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Bees Release Deadly Odor That Shortens Sibling Lifespans

Posted: 02 Dec 2009 03:35 PM PST

nurse_bees_larvae
Here's one way to get back at your sibling: rRlease a deadly odor. Honeybee researchers have discovered the first example of a pheromone that shortens the lifespan of other family members — in this case, older sisters.

"Just one little sniff can change your life," said biologist Gro Amdam of Arizona State University, co-author of a study published Dec. 1 in The Journal of Experimental Biology. "That's kind of cool."

Previous research has shown that the presence of larvae in colonies reduces adult bees' energy stores and shortens the honeybee lifespan. Scientists had also found that larvae release what is known as a "brood pheromone," which causes adults to consume more pollen to keep up with larval food demand. But little else was known about this rare chemical concoction found only in bees.

When Amdam and colleagues fed synthetic pheromone-laced syrup to adult bees, they found something surprising: It depleted vital stores of a protein called vitellogenin from bees' fat tissue and shortened their lives dramatically. The life expectancy of entire colonies dropped below 200 days, making it difficult for honeybees to last through winter.

"Just one whiff of the pheromone has the same effect as if the brood were present. That's pretty mind-boggling," said University of Arizona entomologist Diana Wheeler, who was not involved in the study.

bees The pheromone causes vitellogenin to move from fat tissue into the blood, where it is transported to the head glands and converted into a jelly that older sisters feed to the larvae. In effect, the adult workers give up their energy stores to rear their replacements. "It's the group behavior that matters in the colony, not the life of single bees," Amdam said. "In that way, you can sometimes think of bees as a mob."

"It's the most striking example of colony-level selection I know of," Wheeler said.

Vitellogenin is common across egg-laying species, and its link to health and survival may very well exist in other species. "Nature came up with this protein at some point and stuck with it," Amdam said. "This tells us it must be important for life in general."

For a long time, scientists thought vitellogenin was a relatively uninteresting protein that only provides nutrients to embryos, Amdam said. But she recently found it acts as an antioxidant and regulates immune responses, aging and foraging behavior in bees.

"The direct linkage between the sensory system and aging is absolutely fascinating," Wheeler said. A vitellogenin expert, Wheeler said it's not known whether this protein affects aging in other species, or how it works, but this study provides the launch pad for future research. It also serves as a warning for beekeepers, who sometimes use brood pheromone because it increases crop pollination. The study suggests this practice could lead to colony collapse.

Images: Gro Amdam

Citation: "Brood pheromone suppresses physiology of extreme longevity in honeybees (Apis mellifera)," by B. Smedal, M. Brynem, C.D. Kreibich and G.V. Amdam. Journal of Experimental Biology, vol 212, Dec. 1, 2009.

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