Date of Thesis

5-8-2015

Thesis Type

Honors Thesis (Bucknell Access Only)

Degree Type

Bachelor of Science

First Advisor

Elizabeth Capaldi

Abstract

The worldwide collapse of honey bee colonies, collectively known as "colony collapse disorder" (CCD) has been heavily investigated in recent years. Currently, factors influencing the occurrence of CCD include a number of stressors, including bacterial infections, viruses, fungal infection, food limitations, or pesticide exposure. The synergistic effects of these stressors is currently not understood. The neonicotinoid family of pesticides in particular is reported to have negative effects on honey bee health. Exposure to imidacloprid, a neonicotinoid pesticide, appears to depress immune function in honey bees. Experiment 1 of this thesis examines the effects of exposing honey bees infected with Deformed Wing Virus (DWV) to imidacloprid. Day-old honey bees from the Bucknell University apiary were injected with DWV viral lysate, then exposed to varying levels of sub-lethal doses of imidacloprid over the course of five days. After five days, the levels of viral RNA within the bees were analyzed and quantified using real-time polymerase chain reaction (PCR). The data indicate that exposure to imidacloprid leads to increased levels of functioning DWV in the honey bees. These results suggest that pesticide and viral interactions can synergistically affect honey bee health and act to decrease overall colony health. In a follow-up experiment, we found that bees that had been exposed to high pesticide levels and DWV had higher levels of proline in their brains. Proline is the predominant free amino acid in the bodies of honey bee (Apis mellifera) workers, drones, and queens, and is hypothesized to be involved with many physiological functions. It reduces the super cooling point of bees and allows them to survive cold temperatures without freezing. Other studies suggest that proline plays a role in honey bee immunity. Proline is decreased in bees afflicted with the microsporidian parasite Nosema ceranae, perhaps by creating nutritional or energetic stress. Proline accounts for 10 out of the 34 amino acids in abaecin, a major antibacterial response peptide. We then investigated the role of dietary proline on the bee immune response after artificial stimulation using a lipopolysaccharide injection. In a laboratory assay, we determined if the haemolymph of bees raised with a diet enriched in proline had greater ability to destroy bacterial colonies than those raised on a standard diet. We observed high levels of variation between our treatment groups, meaning that we cannot determine if the proline-enriched diet affected the immune response. This study remains about proline in the honey bee diet remains inconclusive, but it contains novel experimental methods that could be used for future investigations.

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