Venom  Composition
    Australian Elapidae venom may contain as many as four toxic components.  Two of the four,  procoagulants (prothombin activators) and neurotoxic phospholipase A2s, are fairly common in Elapid venom.  Procoagulants deprive the blood of fibrin, a key component in the clotting of blood, by inducing massive consumption of its precursor, fibrinogen, thereby preventing the clotting factor in blood and increasing the risk of haemorrhage (Fry 1999).  PA2's exhibit non-lethal esterase activity (i.e. digestive acitivity) and toxic neurological activity where they pre- or post-synaptically block neuromuscular nerve transmission.  The blockage prevents neuromuscular transmission, and death results from suffocation, as the main nerve leading to the diaphragm stops firing action potentials and breathing ceases.  PA2's that have curare-like action and bind post-synaptic skeletal muscle nicotinic acetylcholine receptors are called alpha-neurotoxins.  Symptoms include nausea, drooping of the eyelids, paralysis of the eye muscles, muscle soreness, and respiratory paralysis.  Alpha-toxins are found prominently in the Death Adder, as well as the Common Brown Snake, Tiger Snake, Taipan, and Red-bellied Black Snake.  Alpha-toxins are absent in the venom of the King Brown Snake (Bauchot 1994; Pough 1998).  Beta-neurotoxins, on the other hand, keep nerve endings from liberating acetylcholine.  They are an example of a presynaptic neurotoxin, and are the most toxic substances isolated from any snake venom to date. They can cause irreversible paralysis in as little as 3-5 minutes.  Notexin, found in Tiger Snake venom, Taipoxin, found in Taipan venom, and Textilon, found in Common Brown Snake venom, are all examples of alpha-neurotoxin.  (Greene 1997; White1981)
    The other two components of Elapid venom are myotoxins and nephrotoxins and are not contained in the venom of as many species as the more common PLA2's and haematoxins (procoagulants).  Myotoxins attack skeletal muscle and result in damage to muscle fibers.  Symptoms include muscle weakness and pain upon moving.  Tiger Snakes, Mulga Snakes, and Red-bellied Black Snakes all have venom that have myolytic activity.  Nephrotoxins cause renal failure and have only been discovered in the venom of one genus, Pseudonaja (White 1981)
Venom Content is highly variable among different species, as demonstrated in the following table.
Species Venom Enzyme Content Symptoms
Taipan (Oxyuranus) haematoxin, alpha- and beta-neurotoxin, possible nephrotoxin vomitting, muscle soreness, drooping eyelids, blood in urine
and stool, and eventual respiratory paralysis
Tiger Snake (Notechis) haematoxin, myotoxin, alpha- and beta-neurotoxin pain in area where bite occurred, head aches, nausea, vomiting, collapse, paralysis, coagulopathy, muscle wasting, eventual respiratory paralysis
Red-bellied Black Snake (Pseudechis porphyriacus) myotoxin, haematoxin pain at site of bite, headache, nausea, and 
vomitting, and possibility of defibrination syndrome
King Brown Snake (Pseudechis australis) myotoxin, haematoxin, alpha-neurotoxin nausea, vomiting, headache, severe muscle 
damage and necrosis, respiratory paralysis
Common and Western Brown Snakes (Pseudonaja textilis and nuchalis) haematoxin, nephrotoxin, beta-neurotoxin head aches, nausea, vomiting, coagulopathy (including wound ooze and blood in urine), possibility of early collapse
Death Adder (Acanthophis) alpha-neurotoxin mild symptoms that include headache and occasional vomiting,
until respiratory paralysis occurs
(White 1981; Fry 1999)

To see a diagram of various toxins and enzymes in snake venom, including the alpha- and beta-neurotoxins, click here.


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This page is an assignment for Biology 312, Animal Physiology, and is for educational purposes only.
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