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Home / Science / Study shows that pesticide exposure can dramatically affect the social behavior of bees

Study shows that pesticide exposure can dramatically affect the social behavior of bees



A bumble bee worker (Bombus impatiens) looking for food outdoors and equipped with a unique tracking tag (BEEtag). Picture credits: James Crall

For bees, it's all about being social.

Whether it's foraging, caring for the young, using their bodies to generate heat or fanning the nest, or to build and repair nests, a bee colony does almost everything as a unit.

Recent studies in a new study led by James Crall have shown that these effects could only be the tip of the iceberg.

Postdoctoral fellowship in the laboratory of Benjamin de Bivort, Thomas D. Cabot, associate professor of organismic and evolutionary biology, Crall, is the lead author of a study that has shown that exposure to neonicotinoid pesticides ̵

1; the most prevalent used class of pesticides in agriculture – has profound implications for a variety of social behaviors

Crall and co-authors such as de Bivort and Naomi Pierce, Sidney A. and John H. showed with an innovative robot platform for observing the behavior of bees. Hessel, a professor of biology, said that this was after pest exposure I've spent less time keeping bees nourished and less social than other bees. Additional tests showed that the exposure affected the ability of the bees to heat the nest and build insulating wax caps around the colony. The study is described in an article of November 9 in Science .

In addition to Crall, de Bivort and Pierce, the study of Callin Switzer, Co. 18, Stacey Combes of UC Davis, Former Assistants to Organismic and Evolutionary Biology, Robert L. Oppenheimer and Mackay Eyster and Harvard Student Andrea Brown, 19

"These pesticides did not arrive until the mid-1990s is now the most widely used class of insecticides in the world, "said Crall. "They usually work with seed treatment – high concentrations are dosed on the seeds, and farmers and pesticide companies like these compounds are used because they are systematically absorbed by the plants, but the problem is that they are also present in the pollen and pollen nectar bees that continue to feed. "

Over the past ten years, pesticide exposure has been linked to malnutrition disorders in several studies." However, there were reasons to suspect this was not the whole picture. "[19659011] "Foraging is only part of what bumblebees do," Crall said. "These studies have picked up on the important implications of these compounds on what's happening outside the nest, but there's a whole world of really important behaviors inside … and that's a black box we wanted to open a bit."




Automated Persecution of nest workers in a bumble bee colony (Bombus impatiens). Credit: James Crall

To this end, Crall and his colleagues developed a unique table system that allowed them to simultaneously track the activity of bees in as many as a dozen colonies.

"What we do is a black and white tag with a simplified QR code on the back of each bee," he said. "And there's a camera that can move across the colonies and automatically track the behavior of each bee with the help of computer vision, so we can look into the nest."

With this system, Crall and his colleagues were able to dose specific, individual bees with the pesticide and observe the changes in their behavior – less interaction with nestmates and more time at the periphery of the colony – but these experiments are limited in several ways.

"One is physiological," Crall said. "Although we have given the bees realistic doses of pesticides, drinking one serving of coffee daily in five minutes will be a little different than distributing them throughout the day, so it's not entirely realistic to administer one large dose of another important thing is that a bee colony is a functional unit, it does not make sense to treat individuals, because if you do that, that's the colony's natural social structure. "

With the Robotic System, however, researchers can call a whole colony to treat a unit.

Each of the system's 12 units, Crall says, houses a single colony where bees have access to two chambers – one to mimic the nest and the other to act as a space for foraging.

"This allows us to conduct multiple exposures to colony formation and continuous monitoring," Crall said. "We believe that this is much closer to natural behavior, and it also enables us to automate the tracking of behavior across multiple colonies simultaneously."

As shown in previous studies, exposed bees had exposed bees in their activity levels and socialization and spent more time at the edge of the nest, but the tests also showed that the results were strongest overnight.

"Bees actually have a very strong circadian rhythm," Crall explained. "So we found out that there were no statistically observable effects during the day, but at night we could see that they crashed, we do not yet know if (the pesticides) interfere with circadian gene regulation or if this is just a few, maybe physiological, feedback … but it suggests that from a practical point of view it is very important to look at the effects overnight if we want to understand or study these compounds. "




Manual feeding of a bumblebee (Bombus impatiens) worker during acute exposure experiments. Credit: James Crall

Other experiments with temperature probes placed in outdoor beehives indicated that pesticides have a profound effect on bees' ability to regulate nest temperature.

"As temperatures drop, bees block their wings and your muscles tremble to produce heat," Crall said. "But we found that in control colonies, even when the temperature fluctuated greatly, they kept the temperature in the colony constant at a few degrees, but the exposed bees lose their ability to regulate the temperature

in addition to the impairments The ability of the bees to directly heat or cool the nest also showed the experiment that the exposure of pesticides influenced the bees' ability to build an insulating wax cap over the colony.

"Almost everything under our control built colonies this cap, "Crall said," and it seems to be completely wiped out in the pesticide-exposed colonies, so they lose this ability to carry out this functional restructuring of the nest. "

In the future, Crall says The study raised some additional questions he hopes to speak about.

"This work – especially on Therm oregulation – raises new questions, not only about the direct impact of pesticides, but also about how these pesticides affect colonies' ability to cope with other stressors. "he said." This work suggests that in particularly extreme environments, the effects of pesticides are likely to be worse. This changes both the approach to the practical testing of agrochemicals in general and the question of whether a stronger effect is expected. In certain environments, the decline decreases.

In conclusion, Crall believes that the results suggest that neonicotinoids and other pesticides that may affect bees need to be more strictly regulated.

"I think we are at a point where we should be very "Very concerned about how the ways in which we change the environment undercut and decimate insect populations that are not only important to the functioning of every ecosystem … but also very important for food production," he said. "Our food system becomes more and more dependent on the pollinator over time – nowadays about one-third of food crops depend on pollinators, and that only increases. So far we have had this abundant, natural gift of pollinating us all to do work for us, and now we begin to understand that this is not a matter of course, so we should be very worried about it. "


Explore further:
Neonicotinoid pesticides affect the foraging and social interaction of bumblebees

Further information:
J.D. Crall el al. "Neonicotinoid exposure disturbs the behavior of bumblebee star, social networks and thermoregulation", 19459016, Science (2018). science.sciencemag.org/cgi/doi… 1126 / science.aat1598

"Pesticides Affect the Social Behavior of Bees" Science (2018). science.sciencemag.org/cgi/doi… 1126 / science.aav5273

Magazine Reference:
science

Provided by:
Harvard University


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