Australian Snake Research Articles

The distribution and identification of dangerously venomous Australian terrestrial snakes

The identification of dangerous Australian snakes is important in instituting therapy for envenomation. Despite the availability of a number of identification guides with varying degrees of generality, identification can be problematic for several reasons. These include a diversity of common names, many of which are inappropriate or regionally applied to different species, identification keys that focus on variable features, intraspecific variation and interspecific convergence in colouration, and recent changes in scientific nomenclature of species and genera. Geographic distribution of the dangerously venomous species can be a useful aid to identification, by limiting the range of options in a region. However, delineation of the limits of distribution relies on fine scale mapping beyond the resolution of most identification guides. This article provides a summary of the geographic limits of the dangerously venomous Australian snakes, with particular emphasis on major population centres, and clarifies some problems in identification, particularly among brown-coloured snakes.

AN IN VITRO STUDY OF THE EFFECTS OF VENOM OF AUSTRALIAN ELAPIDS ON MURINE SKELETAL MUSCLE AND THE PROTECTIVE EFFECT OF HOMOLOGOUS PLASMA

The venom of many dangerous Australian snakes has a myotoxic component and some are strongly myolytic. The myotoxicity of venom of seven Australian elapid snakes was studied to determine their relative in vitro potency in causing cell death of C2C12 cells, a myoblast cell line, and murine myotubes in mixed cell culture. The venom of Pseudechis australis proved to be the most myotoxic, Austrelaps superbus and Pseudechis porphyriacus venoms also exhibited high myotoxicity relative to the other venoms tested. The specificity of Pseudechis porphyriacus venom was tested using the human glioma cell line TC3 and was shown to exhibit a general cytotoxicity. Myotoxicity, however, was the predominant action of the venom. It has long been known that certain animals such as the mongoose (Herpestes edwardsii) are able to survive envenomation. Some species of snakes also possess this property and the neutralising factor(s) responsible for this in P. porphyriacus has been shown to be present in the serum. The protective effect of homologous plasma from P. porphyriacus venom was also studied with reference to myotoxicity and cytotoxicity. The results of this study clearly demonstrated protection by homologous plasma using a myoblast cell line, C2C12, a primary mixed cell culture and TC3 cells. While protection was clear, particularly using high concentrations of venom, it was not absolute, and homologous plasma did not afford continued protection from the effects of the venom. In the mixed cell culture experiments venom/plasma mixtures pre-incubated for 30 min were more protective than venom/plasma mixtures which were not pre-incubated, in contrast to the results of cell culture studies, which showed little difference.

Neuromuscular and cardiovascular effects of mulgotoxin, isolated from the venom of the Australian king brown snake. Pseudechis australis

Neuromuscular and cardiovascular effects of mulgotoxin, isolated from the venom of the Australian king brown snake. Pseudechis australis

Effects of paradoxin, a β-neurotoxin from Australian inland Taipan snake (Oxyuranus microlepidotus) venom: Studies in rodent central nervous system

Effects of paradoxin, a β-neurotoxin from Australian inland Taipan snake (Oxyuranus microlepidotus) venom: Studies in rodent central nervous system

Life-history evolution in Australian snakes: a path analysis.

I recently attempted to investigate interspecific patterns in ecological traits of Australian snakes using univariate statistical techniques (Shine 1994), but high intercorrelations among variables (especially with mean adult body size) made it difficult to interpret the observed patterns. In the present paper, I attempt to tease apart causal factors using multivariate (path) analysis on the same data set (103 species, based on dissection of >22000 museum specimens). Two separate path analyses were conducted: one that treated each species as an independent unit (and thus, ignored phylogeny) and the other based on independent phylogenetic contrasts. Path coefficients from the two types of analyses were similar in magnitude, and highly correlated with each other, suggesting that most interspecific patterns among traits may reflect functional association rather than phylogenetic conservatism. Path analysis showed that indirect effects of one variable upon another (i.e., mediated via other traits) were often stronger than direct effects. Thus, even when two variables appeared to be uncorrelated in the univariate analysis, this apparent lack of relationship sometimes masked strong but conflicting indirect effects. For example, a tradeoff between clutch size and offspring size tends to mask the direct effect of mean adult body size on clutch size. Path analysis may also suggest original causal hypotheses. For example, interspecific allometry of sexual size dimorphism (as seen in Australian snakes, and many other animal groups) may result from a strong effect of another allometrically-tied trait (offspring size) on growth trajectories of females.

