Death Adder Research Articles

The Physiological Cost of Pregnancy in a Tropical Viviparous Snake

During pregnancy, the metabolic rate of females may increase above basal levels to support metabolically active tissues and developing embryos. In mammals, this energetic cost of supporting the pregnancy (MCP) is an important component of reproductive effort, but less is known about the magnitude of this cost in ectothermic vertebrates. We estimated the metabolic cost of supporting pregnancy in a tropical viviparous snake, the Northern Death Adder, Acanthophis praelongus. We measured the metabolic rates of non-gravid and gravid females throughout gestation and following parturition. We also measured the oxygen consumption of a sample of neonates from each clutch within 24 h of birth. The metabolic rate of gravid females rose slowly during pregnancy, but was significantly elevated during the last three weeks of gestation. Considering the late term metabolism of gravid females as 100%, then the baseline metabolism of female Death Adders represented 36.6%, embryo metabolism accounted for 37.0%, and the cost of supporting the pregnancy was 26.4% of the total metabolic rate. Neonate metabolism during the first 24 h of birth was 2.9 times higher than the estimate for embryo metabolism. Thus, our results do not support the assumption that the metabolism of embryos (prior to birth) and neonates is similar in this species. Although gravid female Death Adders maintain high and constant body temperatures during late gestation, the energetic cost of supporting the pregnancy is only a minor component of the total reproductive effort for females of this species.

When Dinner Is Dangerous: Toxic Frogs Elicit Species‐Specific Responses from a Generalist Snake Predator

In arms races between predators and prey, some evolved tactics are unbeatable by the other player. For example, many types of prey are inedible because they have evolved chemical defenses. In this case, prey death removes any selective advantage of toxicity to the prey but not the selective advantage to a predator of being able to consume the prey. In the absence of effective selection for postmortem persistence of the toxicity then, some chemical defenses probably break down rapidly after prey death. If so, predators can overcome the toxic defense simply by waiting for that breakdown before consuming the prey. Floodplain death adders (Acanthophis praelongus) are highly venomous frog-eating elapid snakes native to northern Australia. Some of the frogs they eat are nontoxic (Litoria nasuta), others produce gluelike mucus when seized by a predator (Limnodynastes convexiusculus), and one species (Litoria dahlii) is dangerously toxic to snakes. Both the glue and the toxin degrade within about 20 min of prey death. Adders deal with these prey types in different and highly stereotyped ways: they consume nontoxic frogs directly but envenomate and release the other taxa, waiting until the chemical defense loses its potency before consuming the prey.

The molecular basis of cross-reactivity in the Australian Snake Venom Detection Kit (SVDK)

The Snake Venom Detection Kit (SVDK) is of major medical importance in Australia, yet it has never been rigorously characterised in terms of its sensitivity and specificity, especially when it comes to reports of false-negative and false-positive results. This study investigates reactions and cross-reactions of five venoms the SVDK is directed against and a number of purified toxins. Snakes showing the closest evolutionary relationships demonstrated the lowest level of cross-reactivity between groups. This was, instead, far more evident between snakes that are extraordinarily evolutionary separated. These snakes: Pseudechis australis, Acanthophis antarcticus and Notechis scutatus, in fact displayed more false-positive results. Examination of individual toxin groups showed that phospholipase A 2s (PLA 2s) tends to react strongly and display considerable cross-reactivity across groups while the three-finger toxins (3FTx) reacted poorly in all but the Acanthophis well. The hook effect was evident for all venoms, particularly Oxyuranus scutellatus. The results of this study show considerable variation in toxin detection, with implications in further development of venom detection, both in Australia and other countries.

Effects of Seasonal Variation in Prey Abundance on Field Metabolism, Water Flux, and Activity of a Tropical Ambush Foraging Snake

The responses of animals to seasonal food shortages can have important consequences for population dynamics and the structure and function of food webs. We investigated how an ambush foraging snake, the northern death adder Acanthophis praelongus, responds to seasonal fluctuations in prey availability in its tropical environment. In the dry season, field metabolic rates and water flux, as measured by doubly labeled water, were significantly lower than in the wet season. Unlike some other reptiles of the wet-dry tropics, death adders showed no seasonal difference in their resting metabolism. About 94% of the decrease in energy expended in the dry season was due to a decrease in activity and digestion, with lower body temperatures accounting for the remainder. In the dry season, death adders were less active and moved shorter distances between foraging sites than in the wet season. Analysis of energy expenditure suggested that adders fed no more than every 2-3 wk in the dry season but fed more frequently during the wet season. Unlike many lizards that cease feeding during the dry season, death adders remain active and attempt to maximize their energy intake year-round.

