Pesticides Stunt Baby Bee Brains, New Study Discovers

Published on March 26th 2020
A close up of a yellow wall
Sadly, we are becoming all too familiar with the word 'pathogen' these days.
In agriculture and gardening, pesticides play an important role in protecting food supplies and plants from harmful bacteria, infectious disease or plant pathogens.
But while they might help ensure harvests and prevent plant threats, many chemicals designed to ward off pests can also have terrible, if unintended, consequences for biodiversity. Often it is helpful garden pollinators such as bees that are collateral damage.

Colony contamination

Using micro x-ray scanning, scientists at the Imperial College London have found harrowing evidence of what some pesticides do to young bees and the delicate fabric of their ecosystem.
We already know that manmade pesticides can kill wildlife. But the latest study reveals how contaminants brought back to bee colonies can physically stunt the development of larvae and harm brain function of bees into their adult life.
Such damage not only harms the bees themselves but a deterioration in brain capacity in the insects has wider implications on colonies as a whole as, for example, worker bees could struggle to manage the hive.
“Bee colonies act as superorganisms, so when any toxins enter the colony, these have the potential to cause problems with the development of the baby bees within it,” said lead researcher Dr Richard Gill, of Imperial College’s Department of Life Sciences, in a statement.
“Worryingly in this case, when young bees are fed on pesticide-contaminated food, this caused parts of the brain to grow less, leading to older adult bees possessing smaller and functionally impaired brains; an effect that appeared to be permanent and irreversible.”
bee closeup
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Pesticide tests

Published in the Proceedings Of The Royal Society B journal, the study relied on micro CT scanning at the Natural History Museum to study the brains of the insects.
In a test case of around 100 bees, the researchers provided a colony with “neonicotinoid spiked nectar”. Neonicotinoid is a class of pesticide which is largely banned in the EU but still used globally.
The brain capacity of baby bees were assessed after 3 days and 12 days in tests that saw the insects essentially tasked with learning to associate a smell with food.
The brain function of bees that had been exposed as larvae to the neonicotinoid was then compared with bees that had not come into contact with the chemicals.
Bees that had been in contact with the pesticide as larvae had “significantly impaired” learning capacity, according to the study.
A section of the insect brain known as the “mushroom bodies” - associated with memory and learning - was found to be much smaller in these bees. The neural areas of the insect brain get their name due to the distinctive mushroom-like shape.
Fellow author of the study Dr Dylan Smith has suggested that it’s not only direct exposure that bees need to be protected against.
He highlighted that a build-up of pesticides inside a colony can affect a hive’s future workforce “weeks after they are first exposed”.
Perhaps like a dangerous bacteria, pesticides have the potential to contaminate a whole colony and way of life for bees as they go about their business.
“Bees’ direct exposure to pesticides through residues on flowers should not be the only consideration when determining potential harm to the colony,” Dr Smith said.
“The amount of pesticide residue present inside colonies following exposure appears to be an important measure for assessing the impact on a colony’s health in the future.”
It is perhaps an impact to consider when it comes down to our own actions in the garden or decisions when buying certain foodstuffs.
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