Efficacy and Potency of Antivenoms in Neutralizing the Procoagulant Effects of Australian Snake Venoms in Dog and Human Plasma

The efficacy and potency of Commonwealth Serum Laboratories (CSL) snake antivenoms in neutralizing the procoagulant action of Australian snake venoms was studied in vitro. The procoagulant action of venoms from Tiger, Brown and Taipan Snakes were measured in pooled canine or pooled human plasma. Mixtures of the venoms and their appropriate antivenoms, ranging from 0.1 to 15 times the recommended neutralizing dose of antivenom were then added to pooled canine or pooled human plasma and the efficacy and potency of the antivenoms in preventing the procoagulant action was measured. Neutralization was achieved by the addition of the appropriate antivenom in concentrations of 0.5 (Taipan), 10 (Tiger), 10 (Gwardar), 15 (Dugite) and an estimated 20 (Common Brown) times the dose expected. Similar results were obtained in canine and human plasma. The potency of Tiger and especially Brown Snake antivenom is substantially lower (10-20 times) than that predicted by CSL. These findings support an increase in the dose of antivenom to be used for the treatment of Tiger and especially Brown Snake envenomation complicated by coagulopathy. The in vitro canine model may be suitable for studying the procoagulant effects of Australian snake venoms.

Biochemical and neurotoxicological characterization of paradoxin, a β-neurotoxin from Australian inland taipan snake (Oxyuranus microlepidotus) venom

Biochemical and neurotoxicological characterization of paradoxin, a β-neurotoxin from Australian inland taipan snake (Oxyuranus microlepidotus) venom

Characteristics of the procoagulant front the venom of the Australian common brown snake (Pseudonaja textilis)

Characteristics of the procoagulant front the venom of the Australian common brown snake (Pseudonaja textilis)

Isolation, characterization and diagnostic potential of texlarin, a prothrombin activator from the venom of the Australian eastern brown snake Pseudonaja textilis

Isolation, characterization and diagnostic potential of texlarin, a prothrombin activator from the venom of the Australian eastern brown snake Pseudonaja textilis

Allometric Patterns in the Ecology of Australian Snakes

This paper summarizes published and original data on ecological characteristics of 103 species of Australian snakes, based on dissection of > 22,000 specimens in museum collections. Principal Component Analyses suggest that much of the interspecific variance in ecology is the result of differences in mean adult body sizes. Thus, I examine the degree to which absolute body size is correlated with other ecological variables in interspecific comparisons and investigate interspecific associations between ecological traits after the confounding effect of absolute body size is removed from the analysis. Mean adult body size is significantly correlated with measures of population structure (adult sex ratio), growth trajectories (size at maturation relative to mean adult size, and sexual size dimorphism), mating systems (presence or absence of male-male combat), reproductive biology (offspring size, clutch size, reproductive mode, and reproductive frequency in females), and food habits (proportional composition of major prey types). Phylogenetically based analyses show that some of these interspecific correlations are the result of phylogenetic conservatism, whereas others reflect underlying functional relationships. When these kinds of allometric effects are taken into account, clear patterns in interspecific variation in life-history attributes are revealed. For example, a trade-off is apparent between clutch size and offspring size: species with relatively large clutches produce relatively small offspring. Offspring size is unaffected by shifts in reproductive mode (oviparity/viviparity) but is correlated with the extent of postmaturational growth by females (in species with relatively large offspring, females delay maturation until they reach a large size). The presence or absence of male-male combat in a species affects adult sex ratio in collections (probably via sex biases in catchability), growth trajectories in males, and the degree of sexual size dimorphism.

