Living amphibians include frogs and salamanders and the limbless worm-like caecilians (order Gymnophiona). Caecilians have cylindrical bodies with a compact, bullet-shaped skull that helps them burrow underground. Now exclusively home to South and Central America, Africa, and southern Asia, they spend their lives burrowing in leaf-litter or soil searching for prey such as worms and insects.
“Our research provides a textbook example of how a single predatory pressure can trigger an evolutionary cascade where the same way of fighting back arises independently multiple times in a species’ different lineages,” said University of Queensland’s Dr. Bryan Fry, senior author on the study.
“In this case, the key predatory pressure was the rise of the elapid snakes, such as cobras and coral snakes, characterized by the evolution of a new way of delivering venom via their hollow, fixed, syringe-like fangs.”
“Despite being quite slippery, caecilians are worm-like in their locomotion and speed and were incredibly easy prey to cobras and other snakes, which used their fangs to kill them and eat them later.”
“It would have been absolute carnage to the point where elapids were basically grazing on caecilians, contributing to the rapid spread of elapid snakes across Africa, Asia, and the Americas.”
“The caecilian’s ability to persevere and evolve despite these pressures is like a movie — like the survivors of Judgement Day fighting back by changing the chemical landscape.”
In the study, Dr. Fry and colleagues sequenced a part of the neuromuscular receptor in 37 caecilian species, representing all currently known families of caecilians from across the Americas, Africa, and Asia, including species endemic to the Seychelles islands never reached by elapid snakes.
They showed that resistance to elapid snake venom neurotoxins has evolved on at least 15 times.
“A particularly interesting validation of the theory was that the caecilians on the…
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