The spiny texture of sunflower pollen reduces infections of a common gut pathogen in bees by up to 94 per cent.
Wild plants and food crops rely heavily on bees for pollination. The loss of habitat and widespread pesticide use has pushed most bee species into decline and made them . But like humans, bees can tailor their diet to boost their gut and immune health.
Earlier studies have established that pollen from certain species of plants – especially sunflowers – can help bees resist some infections. But no one knew why sunflower pollen was so effective at suppressing the gut pathogen Crithidia bombi, which can decrease the ability of eastern bumblebee (Bombus impatiens) queens to successfully establish a colony. “It could be because of the really spiny shape, it could be the unique chemistry, or it could be both,” says at the University of Massachusetts Amherst.
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To test what gave the pollen its anti-parasitic power, Figueroa and her colleagues first separated the pollen’s outer shell from the chemical metabolites in its core. They then fed the shell-only pollen to one group of bees and gave the metabolite centres to the others. A third group received whole pollen.
They found that bees munching on the spiny shells or whole pollen had between 81 per cent and 94 per cent less C. bombi in their cut than those eating only the chemical-packed pollen centres. Bees that ate pollen exteriors had the same reduction in the harmful gut pathogen as those eating whole pollen. “The chemistry isn’t the main driver – it’s the physical structure,” says Figueroa. “It was a really clear pattern.”
Because has focused on sunflower pollen’s chemistry, “the study adds a new brick to the pollen and bee relationship by pointing out the physical effects”, says at the French National Institute for Agriculture, Food and Environment, who wasn’t involved in the work.
These disease-fighting abilities may be shared across multiple species in the sunflower family. The researchers compared the pollen performance of related plants including ragweed, dandelion and dog fennel and found they suppressed C. bombi infections in eastern bumblebees by around 77 per cent.
Researchers don’t yet know how pollen spines are working to control C. bombi. Figueroa suspects the rough texture irritates the bees’ gut lining, similar to . “The spikes might be physically scraping those cells off of the bee’s gut lining, or it could be physically hurting the parasites – we don’t know, and those are our next steps,” says Figueroa.
More work is needed to find out how sunflower pollen acts differently across the world’s 20,000 different bee species. It may be possible to add sunflower pollen – or something that mimics its shape – to the diet of bees in commercial rearing facilities to suppress gut parasites.
Functional Ecology
