Author

Corina Wack

Defense Date

6-13-2011

Graduation Date

2011

Availability

Immediate Access

Submission Type

dissertation

Degree Name

PhD

Department

Biological Sciences

School

Bayer School of Natural and Environmental Sciences

Committee Chair

Sarah K. Woodley

Committee Member

Philip E. Auron

Committee Member

Richard P. Elinson

Committee Member

Timothy Smith

Keywords

Corticosterone, GnRH, Metabolism, Salamander, Stress, Vasotocin

Abstract

Pheromones are chemosensory cues released by an individual to cause a behavioral or physiological change in a conspecific. These changes can range from increasing a female's receptivity to altering hormone secretions in the body. The red-legged salamander (Plethodon shermani) is an emerging non-mammalian model for understanding the evolution of chemical communication due to their well-characterized pheromones. Plethodontid salamanders secrete pheromones from their submandibular gland, called mental gland pheromones. Previous studies showed that mental gland pheromones increased receptivity in females during courtship and also increased corticosterone (CORT) concentrations in males. CORT is a metabolic hormone that mediates vertebrate stress responses. To further understand the neuroendocrine mechanisms involved in behavioral and physiological responses to pheromones, I conducted several experiments. First, I investigated whether pheromones altered levels of two neuromodulators in the brain, gonadotropin-releasing hormone (GnRH) and arginine vasotocin (AVT) in P. shermani. GnRH is both a neuromodulator and hormone, and has strong effects on reproductive behavior. Additionally, AVT has broad behavioral effects in vertebrates, particularly in newts. I found that application of mental gland pheromones altered the number of GnRH-immunoreactive neurons, but had no effect on the number of AVT-immunoreactive neurons. Second, I examined the effects of AVT and AVP antagonist on courtship and mating in dusky salamanders (Desmognathus spp.). There was no effect of AVT or antagonist on reproductive behaviors in dusky salamanders. Finally, I investigated the role of increased CORT concentrations in male P. shermani. I first validated a non-invasive method to transdermally deliver CORT through a dermal patch. I then used dermal patches to exogenously elevate plasma CORT and examine the effects of CORT on behavior (activity and chemoinvestigation) and metabolism. CORT had no effect on behavior, but increased metabolic rates in male red-legged salamanders. Together these studies provide insight into the mechanisms by which pheromones work to alter behaviors and physiological functions in vertebrates.

Format

PDF

Language

English

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