Biology Reference
In-Depth Information
become pollen foragers has been a constant dii culty for our foraging-
comparison studies. High-strain pollen and nonpollen foragers were also
signii cantly dif erent in their responses to 30 percent sucrose solution.
Dif erences between high-strain pollen and nonpollen foragers were
probably due to ef ects of foraging. Dif erences between high- and low-
strain nonpollen foragers most likely were due to genetic dif erences, but
we could not exclude dif erences in foraging behavior because we did not
know their foraging experiences before they were captured.
Foragers return to the nest, pass of their nectar loads, feed, and then
go out again. We know that feeding bees to repletion at er they return
from foraging trips reduces their responsiveness to water and sensitivity
to sugar. We hypothesized that the time foragers spend in the nest at er
returning, before they initiate their next trip, resets their responses to
water and sugar. We collected high- and low-strain bees as they departed
the hive and then subjected them to the proboscis extension response
(PER) sucrose assay. Departing high-strain bees were more responsive
to water and more sensitive to sucrose than departing low-strain bees.
h ese results showed that at least the dif erences in PER responses of
high- and low-strain foragers persisted throughout their foraging
events. But dif erences still could be largely or entirely due to their
foraging experiences rather than fundamental dif erences in sensory
responses to water and sugar stimuli—the classic chicken-and-egg
question (compare H1 with H3 in Figure 5.8).
We tested young workers for PER responses. We were frustrated that
we could not separate the ef ects of foraging behavior from the potential
ge ne tic ef ects on responses. Perhaps genetic dif erences just put dif erent
bees in dif erent foraging roles, and then the foraging experiences
themselves modulated their stimulus-response systems (H1 or H2 in
Figure 5.8). Or perhaps the genotype of a bee (her genetic complement)
af ects the response systems, which in turn af ect their foraging deci-
sions (H3 or H4). Tanya Pankiw took newly emerged high- and low-strain
bees, marked them, and placed them in common hives. She monitored
the hives to make sure that none of the bees she tested had begun forag-
ing. She tested bees of three age cohorts: (1) within the i rst 48 hours of
life, (2) within the i rst week of life, and (3) within the second week of
