International Union for the Study of Social Insects (IUSSI2018), August 5-10, 2018 in Guarujá, Brazil.

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Age- and daytime affect octopamine and dopamine receptor expression in the mushroom bodies of honeybee foragers

Author(s):
Tianfei Peng, Tianfei Peng , Timo Bauer , Christoph Grüter
Institution(s):
Institute of Organismic and Molecular Evolutionary Biology, Johannes-Gutenberg University of Mainz, Mainz, Germany.; Institute of Organismic and Molecular Evolutionary Biology, Johannes-Gutenberg University of Mainz, Mainz, Germany. ; Institute of Organismic and Molecular Evolutionary Biology, Johannes-Gutenberg University of Mainz, Mainz, Germany. ; Institute of Organismic and Molecular Evolutionary Biology, Johannes-Gutenberg University of Mainz, Mainz, Germany.
Honeybees use the waggle dance to acquire information about the location of profitable food sources.  Experienced foragers (older) were reported to follow fewer dances and rely more on memory to locate a food sources compared to younger foragers. Octopamine (OA) and dopamine (DA) signalling in the brain might play important roles in mediating the decision to follow dances (use social information) or return to known food locations (use private information), as they are involved in reward perception. In accordance with this, a recent study has found that systemic treatment with OA and DA affects the use of social and private information in honeybee foragers (see talk by Melissa Linn). Thus, age related changes in dance following might be linked to age related changes in OA and DA signalling. Here, we explore whether the expression of OA and DA receptor genes (DopR1, DopR2, OctR1 & Octβ2R) depends on forager age and the time of day. To this end, we introduced newly emerged, marked bees into observation hives and captured them when they were either ~3 weeks (young foragers) or ~5 weeks (old foragers) old. Bees were caught either early in the morning (~9 a.m.), around noon (~12 a.m.), in the afternoon (~4 p.m.) or at night (~10 p.m.). We used qPCR to quantify gene expression in the mushroom bodies, a brain area known to be important for information processing and integration. We found that expression levels of all four receptors were significantly higher in older foragers than in younger foragers. Furthermore,   DopR1  showed significant down-regulation in the morning, whereas OctR1 showed significant up-regulation in the morning. The expression of the other genes did not change during the day. These results are consistent with the hypothesis that age and/or experience related changes in waggle dance following are linked to age and/or experience related changes in OA and DA signalling.
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