Graduation Year

2022

Document Type

Campus Only Senior Thesis

Degree Name

Bachelor of Arts

Department

Biology

Reader 1

Tessa Solomon-Lane

Reader 2

Melissa Coleman

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© 2022 Emma Thompson

Abstract

Puberty is a developmental period in which an individual becomes sexually mature. While the sequence of pubertal changes is relatively well understood, the timing and pattern of these changes are largely unknown for many animals. Hormonal regulation and activation, gene expression, and social environment are speculated to impact individual variation during puberty. In this study, the sex steroid hormone levels from adolescent African cichlid fish, Astatotilapi burtoni, were used to investigate developmental trajectories. A. burtoni are used due to the quick nature in which they mature, and the critical role sex steroid hormones play in adult social behavior, morphology, and growth. A. burtoni, form social hierarchies that include three different phenotypes: dominant males, subordinate males, and females. The social status phenotypes are highly plastic as dominant and subordinate males switch phenotypes. The sex steroid hormones, testosterone, and estrogen were measured in juveniles along with body size and growth. Testosterone and estrogen concentrations, along with proxy calculations of the conversion rate of testosterone to estrogen were analyzed in relation to growth and to developing phenotypes of the fish. We successfully measured growth in all experimental fish and found variation in and between different communities. We found that hormones play a role in the regulation of growth in the latter half of puberty in juveniles. Fish that began to develop in dominant males demonstrated higher concentrations of testosterone, estrogen, and a higher rate of testosterone-to-estrogen conversion. Through this study, we will gain insight into hormonal regulation of growth, sex determinism, and social hierarchy emergence during sexual maturation in A. burtoni. Overall, we aim to better understand what role sex steroid hormones have during puberty and how individuals uniquely develop.

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