Male Honeybees Inject Queens With Blinding Toxins During Sex

SciTechDaily University of California Riverside By Jules Bernstein September 10, 2019

Queen honeybee in a hive. Credit: Barbara Baer-Imhoff / UCR

Queen honeybee in a hive. Credit: Barbara Baer-Imhoff / UCR

They say love is blind, but if you’re a queen honeybee it could mean true loss of sight.

New research finds male honeybees inject toxins during sex that cause temporary blindness. All sexual activity occurs during a brief early period in a honeybee’s life, during which males die and queens can live for many years without ever mating again.

UC Riverside’s Boris Baer, a professor of entomology, said males develop vision-impairing toxins to maximize the one fleeting opportunity they may ever get to father offspring.

“The male bees want to ensure their genes are among those that get passed on by discouraging the queen from mating with additional males,” said Baer, senior author of the study that discovered these blinding findings published today in the journal eLife. “She can’t fly if she can’t see properly.”

The toxins identified by the team are proteins contained in male bees’ seminal fluid, which is a substance that helps maintain sperm. Earlier work by Baer’s team also discovered honeybee seminal fluid toxins that kill the sperm of rivals. All honeybees make these proteins, though some may make more of it than others.

Baer first became interested in bees’ seminal fluid years ago as a doctoral student. During early projects, he noticed that if bumblebee queens were injected only with the fluid and not the sperm during insemination, the queens stopped mating and became increasingly aggressive toward males. He wanted to understand why.

Roughly 10 years ago, Baer and his international team began analyzing which proteins could be found in honeybees’ fluids.

“We found at least 300 of these ‘James Bonds,’ little secret agents with specific missions,” he said.

It isn’t easy being queen. Queens can mate with as many as 90 males during a single, brief mating flight. Credit: Markus Imhoff / UCR

It isn’t easy being queen. Queens can mate with as many as 90 males during a single, brief mating flight. Credit: Markus Imhoff / UCR

The team was not entirely surprised to find a protein that attacks the sperm of other males, as this behavior can be found in other insects. But they were surprised to find the protein that impacts genes responsible for vision in the queen’s brains.

To test whether the protein had this effect, Baer’s team presented inseminated queens with a flickering light, and measured her response to it via tiny electrodes in her brain. The vision and corresponding flight-impairing effects kick in within hours, but Baer notes that it is likely reversible in the long term because queens do tend to fly successfully later in life when they establish new colonies.

Studying the seminal fluid proteins required an interdisciplinary team of entomologists, biologists, biochemists, and more to identify them and examine their effects on the queens.

This team included Baer’s wife and co-author, Barbara Baer-Imhoof, a UC Riverside pollination specialist. As part of this project, Baer-Imhoof conducted experiments in which she installed tiny tags on queen bees’ backs read by scanners at the hive entrances.

“The tags were similar to those at the self-checkout counter in grocery stores,” Baer-Imhoof said. The experiment showed queens had difficulties finding their way back to their colonies if they had been inseminated.

A molecular understanding of honeybee mating habits could eventually be used to improve breeding programs and help insects that pollinate many of the foods we eat.

“More than a third of what we eat depends on bee pollination, and we’ve taken bees’ services for granted for a very long time,” Baer said. “However, bees have experienced massive die-offs in the last two decades. Anything we can do to help improve their numbers will benefit humans, too.”

Reference: “Seminal fluid compromises visual perception in honeybee queens reducing their survival during additional mating flights” by Joanito Liberti, Julia Görner, Mat Welch, Ryan Dosselli, Morten Schiøtt, Yuri Ogawa, Ian Castleden, Jan M Hemmi, Barbara Baer-Imhoof, Jacobus J Boomsma, and Boris Baer, 10 September 2019, eLife.

Bee Mite Arrival in Hawaii Causes Pathogen Changes in Honeybee Predators

UC Riverside By Iqbal Pittalwala January 8, 2019

bee mite arrival in Hawaii.jpg

UC Riverside-led research, done on the Big Island, shows effects of mite introduction have cascaded through entire pathogen communities

The reddish-brown varroa mite, a parasite of honeybees and accidentally introduced in the Big Island of Hawaii in 2007-08, is about the size of a pinhead. Yet, its effects there are concerning to entomologists because the mite is found nearly everywhere honeybees are present.

A team led by entomologists at the University of California, Riverside, performed a study on the Big Island and found viruses associated with the mite have spilled over into the western yellowjacket, a honeybee predator and honey raider. The result is a hidden, yet remarkable, change in the genetic diversity of viruses associated with the larger pathogen community of the mite and wasp, with repercussions yet to be understood.

