Bees Have a Sweet Claw (Not Tooth)

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Honeybees love sugar-rich nectar produced by plants, and one of the main ways they detect it is with claws on their front legs, according to a new study.

The research, published in the journal Frontiers in Behavioral Neuroscience, reveals how that works, including what happens if a bee dips one clawed leg into sugar, while another is dipped into salty water.

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The tasting happens via sensilla, which are hair-like structures on the bee’s body that contain receptor nerve cells. These cells, in turn, are sensitive to particular substances, such as the bee buzz-inducing sugar.

In honeybees, the sensilla are on their little clawed legs, on their mouths, and on their antenna. With all of that potential for tasting, Gabriela de Brito Sanchez of the University of Toulouse and her colleagues wondered how the system came together.

She and her team studied hundreds of honeybees, observing what happened when sugar, bitter and salty solutions were applied to the claws (technically known as tarsomeres) of their forelegs. (This drawing allows you to see one by itself in detail.) They wanted to see if the bees would stick out their tongues- indicating something yummy is around to lap up- or if they would retract their tongues, as if to say, “Yuck.”

Everything went as planned, with the bees extending their tongue out when their claws “tasted” sugar, and doing just the opposite in the presence of bitter and salty substances.

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“Honeybees rely on their color vision, memory, and sense of smell and taste to find nectar and pollen in the ever-changing environment around the colony,” co-author Martin Giurfa of the University of Toulouse said in a press release.

He continued: “The high sensitivity to salts of the tarsomeres and to sugar of the tarsal claws is impressive, given that each tarsus has fewer sensilla than the other sense organs. The claw’s sense of taste allows workers to detect nectar immediately when they land on flowers. Also, bees hovering over water ponds can promptly detect the presence of salts in water through the tarsomeres of their hanging legs.”

But what happens when one leg registers “sweet” and another registers salty or bitter?

In those cases, the bee’s brain gives preference to the clawed leg that is the first to taste something. So if it encounters something sweet first, it will make a beeline to whatever it is.

Photo: de Brito Sanchez et al. / Frontiers in Neuroscience

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