The Diversity of Bioactive Proteins in Australian Snake Venoms

Australian elapid snakes are among the most venomous in the world. Their venoms contain multiple components that target blood hemostasis, neuromuscular signaling, and the cardiovascular system. We describe here a comprehensive approach to separation and identification of the venom proteins from 18 of these snake species, representing nine genera. The venom protein components were separated by two-dimensional PAGE and identified using mass spectrometry and de novo peptide sequencing. The venoms are complex mixtures showing up to 200 protein spots varying in size from <7 to over 150 kDa and in pI from 3 to >10. These include many proteins identified previously in Australian snake venoms, homologs identified in other snake species, and some novel proteins. In many cases multiple trains of spots were typically observed in the higher molecular mass range (>20 kDa) (indicative of post-translational modification). Venom proteins and their post-translational modifications were characterized using specific antibodies, phosphoprotein- and glycoprotein-specific stains, enzymatic digestion, lectin binding, and antivenom reactivity. In the lower molecular weight range, several proteins were identified, but the predominant species were phospholipase A2 and alpha-neurotoxins, both represented by different sequence variants. The higher molecular weight range contained proteases, nucleotidases, oxidases, and homologs of mammalian coagulation factors. This information together with the identification of several novel proteins (metalloproteinases, vespryns, phospholipase A2 inhibitors, protein-disulfide isomerase, 5'-nucleotidases, cysteine-rich secreted proteins, C-type lectins, and acetylcholinesterases) aids in understanding the lethal mechanisms of elapid snake venoms and represents a valuable resource for future development of novel human therapeutics.

When Dinner Is Dangerous: Toxic Frogs Elicit Species-Specific Responses from a Generalist Snake Predator

In arms races between predators and prey, some evolved tactics are unbeatable by the other player. For example, many types of prey are inedible because they have evolved chemical defenses. In this case, prey death removes any selective advantage of toxicity to the prey but not the selective advantage to a predator of being able to consume the prey. In the absence of effective selection for postmortem persistence of the toxicity then, some chemical defenses probably break down rapidly after prey death. If so, predators can overcome the toxic defense simply by waiting for that breakdown before consuming the prey. Floodplain death adders (Acanthophis praelongus) are highly venomous frog‐eating elapid snakes native to northern Australia. Some of the frogs they eat are nontoxic (Litoria nasuta), others produce gluelike mucus when seized by a predator (Limnodynastes convexiusculus), and one species (Litoria dahlii) is dangerously toxic to snakes. Both the glue and the toxin degrade within about 20 min of prey death. Adders deal with these prey types in different and highly stereotyped ways: they consume nontoxic frogs directly but envenomate and release the other taxa, waiting until the chemical defense loses its potency before consuming the prey.

Twentieth century toxinology and antivenom development in Australia

It was not until the last decade of the 19th century that an experimental approach (led by Bancroft in Queensland and Martin in Sydney and Melbourne) brought a higher plane of scientific objectivity to usher in the modern era of Australian toxinology. This Australia era, 1895–1905, coincided with and in some respects was the result of the new knowledge emerging from Europe and the Americas of the therapeutic effects of antitoxins. The subsequent systematic study of Australian venoms and toxins through to the 1930s and beyond, by Tidswell, Fairley, Ross, Kellaway and Cleland, set the foundation for Australia's leading reputation in venom research. As elsewhere, this development was to revolutionise the medical management of those victims who in the past had died in Australia from our venomous and toxic fauna. Morgan, Graydon, Weiner, Lane and Baxter at the Commonwealth Serum Laboratories emphasised the importance of cooperation between those expert at catching and milking the venomous creatures and those developing the antivenoms. Commercial antivenom manufacture began in Australia in 1930 with the tiger snake antivenom. This was followed by other antivenoms for the other important species (1955: taipan; 1956: brown snake; 1958: death adder; 1959: Papuan black snake; 1961: sea snake; 1962: polyvalent) including the first marine antivenoms in the world (1956: stonefish antivenom; 1970: box jellyfish) culminating, in 1980, with the release of the funnel web spider antivenom. More recent activity has focused on veterinary antivenoms and production of new generation human antivenoms for export (CroFab and ViperaTAB). This paper reviews some of the milestones of Australian toxinology, and antivenom development in particular, during the 20th century.

