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Spider With No Venom Has a Deadly Trick to Poison Its Prey
In an unexpected twist, a non-venomous spider has been caught poisoning its victims by lacing its silk wrappings with vomited toxins.
The feather-legged lace weaver (Uloborus plumipes), common across Europe and Africa, lacks venom glands on its head, so it was thought to be harmless. But biologists suspected this arachnid uses a different method of chemical warfare.
University of Lausanne ecologist Xiaojing Peng and colleagues have now discovered that lace weavers regurgitate toxins from their midgut onto their silk-wrapped prey to subdue them.
While the gut-toxin compounds are different from those found in the fangs of venomous spiders, they appear to be just as effective at disabling prey.
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"These samples proved highly insecticidal, killing an average of 50 percent of fruit flies within an hour of inoculation," says ecologist Giulia Zancolli, also from the University of Lausanne.
The researchers found these toxic proteins were similar to those in the digestive fluids of other spiders, like Parasteatoda tepidariorum, despite this species having venom glands as well.
"These findings demonstrate that spider toxins are not exclusively confined to specialized venom-secreting glands but also play a role in the digestive system," explain Peng and team in their paper. "This supports an evolutionary link between the two systems, suggesting that toxins may have initially served digestive functions before being co-opted for venom use."
Unlike their venomous counterparts, U. plumipes lack ducts in their fangs for injecting anything, the researchers confirmed. They suspect the lace weaver lost its venom over time, but then compensated by shifting to using its digestive toxins.
While spiders are often feared for their venomous ways, they play a crucial role in our ecosystems, keeping insect numbers at bay while providing food for many birds, reptiles, and other animals, even humans, some while looking quite spectacular, too. Their venoms have also shown promise for potential medical uses, so it might be worth investigating the properties of their gut toxins as well.
This research has been published in BMC Biology.
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