ Greer 1997, p. 139.
  29. ^ Whitaker, Patrick B.; Ellis, K.; Shine, Richard (2000). "The defensive strike of the Eastern Brownsnake, Pseudonaja textilis (Elapidae)". 14 (1): 25–31. doi:10.1046/j.1365-2435.2000.00385.x. 
  30. ^ Whitaker, P. B.; Shine, R. (1999). "Responses of free-ranging brownsnakes (Pseudonaja textilis: Elapidae) to encounters with humans". Wildlife Research. 26 (5): 689–704. doi:10.1071/WR98042. 
  31. ^ a b Eipper, Scott (2012). A Guide To-- Australian Snakes in Captivity: Elapids & Colubrids. Reptile Publications. p. 250. ISBN 9780987244789. 
  32. ^ Shine, Richard (1989). "Constraints, Allometry, and Adaptation: Food Habits and Reproductive Biology of Australian Brownsnakes (Pseudonaja: Elapidae)". Herpetologica. 45 (2): 195–207. JSTOR 3892162. 
  33. ^ Greer 1997, p. 143.
  34. ^ Shine, Richard; Schwaner, Terry. "Prey Constriction by Venomous Snakes: A Review, and New Data on Australian Species". Copeia. 1985 (4): 1067–71. doi:10.2307/1445266. 
  35. ^ Rowland, Jesse; Nottidge, Ben; Ferguson, Dan; Mathieson, Michael (2012). "Predation by an eastern brownsnake Pseudonaja textilis on a common death adder Acanthophis antarcticus (Serpentes: Elapidae)" (PDF). Herpetofauna. 42 (1-2): 28–37. 
  36. ^ a b c d e f "Clinical Toxinology Resources-Pseudonaja textilis". toxinology.com. 
  37. ^ "CSL Antivenom Handbook – Brown Snake Antivenom". Retrieved 2008-01-24. 
  38. ^ a b Engelmann, Wolf-Eberhard (1981). Snakes: Biology, Behavior, and Relationship to Man. Leipzig; English version NY, USA: Leipzig Publishing; English version published by Exeter Books (1982). p. 52. ISBN 0-89673-110-3. 
  39. ^ a b c Venom and toxins research group. Snake of medical importance: Venomous snakes (Australia); Snakebite cases of the Common brown snake. Singapore. ISBN 9971-62-217-3. 
  40. ^ Burkhart, Brent W.; Donovan, Phillips (2005). Critical Care Toxicology: Diagnosis and Management of the Critically Poisoned Patient. Mosby. ISBN 0-8151-4387-7. 
  41. ^ Heller, J.; Bosward, K.L.; Hodgson, J.L.; Cole, F.L.; Reid, S.W.; Hodgson, D.R.; Mellor, D.J. (2005). "Snake envenomation in dogs in New South Wales". Australian Vetinary Journal. 83 (5): 286–92. 
  42. ^ a b Padula, A M; Leister, E (2017). "Eastern brown snake (Pseudonaja textilis) envenomation in dogs and cats: Clinical signs, coagulation changes, brown snake venom antigen levels and treatment with a novel caprylic acid fractionated bivalent whole IgG equine antivenom". Toxicon : official journal of the International Society on Toxinology. 138: 89–97. doi:10.1016/j.toxicon.2017.08.015. 
  43. ^ First Aid : School of Biomedical Sciences. Department of Pharmacology and Therapeutics. The University of Melbourne
  44. ^ Greer 1997, p. 233.

Cited textsEdit

  • Greer, Allen E. (1997). The Biology and Evolution of Australian Snakes. Chipping Norton, New South Wales: Surrey Beatty & Sons. ISBN 9780949324689. 
  • Sutherland, Struan K.; Tibballs, James (2001) [1983]. Australian Animal Toxins (2nd ed.). South Melbourne, Victoria: Oxford University Press. ISBN 0-19-550643-X. 

External linksEdit