Why do male honey bees receive the royal treatment, while female bees do the work? It’s all in the brain, according to a new study by bee researchers at York University in Toronto and the University of Illinois at Urbana-Champaign.
Researchers at the two institutions set out to study differences in how genes are turned on and off in the brains of worker bees (females) and drone bees (males), to understand the striking differences in behaviour between the two sexes, and to learn about the genetics behind altruistic behaviours. Their study, published this month in the journal Genes, Brain and Behavior, found massive differences in the brain profiles of male and female honey bees.
“It’s like a bee battle of the sexes. Male honey bees do not help out around the hive. They wait for female bees to feed them and then when they mature, they go out on mating flights,” says Amro Zayed (left), a biology professor in York University’s Faculty of Science & Engineering. “In a sense, they are the solitary members within highly social societies.”
The research, performed at the University of Illinois’ Bee Research Facility, looked at one-day-old and 21-day-old honey bees, to examine changes in gene expression – how genes are turned on and off – as bees mature. Worker bees spend the first few weeks of their life working inside the hive until they mature and start foraging for pollen and nectar. Male bees also spend a period of time inside the hive before going on mating flights, but do not take part in the division of labour.
The study found that both maturation and sex had huge effects on the brain profiles of honey bees. Workers and drones had expression differences in thousands of genes, many of which are known to affect behaviour, learning and memory.
“But the biggest surprise was that most of the brain changes associated with maturation were shared by both drones and workers,” says Gene Robinson, a professor at the University of Illinois at Urbana-Champaign.
It was previously thought that most of the changes coinciding with the worker’s maturation were directly associated with the altruistic behaviours of nursing and foraging, but this study suggests that this is not the case, because male bees experience similar changes in brain profiles as they mature but do not nurse or forage. The findings support the concept that altruistic behaviours in the honey bee evolved using existing genetic platforms found in insects.
Genes that are expressed as worker bees mature are most likely to help us better understand bees’ great ability to navigate, says Zayed, as well as to learn and remember the location of profitable flowers and communicate this information to their nest-mates.