LIFE SCIENCE

The “happiness factor” decreases, and the bees also “lose their souls”


There is a huge anatomical gap between the brains of insects and vertebrates, can they also have emotions of joy, anger and sorrow?

Recently, a research by Tan Ken, a researcher team at the Xishuangbanna Tropical Botanical Garden of the Chinese Academy of Sciences, and James Nieh, a professor at the University of California, San Diego, published in Contemporary Biology showed that in the face of a huge predation risk, bees will be vigilant, fearful, and disgusted, because the “happiness factor” dopamine in the brain drops rapidly. Conversely, artificially increasing bee dopamine levels can improve its “stress resistance”.

Dancing bees. Photo courtesy of Tan Ken

How the emotions of bees are proven

As early as 2012, Tan Ken discovered an interesting phenomenon.

Some nectar contains alkaloids that are slightly toxic to bees, such as tripterian nectar, and collecting bees will always avoid. But if there are no other sources of nectar, they have to choose. Although they will still tell their companions the direction and distance of the food source through the “dance language” after returning to the nest, the swing dance will be deformed, the “enthusiasm” will be significantly reduced, and the information transmission will be biased.

“When the gathering bees think that the nectar is of poor quality, their dance language is ‘negative’.” Tan Ken told China Science News, “It’s like a student going to the cafeteria to eat, only one dish left, and it’s not comfortable to eat.” When he returned to the dorm, he would complain to his roommates and dissuade them from doing so. ”

The question is, how can we prove that the “emotion” of bees is an objective existence, and what is its biological mechanism?

In 2022, a study by a team of researchers Su Songkun of Fujian Agriculture and Forestry University demonstrated for the first time that there is a “desire system” in the brain of bees. They found that bee swing dance behavior correlated with dopamine levels, and that dopamine, the “pleasure factor,” is an important driver in an individual’s desire system.

In this study, scientists were pleasantly surprised to see that brain dopamine levels were significantly elevated in gathering bees at the beginning of dancing and when they arrived at the nectar source without feeding. When the level of dopamine in collecting bees is artificially increased, their collection frequency is further increased. These results demonstrate that insects possess similar neural mechanisms to mammals that generate desire from positive pleasure stimuli.

The Tan Ken team was inspired immediately. Since bee gathering behavior is guided by positive emotions, are they also influenced by negative emotions?

“Fear” can be reversed

“In nature, positive activation signals and reverse suppression signals often coexist, such as bees visiting the honey source less when there is danger in the honey source.” Tan Ken explained.

When gathering bees are in danger at their source, they return to the hive and transmit a “stop signal” in which they hit the dancing bees with their heads. After receiving the “stop signal”, the dance bee quickly ends the dance and transmits the warning.

In the latest experiment, the researchers artificially placed the golden ring wasp, the natural enemy of bees, in the honey source, then captured the collection bees, froze them with liquid nitrogen, and performed high performance liquid chromatographic measurements on the bioamine levels of the brains of individual collecting bees to obtain dopamine content.

Experimental operation process. Photo courtesy of Tan Ken

The results showed that when normal collecting bees performed dances after returning to the nest, the dopamine content was higher, and the collection bees that were “lost in soul” due to wasp intimidation sent a “stop signal” after returning to the nest, the dopamine content was lower, and those dancing bees that received the “stop signal” also had a rapid decline in dopamine levels, and the frequency of visiting the nectar source decreased.

“This study reveals that ‘stop signal’, as a communication signal associated with negative emotions, can achieve suppression of dance and foraging behavior by regulating dopamine levels in bee brains.” Tan Ken told China Science News.

In addition, when the research team added dopamine to the honey source, artificially increasing the level of dopamine in the brains of the collecting bees, it could reverse the bees’ “fear” of wasps. Instead of fleeing because of fear, the gathering bees have extended their feeding time under the coercion of wasp predation, and the “stop signal” generated after returning to the hive has been reduced, and even continue to perform swing dances. It can be seen that the predator-induced fear effect can be counteracted by increasing bee dopamine levels.

Bees consume dopamine solution, which can reverse the “fear” of wasps. Photo courtesy of Tan Ken

In the future, researchers may be able to intervene in the collection behavior of bees by controlling their dopamine levels in their brains. “When pollinating plants with pesticides, it stimulates more negative emotions in gathering bees; On the contrary, when plants need to improve pollination efficiency, they mobilize the positive emotions of bees. Tan Ken said. (Source: Hu Minqi, China Science News)

Related paper information:https://doi.org/10.1016/j.cub.2023.03.072



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