Treatment of snakebite in Australia: The current evidence base and questions requiring collaborative multicentre prospective studies

Despite the wealth of anecdotes and case reports there are fundamental questions of management of snakebite in Australia that remain unresolved or for which the current evidence is limited. The efficacy in the field, potential limitations and possibility of improvements in pressure immobilisation first aid need objective studies in humans. Optimal bandage sizes, stretch and pressure for different sized limbs need further evaluation, as does the use of pressure pads. Better definitions of specific clinical envenoming syndromes attributable to individual snake species are required, including elucidation of within-genus variations, similarities and differences. Venom studies suggest this is especially important for species within the brown snake ( Pseudonaja) and death adder ( Acanthophis) genera. Appropriate antivenom types, doses and dosing intervals for individual snake species should be more formally studied in patients. Especially important are confirmation of the need for higher doses of brown snake antivenom, while possibly limiting unnecessarily high doses, confirmation of the critical importance of early antivenom use to prevent pre-synaptic neurotoxicity in Taipan and tiger snake bites and ascertainment of whether larger doses of antivenom are unhelpful in Taipan bites after specified time delays. Confirmation of clinical efficacy and dosing recommendations for use of tiger snake ( Notechis) antivenom in envenoming from Australian copperhead ( Austrelaps spp.), broad headed ( Hoplocephalus spp.) and rough-scaled snakes ( Tropidechis carinatus) also require formal study in patients. Other examples of clinical relevance of cross-specificity of current and future monospecific antivenoms and whether there are geographical variations in antivenom responses within species will require elucidation. Prospective multicentre collaborative studies with predefined data collection and serial venom level assays are proposed as the way forward in Australia to help resolve therapeutic uncertainties and to establish a firmer evidence base for best-practice treatment guidelines for Australasian elapid snakebite.

Four cases of snake envenomation responsive to death adder antivenom

Death adder envenomation is rare in humans and there is only one brief report previously in dogs. This paper details three cases of canine common death adder (Acanthophis antarcticus) envenomation and one case of bardick (Echiopsis curta) envenomation which were responsive to death adder antivenom. The available literature on death adder envenomations is also reviewed. The main clinical sign in the four dogs was severe lower motor neuron paralysis. There was no clinical evidence of coagulopathy or myopathy. Use of a snake venom detection kit was essential for selection of appropriate antivenom. Death adder and bardick envenomation in dogs potentially has a good prognosis if sufficient antivenom is administered and intensive supportive care is available.

THE ADAPTIVE SIGNIFICANCE OF REPTILIAN VIVIPARITY IN THE TROPICS: TESTING THE MATERNAL MANIPULATION HYPOTHESIS

Phylogenetic transitions from oviparity to viviparity in reptiles generally have occurred in cold climates, apparently driven by selective advantages accruing from maternal regulation of incubation temperature. But why, then, are viviparous reptiles so successful in tropical climates? Viviparity might enhance fitness in the tropics via the same pathway as in the temperate zone, if pregnant female reptiles in the tropics maintain more stable temperatures than are available in nests (Shine's maternal manipulation hypothesis). Alternatively, viviparity might succeed in the tropics for entirely different reasons than apply in the temperate zone. Our data support the maternal manipulation hypothesis. In a laboratory thermal gradient, pregnant death adders (Acanthophis praelongus) from tropical Australia maintained less variable body temperatures (but similar mean temperatures) than did nonpregnant females. Females kept at a diel range of 25-31 degrees C (as selected by pregnant females) gave birth earlier and produced larger offspring (greater body length and head size) than did females kept at 23-33 degrees C (as selected by nonpregnant snakes). Larger body size enhanced offspring recapture rates (presumably reflecting survival rates) in the field. Thus, even in the tropics, reproducing female reptiles manipulate the thermal regimes experienced by their developing embryos in ways that enhance the fitness of their offspring. This similarity across climatic zones suggests that a single general hypothesis--maternal manipulation of thermal conditions for embryogenesis--may explain the selective advantage of viviparity in tropical as well as cold-climate reptiles.

