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Bee queens are Notch-blocking their minions, say boffins

From each according to her ovary, to each according to her: Oh snap I'm infertile

Scientists have identified a molecular mechanism that explains how queen bees stop worker bees from laying eggs in order to keep bee society from entering the Apocalypse.

Bees are eusocial animals. The different types of bees in a nest can be identified by distinct jobs each bee must perform.

Queen bees are in charge of maintaining and growing the hive’s population. Only drone bees are males, whilst worker bees are all female. Their task is to forage for pollen as well as tend to the bee larvae hatched from the queen’s eggs.

The queen bee keeps the rigid division of labour in place by suppressing the worker bees’ fertility. Scientists working at the University of Otago have now figured out how the queen bee activates a biological pathway that crushes the reproductive power of worker bees’ ovaries.

Worker honeybees (Apis mellifera) were treated with Notch signalling inhibitor DAPT in the presence and absence of a queen.

Queen bees release queen mandibular pheromone (QMP), which inhibits reproduction by stimulating Notch signalling in worker bee ovaries.

The scientists checked for reproductive levels by dissecting the ovaries to see if the worker bees had formed eggs, and published their results today in Nature Communications.

The fertility rating was scored on a number from zero to three. Zero indicated inactive reproductive activity in the ovaries, whilst three was for ovaries that contained fully developed eggs.

Scientists found that 28 per cent of bees not exposed to QMP were actively laying eggs (ovary score=3) during this late summer period, and exposure to QMP efficiently repressed this to just 5 per cent. The researchers noted: "We could overcome the inhibitory activity of QMP, at least partially, by treating bees with the inhibitor of Notch signalling DAPT. We observed that the proportion of bees scored as actively laying eggs (score=3) rose from 5 per cent with just QMP to 15 per cent in the presence of QMP and DAPT."

The loss of QMP means that a queen-less hive reduces the power of the Notch signalling pathway in worker bees, the paper said.

"The Notch signalling pathway is an ancient pathway contained in every animal – even humans. It is involved in developing the nervous system, but in bees it controls the ovaries," Peter Dearden, co-author of the study and professor at the Department of Biochemistry at the University of Otago, explained.

The effect that the queen pheromones have on the Notch signalling pathway has been observed.

“If worker bees try to be sneaky and lay eggs, their eggs are crushed by other bees. But if the hive has no queen, approximately a third of the worker bees will lay unfertilised eggs that hatch into male drone bees. These males will attempt to spread their genes by flying into other nests to try and mate with the queens there,” Dearden told The Register.

Over time if a population contains no queens, the number of worker bees starts to dwindle and the hive declines.

But the population can survive if a queen bee larva is raised. These special larvae are fed royal jelly-enriched diets in order to hatch them into queen bees. They will emit QMP to further squash the fertility of worker bees and rebalance the bee society once again. ®

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