Date of Award

5-2019

Degree Type

Thesis

Degree Name

Departmental Honors

Department

Biology

First Advisor

Karen Kapheim

Second Advisor

Kim Sullivan

Third Advisor

Erin Bobeck

Abstract

Within the span of an insect's lifetime, new synaptic connections between neurons are made in response to age and experience. This neuroplasticity leads to anatomical changes within individual brain regions that represent investment in different brain functions. The neuroplasticity of female bumble bees has been well studied, but almost nothing is known about how the male bee brain responds to life experiences. Due to the complex sensory requirements of mate finding and copulation for males, neuroplasticity is likely to be an important component of reproduction. These sensory requirements include olfactory and optic inputs, which are processed in the calyces of insect brains. The aim of my project is to document anatomical changes in brain structures associated with reproductive maturity in male bumble bees (Bombus impatiens). I hypothesized that neurological investment in optic and olfactory function will change as male bees reach reproductive maturity, as they use these senses to locate mates. Because the mushroom body calyces are the structures that receive inputs from optic and antennal lobes, I predicted that the volumes of these mushroom body calyces will increase in volume as the bees age. My work initially consisted of designing a unique protocol, then caring for the microcolonies that produced the males used in the study. Males were collected either promptly after emerging or ten days later, then sacrificed for the purpose of investigating their brains. The brains were dissected, cleaned, and bleached using a protocol specific to this project. Using confocal microscopy, brain images were taken at 5 μm intervals, which were then traced using lmageJ software to create 3D renderings. Volumetric measurements were obtained for individual brain structures, then analyzed to procure the proportion of half of the whole brain constituted by each structure. I then ran t-tests on the data, looking for a significant increase or decrease in the size of brain structures between newly-emerged and 10-day-old bees. A significant increase in the size of the calyces was observed, confirming this structure's likely involvement in the preparation for reproduction. This study helps to set the stage for future research into the neural workings and associations of these bees.

Included in

Biology Commons

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