Bees Know Friend from Foe by Gut Bacteria Scent
The security and integrity of the hive is a most important and fundamental necessity in honey bee society. Therefore, recognizing your nest mates is one of the most critical skills for a honeybee.
How does one bee know if another bee belongs in her hive?
According to new research studies at Washington University in St. Louis, it is not genetic relatedness that honey bees rely on to identify who is a colony member and who is not, but chemical cues that are related to their shared gut microbial communities.
The chemical signals bees produce can be detected by other bees from skin compounds known as cuticular hydrocarbons, or CHCs. Every honeybee recognizes and responds to these scent cues.
The difference between a nestmate and an invader can mean a hive well-stocked with honey or a long and lean winter.
This is a 1:22-minute video by Washington University in St. Louis about how bees recognize nestmates:
Yehuda Ben-Shahar is a professor of biology at Washington University and is also the author of a new study in Science Advances. He indicates that while most people only pay attention to the genetics of the actual bee, their research shows that it is the genetics of the bacteria that counts.
As the new study shows, a bee’s particular CHC profile depends on its microbiome. This is the bacteria that makes up its gut microbial community. This is not genetic or innate to the bee alone.
The study reveals some previously unknown information about bees. The first author is Cassondra L. Vernier, postdoctoral associate at the University of Illinois. She earned her biology PhD working with Ben-Shahar at Washington University.
According to Vernier, it has never been shown before that different colonies have colony-specific microbiomes. The microbiome is involved with the basic social biology of honey bees, and not just affecting their health. She goes on to explain that bees constantly share food with each other and exchange this microbiome just within their colony. Their microbiome is involved in how their colony functions as a whole and how they defend their nest, not just immune defense in an individual bee.
The honey bee gut microbial community—or microbiome—plays a critical role in identifying the tightly regulated chemical signals for group membership, this new study shows.
Bee hive body odor, as Ben-Shahar jokes, is what most scientists thought until recently was used by honeybees to identify nestmates. This was defined as a sort of homogenized scent that they recognize from colony members.
Researchers realized that since baby bees could be inserted into other colonies without being rejected, up to a certain age and level of development, the chemical signals that bees recognize one another by are not determined by genetics alone.
Vernier explains that their nestmate recognition cues must be something they acquire during their lifetimes.
Vernier and Ben-Shahar showed in previous work that bees develop different scent profiles as they age. Gatekeeper bees respond differently to hive-bound foragers compared with younger bees that have never left the hive.
Only when a bee is old enough to interact with others outside of the hive does it become recognizable to others. That was a clue for the researchers. If a honey bee grows in isolation, it will never develop a complete microbiome, according to Vernier. It must acquire most of it from interactions with other bees.
Ben-Shahar says that some of the most complex aspects of bees’ social behavior depends on bacteria above all else.
No matter how related they are, according to Ben-Shahar their ability to say ‘you belong to this group’ is basically dependent on getting the right bacteria at the right time, or else they are blind to it.
Bee ID is key, because the biggest honey bee enemies are other bees.
Robbing is a problem, especially during autumn, when plants stop producing nectar. According to Vernier, there is a time when robbing is very prevalent in colonies. If one robber bee can get into another colony and take some honey, she will fly home and tell her nestmates where there is a hive full of honey that they can go steal because the guards are lax.
Robber bees will go plunder the honey and leave the colony to starve. It is heavy pressure and pretty brutal. Robbing deprives both host bees and their associated bacteria of important resources. This may have been the original impetus to form this unique bacteria-animal partnership, according to the researchers.
Additional coauthors on this research are from the University of Toronto, Mississauga and Washington University in St. Louis. The work was conducted partly with bees housed at Tyson Research Center, the environmental field station for Washington University.
To read the original article that inspired this blog post, please visit the source.
Original study: DOI: 10.1126/sciadv.abd3431
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