Sunflower pollen’s spiky texture reduces infections of a common gut pathogen in bumblebees by 94%.
Wild plants and food crops rely heavily on insects including bees for pollination. Unfortunately, habitat loss and widespread pesticide use has caused many bee species to decline and made them more vulnerable to infections. However, bees, like humans, can improve their gut and immune health by adjusting their diet.
Previous research has shown that pollen from certain plant species, particularly sunflowers, can aid bees in resisting certain infections. However, the reason behind the effectiveness of sunflower pollen in suppressing gut pathogens, which can decrease the ability of bumblebee queens to successfully establish a colony, was not known.
To investigate the source of sunflower pollen’s anti-parasitic properties, a team of researchers separated the outer shell of the pollen from the chemical metabolites in its core. They conducted an experiment where one group of bees were given only the shell, another group was given only the metabolite centres, and a third group was given the whole pollen.
The study found that the bees that fed on the spiny shells or whole pollen between 81 to 94 percent less of the gut pathogen Crithidia bombi compared to those that ate only the chemical-packed pollen centres. This showed that it is the physical structure of the pollen rather than the chemistry that is the main driver.
These disease-fighting abilities may be shared across multiple species in the sunflower family. The researchers compared the pollen performance of related plants and found they suppressed C. bombi infections in bumblebees by around 77 per cent.
Researchers don’t yet know how pollen spines are working to control C. bombi. It could be that the rough spiky texture is physically scraping those cells off of the bee’s gut lining, or it could be physically hurting the parasites. Either way, Sunflower pollen could be an important resource for promoting the health of wild bees by suppressing gut parasites.
Figueroa, L. L., Fowler, A., Lopez, S., Amaral, V. E., Koch, H., Stevenson, P.C., Irwin, R. E., Adler, L. S. (2023). Sunflower spines and beyond: Mechanisms and breadth of pollen that reduce gut pathogen infection in the common eastern bumble bee. Functional Ecology, 37 (6), pp. 1757-1769. DOI: 10.1111/1365-2435.14320