Environmental effects Scottish scientists believe findings illustrate how chemicals inhibit responses within bees
Scottish scientists have concluded in a study that insecticides hamper brain functioning in bees, hindering memory and the insect’s ability to learn.
In the report published March 28 in Nature Communications, researchers wanted to understand how imidacloprid and clothianidin, Bayer insecticides used for seed treatments, affect processes inside a bee’s brain.
As well, the scientists studied coumaphos, an insecticide used to kill varroa mites living in bee colonies.
“Although sub-lethal levels of neonicotinoids are known to disrupt honeybee learning and behaviour, the neurophysiological basis of these effects has not been shown,” the scientists noted in the paper’s abstract.
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University of Dundee scientist Chris Connolly and his team exposed bee brain cells to neonicotinoids and coumaphos at concentrations comparable to levels in beehives. Connolly’s team concluded the chemicals blocked neural firing and inhibited responses within the bee’s brain.
“Our findings demonstrate a neuronal mechanism that may account for the cognitive impairments caused by neonicotinoids,” the scientists said.
According to a University of Dundee news release, this is the first study to show that pesticides have a “direct impact on pollinator brain physiology.”
Critics of similar laboratory studies have said in the past that it is not clear whether lab experiments are able to properly mimic field conditions and real world exposure levels.
Last year, a French study concluded that thiamethoxam, a Syngenta in-secticidal seed treatment sold under the brand name Cruiser, interferes with bees’ ability to navigate. Bees dosed with the neonicotinoid partially lost their homing instinct and were two to three times more likely to die away from the hive.
As well, in a paper published earlier this year, Newcastle University investigators looked at the relationship between neonicotinoids, coumaphos and bee behaviour.
“When bees had been exposed to combinations of these pesticides for 4 days, as many as 30 percent of honeybees failed to learn or performed poorly in memory tests,” a news release for the study noted. The scientists evaluated bee learning and memory by monitoring proboscis extension towards an odour associated with a reward.
Geraldine Wright, one of the Newcastle scientists behind the study, said bees have to recall scents related to foraging and food.
“Disruption in this important function has profound implications for honeybee colony survival, because bees that cannot learn will not be able to find food.”
Put together, the Newcastle and Dundee studies suggest that insecticide exposure may “profoundly impact pollinator survival”, Connolly said.
“These studies highlight potential dangers to pollinators of continued exposure to pesticides that target the insect’s nervous system.”
