Degree Name

PhD (Doctor of Philosophy)

Program

Biomedical Sciences

Date of Award

8-2016

Committee Chair or Co-Chairs

Thomas C. Jones

Committee Members

Darrell J. Moore, David S. Roane, Stacy D. Brown, Antonio E. Rusinol

Abstract

The importance of social behaviour is evident in human society, but there are both costs and benefits associated with cooperation and sociality throughout the animal kingdom. At what point do the benefits outweigh the costs, and when do selective pressures favour sociality and colonization over solitude and independence? To investigate these questions, we have focused on an anomalous species of spider, Anelosimus studiosus, also known now as the northern social spider. Throughout its broad range, A. studiosus is solitary and aggressive, but recently, colonies of cooperative and social individuals have been observed at northern latitudes. This leads to two research questions: 1) what characteristics differentiate the two variants behaviourally, and, 2) how are they different physiologically? Colonies and individuals were collected from multiple populations throughout the Tennessee River watershed area and maintained in a laboratory environment for quantitative and qualitative assessment of behavioural traits as well as specific neurochemical analysis by high performance liquid chromatography with electrochemical detection. After classifying individuals as social or aggressive, I looked at the influence of factors such as age, reproductive state, nutritional state, and time of day on behaviour and neurophysiology. I found correlations between social behaviours and serotonin, aggressive behaviours and octopamine (invertebrate counterpart of norepinephrine), and several other compounds associated with an increase or decrease in aggression. These studies combine techniques from multiple disciplines to contribute to the greater understanding of the proximate control of social and aggressive behaviours as well as factors influencing the evolution of sociality.

Document Type

Dissertation - Open Access

Copyright

Copyright by the authors.