Image Courtesy Bruno Santos
Binford uses the data she collects from venom to piece together the evolutionary history of spider species. But why bother? Binford explains that the most powerful tool we have in understanding venom is the evolutionary tree itself. There are over 41,000 spiders species alone, and perhaps hundreds of thousands of other venomous animals, so our current picture of how all the venomous species are related is fairly spotty. But a more complete understanding of how and where venom evolved would help explain how certain toxins ended up in certain places along the evolutionary tree. This could enable scientists to more easily decipher what's in the venom samples they already have, and to make predictions about what kinds of toxins we'll find in newly discovered species. Evolution turns out to be a great structural framework for understanding venom chemistry.
And understanding venom chemistry is beginning to have some exciting new applications. Glenn King, a professor at the University of Queensland in Australia, is developing ways to use components of spider venom as targeted pesticides. From an evolutionary perspective, this makes perfect sense. Spider venom has evolved specifically to target insects, so if we can isolate the toxic proteins that kill insects without harming humans, we'd have some very effective and completely biodegradable pesticides.
To figure out which proteins accomplish that goal, King tests possible toxins on newborn mice, mammals that are especially sensitive to neurotoxins. None of the toxins being developed are at all harmful to the newborn mice, even at very high doses. King acknowledges that a lot of people might be hesitant to spray their plants with spider toxins, but says this is a problem of perception rather than reality. Only a microscopic percentage of spider toxins are harmful to humans anyway, and tests like the ones on baby mice weed those out long before they come in contact with our food.
Evolution and natural selection may have created chemicals that do their jobs better than the synthetic ones humans create. We have nature--and the spiders themselves, of course--to thank for these incredible toxins. And as scientists continue fill in the gaps in the spider's evolutionary tree, they are bound to discover even more ways to take advantage of their unique adaptations.
This is the third installment of The Venom Chronicles, a blog series by Hannah Krakauer, a research intern at NOVA and a student at Stanford University. From more on the science of venom, watch Venom: Nature's Killer streaming online, or check your local listings to find out when it will air near you.