Biology Reference
In-Depth Information
cause high-strain bees have higher motor activity, we expected them
to have lower titers of serotonin. We found that 12-day-old bees had
higher titers than 1-day-old bees, another prediction based on previ-
ous studies by Gene Robinson and his collaborators and consistent
with increases with age in sucrose responsiveness, but the highs and
lows did not dif er from each other for any bioamine in any part of the
brain, for either age group. h erefore, bioamine titers apparently are
not directly responsible for dif erences in behavior of young high- and
low- strain bees.
Behavioral dif erences between highs and lows could be attributed to
other components of the signal pathways. Merideth Humphries found
that high-strain newly emerged bees have higher brain levels of mes-
senger RNA (mRNA) for the tyramine receptor
Amtyr1
(see Section 6.7
for an explanation of mRNA). If we assume that the amount of ex-
pressed
Amtyr1
mRNA is proportional to the amount of receptor pro-
tein that is active on the membranes of neurons, the tyramine receptor
signal pathway could be more active in high-strain workers, which
could perhaps explain some dif erences in behavior.
We looked at other genes in the signal cascade that are downstream
from
Amtyr1.
High-strain bees contain more protein kinase A. PKA is
the target of cAMP that is modulated by tyramine and octopamine.
High-strain bees also have more protein kinase C (PKC) and protein
kinase G (PKG), activation targets of cAMP, cGMP, phospholipase C,
and nitrous oxide (NO). Sucrose stimulation results in activation of
both PKA and PKC in the antennal lobes of the honey bee brain, and
cGMP is likewise involved in sucrose perception. h erefore, it is plau-
sible that at least some dif erences observed in behavior between high-
and low-strain bees (and potentially nectar- and pollen-biased forag-
ers) involve dif erences in these key neurobiochemical signal-pathway
components.
5.9 Anatomy of Worker Ovaries and Vitellogenin
High-strain worker bees have more ovarioles per ovary than do low-
strain workers. Ovarioles are the i laments that make up the ovary.
