Friday , April 23 2021

The study shows that exposure to pesticides can have a major impact on the social behavior of bees



Blacksmith (Bombus impatiens), a worker who is used outdoors, is equipped with a unique track mark (BEEtag). Credit: James Crall

Bee is social everything.


In the case of food feeding, care for young people, using their bodies for generating heat or for nesting nests, or building and repairing nests, the beekeeper colony makes almost everything that is a unit.

Although recent studies show that exposure to pesticides could affect behavior in feed, a new study led by James Crall showed that these effects can only be the tip of the iceberg.

A postdoctoral associate who works in Laboratory Benjamin de Bivort, Thomas D. Cabot Associate Professor of Organic and Evolutionary Biology, Crall is the leading author of a study that shows exposure to neonicotinoid pesticides – the most commonly used pesticide classes in agriculture – has a profound effect on a multitude of social behaviors.

Using an innovative robotic platform to observe the behavior of bees, Crall and co-authors, including de Bivort and Naomi Pierce, biology professors Sidney A. and John H. Hessel, showed that bees after using the pesticide spent less time lamb care and they were less social in order to stay the bees. Additional tests have shown that exposure to weakened bees is able to heat the nest and build insulating wax caps around the colony. The study is described in November paper in Science.

In addition to Crall, de Bivort and Pierce, Dr. Callin Switzer. & # 39; Stacey Combes from UC Davis, former scientists in Organic and Evolutionary Biology Robert L. Oppenheimer and Mackay Eyster and Harvard Andrea Brown, undergraduate student, & # 39;

"These pesticides were first used in the mid-1990s and are now the most widely used insecticide class worldwide," said Crall. "They usually work with cleaning the seeds – high concentrations are dosed on seeds, and one reason is that farmers and pesticide companies, such as these compounds, because they are systematically taken over by the plants … so the idea is to provide a comprehensive plant resistance, but the problem is that they also occur in pollen, while the nectars of bees are kept. "

Over the last decade, he said that many studies linked exposure to pesticides with food-related disorders, "but there were reasons to suspect that this was not the whole picture."

"Foraging is just a part of those miraculous creatures," said Crall. "These studies tackled the important effects that these compounds had on developments outside the nest, but inside the whole world of really important behaviors … and this is the black box that we wanted to open."

Automatic tracking of nesting workers in the Bumbus impatiens colony. Credit: James Crall

To do this, Crall and colleagues developed a unique benchtop system that allowed them to monitor bee activity in more than ten colonies simultaneously.

"What we are doing 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 through colonies and automatically monitor the behavior of each bee by means of computer vision … so that we can look into the nest."

By using the system, Crall and colleagues were able to dozing specific, individual bees with pesticide and monitor changes in their behavior by less interaction with nesters and spend more time on the outskirts of the colony – but these experiments are limited in several important ways.

"One is physiologically," said Crall. "Although bees have been given realistic doses of pesticides, drink daily coffee allocation in five minutes, it will vary from spread over the course of the day, so one large dose may not be quite realistic." Another important thing is that the beehive colony is a functional unit, if individuals were treated, because what you lose when you do it is the natural social structure of the colony. "

With the robotic system, researchers can treat the whole colony as a single unit.

Each of the 12 units of the unit, said Crall, houses one colony, where bees have access to two chambers – one that imitates the nest, the other acts as a nourishment.

"This allows us to do multiple exposure at colony level and continually monitor," said Crall. "We think that this is much closer to how their natural behavior works, and at the same time allows us to simultaneously automate behavioral tracing across multiple colonies."

As in previous studies, Crall said, exposed bees showed changes in activity levels and socialization, and spent more time on the verge of nests, but tests also showed that the results were the strongest overnight.

"Bees actually have a very strong circadian rhythm," explained Crall. "So we found that there was no statistically significant effect during the day, but at night we could see that they crash. We do not know whether (pesticides) interfere with circadian gene regulation or if this is just some, perhaps physiological feedback … but suggests that, from a practical point of view, if we want to understand or study these compounds, watch overnight effects are very important. "

Manual Bombus impatiens of the worker during acute exposure tests. Credit: James Crall

Additional experiments in which the temperature probes were placed inside outer stumps, the proposed pesticides have a strong influence on the ability of bees to regulate the temperature inside the nest.

"When the temperatures drop, the bees lock the wings down and turn their muscles to create heat," Crall said. "But we found that in control colonies, even if the temperatures were very fluctuating, they could maintain the temperature in the colony in a few degrees, but the exposed bees dramatically lose the ability to regulate the temperature."

In addition to interrupting the ability of bees for direct heating or cooling of nests, the experiment also showed that exposure to pesticides affects the ability of bees to build an insulating lid for waxing over the colony.

"Almost all of our control colonies built this ceiling," Crall said. "It seems that colonies exposed to pesticides are completely eradicated, so this functional restructuring of the nest loses."

In the sequel, said Crall, there are some additional questions prepared by the study, which she hopes will be tackled.

"This work, especially in thermoregulation, opens up a new set of questions, not just about the direct effects of pesticides, but how these pesticides reduce the ability of colonies to deal with other stressors," he said. "This work shows that in particularly extreme environments, we can expect that the effects of pesticides will be worse, by changing how practical testing of agrochemicals in general, but it raises specific questions as to whether we may see a stronger decline in certain environments . "

Together, he believes that the findings point to the need for stricter regulation of neonicotinoids and other pesticides that may affect bees.

"I think we are at a point where we should be very, very concerned about how the ways in which we change the environment are the undercutting and destruction of insect populations that are important not only for the function of each ecosystem … but which are very important for food production, "he said. "Our food system is becoming increasingly dependent on the pollinator over time – today about one third of the foods are dependent on pollinators, and this is just as rising. So far, we have had this plentiful natural pollinator gift that does it for us, and now we are starting to realize that it's not given, so I think we should be very worried about it. "


Explore also:
The neonicotinoid pesticide affects nutrition and social interaction in the intestinal species

More information:
J.D. Crall el al., "Neonicotinoid exposure disrupts nesting bumblebee nests, social networks and thermoregulation" Science (2018). science.sciencemag.org/cgi/doi … 1126 / science.aat1598

"Pesticide affects the social behavior of bees" Science (2018). science.sciencemag.org/cgi/doi … 1126 / science.aav5273

Reference number:
Science

Provided by:
Harvard University


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