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4 hours ago
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Honeybees blend a special “baby food” to give their larvae a balanced diet, with adult bees also able to regulate their feeding to avoid overconsuming certain nutrients, according to a study.
Researchers have discovered that bees can adjust how much they eat when pollen sources do not provide them with the ideal balance of essential amino acids, the essential building blocks of protein that animals cannot make for themselves and must obtain from their diet.
The findings of the study in Current Biology suggest that wild bee species, many of which feed pollen directly to their larvae, require a diversity of pollen sources to flourish, and landowners providing pollinator-friendly planting schemes should consider not just the number of flowers planted but the diversity of pollen sources and their nutritional quality.
Nectar from flowers provides mainly sugar, while pollen is a bee’s main source of protein. But pollen is the male reproductive material of plants and so does not always provide the balance of nutrients that bees need to thrive.
Geraldine Wright, professor of entomology at the University of Oxford, and lead author of the study, said: “Although pollen is often assumed to be a near-perfect food for bees, it is the male gamete of plants and, unlike nectar, it is rarely produced solely as a reward for pollinators. This creates a conflict of interest between the plant and the pollinator.”
Wright and colleagues from four other universities compared the essential amino acid profiles of honeybee tissues with that of pollen from 99 species of British flowering plant. They then created artificial diets that either replicated the amino acid profiles of different pollen sources or honeybee tissues and fed these to newly emerged worker honeybees in controlled laboratory experiments.
They found that most pollen sources tested were a poor match for the essential amino acid profile of bee tissues. Bees that were fed diets that more closely matched their own tissue composition ate more, gained more body mass and consumed a more protein-rich balance of food.
The researchers hypothesised that this response was linked to histidine, an essential amino acid that bees need only in small amounts. To test this, they fed bees artificial diets where histidine was either high or low relative to other amino acids that are important for bee growth. When histidine was relatively high, the bees ate less food overall, including protein and carbohydrate.
The researchers from the University of Southampton, Newcastle University, Lancaster University and the Hebrew University of Jerusalem also discovered that honeybees appear to have developed a strategy to ensure their developing young obtain a balanced diet.
Honeybees collect pollen from many different flowers and store it in the hive as “bee bread”. It is eaten by nurse bees, which then convert nutrients from pollen into glandular secretions, including royal jelly, which are fed to larvae.
When the researchers analysed bee bread, they found that its essential amino acid profile was better balanced than most single pollen sources. Royal jelly was better still, closely matching the amino acid profile of bee tissues. This suggests that pollen mixing and processing by nurse bees may help honeybee colonies overcome the nutritional limitations of individual plant pollens.
“We predict that honeybees have evolved to create glandular secretions which are the perfect food for their larvae, providing them with the ratios of essential amino acids that maximise growth,” said Wright. “Our results suggest that planting for pollinators should not only focus on providing flowers throughout the season, but also on ensuring a diversity of pollen sources. A varied diet may be essential for bees to obtain the right balance of nutrients.”
