After ingesting minute doses of a pesticide called chlorpyrifos, bees suffered severe deficits in memory and learning, potentially threatening their survival, according to a research from the University of Otago in New Zealand.

For the study, published in the Journal of Chemical Ecology, researchers collected bees from 51 hives in 17 locations across Otago in Southern New Zealand, detecting low levels of chlorpyrifos in samples from six of the hives and three of the 17 sites.

The presence of the pesticide was not actually surprising because chlorpyrifos has been found in plant, water and air samples even from areas not sprayed, because of the pesticide's high volatility and great ability to travel distances.

In the lab, the researchers fed other bees with the pesticide at levels similar to what they recorded from the samples and them carry out certain tasks to test learning performance.

Based on their findings, the researchers saw that those bees fed with the pesticide performed worse in odor-learning tasks, recalling odors poorly even when the chlorpyrifos dose was considered to be at a "safe" level. For instance, the dosed bees were not able to respond as intended to odors that have been previously deemed as rewarding.

Elodie Urlacher, the study's lead author, explained that honeybees rely on memory mechanisms to find flower targets. Given the result of the study, it appears that chlorpyrifos is stunting bees' effectiveness as nectar foragers and pollinators.

The researchers also identified the dose threshold for the pesticide that prompts sub-lethal effects involving memory and odor learning, setting it at 50 picograms.

This figure is thousands lower than the lethal dose for pure chlorpyrifos and is at the lower range of pesticide levels detected in bees in collected in the field.

According to Urlacher, the results of their work raise serious questions about pesticide use, highlighting the need to review regulations, now that it has been shown that even non-lethal doses can affect honeybees, which also hint at potential dramatic effects for hives around the world.

Other researchers involved in the study include: Alison Mercer, Kimberly Hageman, Sue Michelsen-Heath, Christie Lombardi, Freddie-Jeanne Richard, Coraline Rivière, and Coline Monchanin.

Photo: Courtney Collison | Flickr

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