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Shedding light on the secret reproductive lives of honey bees

Credit: Photography by Alison McAfee.

Honeybee health has been in decline for two decades, with beekeepers in the United States and Canada now losing roughly 25 to 40% of their colonies annually. And queen bees fail faster than in the past in their ability to reproduce. The reason was a mystery, but researchers at North Carolina State University and University of British Columbia are finding answers.

Their most recent research was published January 8 in the journal Communication Biology, Provides clues as to why the queen bee fails, as it has discovered that when sperm vitality is low, the expression of a protein known to act against pathogens such as bacteria and viruses is high.

David Tarby, a researcher at University College and professor in the Department of Entomology and Plant Pathology in North Carolina, says the study has important implications for beekeepers, their customers, and the farmers who depend on honey bees to pollinate their crops.

“Beekeepers have identified problem queens as a top management concern, but the cause of the problem is largely invisible.” Queens are getting worse, and we don’t know why, Tarby said.

Alison McAfee, a postdoctoral scientist at NC State and UBC, was the lead author of the study. To have a healthy beehive, she explained, honey bees depend on a healthy queen, which is the only female bee in the colony that can reproduce.

The queen mates with several males, but only early in her life does she store all of the sperm that she will use throughout her life in her sperm, an abdominal organ that resembles a tiny pearl. When the sperm begins to die, the queen is unable to produce many fertilized eggs. This causes the colony’s population to decrease.

McAfee said, “Queens have the ability to live for five years, but these days, queens are replaced (in honey bee colonies) half the time during the first six months because they fail.” “If a beekeeper is really lucky, the queen may live for two years. Beekeepers need answers as to why their queens fail.

“The more we can figure out what is really going on inside these failed queens, the closer we get to understanding why this queen failure happened in the first place.”

In their research, McAfee, Tarpy and their colleagues found that queens that failed to conceive had significantly fewer sperms than those that were thriving at childbearing. And a higher percentage of their sperms died. The researchers also discovered that, compared to queens with healthy reproduction, failed queens were more likely to be infected with higher levels of two viruses – the incubation virus and the black queen cell virus.

“The high levels of these viruses and the poor ability of the sperm to survive made us interested to see if there was a tradeoff occurring in the honeybee queen,” McAfee said. “There is a classic hypothesis in reproductive biology that you can’t do everything well, so there is a trade-off between immunity and reproductive capacity. It has been found in quite a few other organisms, including insects, that there are such trade-offs.”

To see if the same was true of the honey bee queen, the researchers used an instrument known as a mass spectrometer to get a better picture of what is happening in the sperms of healthy and failing queens. They identified 2,000 different proteins and determined which were related to the viability of the sperm.

McAfee said one of the most important proteins associated with sperm survival is lysozyme. Lysozyme is an enzyme that is part of the immune system of animals.

“The queens with the highest sperm capacity had the least abundance of lysozyme, indicating that they did not invest resources in this type of immune response,” McAfee added. “This supports this idea that there is a trade-off between the ability of queens to fight infection and the ability to preserve stored sperm.”

The research could start with allowing researchers to find the reason for the queen’s failure and find molecular tools that could “help identify bad queens at the start of the process, before the beekeeper uses them and before they realize they are bad,” Tarby said.

For now, the reason for the Queen’s failure is unclear. It could be the mechanisms underlying the disease. They can be pesticides. It could be inappropriate feeding, ”he said.“ We don’t know, so we’re working our way back to identifying the causes. ”

Once the causes are clearly understood, Tarby added, scientists can then work forward “to help beekeepers keep mortality levels low to sustainable levels and thus keep their colonies thriving.”

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This research was supported by grants from the Natural Sciences and Engineering Research Council of Canada, Genome Canada, the British Columbia Genome, the Apis Project, the Bon Hodgson-Wilkinson Fund, the Canadian Bee Research Fund, and the US Department of Agriculture’s National Institute of Agriculture.

The paper summary follows.

“Tradeoffs between sperm vitality and immune protein expression in honey bee queens (Apis mellifera)”

DOI: 10.1038 / s42003-020-01586-w

Authors: Alison McAfee, University of North Carolina and University of British Columbia; Abigail Chapman, Leonard J. Foster, University of British Columbia; Geoffrey S. Betis, Betis & Company; And David R. Tarby, North Carolina State University

Publication date: January 8, 2021 Communication Biology.

Many social queens of the hymen have kept sperm alive within a specialized storage organ, the sperm, for years, challenging the typical trade-off between age and reproduction. However, whether honey bee queens (Apis mellifera) face a trade-off between reproduction and immunity is unknown, and the biochemical processes underlying sperm vitality are not well understood. Here, we scan quality measures and viral loads of honey bee queens from nine genetic sources. Queens that were classified as “ failed ” by beekeepers had lower sperm viability, fewer sperms, and higher levels of brood virus and black queen cell virus. Quantitative proteins appear on N =? 123 semen samples, after counting sperm count, health status, and haemolytic effects, five semen proteins are highly correlated with sperm capacity: odor binding protein (OBP) 14, lysozyme, serpene 88Ea, artichoke, and heat shock protein (HSP) 10. The significant negative association between lysozyme – a conserved immunoglobulin – with the viability of sperms corresponds to reproduction versus reproduction. Immunity swaps in honeybee queens.

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