Lonely bee secrets exposed


Rebecca Pool

Monday, June 19, 2017 - 22:45
Image: Bee antennae holds key to communication [[Bernadette Wittwer, University of Melbourne]
Using environmental scanning electron microscopy, researchers have discovered that a social halictid bee has more sensory machinery than solitary relatives. 
Sarah Kocher from the Lewis-Sigler Institute for Integrative Genomics, Princeton University, and colleagues measured the differences in density of tiny, hollow sensory hairs called sensilla on the antennae of this bee species.
They discovered that solitary bees showed a repeated reduction of hair-like sensilla on the antennae.
What's more, the chemical signals used by social and solitary forms of the same species, to identify each other and coordinate tasks, were different.
According to the researchers, as bees' social behaviour evolve, their complex chemical communication systems evolve in concert.
SEM imaging of bee antennae: researchers obtained information about the antennae's surface topography and composition. [Bernadette Wittwer, University of Melbourne]
To study the bees' social machinery, Kocher and colleagues used a Zeiss EVO 55 with an Everhart–Thornley SE detector.
They imaged the antennae of adult females from 36 species either netted in the wild or secured from specimens from the Museum of Comparative Zoology at Harvard University and the American Museum of Natural History in New York.
Analyses revealed detail on the antennae's surface topography and composition with the researchers observing convergent changes in both sensilla structures and the chemical signals of the groups as sociality was gained and lost.
According to Kocher, by investing in higher numbers of sensilla, social bees may increase the number of receptors available and thereby increase the speed and accuracy of their response to social signals.
In contrast, solitary females can still recognise relevant stimuli but no longer require dense, costly sensilla to perceive complex social signals.
As Kocher highlights: "This study demonstrates that changes in social structure are reflected in changes to the sensory systems of insects."
"[It] not only illustrates the evolutionary shift from reproducing as an individual to having to coordinate reproduction as a group, but also how this behavioral change can create an evolutionary feedback loop in which traits are selected in order to increase sociality in subsequent generations," she adds.
Research is published in PNAS.
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