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http://hdl.handle.net/11375/23821
Title: | Physiology of social ascension in a group-living cichlid fish |
Authors: | Culbert, Brett |
Advisor: | Balshine, Sigal |
Department: | Psychology |
Publication Date: | 2018 |
Abstract: | Animals living in groups often form social hierarchies as a result of competition over limited resources. While the behavioural and physiological consequences of social rank in stable groups have been well studied, few investigations have considered how these traits vary during times of social transition. In this thesis, I used a group-living cichlid fish, Neolamprologus pulcher, to investigate how subordinate males adjust their physiology as they ascend to social dominance. Specifically, I focused on the mechanisms responsible for the regulation of stress (Chapter 2) and growth (Chapter 3). In Chapter 2, I found that subordinate males rapidly assumed behavioural dominance in their social groups following an experimentally created vacancy. However, 72 h post ascension ascenders had higher transcript abundance of key steroidogenic genes in the head kidney and maintained elevated circulating cortisol levels, consistent with cortisol levels of subordinates. Cortisol production appeared to decline as groups regained social stability, because cortisol levels were lowest in ascenders that performed few aggressive acts towards their group mates. Ascenders also had higher transcript abundance of glucocorticoid receptors 1 and 2 in the preoptic area of the brain, supporting an enhanced capacity for negative feedback regulation of cortisol production. In Chapter 3, I found that ascending males became more active, performed more social behaviours, and increased their growth. These energetically-costly adjustments seemed to be fuelled by utilizing onboard energy stores, because ascenders exhibited a 50% reduction in liver glycogen reserves but did not increase food intake. In addition, faster growth during social ascension appeared to be mediated by reduced production of insulin-like growth factor binding proteins, likely increasing bioavailability of the growth stimulating hormone, insulin-like growth factor 1. Overall, the results of my thesis enhance our understanding of the regulatory mechanisms responsible for physiological differences observed in social hierarchies, and provide insight into how these regulatory mechanisms change during periods of social transition. |
URI: | http://hdl.handle.net/11375/23821 |
Appears in Collections: | Open Access Dissertations and Theses |
Files in This Item:
File | Description | Size | Format | |
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Culbert_Brett_M_2018_08_MSc.pdf | 1.89 MB | Adobe PDF | View/Open |
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