Vocalizations: Foot Signaling (Semaphoring), Vocalization, and Repositioning Orientation
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INFORMATION TO USERS This manuscript has been rqiroduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter 6ce, \ ^ e others may be from aity type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely afreet reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, b^inning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6” x 9” black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. UMI A Bell & Howell Information Company 300 Noith Zed} Road, Ann Aibor MI 48106-1346 USA 313/761-4700 800/521-0600 BEHAVIORAL, NEUROPHYSIOLOGICAL, AND BIOPHYSICAL STUDIES ON COMMUNICATION IN “EARLESS” FROGS DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Erik D. Lindquist, B.S., M.S. The Ohio State University 1997 Dissertation Committee: Approved by Dr. Thomas E. Hetherington, Adviser Dr. W. Mitchell Masters Adviser Ms. Sandra L. L. Gaunt, M.S. Zoology Department Dr. Brian H. Smith UMI Number: 9801734 UMI Microform 9801734 Copyright 1997, by UMI Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. UMI 300 North Zeeb Road Ann Arbor, MI 48103 ABSTRACT Information on developmental stages (larvae, recent metamorphs and subadults) and ecology of the Panamanian golden frog [Atelopus zeteki) is presented. Tadpoles were found in stream pools away from swift torrents and recent metamorphs were observed on gravel bars adjacent to these pools. Water quality of A. zeteki streams was found to have high dissolved oxygen content, neutral pH, low turbidity, and low levels of sulfates, nitrates, and reactive phosphorous. As opposed to the aposematically colored adults, metamorphs and subadults of the two populations studied were cryptically colored, suggesting the absence of significant skin toxicity in juveniles. Subadult juveniles often were seen in close proximity to adult males. This is surprising because outside of courting gravid females, adult males are aggressive toward other conspecifics within sight. Field studies were done on the visual and acoustic behavior of Atelopus zeteki, a species lacking a tympanic middle ear. Males displayed three stereotyped behaviors in response to playbacks of male pulsed vocalizations: foot signaling (semaphoring), vocalization, and repositioning orientation. Frequencies of semaphoring and orientation responses were significantly increased by presentation of playback calls. Vocal responses also increased (non-significantly) during the playback period and continued to increase during post-playback silence. These results provide the first experimental evidence that an "earless" anuran species displays behavioral responses to sound, and that vocalization mav play an important role in communication. Orientation by the frogs toward the playback speaker suggests that this "earless" species is capable of localizing a sound source. Social communication in anuran amphibians is mediated predominantly by acoustic signals. The semaphoring observed in this species appears to represent visual signals used intraspecifically in male agonistic behavior. The use of visual signaling by A. zeteki may be correlated with their noisy, montane stream habitat. The communicative nature of semaphoring was supported by experimental manipulations using mirrored self-image presentations and nonresident introductions. Male frogs semaphored significantly more when presented with a mirrored self-image than with a nonreflective control. Novel encounters between resident males and nonresident frogs showed that semaphores were used directionally and were displayed toward target m individuals. Females semaphored frequently and this observation represents a rare case of signaling by females in a typically male-biased communicative regime among anurans. Semaphore actions were clearly linked to a locomotory gait pattern and appear to have originated as an elaboration of a standard stepping motion. Laboratory studies were conducted on the acoustic responsiveness of various body surface tissues and auditory midbrain sensitivities to sound in species of Atelopus that either possess or lack a tympanic middle ear. Acoustic responsiveness of body tissues was measured with a laser Doppler vibrometer, and the body wall directly overlying the lung was found to be highly responsive to sound in all species tested. The otic (lateral head) region showed little responsiveness in earless species. The otic region of the eared A.flavescens showed significant responses to high frequency sound, but body wall responsiveness was higher than otic responses over the entire frequency range. Peak body wall responsiveness occurred within the dominant frequency range of each species’ advertisement vocalization. Peak responsiveness of the otic region of the eared A. flavesceiis also occurred within the dominant frequency range for the species advertisement vocalization. Multi-unit neurophysiological recordings of the auditory midbrain {toms semicircularis) were obtained for one eared and two earless species of Atelopus. Auditory sensitivity curves were constructed and showed three distinct regions IV of sensitivity at low, middle, and high frequency ranges, the latter sensitivity falling within the dominant frequency range of each species’ advertisement vocalization. Auditory sensitivity curves showed a close match with the acoustic responsiveness of the body wall of all species and with that of the otic region of the eared species. This correlation suggests that the body wall/lungs serves as the route of sound transfer to the inner ear in earless species and possibly in eared species as well. The mechanisms of hearing in the earless frog Bombina orientalis were studied using laser Doppler vibrometric and neurophysiological techniques. Laser vibrometry demonstrated that the body wall overlying the lung was highy responsive to sound compared to the lateral head surface overlying the inner ear. Detemtination of auditory midbrain thresholds found that covering the body surface between the forelimbs and hindlimbs dramatically decreased auditory sensitivity at all tested frequencies. Filling the lungs with oxygenated saline also drastically decreased hearing sensitivity. Tests showed that suturing the glottis closed had a minimal effect on midbrain responses to sound, suggesting that sound transfer from the lungs to the inner ear via the buccal cavity is relatively unimportant. The precise route of lung-based sound transfer remains unclear. The lung-based hearing system of the earless Bombina ürimtalis may represent the retention of a system used by primitive aquatic vertebrates that possessed a lung. Results of this study demonstrate that such a lung-based system can be used for hearing airborne sound as well. VI Dedicated to mv wife Mollv Vll ACKNOWLEDGMENTS I wish to thank Thomas Hetherington for the constant support that he provided me in the field and in the laboratory. I am grateful for his technical and intellectual assistance during the experimentation, observation, analysis, and dissemination of this dissertation research. I thank A. Stanley Rand, Roberto Ibanez, and Neal Smith for their technical support while working in Panama. Also I am indebted to the logistical staff of the Smithsonian Tropical Research Institute for their help and insight: namely Georgina de Alba, Maria Morello, and Gloria Maggiori. I thank Marty Crump, Roy McDiarmid, Alan Jaslow, Roberto Ibanez, Carlos Navas, and Robin Saunders for information and insight on the genus Atelopus. I thank Susan Volman, W. Mitch Masters, Kris Schuett, Andrew Hocknian, and Jim Fox for their technical support related to laboratory experimentation. I am grateful for the field assistance by Tom Hetherington, Alberto Castillo, Dan Badgley, David Swihart, Molly Lindquist, David Dennis, and v u I Vasco Morales. I also wish to recognize the superb illustrative and photographic work provided by David Dennis. I thank Brian Smith, Doug Nelson, and Paul Doherty for their assistance in the statistical analysis of this research. I am grateful to Sandra Gaunt, Doug Nelson and the Horror Laboratory of Bioacoustics for use of recording, playback, and analysis equipment. I thank the following people for their numerous contributions and suggestions they made in revising the published portions of this dissertation: A. Stanley Rand, Marty Crump, Roy McDiarmid, Tom Grubb, Jerry Downhower, Sandy Gaunt, Susan Volman, and Alison Snow. 1 appreciate the support given by IN.RE.NA.RE. through the granting of scientific