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Description
Of all the signals and cues that orchestrate the activities of a social insect colony, the reproductives' fertility pheromones are perhaps the most fundamental. These pheromones regulate reproductive division of labor, a defining characteristic of eusociality. Despite their critical role, reproductive fertility pheromones are not evenly expressed across the development of a social insect colony and may even be absent in the earliest colony stages. In the ant Camponotus floridanus, queens of incipient colonies do not produce the cuticular hydrocarbons that serve as fertility and egg-marking signals in this species. My dissertation investigates the consequences of the dramatic change in the quantity of these pheromones that occurs as the colony grows. C. floridanus workers from large, established colonies use egg surface hydrocarbons to discriminate among eggs. Eggs with surface hydrocarbons typical of eggs laid by established queens are nurtured, whereas eggs lacking these signals (i.e., eggs laid by workers and incipient queens) are destroyed. I characterized how workers from incipient colonies responded to eggs lacking queen fertility hydrocarbons. I found that established-queen-laid eggs, incipient-queen-laid eggs, and worker-laid eggs were not destroyed by workers at this colony stage. Destruction of worker-laid eggs is a form of policing, and theoretical models predict that policing should be strongest in incipient colonies. Since there was no evidence of policing by egg-eating in incipient C. floridanus colonies, I searched for evidence of another policing mechanism at this colony stage. Finding none, I discuss reasons why policing behavior may not be expressed in incipient colonies. I then considered the mechanism that accounts for the change in workers' response to eggs. By manipulating ants' egg experience and testing their egg-policing decisions, I found that ants use a combination of learned and innate criteria to discriminate between targets of care and destruction. Finally, I investigated how the increasing strength of queen-fertility hydrocarbons affects nestmate recognition, which also relies on cuticular hydrocarbons. I found that queens with strong fertility hydrocarbons can be transferred between established colonies without aggression, but they cannot be introduced into incipient colonies. Queens from incipient colonies cannot be transferred into incipient or established colonies.
ContributorsMoore, Dani (Author) / Liebig, Juergen (Thesis advisor) / Gadau, Juergen (Committee member) / Pratt, Stephen (Committee member) / Smith, Brian (Committee member) / Rutowski, Ronald (Committee member) / Arizona State University (Publisher)
Created2012
Description
Nicotine addiction remains a prevalent public health issue, and the FDA has released a statement outlining the systematic reduction of nicotine to non-zero levels in the coming years. Current research has not yet established the effects of abrupt nicotine dose reduction on vulnerability to relapse, nor has abrupt nicotine dose reduction been evaluated in terms of behavioral economic characteristics of demand and elasticity been evaluated for reduced doses of nicotine. Using a rat model, we first evaluated the comparability of between- and within-session protocols for establishing characteristics of demand and elasticity for nicotine to shorten experimental timelines for this study and future studies. We then tested environmental enrichment and sex as factors of elasticity of demand for nicotine. Using a rat model of relapse to cues, we also examined the effects of nicotine dose-reduction on vulnerability to relapse. We found differences in maximum consumption and demand between the between- and within-session protocols, as well as sex differences in elasticity of demand on the within-session protocol where male demand was more elastic than female demand. Additionally, we found that enrichment significantly increased elasticity of demand for nicotine for both males and females. Finally, preliminary analyses revealed that nicotine dose reduction yields more inelastic demand and higher maximum consumption, and these outcomes predict increased time to extinction of the association between nicotine and contingent cues, and increased rates of relapse. These studies highlight the usefulness and validity of within-session protocols, and also illustrate the necessity for rigorous testing of forced dose reduction on nicotine vulnerability.
ContributorsCabrera-Brown, Gabriella Paula (Author) / Gipson-Reichardt, Cassandra (Thesis director) / Olive, M. Foster (Committee member) / Davis, Mary (Committee member) / Sanford School of Social and Family Dynamics (Contributor) / Department of Psychology (Contributor) / Barrett, The Honors College (Contributor)
Created2017-12