The Post-Metamorphic Development of The Peripheral Auditory System of The Bullfrog, Rana Catesbeiana: An Anatomical and Physiological Study
Shofner, William Phillip, Jr.
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https://hdl.handle.net/2142/71424
Description
Title
The Post-Metamorphic Development of The Peripheral Auditory System of The Bullfrog, Rana Catesbeiana: An Anatomical and Physiological Study
Author(s)
Shofner, William Phillip, Jr.
Issue Date
1983
Department of Study
Physiology and Biophysics
Discipline
Physiology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Animal Physiology
Abstract
This thesis is an investigation of the post-metamorphic development of the peripheral auditory system of the bullfrog, Rana catesbeiana. The acoustic responses of single fibers of the VIIIth cranial nerve were studied in juvenile and adult frogs. Three populations of auditory fibers are found in both groups, but there is a downward shift in their best excitatory frequencies (BEFs): low frequency fibers with BEFs from 100-800 Hz in juveniles and 100-400 Hz in adults; intermediate frequency fibers with BEFs from 1000-1700 Hz and 500-900 Hz in juveniles and adults, respectively; high frequency fibers with BEFs broadly distributed from 1800-2500 Hz in juveniles, but centered around 1200-1400 Hz in adults. Low frequency fibers in both groups of frogs exhibit two-tone inhibition, but the distribution of best inhibitory frequencies shifts downward from 1000-1700 Hz in juveniles to 500-900 Hz in adults. The thresholds of excitation are widely distributed in both juveniles and adults ranging from 20-130 dB SPL and from 20-100 dB SPL, respectively.
The anatomy of the basilar and amphibian papillae was quantitatively studied using light and scanning electron microscopy. For the basilar papilla, there is (1) an increase in the lumen volume and contact membrane area which respectively alter the acoustic compliance and acoustic inertance of the organ, and (2) an enlargement of the volume (or mass) of the tectorial membrane. For the amphibian papilla, the cross sectional area (or mass) of the tectorial membrane is spatially graded in a more or less step wise manner in juvenile and adult frogs, and the spatial gradations in the adult tectorium can be related to the known tonotopic map of this organ. During the post-metamorphic development, (1) the absolute area (or mass) of the amphibian papilla tectorial membrane increases, and (2) the stereocilia height of the predominant hair cell type increases in the caudal tail of the amphibian papilla. The changes in morphological characteristics of the auditory organs contribute to the shifts in the three populations of auditory fibers.
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