By Clint Jasper and Stuart Gary
Honey isn’t the only powerfully anti-microbial fluid bees are capable of producing, with new research revealing the seminal fluid of male honey bees can destroy the fungal spores of one of the most wide-spread bee pathogens.
The fungal pathogen Nosema apis is frequently found in bee colonies, and when hives come under stress, from bad weather or hunger, it can spread, leading to complete colony collapse.
While the pathogen can be transmitted among infected bees, through bodily contact or faecal matter, it was recently discovered the pathogen could be sexually transmitted as well, leading to concerns about the damage it could do to breeding programs.
But in a new study, published in the Proceedings of the Royal Society B, scientists at the University of Western Australia’s Centre for Integrative Bee Research (CIBR) discovered the seminal fluid of male bees is capable of destroying the fungal spores in two ways.
“What excites me about this research is that is shows the bee can strike back, it has an immune system that is active and can control infections,” CIBR director Dr Boris Baer said.
- Antimicrobial molecules identified in honeybee semen
- Molecules target common fungal pathogen Nosema apis
- Study finding may help in fight against bee colony collapse
Dr Baer said colony collapse disorder had affected populations of bees in Europe, America and Asia.
“Every now and then we see bee keepers losing 80 to 90 per cent of their stock,” he said.
“People called it colony collapse disorder without really knowing what it is.
“We now know it’s not a single cause but multiple factors often in combination which leads to a sudden decline.”
These factors included disease, pesticides, bad bee-keeping practices and nutrition.
“We know that the fungal pathogen Nosema is a contributing factor towards colony collapse disorder, and it’s the most widespread disease popping up everywhere, so we know it’s a real problem,” Dr Baer said.
To study the host-parasite interaction, the scientists collected around 200 drones, placing them in a cage for 10 minutes before inducing ejaculation by gassing them with chloroform, they then squeezed the fluid from the drones with a pipette.
Fungal spores were collected from hives known to be infected.
Pure seminal fluid was capable of killing most of the spores within five minutes, although diluted samples of seminal fluid were still highly effective.
Research on new diseases
Dr Baer said now scientists have a firmer idea of the kinds of molecules and mechanisms involved in controlling this disease, researchers can start searching for bees with higher levels of tolerance, and use them in artificial insemination
In the long term, researchers at CIBR are hopeful they can extend the research to some of the industry’s most threatening bee diseases, like the Varroa mite.
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“We’ve already initiated research into the Varroa mite, trying to find bees that have higher levels of tolerance, so we can safeguard bees and the pollination services they provide,” Dr Baer said.
It has been a common assumption that insect immune systems are primitive, but Dr Baer said this research provides evidence that in fact, it can be highly targeted.
“We demonstrate redundancy, that the bee is able to kill the spore in at least two different ways, which is quite a new concept.
“We presented the seminal fluid to other common microbes bees are exposed to, and it was not active against them, showing how specific it is to this fungal pathogen.”
Chemicals in bee semen analysed
The authors used molecular technologies called proteomics to see what kind of chemicals were in the honeybee semen.
They found both a protein that caused the Nosema spore to germinate prematurely preventing infection of the queen bee, and a small molecule that could kill the spore outright.
Separate research by team members also identified the Nosema spores in the honeybee semen.
“Ejaculation is fatal for the male honeybee causing major trauma and tissue damage and allowing contamination by the spores,” Dr Baer said.
The new research used florescent dyes to distinguish between live and dead spores, which allowed the authors to quantify what effect the semen had on the spores.
“We found as soon as you present seminal fluid to these spores the spores are killed and the exciting thing is they’re killed at a very high proportion,” Dr Baer said.
However, he said it was unknown whether bees exposed to the fungus elsewhere in the world have the same antimicrobial molecules in their immune system as the Australian-bred bees.