"Sweet nectar for me", says the sick bumblebee

Bee useful

Several animals reach inside Mother Nature's medicine cabinet when they get sick.

Chimps with parasitic worms have been observed swallowing whole leaves from certain trees.

Research suggests sick bumblebees self-medicate, too.

"Self-medication is a well-known phenomenon in vertebrate, and the fact that even insects can self-medicate really has attracted my curiosity," says David Baracchi, first author of a recent F1000Research study about bumblebees' interactions with nicotine-rich nectar.

In nature, bumblebees visit several different species of flowers, many of which have nectar containing antimicrobial molecules, like nicotine.

Baracchi spent nearly two years as a postdoctoral fellow at Professor Lars Chittka's Bee Sensory and Behavioural Ecology Lab at Queen Mary, University of London studying whether nicotine actually helps bumblebees, especially bees infected with or exposed to the C. bombi parasite.

The study revealed some interesting findings, though Baracchi cautions the emerging research reveals more questions than answers at this point.

In Baracchi's experiments, nicotine didn't stop healthy bees from catching the C. bombi parasitic infection from the sick bees.

Once a bee had the parasitic gut infection, though, the nicotine kept the parasite cell count down drastically. (Performing the parasite cell count required examining bee feces. Appeasing scientific curiosity, Baracchi assures, "If you look at them through the microscope, they look like murky water with a lot of small particles and pollen grains. Nothing really exciting!")

Baracchi also looked at nectar preferences within the healthy and sick bee populations.

He filled plastic flowers with sugar water to simulate nectar, adding nicotine to some of them. Then he released the bees, giving them free rein for 'pollination'.

When left to their own devices, the healthy bees visited both types of artificial nectar without preference. The sick bees however, tended to drink more from the nicotine-rich mix.

"Nicotine repels honey bees and hummingbirds, and we don't know whether bumble bees are attracted or deterred, even though they get a beneficial effect of consumption," says Leif Richardson, postdoctoral fellow at the University of Vermont. "It might be useful to state that the effects-- deterrence, medicative and lethal--are all dose-dependent."

Like Baracchi, Richardson explores the relationship between pollinators and plant chemistry. Though not part of the current study, Richardson does similar research.

In one field study involving a different group of chemicals naturally found in nectar called glycosides, Richardson found that sick bees tended to seek the most bitter-tasting nectars--the nectars with the highest chemical concentrations.

They also spent much longer inside these flowers than they did inside flowers with lower chemical concentrations. The healthy bees didn't distinguish between the nectars.

Of course, there are many factors to consider in pollination ecology: different bee species, parasite strains and  chemical-laced nectars.

"There's so many things going on at the same time, it's hard to find patterns," Richardson says.

Finding those patterns is crucial, however, as bee populations continue to decline drastically worldwide.

"Understanding the relationship between plants and pollinators may really make the difference in helping to support their health and, indirectly, our economy," Baracchi says.

Mention the bee decline, and most people immediately think of honeybees.

Honeybees are important pollinators, but often, wild bees like bumblebees and solitary bees, play the greatest role in pollinating crops.

"What's striking is that these animals often perform this service without us doing anything, but get harmed by pesticides and such," says Richardson, who's currently studying pollination ecology on blueberry farms.

Pollination ecologists have several research questions ahead of them, but Baracchi stresses an interesting point: even pure research studies, like his, hold important implications for science.

"If self-medication--so far just hypothesized by our data--is confirmed by future studies, [our research] may help support pollinators that are threatened globally by emergent disease," Baracchi says.

 

 

(Image courtesy: David Baracchi)


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