Biology Reference
In-Depth Information
Our i rst prediction was that there should be dif erences in the dy-
namics of vitellogenin between highs and lows. We reasoned that be-
cause Vg was important for the onset of foraging, and there were clear,
big dif erences in the age of foraging onset between highs and lows,
there should be dif erences in Vg dynamics. We sampled newly emerged
high- and low-strain bees and placed others in wild-type colonies to
age for 5 and 10 days. In the sample bees, we looked at Vg protein titers
in the blood and also at
vg
messenger RNA (mRNA) titers. h e mRNA
titers show how much transcription of the vitellogenin gene is taking
place. We found that mRNA and Vg protein correlated, as expected,
over the 10 days. Vg protein and
vg
mRNA levels were higher in high-
strain bees than in lows, as predicted.
Next, we hypothesized that high-strain bees should be in a higher
state of ovary activation than bees from the low strain and should de-
velop their ovaries more rapidly in the absence of the queen because
they were already in a higher reproductive state. In the absence of the
inhibiting ef ect of the queen, worker ovaries develop, and some will lay
eggs (see Section 3.9). Our i rst test compared ovaries from newly
emerged high- and low-strain workers. We found that workers from the
high strain were much more likely to have ovaries that had been acti-
vated and were previtellogenic: opaque, somewhat swollen ovarioles,
unlike the clear, thin i laments of ovaries that are not activated (see
Figure 7.4).
We employed an undergraduate, Angela Csondes, to work in my lab
that summer. She was trained to do the dissections and score the ova-
ries. She commented that she thought that the high-strain bees had
larger ovaries than the lows. She was right. Dissections showed that the
high-strain bees she examined had on average six ovarioles, while the
lows on average had only three. We also noted a correlation between
ovariole number and ovary activation. Bees with more ovarioles were
more likely to have them activated. h is was true even for newly
emerged bees (Figure 7.4). We then put newly emerged high- and low-
strain workers into colonies with and without queens and dissected
them 10 to 21 days later. In colonies with a queen, we found that about
30 percent of the high-strain workers had activated ovaries, compared
