Venom from spitting cobras has evolved to cause predators extreme pain as aform of self-defence, rather than for capturing prey, according to newresearch.

An international team including scientists from The University of Queensland,made the discovery by studying the composition of spitting cobra venoms fromthree groups of snakes — Asian spitting cobras, African spitting cobras andrinkhals.

Co-authors Professor Irina Vetter and Dr Sam Robinson from UQ’s Institute forMolecular Bioscience are among the team which demonstrated that the defensivemechanism had developed as a dominant genetic trait.

“The fangs of these snakes are adapted to spray venom as far as 2.5 metres —the venom is aimed directly at the face, specifically the eyes, causingintense pain and can lead to the loss of eyesight,” Dr Robinson said.

Professor Vetter said the snakes had independently evolved the ability to spittheir venoms at enemies.

“We tested how venom components affected pain-sensing nerves and showed thatspitting cobra venoms are more effective at causing pain than their non-spitting counterparts,” she said.

The three different groups of venom-spitting snakes had increased productionof an enzyme toxin, phospholipase-A2, which works cooperatively with othervenom toxins to maximise pain.

Lead author Professor Nick Casewell from the Liverpool School of TropicalMedicine said venom spitting was ideally suited to deterring attacks fromhumans.

“It is intriguing to think that our ancestors may have influenced the originof this defensive chemical weapon in snakes,” he said.

Professor Vetter and Dr Robinson are pain researchers, studying the molecularmechanisms of pain with the goal of developing new and more effectivepainkilling drugs.

“Pain-causing toxins from animal venoms can be useful tools to help usunderstand pain signalling at a molecular level, and are helping us toidentify new targets for future painkillers,” Dr Robinson said.

Image: The Mozambique spitting eSwatini. ©Wolfgang Wüster Naja.

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