Chemical communication in a declining North American anuran amphibian, the northern leopard frog (lithobates pipiens)

Chemical signaling is known to be an important communication mechanism for amphibians. However, very few studies have directly investigated chemical signaling in anuran groups (frogs and toads), particularly adult anurans. Previous work has focused primarily on salamander and larval anuran behavioral responses. Additionally, chemoreceptor (CR) genes have only been identified for Xenopus species with no previous identifications for any other adult anuran species. Here, I examine the evolutionary and functional implications of northern leopard frog (Lithobates pipiens) CRs, identified through collaboration, by conducting a phylogenetic analysis for each CR type identified using a Maximum Likelihood approach (Chapter 1). I incorporated amino acid CR sequences spanning aquatic, semiaquatic, and terrestrial vertebrate species, and the resulting trees indicate split divergence patterns across CR types. More specifically, olfactory receptors (ORs) and trace amine associated receptors (TAARs) appear to be most closely related to transitional vertebrate and terrestrial species’ orthologs, and vomeronasal receptors (VRs Types I and II) appear to be most closely related to transitional vertebrate and aquatic vertebrate orthologs, hinting at both volatile and aquatic (water soluble and nonvolatile) detection of chemicals. In this study, I also investigate terrestrial, sex-biased anuran behavioral responses to conspecific chemical cues in adult L. pipiens, comparing time spent on cue and non-cue sides of an experimental terrarium (Chapter 2) to expand on current knowledge of chemical detection in a declining, North American species. Results show nuanced response profiles for males and females, based on familiarity (odors of individuals housed together and those that were housed in separate enclosures) and same-sex vs. opposite-sex cues. Females were more responsive overall (P <0.005), investigating unfamiliar, opposite sex and familiar, same-sex odors. Though not statistically significant (P=0.40), the data (see Figure 7.) suggest that male investigation of cue and non-cue sides differed slightly for familiar, same-sex conspecifics. Neither sex appeared to respond to unfamiliar, same-sex odors. Intuitively, ecological benefits associated with familiar odor detection and mate localization are likely responsible for these trends. Collectively, my results expose CR divergence patterns across aquatic, semiaquatic, and terrestrial species and help elucidate conspecific ligand functional roles that influence L. pipiens behavior.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Natural Res & Env Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2018

Author dc:creator

• Graham, Brittney

Contributors dc:contributor

• Sperry, Jinelle H.
• Ward, Michael P.
• Bell, Alison M.
• MacAllister, Irene E.

• amphibian
• olfactory epithelium
• G-protein
• vomeronasal organ
• olfactory receptor
• pheromone receptor

Statement dc:rights

• Copyright 2017 Brittney Graham

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/99433

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/99433