Baby bees hatch with damaged brains thanks to pesticides
Study finds that a colony's exposure to pesticides impairs offspring.
- Pesticide contamination in bee hives damages the learning capabilities of offspring, according to a recently published study.
- A key area of the affected bees' brains never correctly develops after pesticide exposure.
- Early impairment appears to be irreversible and is likely a factor in falling bee populations.
According to the U.S Department of Agriculture, some 35% of our food crops depend on bee pollination. That means about one of out every three bites of food comes to us courtesy of insects including bees, butterflies, and beetles, or from birds and bats. With the world's pollinator populations in a snowballing state of decline, scientists are racing to discover what's causing this and how it can be stopped. In the case of bees, pesticides — especially neonicotinoids — are the leading suspect, and studies find these chemicals infiltrating a significant percentage of bee hives. (Pesticides also show up in our own food and drink.)
Research prior focused on the damaging effects these neurotoxins have on adult bees. Now a study of young bee brains, led by Richard Gill of Imperial College in London and published in Proceedings of the Royal Society B, shows that neonicotinoids do disastrous, irreversible damage to bees' neurological development.
The study involved introducing neonicotinoids to the nectar consumed by members of 22 Bombus terrestris audax (buff-tailed honeybee) colonies. The learning abilities of their offspring were then measured against a control group of young bees from colonies whose food supply had not been contaminated.
The test assessed the extent to which a bee could learn to associate a specific smell with a reward, which was a sucrose solution. The bees from the neonicotinoid colony consistently fared more poorly than the control population.
Image source: Mr. Meijer/Shutterstock
Tiny computed micrography (CT) scans
In hopes of identifying a structural explanation, the researchers stained the brain cells of 100 bees from the exposed colonies and took non-invasive micro-CT scans in a machine similar — albeit smaller — to those in which humans are medically imaged.
The researchers discovered a clear difference in brains of the young bees from pesticide-exposed colonies. A key brain area, the mushroom body, was found to be much smaller in these bees' brains than it was in those from control colonies. This makes sense, since this region is believed to be involved in olfactory learning and memory.
The tests and scans were performed three days after pupal hatching and again after 12 days. The substandard learning capabilities and mushroom body sizes had not been resolved by the second test, indicating to the researchers that the damage caused by the neonicotinoids was irreversible.
(A honeybee's life expectancy depends on its role. Drones live roughly 8 weeks, while sterile workers live for about 6 weeks in the summer or 5 months in the winter. A queen can live for a few years.)
Several views of the mushroom body
Image source: Gill, et al
Why this matters
The study's conclusion does not say definitively that the mushroom area is the only brain region impacted by pesticides. However, a smaller mushroom area is significant, explaining, as it does, the mechanism by which a bee's learning abilities and behavior may be impaired over the course of its life.
Gill says in a press release, "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."
In fact, after the young bees were returned to their colonies, researchers saw lower-than-expected colony growth two to three weeks after the subjects' reintroduction.
"If future generations of workers are predisposed to be inefficient functioning cohorts, this could lead to a density-dependent build-up of colony-level impairment increasing the risk of colony collapse." — Gill, et al
Illustration of *Bombus terrestris audax*
Image source: Duda Vasilii/Shutterstock
And then there’s the adult bees
In addition to the problems caused by the behavior of bees hatched with pesticide damage, it's not as if pesticide exposure necessarily abates later on. As lead author of the study Dylan Smith explains, "There has been growing evidence that pesticides can build up inside bee colonies. Our study reveals the risks to individuals being reared in such an environment, and that a colony's future workforce can be affected weeks after they are first exposed."
The study concludes that simply looking at the damaging effect of pesticide on adult bee population misses a significant, and more far-reaching, part of the story:
"Bees' direct exposure to pesticides through residues on flowers should not be the only consideration when determining potential harm to the colony. 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. " — Gill, et al
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What would happen if you tripled the US population? Join Matthew Yglesias and Charles Duhigg at 1pm ET on Monday, September 28.
Whether or not women think beards are sexy has to do with "moral disgust"
- A new study found that women perceive men with facial hair to be more attractive as well as physically and socially dominant.
- Women tend to associate more masculine faces with physical strength, social assertiveness, and formidability.
- Women who display higher levels of "moral disgust," or feelings of repugnance toward taboo behaviors, are more likely to prefer hairy faces.
