City University of New York (CUNY) CUNY Academic Works All Dissertations, Theses, and Capstone Projects Dissertations, Theses, and Capstone Projects 2-2016 Status Signaling and the Characterization of a Chirp-Like Signal in the Weakly Electric Fish Steatogenys elegans Caitlin E. Field Graduate Center, City University of New York How does access to this work benefit ou?y Let us know! More information about this work at: https://academicworks.cuny.edu/gc_etds/743 Discover additional works at: https://academicworks.cuny.edu This work is made publicly available by the City University of New York (CUNY). Contact: [email protected] STATUS SIGNALING AND THE CHARACTERIZATION OF A CHIRP-LIKE SIGNAL IN THE WEAKLY ELECTRIC FISH STEATOGENYS ELEGANS by CAITLIN E. FIELD A dissertation submitted to the Graduate Faculty in Psychology in partial fulfillment of the requirements for the of Doctor of Philosophy, The City University of New York 2016 ii 2016 CAITLIN E. FIELD All Rights Reserved iii STATUS SIGNALING AND THE CHARACTERIZATION OF A CHIRP-LIKE SIGNAL IN THE WEAKLY ELECTRIC FISH STEATOGENYS ELEGANS by Caitlin E. Field This manuscript has been read and accepted for the Graduate Faculty in Psychology in satisfaction of the Dissertation requirement for the degree of Doctor of Philosophy Christopher B. Braun ____________________________________________________________________________________________________ _______________________________ __________________________________________ Date Chair of Examining Committee Maureen O’Connor ____________________________________________________________________________________________________ _______________________________ __________________________________________ Date Executive Officer Peter Moller _____________________________________________________________________________________________________________________________________________ James Gordon _____________________________________________________________________________________________________________________________________________ Paul Forlano _____________________________________________________________________________________________________________________________________________ Eric Fortune _____________________________________________________________________________________________________________________________________________ Supervisory Committee THE CITY UNIVERSITY OF NEW YORK iv Abstract STATUS SIGNALING AND THE CHARACTERIZATION OF A CHIRP-LIKE SIGNAL IN THE WEAKLY ELECTRIC FISH STEATOGENYS ELEGANS by Caitlin E. Field Adviser: Christopher B. Braun Sensory systems are critical to both exploratory and communicatory processes, the study of which is critical to our understanding of how animals perceive and respond to their environments. In weakly electric fishes the electrosensory system is utilized for both of these purposes. One type of communication, status signaling, is widespread across taxa and frequently hormonally modulated. This hormonal modulation keeps the signal honest, wherein the status of the sender and the production of the status signal itself are both hormone dependent. We investigated exploratory and communicatory strategies of the electromotor system in pulse-type gymnotiforms, with a focus on status communication in Steatogenys elegans and its hormonal modulation. S. elegans sometimes responds with brief increases in electric organ discharge rate coupled with decreases in amplitude when presented with interfering playback stimuli. This response is similar to the chirp electric organ discharge (EOD) modulation in other weakly electric fish species. Our initial work catalogued exploratory electromotor behavior in S. elegans along with three other pulse-type gymnotiforms (Hypopygus cf. lepturus, Microsternarchus bilineatus, & Brachyhypopomus sp.), with the aim of determining the electromotor repertoires of v these species under solitary conditions without experimental stimulation. We then characterized the chirp in S. elegans to determine its structure and the context in which it is produced. Finally, we implanted S. elegans subjects with dihydrotestosterone (DHT) and monitored changes in chirp propensity and characteristics, in an effort to determine if the chirp is hormonally modulated. In our exploratory behavior investigations, all species exhibited faster EOD rates with a smaller range of frequencies during night (active) periods than day (quiescent) periods. Pacemaker stability did not appear to vary throughout the day, but all species except Brachyhypopomus sp. showed more rate variability at night than during the day. All species displayed stereotyped short-term EOD behaviors such as frequency rises, yet the chirp differs from these other behaviors in its rapid and large frequency increase with an equally rapid return to baseline rate, its decrease in EOD amplitude, and its short duration of just a few pulses as compared to other short-term EOD behaviors which last 10s to 100s of pulses with more gradual changes in frequency. We found that the chirp is most readily produced in response to interfering playback stimuli, and that DHT implanted subjects produced more chirps and produced them in response to a broader range of playback stimuli. Additionally, their chirps were modulated in such a way that their frequency, duration, and amplitude characteristics were exaggerated. The chirp in S. elegans appears to be similar to the chirp in other weakly electric fish species, may serve as a hormonally dependent honest communicatory signal, and is a promising model system for investigations into status communications and their hormonal control. vi Acknowledgements Many people have helped me through my graduate career and I owe them a debt of gratitude. First I would like to thank my committee: James Gordon and Peter Moller for having provided support and guidance since my time as a Masters student at Hunter, and Paul Forlano and Eric Fortune for their assistance in the later days of this work. Along with my committee, I would like to thank Mark Hauber for his support, both during my time as a graduate student, and in my new career with NYC Parks. I would also like to thank those lab members who have assisted me along the way: Rebecca Berry for setting precedent, Lauren Witter for leaving some very hard to fill undergrad shoes, Heather Leigh, Aleksandra Zviaguine, and Nicola Kriefall for filling those shoes easily, Kurumi Aoki for tirelessly analyzing data, and Aida Davila and Kevin Yiu for helping with portions of my final data collection. Zak Aidala and Beki Croston, you have provided incredible friendship through these years. Your company and companionship during lunch outings, camping trips, workouts, weddings, data analyses, and dissertation edits was and continues to be invaluable. To Morgan Hart, thank you for your love and support during the bulk of my graduate career, for naming the fish when I said I wouldn’t, and for encouraging me in this process even when it wasn’t an easy one. I had a lot of processing to do during these years, and I am incredibly grateful to Deborah Waksbaum for being there to help me through it. I really feel that I may not have been able to accomplish this without her. I would like to thank my parents, my stepdad Billy, my grandparents, and Eve for their support and encouragement. Even when I may not have explained what I was doing very vii frequently, you went with it all anyway, and have always stood behind me in my pursuits from sailboats to cockroaches to fish. I can’t thank you enough for always believing in me. I also owe a huge thanks to my boat family at Classic Harbor Line. In these years as a graduate student, you gave me the opportunity to also develop my maritime career. I started working at CHL the year before I started this Ph.D. program, so my identities as a scientist and mariner have been incredibly intertwined. Thank you for your confidence in me in both of those identities, and for so many fun non-academic times. I would also like to thank my co-workers of this past year, the Freshkills Park development team, for giving me the opportunity to use the skills I have acquired in a whole new light, for allowing me to pursue my scientific interests through new research projects, and for being supportive of me still wanting to work with fish. To my partner, Julia Sullivan, you have been with me for what is certainly the hardest part of this process. Thank you for being charmed by my ramblings about the genetics of friendship1, for trusting in our partnership even while I have retreated into writing, and for pushing me to see this through. I know this part has not been easy and I am looking forward to re-emerging into fabulous adventures with you. And to my adviser, Chris Braun, thank you for supporting me for all of these years. You allowed me to pursue my interests and varied endeavors, and I am forever thankful for your guidance in science and in life. You have been both a mentor and a friend. 1 Fowler, J.H., Settle, J.E., & Christakis, N.A. (2011). Correlated genotypes in friendship networks. PNAS, 108(5), 1993-1997. viii Table of Contents Abstract .......................................................................................................................................... iv Acknowledgements ........................................................................................................................ vi Table of Contents ........................................................................................................................