Honey bees are tuned in to the social culture of the hive as larvae, becoming more or less aggressive depending on who raises them, researchers have found.
University of Illinois entomology professor and Carl R Woese Institute for Genomic Biology director Gene Robinson, who led the research with postdoctoral researcher Clare Rittschof and Pennsylvania State University professor Christina Grozinger studied very young bees that were weeks away from adulthood.
“In a previous study, we cross-fostered adult bees from gentle colonies into more aggressive colonies and vice versa, and then we measured their brain gene expression,” said Robinson.
“We found that the bees had a complex pattern of gene expression, partly influenced by their own personal genetic identity and partly influenced by the environment of the colony they were living in,” Robinson said.
“This led us to wonder when they become so sensitive to their social environment,” Robinson said.
In the new study, the researchers again cross-fostered bees, but this time as larvae in order to manipulate the bees’ early life experiences.
The larvae were from a variety of queens, with sister larvae divided between high- and low-aggression colonies.
The larvae were removed from their foster hives and put into a neutral laboratory environment one day before they emerged as adults.
The researchers tested their aggressiveness by exposing them to an intruder bee. They found that the bees retained the social information they had acquired as larvae.
Those raised in aggressive colonies were 10 to 15 per cent more aggressive than those raised in the gentler colonies.
“Even sisters born of the same queen but reared in different colonies differed in aggression, demonstrating the potency of this environmental effect,” Robinson said.
The finding was surprising in part because bee larvae undergo metamorphosis, which radically changes the structure of their bodies and brains.
“It’s hard to imagine what elements of the brain are influenced during the larval period that then survive the massive reorganisation of the brain to bias behaviour in this way,” Robinson said.
The aggressive honey bees also had more robust immune responses than their gentler counterparts, the team found.
The researchers don’t yet know how the social information is being transmitted to the larvae.
They tested whether the bees differed in size, which would suggest that they had been fed differently, but found no size differences between aggressive and gentle bees.
The study was published in the journal Scientific Reports.