Date of Award

Spring 2022

Project Type

Dissertation

Program or Major

Biological Sciences

Degree Name

Doctor of Philosophy

First Advisor

Elizabeth Harvey

Second Advisor

Donald Chandler

Third Advisor

Norman Lee

Abstract

In a climatically and structurally changing world, it is important to understand how different thermal and social environments influence the behavior and physiology of the pillars of terrestrial ecosystems: insects. In this dissertation, I explored how insects, specifically Nicrophorus beetles, respond to biotic and abiotic challenges. Through this research, I addressed 1) how daily fluctuations in temperature influence Nicrophorus americanus reproductive success, 2) the context in which breeding pairs use stridulation during carcass burial, and subsequently how inhibition of stridulation influences reproductive success, 3) if the clypeal membrane on Nicrophorus beetles has the physiological properties of a tympanum, and if clypeal membrane alteration impacts reproductive success, and 4) how daily thermal fluctuation and different social contexts influence antennal glomeruli volume and brain volume. For the first question, I used environmentally controlled experimental chambers to simulate different levels of daily temperature fluctuation. I found that thermal fluctuation during carcass burial and offspring rearing significantly reduced reproductive success. For the second question, I made audio and video recordings of Nicrophorus marginatus pairs during carcass burial to determine the context of stridulation during carcass burial. I also removed stridulation capabilities in males, females, or both sexes during reproduction and offspring rearing to determine the importance of stridulation during these periods. I found that removing stridulation capabilities significantly increased carcass burial time, but had no effect on reproductive success. I also found that N. marginatus uses different stridulatory sounds for different behavioral contexts during carcass burial. For the third question, I 1) occluded the clypeal membrane and observed how reproductive success is impacted after occlusion, and 2) explored the vibrational properties and internal structures associated with the membrane. I found that the clypeal membrane vibrates in response to airborne sound, and has associated internal structures analogous with insect tympana. However, occluding the membrane had no influence on reproductive success. For the final question, I used micro-CT scans to determine how temperature fluctuation and different social contexts (partner/both adults silenced) during carcass burial influenced antennal glomeruli volume and overall brain volume in adult female Nicrophorus. I found that silencing both adults during the reproductive process significantly reduced brain volume, but daily thermal fluctuation had variable impacts on brain volume. This research adds to the body of knowledge surrounding how these beetles respond to thermal pressures while enhancing our understanding of Nicrophorus communication. Moreover, this study provides insight into how different thermal environments and social contexts influence Nicrophorus brain morphology.

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