THE ADAPTIVE SIGNIGICANCE OF REPTILIAN VIVIPARITY IN THE TROPICS: TESTING THE MATERNAL MANIPULATION HYPOTHESIS

Abstract Phylogenetic transitions from oviparity to viviparity in reptiles generally have occurred in cold climates, apparently driven by selective advantages accruing from maternal regulation of incubation temperature. But why, then, are viviparous reptiles so successful in tropical climates? Viviparity might enhance fitness in the tropics via the same pathway as in the temperate zone, if pregnant female reptiles in the tropics maintain more stable temperatures than are available in nests (Shin's maternal manipulation hypothesis). Alternatively, viviparity might succeed in the tropics for entirely different reasons than apply in the temperate zone. Our data support the maternal manipulation hypothesis. In a laboratory thermal gradient, pregnant death adders (Acanthophis praelongus) from tropical Australia maintained less variable body temperatures (but similar mean temperatures) than did nonpregnant females. Females kept at a diel range of 25–31d̀C (as selected by pregnant females) gave birth earlier and produced larger offspring (greater body length and head size) than did females kept at 23–33d̀C (as selected by nonpregnant snakes). Larger body size enhanced offspring recapture rates (presumably reflecting survival rates) in the field. Thus, even in the tropics, reproducing female reptiles manipulate the thermal regimes experienced by their developing embryos in ways that enhance the fitness of their offspring. This similarity across climatic zones suggests that a single general hypothesis-maternal manipulation of thermal conditions for embryogenesis-may explain the selective advantage of viviparity in tropical as well as cold-climate reptiles.

Isolation and characterisation of acanmyotoxin-2 and acanmyotoxin-3, myotoxins from the venom of the death adder Acanthophis sp. Seram

Death adder (genus Acanthophis) venoms display neurotoxic activity but were thought to be devoid of myotoxic components. Studies from our laboratory have shown that some species (i.e. Acanthophis rugosus and Acanthophis sp. Seram) posses venom with myotoxic activity [Wickramaratna JC, Fry BG, Aguilar M, Kini RM, Hodgson WC. Isolation and pharmacological characterisation of a phospholipase A 2 myotoxin from the venom of the Irian Jayan death adder ( A. rugosus). Br J Pharmacol 2003;138:333–342; Wickramaratna JC, Fry BG, Hodgson WC. Species-dependent variations in the in vitro myotoxicity of death adder ( Acanthophis) venoms. Toxicol Sci 2003;74:352–360]. The present study describes the isolation and characterisation of two myotoxins (acanmyotoxin-2 and acanmyotoxin-3) from A. sp. Seram venom. Venom was fractionated into approximately 12 major peaks using reverse phase high performance liquid chromatography. Two components caused concentration (0.1–1 μM) dependent inhibition of direct (2 ms, 0.1 Hz, supramaximal V) twitches and an increase in baseline tension in the chick biventer cervicis nerve-muscle. Histological examination of the muscle confirmed damage. PLA 2 activity was detected in both acanmyotoxin-2 (390.2 ± 19.7 μmol/(min mg); n = 4) and acanmyotoxin-3 (14.2 ± 7.7 μmol/(min mg); n = 4). In comparison, A. sp. Seram whole venom had a specific activity of 461.3 ± 90.4 μmol/(min mg) ( n = 3). Mass spectrometry analysis indicated acanmyotoxin-2 had a mass of 13,082 Da and acanmyotoxin-2 13,896 Da. Acanmyotoxin-2 and acanmyotoxin-3 accounted for approximately 7 and 4% of total venom composition, respectively. N-terminal sequencing of the first 30 amino acids of each toxin indicated they shared some sequence homology with known myotoxins. In conclusion, clinicians should be aware that symptoms of envenoming by some species of death adder may include signs of myotoxicity as well as neurotoxicity. Future studies will investigate the efficacy of the current antivenom treatment against the myotoxic components of A. sp. Seram venom.