The expression of vimentin in satellite cells of regenerating skeletal musclein vivo

The expression of the intermediate filament protein, vimentin, was studied in skeletal muscle during a cycle of degeneration and regeneration. Venom from the Australian tiger snake, Notechis scutatus scutatus, was used to initiate the breakdown of the soleus muscle of young, mature rats in vivo. Cryosections and Western blots of muscle samples were labelled using antibodies to vimentin, and examined at fixed time points after venom injection. Vimentin was absent in control adult muscle fibres, but was identified in activated satellite cells 12 h after venom assault. The amount of this protein rose during the early stages of regeneration, reaching its peak at 2-3 days. At this time, the expression of muscle-specific intermediate filament protein, desmin, began. As the abundance of desmin increased with the maturation of the regenerating myofibres, the abundance of vimentin declined until it was no longer detectable in mature regenerated fibres. It is suggested that vimentin plays an important role during satellite cell activation in the early stages of regeneration, and that the expression of vimentin may act as a stimulus for the expression of desmin at later stages of regeneration.

Seasonal Changes in Dorsal Reflectance of Two Species of Australian Elapid Snakes

Seasonal Changes in Dorsal Reflectance of Two Species of Australian Elapid Snakes

Australian Snakes: A Natural History

Australian Snakes: A Natural History

Australian Snakes: A Natural History, by Richard Shine. [Review

Australian Snakes: A Natural History, by Richard Shine. [Review

Australian snakes: a natural history

Australian snakes: a natural history

The fate of dystrophin during the degeneration and regeneration of the soleus muscle of the rat

Immunocytochemistry and Western blotting were used to monitor the fate of dystrophin in the soleus muscle of the rat during a cycle of degeneration and regeneration induced by inoculation of the muscle with the venom of Notechis scutatus scutatus (the Australian tiger snake). In control muscle dystrophin was localised close to the plasma membrane. Dystrophin began to break down 3-6 h after venom inoculation, giving a characteristic discontinuous labelling pattern. At 12 h dystrophin was absent from the plasma membrane, and by 1 day the architecture of the muscle fibers had completely broken down. By 2 days post inoculation regeneration had commenced. The regenerating myofibres possessed well-organised myofibrils and the plasma membrane was intact. Dystrophin was detected by Western blot at 3 days, but was not seen in sections until regeneration of the muscle was well advanced, at 4 days post inoculation. The results suggested that although dystrophin was present in the myofibres at 3 days, it was not incorporated into the plasma membrane until 4 days post inoculation. This may be due to the influence of the functional reinnervation of the regenerating fibres, which occurs at 4-5 days, or to the growing fibres reaching a critical diameter.

Studies on the subunit structure of textilotoxin, a potent presynaptic neurotoxin from the venom of the Australian common brown snake (Pseudonaja textilis). 2. The amino acid sequence and toxicity studies of subunit D

Textilotoxin is a presynaptic neurotoxin in the venom of the Australian common brown snake, Pseudonaja textilis. It has the highest lethality and is structurally the most complex of any known snake venom neurotoxin. Reverse-phase HPLC was used to resolve textilotoxin into subunits A, B, C and D. Subunit D consists of two identical covalently linked polypeptide chains. Its sequence is now reported. It is an acidic, slightly glycosylated polypeptide of 133 amino acid residues in each chain. Although it is not itself neurotoxic, it was found to be essential for the neurotoxicity of textilotoxin.

