Theses and Dissertations

Date of Award


Document Type


Degree Name



Biological Sciences

Committee Chair

Dr. Jonathan H. Perez


Dr. Jason L. Strickland and Dr. Heidi Lyn


The regulation of reproductive physiology in animals is mediated by the Hypothalamus-Pituitary-Gonad (HPG) axis. In seasonal breeders, a conserved reciprocal switching of deiodinase enzymes alters thyroid hormone signaling, which controls HPG activity. This study tested the hypothesis that neural regulation of the HPG axis as described in seasonal systems is conserved and repurposed to respond to other cues in aseasonal species. Using water deprivation and nest restriction in the opportunistic Zebra Finch, we were able to create a breeding group and non-breeding group, confirmed by egg laying and changes in ovarian anatomy. Breeding females had clear follicular hierarchy, increased ovary mass, and follicle size, as well as elevated follicle-stimulating hormone expression. Upstream neural mechanisms showed elevated deiodinase 2 expression in non-breeding birds, while the repressive deiodinase 3 did not change between breeding groups. Ultimately, high inter-individual variation complicated interpretation and points to the need for further investigation and direct experimental manipulations of the proposed pathways. Overall, our study suggests that females are more responsive to environmental cues than males.

Available for download on Thursday, May 08, 2025