Bees. People love bees. Unless they have an allergy to bee stings. Or a phobia of bees. Or a picnic, or an ice-cream… Bloody bees.
Maybe it would be more accurate to state that bees make great headlines right now.
Guess what don’t? Parasites.
And so, exploiting the popularity of bees to push my own agenda [insert parasite joke], and in the hope of dragging in readers who aren’t in love with infectious diseases, have a look at this.
Bees. Without them we would lose much of our pollination; we’d have lower yields from food crops (about one quarter of our crops rely on pollination by honey bees), a reduction in plant diversity, and a reduction in the animal species that rely on them. That includes us.
The European honey bee, Apis mellifera, is one of the world’s most important pollinators. Nosema apis is a microsporidian, a parasite that infects the gut of A. mellifera. N. apis causes nosemosis – dysentery, crawling (rather than flying) increased girth of abdomen, missing sting reflex and early replacement of the queen bee. It has been assumed to be of low virulence, but might an N. apis infection, as well as causing early death, be having an effect on the ability of surviving bees to pollinate?
The decline in the number of bees has been the main consideration in reduced pollination, but changes in the behaviour in surviving pollinators may also significantly negatively affect pollination. This is the first paper to track foraging behaviour of individual N. apis infected bees.
This research looked at 960 A. mellifera worker bees and gave them either sucrose solution or N. apis spores in sucrose solution, and tagged the bees with unique radio frequency identification tags (awesome) to monitor their foraging behaviour.
- Spore-fed bees were less likely to forage than sucrose-only fed bees (p =0.0029)
- Spore-fed bees that did forage started older (p=0.04) and stopped younger (p=0.008).
- There was not a significant difference between the groups in:
- the number of foraging trips taken per day (p=0.08).
- the total hours foraged over a lifetime (p=0.19).
- homing ability.
- Spore-fed bees were 4.3 times less likely to be carrying available pollen.
- The number of pollen grains carried was negatively correlated with the number of apis spores (p=0.009).
- There was a difference (p=0.061) in the choice of spore-fed bees to choose artificial sugar flowers over artificial pollen flowers, while sucrose-fed bees visited both equally.
The results are mixed. In this paper, N. apis infection of bees affected some measures of pollination behaviour and pollination carriage, and not others. Innoculated bees were more likely to die earlier, as had been found in previous studies. Precocious pollination had been found in previous studies, but was not seen here.
N.apis infection may have a negative effect on the pollination behaviour and carriage of A. mellifera – bee parasites might be reducing bee pollination.
And how did the researchers attach the unique radio frequency identification tags to the bees to measure all this?
We just had to hold them in our hands and hope the glue dried quickly. It was actually quite a process – they had to be individually painted, then individually fed, then the tag glued on. Then individually scanned so we knew which tag was on what color and treatment bee and which hive it was going into. It all had to happen within about eight hours of emergence because as the day goes on they start learning how to fly and they get better at stinging.
Dr Lori Lach, James Cook University
Edited 15/07/15 to correct spelling (Mellifera), 16/07/15 to correct mistake (the first paper to track foraging behaviour of individual N. apis infected bees.)