Australian snake venoms and their in vitro effect on human platelets

Thrombocytopenia is generally not associated with cases of envenamation by Australian snakes, however the clinical evidence is conflicting. The in vitro effect of these venams upon platelets had hitherto not been studied. This study systematically examines the effect on human fresh and fixed platelets of twenty Australian snake venoms, nineteen elapid and an hydrophiid; for comparision four crotalid venoms from the Americas and S.E. Asia were also included. Electron micrographs were taken of platelets after exposure to some of the venoms. Results demonstrated that all venoms except the hydrophiid venom caused fresh platelets to irreversibly aggregate directly, and this was associated with degranulation as evidenced by electron microscopy(EM). Response to all venoms by fixed platelets was less marked and also suggests, that metabolically, active platelets are necessary for the venoms to exert their maximal effect. The hydrophiid venom's action on fresh platelets was unique, as a plasma co-factor was required before aggregation could be induced. Crotalid and hydrophiid venoms were more active against platelets than the elapid venoms. Nevertheless, platelet aggregation and degranulation in the presence of elapid venoms suggests that a platelet response in vitro may be a significant factor in the “defibrination syndrome” induced in humans by Australian snakes.

Dentition and diet in snakes: adaptations to oophagy in the Australian elapid genus Simoselaps

Most small fossorial proteroglyphous Australian snakes of the genus Simoselaps feed on adult lizards, but the species of one lineage (the semifasciatus group) feed exclusively on the eggs of squamate reptiles. Examination of cleared, alizarin preparations showed that dentition of the saurophagous species is similar to that of other elapids, but dentition of the oophagous taxa is highly modified. The anterior (palatine and maxillary) teeth other than the fangs are reduced in size and number whereas those of the pterygoid (and in S. ‘ropert’, the dentary) are enlarged posteriorly, becoming compressed along a longitudinal plane and angled medially. The shape of the pterygoid and quadrate is also modified.Two Simoselaps species with broader diets (eating both adult lizards and their eggs) show typical ‘saurophagous’ dentition in one case, ‘oophagous’ dentition in the other, showing that either type of dentition can be used to capture and ingest either type of prey. We suggest functional explanations for the dentitional modifications in the egg‐eating snakes, primarily in terms of the advantages of applying considerable force to the eggshell. Oophagous modifications within Simoselaps are convergent with those seen in several independently‐derived lineages of oophagous colubrid snakes, but (perhaps because of the presence of the fang) differ in having the enlarged blade‐like teeth on the pterygoid or dentary rather than the maxilla.

Food Habits and Reproductive Biology of Small Australian Snakes of the Genera Unechis and Suta (Elapidae)

Dissection of 1607 provided data on natural history of nine species of small (<50 cm snout-vent length), widely-distributed Australian elapids. Males and females matured at similar sizes, with males tending to attain slightly larger maximum sizes. All species examined are viviparous, and show similar litter sizes (means of 3 to 9 offspring) and offspring sizes (10 to 18 cm SVL). Fecundity and offspring size were highly correlated with mean maternal SVL in an interspecific comparison. Ovarian follicles of adult females undergo vitellogenesis in spring, with ovulation later in spring and parturition in summer. Museum collections of all species contain approximately equal numbers of adult males and females, as is generally true of small, cryptic elapids. However, the proportion of adult females which were gravid (<3% of adult females) was surprisingly low. All eight species of Unechis feed mainly on scincid lizards (83% to 100% of all prey items recorded), whereas the single species of Suta studied consumes a broad range of skinks (37% of prey items), geckos (17%), agamids (17%) and mammals (20%). The overwhelming importance of scincid lizards in the diet of Unechis is similar to the situation in most other small Australian venomous snakes. This paper describes general ecology of nine species of small black-headed snakes belonging to the genera Unechis and Suta. Snakes of these two groups are abundant and widely distributed in many Australian habitats. Most species of Unechis, like most of the other viviparous elapids, are found in the relatively cool and mesic south- western and eastern parts of the continent (U. flagellum, U. gouldii, U. nigriceps, U. spec- tabilis). Some species (e.g. Suta suta, Unechis monachus and U. dwyeri) extend into more arid habitats, while the two remaining species, U. nigrostriatus and U. carpentariae, are restricted to northeastern Australia. The