Common pesticide found to interfere with the sleep cycles of bees

Bee populations are declining at alarming rates around the world, and that could have profound consequences for human civilization. Along with things like drought and habitat loss, the widespread use of pesticides is a huge driving force behind these dwindling numbers, and a new study has shone further light on the most common one of all, finding that it interferes with the insect’s natural sleep cycles and their daily behavior as a result.

Because bees play an important role in pollinating the many crop species that we eat, healthy bee populations are critical to food security around the globe. In 2016, the US Fish and Wildlife Service placed seven species of bee on the endangered list for the first time, in an effort to protect the fragile and shrinking populations.

Pesticides are one of the most significant drivers of this trend, and at the very center of the issue are a type called neonicotinoids, which the EU banned in 2016 but are still in use around the world. These pesticides are applied to crops to protect the growing plants from other critters, but the scattergun approach means bees get caught in the crossfire. The chemicals interfere with the bees’ energy-producing molecules and can leave them immobile and starving.

This new work carried out by scientists at the University of Bristol dives a little deeper into the effects neonicotinoids can have on bees. The researchers subjected bumblebees to concentrations of the pesticide equal to what they would endure on a farm, and found that it brought about significant disruptions to their natural sleep cycles.

The affected bees were found to be more active at night and sleep more during the day. This had the effect of shaking up the insect’s daily behaviors, impacting their memories and lowering their foraging activity and locomotion. The researchers suggest that this could reduce pollination opportunities and, in turn, the ability of the colony to grow and reproduce.

"Being able to tell time is important for knowing when to be awake and forage, and it looked like these drugged insects were unable to sleep,” says co-author Dr James Hodge. “We know quality sleep is important for insects, just as it is for humans, for their health and forming lasting memories."

The researchers also carried out experiments on fruit flies, and found that exposure to neonicotinoids had much the same effect.

"Bees and flies have similar structures in their brains, and this suggests one reason why these drugs are so bad for bees is they stop the bees from sleeping properly and then being able to learn where food is in their environment,” says co-author Dr Sean Rands.

The bee study was published in the journal iScience, while the fruit fly study was published in Scientific Reports.

Source: University of Bristol