Honey bees increase social distance when their hive is threatened by a parasite, according to a new study by an international team involving researchers from UCL and the University of Sassari, Italy.

The study, published in Scientists progress, has shown that honey bee colonies respond to a pest mite infestation by altering space use and interactions between nest mates to increase social distance between young and old bees.

“Here, we have provided the first evidence that bees alter their social interactions and the way they move around their hive in response to a common parasite,” said Co-author Alessandro Cini, UCL Center for Biodiversity & Environment Research. “Bees are a social animal because they benefit from the division of responsibilities and interactions such as mutual grooming, but where these social activities can increase the risk of infection, bees seem to have evolved to balance the risks and benefits. by embracing social distancing. “

In animals, examples of social distancing have been found in very different species separated by millions of years of evolution: from baboons who are less likely to cleanse individuals with gastrointestinal infections, to ants infected with a pathogenic fungus that relegate to the suburbs of the anthill society. .

The new study assessed whether the presence of the ectoparasitic mite Varroa killer in honey bee colonies induces changes in social organization that could reduce the spread of the parasite in the hive. Among the stressors that affect bees, the Varroa mite is one of the main enemies because it causes a number of harmful effects on bees at the individual and colony level, including the transmission of viruses.

Bee colonies are organized into two main compartments: the outer compartment occupied by foragers and the innermost compartment inhabited by nurses, queen and brood. This intra-colony spatial segregation leads to a lower frequency of interactions between the two compartments than those within each compartment and makes it possible to protect the most valuable individuals (queen, young bees and brood) from the external environment and therefore from the arrival of diseases.

By comparing colonies infested and not infested by the Varroa mite, the researchers found that a behavior, foraging dances, which can increase the transmission of mites, occurred less frequently in the central parts of the hive if it was was infested. They also found that grooming behaviors became more concentrated in the central hive. Researchers say it appears that overall foragers (older bees) move toward the periphery of the nest while young nurse and groomer bees move toward its center, in response to an infestation, to increase nesting. distance between the two groups.

“The observed increase in social distance between the two groups of bees within a single parasite infested colony represents a new and in some ways surprising aspect of how bees have evolved to control the agents. pathogens and parasites, “said themain author Michelina Pusceddu, University of Sassari. “Their ability to adapt their social structure and reduce contact between individuals in response to a disease threat enables them to maximize the benefits of social interactions where possible and minimize the risk of infectious disease when necessary. Bee colonies provide an ideal model for studying social distancing and for fully understanding the value and effectiveness of this behavior. “

Republished courtesy of University College London. Photo: allogrooming behavior of bees (top left) and trophallaxis (feeding, center) Credit: Michelina Pusceddu, University of Sassari.


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