Biology Reference
In-Depth Information
ated with this was the complete loss of one of the six subfamilies from
samples (a presumably susceptible subfamily) and a huge increase in
the proportion of another subfamily relative to the rest (resistant). h e
colony was treated with antibiotics to kill the
P. lar vae,
and subfamily
proportions returned to where they had been before infection. Al-
though these results are anecdotal, they provide support for genetic
variation in larval susceptibility to disease, an expectation of a gene-
for-gene mechanism of resistance, but they do not rule out a polygenic
(multiple-gene) mechanism. Kellie Palmer and Ben Oldroyd did a simi-
lar experiment where they inoculated colonies with multiply and singly
inseminated queens with the same strain of
P. lar vae
and had similar,
but again not conclusive, results.
4.3.2 General Re sis tance
h e most complete and best-known studies of honey bee disease resis-
tance are those of Walter Rothenbuhler. Rothenbuhler worked with an
American-foulbrood-resistant strain of bees derived from the apiary of
a beekeeper, Harold Brown. American foulbrood is one of the most le-
thal honey bee diseases and continuously plagues commercial beekeep-
ing. Ef ective antibiotic chemical treatments exist, and today most bee-
keepers depend on them. However, Brown did not treat his colonies but
let them die of the disease, and eventually the surviving generations
were resistant. Rothenbuhler studied the mechanisms of resistance and
found that they were behavioral, anatomical, and physiological.
Brown's bees displayed the hygienic behavior of uncapping cells with
dead pupae and removing them from the nest. h is is a trait that is
found at low frequencies in most populations but had been selected to a
high frequency in his bees. Removing the dead pupae and scales, the
spore-laden residue of the dead bees, reduced the amount of inoculum
in the hive and greatly reduced levels of infection. Hygienic behavior
has also been shown to be ef ective against chalkbrood, a fungal disease
caused by
Ascosphaera apis.
Brown's bees also were better able to i lter
out bacterial spores from food, presumably because they had a more
ei cient i ltering system on the proventricular valve, a constriction
