Honeybees Can Sense and Limit a Hidden Problem in Their Pollen

Pollen is the main protein source for honeybees, but new research led by the University of Oxford, published in the journal Current Biology, finds that pollen's amino acid content is often a poor match for what bee bodies actually need. Essential amino acids are protein building blocks that animals cannot make themselves and must get from food. Because pollen evolved as a plant's male reproductive material rather than as bee food, its nutrient mix does not necessarily suit pollinators.

Researchers compared the essential amino acid makeup of honeybee tissue with pollen from 99 UK flowering plant species across 26 families, then fed newly emerged worker bees artificial diets built to mimic either pollen or bee-tissue composition. Bees given food closer to their own tissue makeup ate more, gained more body mass and chose a higher-protein diet.

The team traced part of the effect to histidine, an essential amino acid bees need only in small amounts. When diets contained relatively high histidine compared with growth-related amino acids such as leucine and isoleucine, bees cut their overall food intake, including protein and carbohydrate, a response the researchers say may guard against consuming too much of a single amino acid.

Honeybee colonies appear to compensate for this by pooling pollen from many flowers into "bee bread," which nurse bees convert into royal jelly and other secretions for larvae; the study found royal jelly's amino acid profile closely matched the bees' own tissue composition. Wild bees such as bumblebees and solitary bees, which feed pollen directly to their young without this processing step, may struggle more in habitats with few flower species, the researchers said.