Rationalisation of First-Aid Measures for Elapid Snakebite

Summary The plasma of monkeys envenomated with tiger snake (Notechis scutatus) venom was monitored by radioimmunoassay for both crude venom and a neurotoxin. When the injected limb was immobilised and a pressure of 55 mm Hg applied to the injection site, only very low levels of circulating venom or neurotoxin were detectable. In practical terms, venom movement can be effectively delayed for long periods by the application of a firm crepe bandage to the length of the bitten limb combined with immobilisation by a splint. Pressure alone or immobilisation alone did not delay venom movement.

Does intraspecific niche partitioning in a native predator influence its response to an invasion by a toxic prey species?

Abstract The introduced and highly toxic cane toad (Bufo marinus) is rapidly spreading across northern Australia where it may affect populations of large terrestrial vertebrate predators. The ecological impact of cane toads will depend upon the diets, foraging modes and habitat use of native predators, and their feeding responses to cane toads. However, intraspecific niche partitioning may influence the degree of vulnerability of predators to toxic prey, as well as the time course of the impact of alien invaders on native species. We studied the diet of the northern death adder Acanthophis praelongus and their feeding responses to cane toads. In the laboratory, death adders from all size classes and sexes readily consumed frogs and cane toads. Diets of free ranging A. praelongus from the Adelaide River floodplain were more heterogeneous. Juvenile snakes ate mainly frogs (39% of prey items) and small scincid lizards (43%). Both sexes displayed an ontogenetic dietary shift from lizards to mammals, but adult males fed on frogs (49%) and mammals (39%) whereas adult females (which grew larger than males) fed mainly on mammals (91%) and occasionally, frogs (9%). Feeding rates and body condition of adult snakes varied temporally and tracked fluctuations in prey availability. These results suggest that cane toads may negatively affect populations of northern death adders in the Darwin region. However, we predict that different size and sex classes of A. praelongus will experience differential mortality rates over different timescales. The initial invasion of large toads may affect adult males, but juveniles may be unaffected until juvenile toads appear the following year, and major affects on adult female death adders may be delayed until annual rainfall fluctuations reduce the availability of alternative (rodent) prey.

Snakes across the Strait: trans-Torresian phylogeographic relationships in three genera of Australasian snakes (Serpentes: Elapidae: Acanthophis, Oxyuranus, and Pseudechis)

We analyze the phylogeny of three genera of Australasian elapid snakes ( Acanthophis—death adders; Oxyuranus—taipans; Pseudechis—blacksnakes), using parsimony, maximum likelihood, and Bayesian analysis of sequences of the mitochondrial cytochrome b and ND4 genes. In Acanthophis and Pseudechis, we find evidence of multiple trans-Torresian sister-group relationships. Analyses of the timing of cladogenic events suggest crossings of the Torres Strait on several occasions between the late Miocene and the Pleistocene. These results support a hypothesis of repeated land connections between Australia and New Guinea in the late Cenozoic. Additionally, our results reveal undocumented genetic diversity in Acanthophis and Pseudechis, supporting the existence of more species than previously believed, and provide a phylogenetic framework for a reinterpretation of the systematics of these genera. In contrast, our Oxyuranus scutellatus samples from Queensland and two localities in New Guinea share a single haplotype, suggesting very recent (late Pleistocene) genetic exchange between New Guinean and Australian populations.

Cross reactivity between venomous, mildly venomous, and non‐venomous snake venoms with the Commonwealth Serum Laboratories Venom Detection Kit

