for National Geographic News
Tarantulas use the same scare tactics as hot chilies to avoid being eaten, a new study suggests.
Like chili plants, tarantulas produce agony-inflicting toxins designed to repel would-be predators, researchers say.
The hairy arachnid's venom was found to include chemicals that target the same pain pathways as chili peppers, causing maximum distress to bite victims.
The study suggests that animals can defend themselves by activating the sensory nerves of their enemies, just like certain plants do.
While spider toxins that lead to shock, paralysis, and death are well studied, far less is known about how spider venoms cause pain. (Related video: "'World's Largest Spider' Stalks South American Jungles".)
In the new study, a team led by neuropharmacologist David Julius from the University California, San Francisco, identified three pain-causing molecules in tarantula venom.
These neurotoxins were found to activate the same receptor on sensory nerves that produces the burning sensation animals get from capsaicin, the "hot" ingredient in chilies.
The findings, which will appear tomorrow in the journal Nature, are based on the venom of the Trinidad chevron tarantula, a large, long-legged species from the Caribbean (map of Trinidad and Tobago).
Previous research has revealed that chili plants employ capsaicin to cause pain in rodents that might otherwise eat them.
Julius and colleagues found that normal lab mice exposed to the newly discovered spider toxin molecules acted as if in pain, and their paws became inflamed.
However, mice genetically engineered to lack the capsaicin receptor showed no obvious signs of discomfort and only minimal swelling.
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