First posted on 03-30-2012
Researchers at North Carolina State University recently discovered that worker honey bees became healers when the bees’ hives were attacked by a harmful fungus. The fungal infection triggers bees to increase levels of antifungal plant resins.
“The colony is willing to expend the energy and effort of its worker bees to collect these resins,” says Dr. Michael Simone-Finstrom, lead author of the study. “So, clearly this behavior has evolved because the benefit to the colony exceeds the cost.”
Wild honey bees use a mixture of wax and plant resins to produce propolis, with which they line their hives. This sticky substance has both antifungal and antibacterial properties. Domesticated honey bees also use propolis, but they limit its use to filling cracks and gaps in their hives.
Researchers discovered that, when threatened with a fungal attack, honey bees bring in about 45 percent more propolis than they do when pathogens are not present. In addition, workers will also remove infected bee larvae from the hive. These larvae are typically infected with fungal spores that act as parasites to the developing bees.
Honey bee behavior suggests that these intelligent creatures have the ability to self-diagnose as well. They appear to recognize harmful fungi from ones detrimental to the colony. Bees do not increase propolis levels when harmless fungal species are introduced to the hive.
Even though propolis has antibacterial properties, bees do not use it to self-medicate when harmful bacteria attacks the colony, indicating some limits to bee doctoring. Researchers were unsure why bees stopped short of using propolis to ward off bacteria pathogens, but they plan to engage in further study.
The results of this research could have an impact on beekeepers. Across the country, large numbers of honey bees died in colony collapse disorders, threatening farmers who raise honey as well as those that raise fruits and vegetables pollinated by honey bees. Some theories point to fungal pathogens as a trigger to colony collapse. Beekeepers often prefer to work with colonies that use less propolis since the compound’s stickiness was undesirable. However, its protective properties might outweigh the inconvenience.
IMAGE: When faced with pathogenic fungi, bees line their hives with more propolis - the waxy, yellow substance seen here. Photo credit: North Carolina State University.
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