Blue-tongue lizards are resistant to redbellied black snake venom, Australian study finds
Blue-tongue lizards have developed a resistance to the venom of the red-bellied black snake, according to new research.
The largest animals in the skink family, blue-tongues seem to have evolved a chemical resistance to the snake venom, while carnivorous monitor lizards – goannas – that feed on Australia’s venomous snakes have not.
Researchers at the University of Queensland have analysed the effects of seven snake venoms on the blood of two species of blue-tongues – the common blue-tongued skink and the shingleback – and three goanna species, all of which would interact with these snakes in the wild.
In a study published in the journal Toxins, they found the blue-tongues seemed to have evolved a specific blood component – a serum factor – that prevents their blood from clotting when exposed to red-bellied black snake venom.
Associate Prof Bryan Fry of the University of Queensland said they had not yet identified the specific protective protein in the blue-tongue lizards’ blood.
“There’s something in the blood that’s … intercepting the toxins before it can cause its deadly action,” Fry said. “It doesn’t confer complete protection but just means that they’re less likely to die – much like the Covid vaccine doesn’t completely protect you against the virus, it just means you’re less likely to die.”
The blue-tongues were specifically resistant to the venom of red-bellied black snakes – which are mainly found on the east coast of Australia – but not the venom of the other six snake species, including swamp snakes and small-eyed snakes.
“We tested other venomous snakes that live in the same region as blue-tongues but are much smaller and therefore wouldn’t be feeding on a bluetongue.”
“The [blue-tongues’] form of resistance was so selective that it only impeded the red-bellied one but not the other snakes that had similar venom.”
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Fry said the blue-tongue lizards likely evolved the resistance as a chemical defence, because they are slow and cannot easily outrun predators.
The blood of the three goanna species tested was not resistant to the venom – likely because other external protections are sufficient.
Goannas have what Fry describes as “medieval chain mail” – thick scales that each contain bone. “For a good-sized lizard, a venomous snake is not going to be able to get through those kinds of scales.”
The researchers compare the protective factor in the blue-tongues’ blood to that of some squirrels in California, which have developed resistance to rattlesnake venom.
“They have certain proteins in their blood that have been mutated where they’re binding the rattlesnake toxins,” Fry said.
“It’ll be a very interesting comparison to see what has been mutated in the blue-tongue blood versus what has been mutated in the squirrel blood to have the same net outcome of being able to survive a bite by these predators.”