Popular herbicide impairs bumblebee color vision

A new study led by the University of Turku in Finland has found that Roundup, a widely used herbicide containing glyphosate, affects the learning and memory of bumblebees. According to the experts, even after exposure to relatively small doses, bumblebees’ ability to learn and memorize connections between colors and tastes seemed to be impaired – a problem that could significantly diminish their foraging and nesting success.

The researchers exposed bumblebees to an acute dose of herbicide that pollinating bumblebees might be exposed to in a sprayed field. Afterwards, they tested their learning and memory capacities in a ten-color discrimination task, in which the bumblebees learned to associate five specific colors with a rewarding sugary solution, and other five colors with an aversive quinine solution.

While the bumblebees in the control group learned to distinguish colors associated with sweet sugar water from those associated with a bad-tasting compound and could remember what they learned even after three days, those exposed to the herbicide managed to learn significantly less and forgot almost everything they had learned in just a few days.

However, the herbicide treatment did not seem to affect bumblebees’ performance in an easier two-color discrimination task or a ten-odor discrimination task. These findings suggest that, although exposure to the herbicide does not make bumblebees completely color or odor blind, it does impair their fine color vision.

“We focused on the cognitive traits of the bees because these traits determine the successful foraging and social behavior of social insects and therefore their fitness. I am really worried. Even one very small acute dose had a harmful effect on the bumblebees,” said study lead author Marjo Helander, a biologist at the University of Turku. “The result is even more worrying when you take into account how much glyphosate-containing herbicides are used globally.”

“The results are quite worrying considering the importance of color vision for bumblebees. Even small disturbances in color vision can be catastrophic in terms of foraging and nesting success,” concluded study senior author Olli Loukola, a behavioral ecologist at the same university.

The study is published in the journal Science of the Total Environment.

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By Andrei Ionescu, Earth.com Staff Writer