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Description
At the heart of every eusocial insect colony is a reproductive division of labor. This division can emerge through dominance interactions at the adult stage or through the production of distinct queen and worker castes at the larval stage. In both cases, this division depends on plasticity within an individual to develop reproductive characteristics or serve as a worker. In order to gain insight into the evolution of reproductive plasticity in the social insects, I investigated caste determination and dominance in the ant Harpegnathos saltator, a species that retains a number of ancestral characteristics. Treatment of worker larvae with a juvenile hormone (JH) analog induced late-instar larvae to develop as queens. At the colony level, workers must have a mechanism to regulate larval development to prevent queens from developing out of season. I identified a new behavior in H. saltator where workers bite larvae to inhibit queen determination. Workers could identify larval caste based on a chemical signal specific to queen-destined larvae, and the production of this signal was directly linked to increased JH levels. This association provides a connection between the physiological factors that induce queen development and the production of a caste-specific larval signal. In addition to caste determination at the larval stage, adult workers of H. saltator compete to establish a reproductive hierarchy. Unlike other social insects, dominance in H. saltator was not related to differences in JH or ecdysteroid levels. Instead, changes in brain levels of biogenic amines, particularly dopamine, were correlated with dominance and reproductive status. Receptor genes for dopamine were expressed in both the brain and ovaries of H. saltator, and this suggests that dopamine may coordinate changes in behavior at the neurological level with ovarian status. Together, these studies build on our understanding of reproductive plasticity in social insects and provide insight into the evolution of a reproductive division of labor.
ContributorsPenick, Clint A (Author) / Liebig, Jürgen (Thesis advisor) / Brent, Colin (Committee member) / Gadau, Jürgen (Committee member) / Hölldobler, Bert (Committee member) / Rutowski, Ron (Committee member) / Arizona State University (Publisher)
Created2012
Description
The current study sought to reevaluate Cass' Theory of sexual identity formation in terms of lesbian identity development over the past twenty years and how media acts as mediation in lesbian identity development. Ten semi-structured interviews were conducted with only nine useable transcripts analyzed for this thesis. This study is an explanatory investigation into linear stage theory, specifically Cass' theory, as well as the impact of media as a mediator during lesbian identity development. This study had three objectives 1) to gain an understanding of the theory and its components related to lesbian identity development 2) to understand the lesbian identity formation process and 3) to understand the impact and influence if any, media has had on lesbian self-reported identity development. Qualitative methods were used to obtain information and analyze the responses. Results indicate that the participants in this study believed that the coming out process was important. This study's results showed that several of the participants entered each stage of the theory, while others did not. Media had little influence on the identity development, and the participants had mixed reviews of medias portrayal of lesbians. Implications for practice and further research are discussed.
ContributorsHaseley, Hilary (Author) / Lacasse, Jeffrey R (Thesis advisor) / Segal, Elizabeth (Committee member) / Rounds, Tamara (Committee member) / Arizona State University (Publisher)
Created2011