Beards and perceptions of masculinity<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMjU5OTg0MC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY0NzkxMjM3N30.cH-GqNwP5GVqvstgJWAhBPn1B_lYpVEAI0I7iax7EQw/img.jpg?width=1245&coordinates=0%2C1900%2C0%2C849&height=700" id="caae6" class="rm-shortcode" data-rm-shortcode-id="cb0a355a4e8e1899789bc45f3f7aef56" data-rm-shortcode-name="rebelmouse-image" />
Photo Credit: Wikimedia<p>The study used 919 American (mostly white) women ages 18-70 who rated 30 pictures of men they were shown with various stages of facial hair growth. The photographs depicted men with faces that had been digitally altered to look more feminine or more masculine, with a beard and without a beard. The women rated the men according to perceived attractiveness for long-term and short-term relationships. The study found that the more facial hair the men had, the higher the men were rated on their attractiveness, particularly for their suitability for a long-term relationship.</p><p>Part of this might be attributed to facial masculinity — i.e. protruding brow ridge, wide cheekbones, thick jawline, and deeply set narrow eyes — which conveys information to a woman about a man's underlying health and formidability. Women tend to associate more masculine faces with physical strength and social assertiveness. It can also indicate a man with a superior immune response. The researchers suggested that their findings favoring bearded men could be due to the fact that facial hair enhances the masculine facial features on a man's face, like creating the illusion of a thicker jaw line. This could communicate direct benefits to women like resources and protection that would enhance survival among mothers and their infants. In other words, while a beard doesn't mean superior genetics in and of itself, it might be a primitive, ornamental way of saying, "Hey girl, I'm a testosterone-fueled lean, mean, pathogen fighting machine." <br></p><p>It could also be that a beard becomes its own destiny. The researchers in this study cite prior research that found that by growing a beard, men felt more masculine and had higher levels of serum testosterone, which was linked to a higher level of social dominance. They also tended to subscribe to more old-school beliefs about gender roles in their relationships with women as compared to men with clean-shaven faces.<span></span><br></p>
What does disgust have to do with beard preference?<p>Obviously, not all women dig beards. The researchers were particularly interested in what traits make a women prefer bearded men over clean-shaven faces. They looked into several factors including a woman's disgust levels on various concepts, her desire to become pregnant, and her exposure to facial hair in her personal life. </p><p>According to the study, women who were not into facial hair were turned-off by potential parasites or other critters they imagined could be in the hair or skin. Women ranking high on this "ectoparasite disgust" scale might have viewed beards as a sign of poor grooming habits. However, women who ranked higher in levels of "pathogen" did find the bearded men to be desirable, possibly because they perceived beards as a signal of good health and immune function. An intriguing discovery in the study was links to morality. Women who displayed higher levels of "moral disgust," or feelings of repugnance toward taboo behaviors, were more likely to prefer hairy faces. The authors opined that this could reflect a link between beardedness, politically conservative outlooks, and traditional views regarding performances of masculinity in heterosexual relationships.</p>
Additional findings<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMjU5OTg1My9vcmlnaW4uZ2lmIiwiZXhwaXJlc19hdCI6MTYyNDI1NjUyOX0.P9B8WbmJR0q4nfzYZKbuNSA-2SAigVWJgrQE-_Gxlds/img.gif?width=980" id="49143" class="rm-shortcode" data-rm-shortcode-id="2ed3b1d6f20fc170bf2974646e565e8d" data-rm-shortcode-name="rebelmouse-image" />Giphy<p>The correlations that existed between married and single women's rating on the attractiveness of beards were not particularly clear, although the researchers noted that single and married women who wanted children tended to find beards more attractive than the women who didn't want children. They also found that women with bearded husbands found beards to be more attractive, which might indicate that social exposure to beards influences how desirable they are perceived of as being. Or it could be that men with wives who like beards grow beards.</p><p>It's important to note that culture plays a huge role in how attractive women perceive certain male characteristics as being. This study looked at a small, culturally specific group of American women, so no big, universal claims should be made about masculinity, facial hair, and male desirability to women. However, research like this is important in highlighting how human grooming decisions are driven by much more than fashion trends. Sociobiological, economic, and ecological factors all play a part in the way we choose to present ourselves.</p>
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