Vomiting bumblebees show that sweeter is not necessarily better


23-01-2020
  Bumblebee, Bombus terrestris  Credit: Yani Dubin on Flickr

Animal pollinators support the production of three-quarters of the world’s food crops, and many flowers produce nectar to reward the pollinators. A new study using bumblebees has found that the sweetest nectar is not necessarily the best: too much sugar slows down the bees. The results will inform breeding efforts to make crops more attractive to pollinators, boosting yields to feed our growing global population.

Bumblebees drink nectar from flowers, then offload it in their nest – by vomiting –  for use by other bees in the colony. The sugar within nectar makes it appealing, and the more sugar within the nectar, the more energy it contains. But nectar also gets more thick and sticky as the sugar content rises, and this makes it more difficult for bees to drink and regurgitate –  requiring more time and energy. 

Published in the Journal of the Royal Society Interface, the study looked at the mechanics of both nectar drinking and regurgitation in one of the most common bumblebees in the UK, Bombus terrestris. It found that the best concentration of nectar for bumblebees in terms of overall energy gain is lower than might be expected. Nectar that is low in sugar is easy for bees to drink and very easy to vomit back up. As nectar gets more sugary, it gradually takes bees longer to drink, but swiftly becomes much more difficult to vomit. 

“Bumblebees must strike a balance between choosing a nectar that is energy-rich, but isn’t too time-consuming to drink and offload. Nectar sugar concentration affects the speed of the bees’ foraging trips, so it influences their foraging decisions,” said Dr Jonathan Pattrick, first author of this study, formerly a PhD student based jointly in the University of Cambridge’s departments of Plant Sciences and Zoology and now a post-doctoral researcher in the University of Oxford’s Department of Zoology. 

While it has long been known that nectar with a higher sugar concentration takes bees longer to drink, its effect on nectar regurgitation has not previously received much attention. This new information will help scientists make better predictions about which types of nectar bumblebees and other pollinators should like best, and consequently the kinds of flowers and plants they are most likely to visit. This will inform crop breeders in producing the most appealing flowers for better crop pollination and higher yields. 

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Image: Bumblebee, Bombus terrestris

Credit: Yani Dubin on Flickr

Reproduced courtesy of the University of Cambridge

 

The University of Cambridge is acknowledged as one of the world's leading higher education and research institutions. The University was instrumental in the formation of the Cambridge Network and its Vice- Chancellor, Professor Stephen Toope, is also the President of the Cambridge Network.

University of Cambridge (cam.ac.uk)