University of Galway researchers uncover why some spiders have stronger venom than others

Irish Independent

21-05-2025

The team at the university's School of Natural Sciences analysed the venom of over 70 different species of spider.
A number of factors were considered including the size of the spider, the type of prey they hunt and how they hunt it.
The effects of a spider bite can vary significantly from one species to another. A bite from the Brazilian wandering spider can result in serious medical complications, but venom from a giant house spider commonly found in Ireland is of little threat to humans.
The results have been published in the journal Biology Letters.
The researchers, including lead author, Dr Keith Lyons, found spider venoms are 'prey-specific', making the diet of the spider one of the most important factors for determining how potent their venom is.
Spiders that mainly hunt insects are likely to have venom particularly dangerous for insects but their venom has less impact on other prey such as small mammals.
'Our results show that spider venoms have evolved to be especially potent when tested on animals found in their diet in the wild,' Dr Lyons said.
'This may explain why species that are known to occasionally prey upon small mammals, such as the Brazilian wandering spider or black widow, have venoms that can cause medically significant effects in us humans, whereas species that only prey on invertebrates, such as the giant house spider, have evolved venoms that target invertebrate physiologies rather than our own, posing little threat to us.'
The research also examined whether the spiders' use of webs to catch their prey had any relation to the strength or volume of venom.
'We predicted that web-hunting spiders might have less potent venoms because they may have evolved to rely more on their webs to immobilise prey,' senior author and head of the macro-ecology lab at the School of Natural Sciences, Dr Kevin Healy, said.
'Surprisingly, we found no relationship between whether a spider used their web and the potency of their venom, suggesting that webs are likely important for restraining prey in web-hunters, regardless of how deadly their venom is.
'This study helps us to understand the evolution of spider venoms and aids in our understanding of why some spiders, such as the noble false widow, become invasive species in some parts of the world, or how some venoms may be of particular interest for future drug discovery, or the development of pest species-specific, pollinator-friendly insecticides.'
'By understanding the fundamental drivers of venom evolution, we can better predict the types of biomolecules in spider venoms that have yet to be explored for drug discovery and why some species of spiders are more likely to become invasive species,' Dr Michel Dugon, of the Ryan Institute, said.