RUI: COLLABORATIVE RESEARCH: Neuroendocrine basis of gestural display evolution

Smith College, Northampton MA

Investigators

Abstract

The signals that animals use for reproductive communication are vital for survival and progeny, and thus the evolution of such signals is extensively studied. Yet, despite this work, little is known about signal evolution from a physiological perspective, particularly with respect to how the nervous system is changed to support the emergence of novel signals. To address this issue, this research project investigates the mechanisms underlying an unusual reproductive communication signal in frogs, known as the "foot flag." By comparing how androgenic hormones, such as testosterone, act on the spinal cord and hind limb muscles in foot-flagging vs. non foot-flagging frogs, this project aims to understand what changes occurred as foot-flagging evolved in this species group. This project also applies physiological models that have explained motor disease to understanding the evolution of this complex and ecologically relevant behavior. Results provide insight into how neural systems can evolve and function in the natural environment. Additionally, the unique collaboration between researchers at a women's college, a research university, and the world-class Vienna Zoo provide hands-on research experiences for 1st and 2nd year undergraduates, particularly women and first-generation college students. The investigators also incorporate this research into undergraduate courses and fund international research experiences that include public outreach about the biology and conservation of foot-flagging frogs in Borneo, India, and Peru. This project uses a comparative approach and combines molecular and behavioral analyses to test how the action of androgenic hormones is modified in neuromotor systems to support the evolution of new reproductive communication signals. Prior data shows that the emergence of "foot flagging" in male frogs - a signal that is produced by conspicuously waving the hind limb - is marked by a 10-fold increase in the androgenic sensitivity within the skeletal muscles that control this movement. Using quantitative real-time PCR and in situ hybridization to compare androgen receptor levels in foot-flagging vs. non-foot flagging species, this research project tests the hypothesis that changes in expression levels and patterning of androgen receptors within multiple levels of the hindlimb neuromotor pathway are associated with the independent evolution of foot flagging in multiple frog lineages. Furthermore, this project uses pharmacological tools to block androgen receptors in order to test the hypothesis that androgenic signaling in leg muscles is required for foot-flagging behavior and to support the spinal motor circuitry that controls hind limb movement. Though such "bottom up" modification of neuromotor circuitry is reported in studies of motor disease, this project is the first study to explore this as a mechanism for regulating a complex and ecologically relevant motor behavior.