Spiders the answer for bee-safe pesticides
Funnel web venom appears to kill pests but not be harmful to bees. Yi-Di Ng reports.
Across the globe bee populations are crashing in a trend worrying farmers and beekeepers. Scientists now think that the pesticide class known as neonicotinoids is to blame.
Last year the European Union voted to ban the pesticides, which act on the nervous system in a similar way to nicotine, for two years – good for bees, but leaving farmers down a defence in the fight against damaging insect pests. Now a new study by researchers at the University of Newcastle, United Kingdom, suggests that Australia's most poisonous spider, the funnel web, may provide a solution. They found that its venom contains a pesticide that appears to be deadly to insect pests but harmless to bees.
“The potential of this pesticide is huge,” says entomologist Nigel Andrews at the University of New England, Australia.
Spider venom is a cocktail of small proteins, each of which has evolved to act like a guided missile, homing in on a specific target.
Pesticides like neonicotinoids target parts of the central nervous system that are similar across a wide variety of insects, including bees. In contrast, Hv1a, one of the proteins the researchers identified in the funnel web’s venom, works on a part of the nervous system that is different in bees, focusing on calcium channels, a component in the circuit of nervous transmission. Hv1a blocks these channels in aphids and flies, leading to paralysis and death, but not in bees.
“It looks like there is a genetic difference in the calcium channels of bees and other pest insects,” says Elaine Fitches, one of the authors of the paper, which was published in Proceedings of the Royal Society B this month.
Normally a spider injects venom directly into an insect’s bloodstream, a route that isn’t available for artificial insecticides, so the researchers had to come up with another way to deliver the pesticide – through the insects’ mouths.
But they faced a problem. When eaten, the Hv1a protein does not pass from the gut to the bloodstream. To get around this, Fitches and her colleagues found a way to wrap Hv1a in another protein, GNA, which does. The researchers combined the DNA sequences for Hv1a and GNA, and inserted them into yeast. The yeast cells, following the DNA recipe, pumped out the Hv1a proteins wrapped in GNA.
And it worked. When an insect ate the fusion protein, the venomous Hv1a was carried into its bloodstream and blocked its calcium channels, causing paralysis. Yet bees survived even after they were injected with and fed large amounts. And unlike other pesticides, the spider venom cocktail didn’t affect bees’ memory and ability to learn, which is crucial for them to find food thereby pollinating plants.
“Pesticides are not a single silver bullet and need to be used in conjunction with other management tools to keep pest species below threshold levels,” says Andrews, but he believes the development is good news for farmers. “Although we have other pollinators in Australia, bees still pollinate $4 – 6 billion worth of crops in Australia every year.”