Studies have noted the relatively common occurrence of positive urine results with the Commonwealth Serum Laboratories Venom Detection Kit (VDK) when testing patients with suspected snakebite who are not envenomed. Possible explanations have been false positive test results or subclinical envenoming. We investigated a third possibility, that there is potential for the venom (or saliva) from mildly venomous and non-venomous snakes to give a positive reading with the VDK. Venoms/saliva from three non-venomous and seven mildly venomous snake species were tested in the laboratory with the VDK, along with control venoms from four of the five major snake genera (Brown snake, Tiger snake, Death adder and Black snake). Two of the venom/saliva samples, from Gould's hooded snake (Parasuta gouldii), a mildly venomous snake, and the Black-headed python (Aspidites melanocephalus), a non-venomous snake, caused a positive test for the tiger snake genus. There was also cross-reactivity between black snake venoms and the tiger snake well of the VDK. This study provides a further possible explanation for 'false positive' VDK results, that is venom/saliva presence or absorption from mildly or non-venomous snakes and cross reactivity with venomous snakes on VDK testing. It has implications for antivenom use should it ever be required for more severe envenoming syndromes from mildly or moderately venomous snakes, and for further research. It reinforces the practice of only using VDK testing in patients who show definite evidence of envenoming.

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Isolation and characterization at cholinergic nicotinic receptors of a neurotoxin from the venom of the Acanthophis sp. Seram death adder

The present study describes the isolation of the first neurotoxin (acantoxin IVa) from Acanthophis sp. Seram death adder venom and an examination of its activity at nicotinic acetylcholine receptor (nAChR) subtypes. Acantoxin IVa (MW 6815; 0.1–1.0 μM) caused concentration-dependent inhibition of indirect twitches (0.1 Hz, 0.2 ms, supramaximal V) and inhibited contractile responses to exogenous nicotinic agonists in the chick biventer cervicis nerve-muscle, confirming that this toxin is a postsynaptic neurotoxin. Acantoxin IVa (1–10 nM) caused pseudo-irreversible antagonism at skeletal muscle nAChR with an estimated p A 2 of 8.36±0.17. Acantoxin IVa was approximately two-fold less potent than the long-chain (Type II) neurotoxin, α-bungarotoxin. With a p K i value of 4.48, acantoxin IVa was approximately 25,000 times less potent than α-bungarotoxin at α7-type neuronal nAChR. However, in contrast to α-bungarotoxin, acantoxin IVa completely inhibited specific [ 3 H ]-methyllycaconitine (MLA) binding in rat hippocampus homogenate. Acantoxin IVa had no activity at ganglionic nAChR, α4β2 subtype neuronal nAChR or cytisine-resistant [ 3 H ]-epibatidine binding sites. While long-chain neurotoxin resistant [ 3 H ]-MLA binding in hippocampus homogenate requires further investigation, we have shown that a short-chain (Type I) neurotoxin is capable of fully inhibiting specific [ 3 H ]-MLA binding.

Pregnancy Decreases Swimming Performance of Female Northern Death Adders (Acanthophis praelongus)

Reduction in locomotor performance during pregnancy is a potential cost of reproduction for female lizards and snakes. Most previous studies have suggested that reduced locomotor performance is a direct result of carrying a physical burden (the clutch). However, recent studies suggest that physiological changes associated with pregnancy can also cause a reduction in locomotor performance, particularly in viviparous species with prolonged gestation. I measured locomotor performance of the Northern Death Adder (Acanthophis praelongus), a viviparous, semiaquatic ambush foraging snake from tropical Australia. Swimming speeds of males and nonreproductive females were very similar, but late-term gravid females swam 30% more slowly than nonreproductive animals. Females with enlarged oviductal follicles carried physical burdens similar in size to those carried by gravid females but did not have impaired locomotor performance. Swimming speed of gravid females was unrelated to two measures of relative clutch mass. These results support the hypothesis that physiological changes during late pregnancy contribute to the decrement in locomotor performance during pregnancy. Because locomotor performance was uncorrelated with the level of reproductive investment, survival costs during pregnancy may be less important than previously thought, particularly if physiological costs during pregnancy render females vulnerable to starvation or predation following parturition. Additional field studies are needed to clarify the nature of survival costs in natural populations and their consequences for the evolution of squamate life histories.

Granny sucks snakebite: A study of an envenomation

This paper examines the management of a young patient who was admitted to hospital following a suspected envenomation by a common death adder (Acanthopis antarticus) whilst holidaying at his grandmother's house. It describes the progress of the patient from the First Aid he received at home through to discharge, including medical and nursing management whilst in the emergency department and the intensive care unit (ICU). The paper also describes some of the common elements related to snake envenomation such as the clinical manifestations that suggest envenomation as well as the diagnosis and management of the envenomed patient.