...From the pages of Agricultural Research magazine
Bees That Resist Mites Are Busy Groomers
This micrograph shows a bee
trachea infested with mites.
We're not the only ones to brush off an annoying mosquito or other
Honey bees, when plagued by tiny tracheal mites, will use their legs
like a fine-tooth comb to rid themselves of the life-threatening parasites.
But, as entomologists with the Agricultural
Research Service recently confirmed, some honey bees groom themselves
more fastidiously than others.
For the first time, ARS bee researchers Robert Danka and Jose Villa
provoked grooming responses in honey bees by placing tracheal mites
directly onto individual bees. Tracheal mites invade the breathing tubes,
or airways, of adult honey beeseventually harming or killing the
important pollen carriers.
The scientists, who work in the agency's Honey Bee Breeding, Genetics,
and Physiology Research Unit at Baton Rouge, Louisiana, wanted to compare
how a line of genetically resistant bees groomed when faced with tracheal
mitesin contrast to the reactions of a line of susceptible bees.
While grooming has been considered the primary means by which resistant
bee populations are able to fend off damaging infestations of tracheal
mites, it hasn't been clear exactly how genetically resistant bees'
hygiene habits differ from those of other bees.
So Danka and Villa studied 500 honey beesresistant and susceptiblewatching
how each reacted to the arrival of an adult female mite on its thorax.
They gently transferred each minuscule mite to the host bee via the
most delicate instrument available: an eyelash mounted to a small stick.
The bees were housed in a glass-walled observation hive.
"The mites are most vulnerable when they're moving around on a
bee," says Danka. "Small and soft, they can't survive for
long, except for inside the bee's breathing tubes."
The researchers closely monitored each test bee's grooming behavior
for 7 minutes.
Resistant bees appear to be more sensitive in terms of their ability
to detect and respond to parasitic mites on their bodies. "More
resistant bees groomed than susceptible bees," says Danka. "Resistant
bees also groomed themselves more often on the side with the mite, and
they groomed more persistently."
But the study also seemed to show that the resistant bees' tenacious
grooming didn't necessarily result in fewer mites. Danka explains why
this might be a hasty conclusion, though. "We just took a brief,
7-minute snapshot within the first few days of a young bee's life,"
he says. "In a real colony, potential bee hosts may be challenged
by many more mites over a much longer time, and so more-persistent grooming
would likely have a greater impact."By Erin
K. Peabody, Agricultural Research Service Information Staff.
This research is part of Plant, Microbial, and Insect Genetic Resistance,
Genomics, and Genetic Improvement (#301) and Crop Production (#305),
two ARS National Programs described on the World Wide Web at www.nps.ars.usda.gov.
Robert G. Danka and Jose
D. Villa are in the USDA-ARS Honey
Bee Breeding, Genetics, and Physiology Research Unit, 1157 Ben Hur
Rd., Baton Rouge, LA 70820; phone (225) 767-9294 [Danka], (225) 767-9293
[Villa], fax (225) 766-9212.
"Bees That Resist Mites Are Busy Groomers" was published in the December 2004 issue of Agricultural Research magazine.