Honeybee homing affected by parasites
A commonly occurring parasite of honeybees (Apis mellifera) has been found to reduce their chances of returning to the colony after a foraging trip. Researchers at Rothampstead Research found that infection with the microsporidian fungal pathogen, Nosema ceranae, resulted in 35% of the bees not returning home, compared to a less than 10% no-return rate in their uninfected counterparts.
This parasite, an Asian species that has spread widely across the world, is capable of eradicating entire colonies of honeybees. These latest studies, carried out by Dr Stephan Wolf at Rothamstead Research, have involved the use of tiny radar transponders (a mere 16mm long and lighter than a pollen load), to track the progress of uninfected and infected bees, to determine the reasons behind their failure to return home.
While the bees from both groups showed little difference in flight patterns or sense of direction, a proportion of the infected bees stopped more frequently and became exhausted more quickly, before eventually settling on the ground and failing to return to the colony.
Honeybees, together with many wild bee species, are the most important pollinators of food crops across much of the globe, and it is thought that a third of all the food we consume depends on bee pollination. As a result of disease, pesticide use and changing agricultural practices, bee populations have suffered severe declines in recent years. An increased number of honeybees failing to return home could impact on already struggling colonies.
Currently, the only effective treatment against this microsporidian parasite is banned in the EU due to concerns over its environmental safety. New and safer alternatives are currently being developed.
The findings, published in PLOS ONE, have opened up further avenues for research as a proportion of the infected bees were seemingly unaffected by their parasite burdens. “This raises important questions about why some infected bees are able to function exactly the same way as healthy bees, while others are unable to cope,” says Dr Wolf.
Photograph, Apis mellifera, Honeybee, by Jon Sullivan www.public-domain-image.com
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DR PHOEBE CARTER
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