Prey capture may have been the primary driver of viper venom evolution

Snake venom primarily serves to incapacitate and dispatch prey, but it can also play a role in defence against predators. The authors of the study published in Functional Ecology investigated whether an evolutionary trade-off between these two functions could be detected in the venoms of European vipers.

The researchers expected that species feeding on prey that is easier to subdue, such as insects, might have venoms with a higher proportion of components aimed at deterring predators by causing  immediate pain. These were compared to vipers that regularly consume more dangerous prey, such as rodents. The effects of field-collected venom samples were tested on neurons and receptors involved in pain perception (nociception).

No sign of direct pain induction

Although the venom composition of the species differed significantly, regardless of diet, none of the venoms directly activated the nociceptive neurons evaluated. This does not support the hypothesis that the evolution of European viper venoms has been substantially shaped by rapid pain induction required for predator defence.

"This challenges the concept that defensive and trophic functions drive snake venom evolution in divergent directions. Our results suggest that for the species we investigated, prey capture may be the primary driver shaping venom composition," said Bálint Üveges, research fellow at the HUN-REN Centre for Ecological Research and lead author of the study.

The study does not claim that a viper bite is painless. Pain following a bite can develop through indirect effects of the venom components, such as tissue damage and the secondary inflammation that results from it. The investigation specifically tested whether the venom directly activates nociceptive neurons—a hallmark characteristic of defensive venoms.

Why is understanding venom evolution important?

Snake venom composition varies extremely among species, populations, and even individuals. Uncovering the evolutionary causes of this variation can ultimately help researchers better understand the mechanisms behind the symptoms of different snakebites and the factors influencing antivenom efficacy. The current findings contribute to narrowing down the range of potential evolutionary forces shaping the diversity of European viper venoms.

The study integrated methods from venom biology, ecology, evolutionary biology, and neurobiology. From the HUN-REN Centre for Ecological Research, Bálint Üveges and Edvárd Mizsei participated in the study. Experts from Bangor University, the University of Queensland, and numerous European research institutes, universities, museums, and conservation organisations collaborated in the international effort.