Erin Wilson Rankin examines a western yellowjacket. (I. Pittalwala/UC Riverside)

Erin Wilson Rankin examines a western yellowjacket. (I. Pittalwala/UC Riverside)

“Already, we are seeing that the arrival of the varroa mite in honeybee populations in Hawaii has favored a few virulent strains,” said Erin E. Wilson Rankin, an assistant professor of entomologyand lead investigator of the study published Jan. 9 in the Proceedings of the Royal Society B. “We do not know what the effects of these strains will be. What we know is that the effects of the varroa mite have cascaded through entire communities in Hawaii and probably around the world.”

In particular, the researchers saw a loss in the diversity of deformed wing virus, or DWV, variants, resulting in new strains whose impact is hard to predict. DWV, widespread in honeybee populations globally and made up of several variants, is thought to be partly responsible for global die-off of honeybee colonies. DWV infects bumblebees and has been detected in other insects. The yellowjacket wasps can acquire this virus directly or indirectly from honeybees.

The western honey bee.

The western honey bee.

By a stroke of luck, the researchers had the benefit of studying the honeybee and yellowjacket populations on the Big Island both before and after the varroa mite was introduced there. They saw more association of honeybees with pathogens after the appearance of the mite. Indeed, some pathogens were detected in the honeybee and wasp populations only after the mite was introduced to the island.

“This is one of the first descriptions of pathogens in the western yellowjacket,” Wilson Rankin said. “Evidently, pathogens known to be associated with varroa have spread into non-bee species, despite the mite itself being a bee specialist. We suspect the spread in yellowjackets is partly due to the wasp’s propensity to prey upon bees, which is one way the wasps may be exposed to the pathogens.”

Wilson Rankin noted the pathogens are often incorrectly called “bee pathogens” because they were first found in bees. The pathogens, however, are found in a wide variety of insects.

“We are seeing entirely different predators being affected,” she said. “The mite is not vectoring viruses to the wasps. The viral spread is happening through predation and through flowers. Predators may be passing on pathogens to other species. The yellowjacket, for example, preys on both honeybees and native bees, and may explain why both bee populations are showing the same viruses.”

Wilson Rankin explained wasps have been overlooked by researchers because these arthropods do not have “warm, fuzzy, and furry connotations.”

The western yellowjacket is a honey bee predator and honey-raider.

The western yellowjacket is a honey bee predator and honey-raider.

“They look scary,” she added. “People also get stung by them. People are more afraid of wasps than bees. But our work shows we can examine the health of the arthropod community by using species other than bees. We show for the first time that a predator is being affected by a parasite that does not even infect it.”

The researchers sampled 25-45 bees and wasps for one part of the study, and then about 100 individuals, analyzed in groups, for each of the species during the period before and after the mite was introduced to the Big Island. The researchers did not study native bees, focusing instead on honeybees and yellowjacket wasps, neither of which is native to Hawaii. 

“Our findings suggest that pathogen transmission from domesticated bees, such as honeybees, may be important even for non-bee insects like the wasps we studied,” said Kevin J. Loope, the research paper’s first author, who worked as a postdoctoral scholar in the Wilson Rankin lab during the study. “The impacts may be more subtle than previously observed: we found changes in the genetic variation of viruses found in the wasps, but not changes in the amount of virus. These findings suggest we should look more broadly and in greater detail to figure out how moving domesticated bees for agriculture may influence wild populations of insects.

Loope, now a research assistant professor in the Department of Biology at Georgia Southern University, explained that finding overlap in the pathogens of yellowjacket wasps and domesticated bees also means that using pathogens to control undesirable wasp populations is risky.

“Any biological control efforts using pathogens should be carefully evaluated to prevent inadvertent harm to beneficial bees,” he said.

Kevin Loope excavates a yellowjacket nest in Volcano, Hawaii. (Jessica Purcell/UC Riverside)

Kevin Loope excavates a yellowjacket nest in Volcano, Hawaii. (Jessica Purcell/UC Riverside)

He added that the research team was surprised to find a dramatic difference in the viral genetic diversity between the wasp samples from the two periods — before and after the varroa mite was detected on the Big Island.

“We had predicted we would observe a decline in wasp viral diversity matching the decline described in honeybees in Hawaii, but we were still surprised to see this borne out in the data,” he said. “It’s not so often that you see what you’ve predicted in biology.”

Wilson Rankin and Loope were joined in the research by Philip J. Lester of Victoria University of Wellington, New Zealand; and James W. Baty of Malaghan Institute of Medical Research, New Zealand. Genetic analyses on the bee and wasp samples were performed at UCR and in New Zealand.

Wilson Rankin was supported by grants from the National Science Foundation and the Hellman Fellows Fund. Loope was supported by a postdoctoral fellowship from the National Institute of Food and Agriculture of the U.S. Department of Agriculture.