Caecilians evolve “unprecedented” snake venom resistance

In a groundbreaking discovery, an international team of researchers has unveiled an astonishing resistance to snake venom in an unexpected creature—the caecilians, a group of legless amphibians. Published in the esteemed International Journal of Molecular Sciences, the study, led by Associate Professor Bryan Fry from the University of Queensland, sheds light on the fundamental concept of predator-prey interactions and the remarkable ways evolution can unfold.

The researchers found that a significant evolutionary cascade was triggered by a specific predatory pressure—the emergence of elapid snakes like cobras and coral snakes. These elapid snakes possess hollow, syringe-like fangs that allowed them to deliver venom efficiently. The slow-moving and worm-like caecilians became easy prey for these snakes, leading to a veritable carnage as elapids spread across continents, devastating caecilian populations.

However, the caecilians demonstrated incredible resilience and adaptability in the face of this threat. Their ability to evolve independently in response to the same predatory pressure is likened to a riveting movie plot—akin to the survivors of Judgment Day fighting back by altering their chemical makeup.

The study covered caecilian species from all known families worldwide, including those inhabiting the Seychelles islands, which were never reached by elapid snakes. By analyzing tissue collections and sequencing a specific part of the neuromuscular receptor targeted by snake venom toxins, the researchers discovered that resistance to elapid snake venom neurotoxins had evolved at least 15 times—a phenomenon never seen before.

One of the lead authors, Marco Mancuso from Vrije Universiteit Brussel’s Amphibian Evolution Lab, explained that some caecilians developed resistance to venom by building a barricade that prevented toxins from reaching lethal receptors. Others evolved by altering the physical shape of the receptor, making it incompatible with the toxins. Additionally, caecilians deployed an electromagnetic “weapon” that caused a positive-to-positive charge repulsion during toxin-receptor interactions, effectively repelling the venomous attack.

Notably, the caecilians on the Seychelles islands lacked venom resistance, in line with the absence of elapid snakes on the islands. The survivors of the elapid snake onslaught were those caecilians who were less sensitive to venom or had mutations that granted them complete immunity, enabling them to repopulate the Earth.

While this research might not directly benefit humans with new antivenom, it provides a captivating insight into an essential aspect of evolution—an eternal battle between animals, wherein prey evolve ingenious strategies to escape the clutches of predators. This fascinating discovery will undoubtedly inspire and captivate the next generation of scientists, instilling a passion for understanding the wonders of nature.

Source: University of Queensland

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