Biology Reference
In-Depth Information
insulin-insulin-like signaling pathways, reproductive hormones, and
signaling proteins and peptides. h ey also show dif erences in ovary
anatomy. h erefore, there must have been fundamental dif erences dur-
ing development. We found several developmental signatures of our se-
lection program. A signature is a developmental dif erence that leads to a
dei nable dif erence in phenotype that af ects the trait we were selecting,
pollen hoarding.
8.3.1 Ovariole Number and Elevated JH
Titers in Developing Larvae
High-strain bees have more ovarioles than do low-strain bees, probably
because they have higher JH titers during larval development, which
protect more ovarioles in high-strain bees from programmed cell
death. Colin Brent and Gro Amdam sampled developing high- and
low-strain larvae at 3, 4, and 5 days at er hatching and tested their he-
molymph for JH. High-strain bees had higher titers on all three days,
the critical window where ovarioles are “rescued” from cell death.
8.3.2 Sensitivity of Ovary Size to Body Size
High-strain bees show more ovary response (increase in ovarioles) with
increasing body mass across the phenotypic range of normal worker
body mass (Figure 8.6). h is shows that the growth relationship is not
i xed and is selectable. Pollen-hoarding selection steepened the develop-
mental relationship in high-strain relative to low-strain bees, resulting in
more ovarioles.
8.3.3 Uncoupling of the JH/Vg Switch
h e hypothesis of a JH/Vg double-repressor switch has been con-
i rmed repeatedly for honey bees and is a robust i nding (Section
7.5.4). It is interesting that it seems to be unique to honey bees, at least
in species looked at so far. Usually JH regulates Vg; Vg does not regu-
late JH. So we can look at the JH/Vg double-repressor switch as a signa-
