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Behavioral auditory sensitivity11/7/2023 ![]() ![]() ![]() In this study, we used the midpoint of the range of lowest thresholds observed across individuals when available. for details on the species and methods used in each study.Īcross studies of hearing sensitivity, most methods used electrophysiological techniques in which immobilized frogs were exposed to sound playback of varying amplitude, and action potential responses were measured using electrodes. and differentiated between these two peaks. Because frogs generally have sensitivity peaks in both a low frequency and high-frequency range (which typically corresponds to the AP and BP sensitivity peak, respectively), we examined all references in Taylor et al. ![]() , which covers measurements using a variety of methods. We based our measurements of hearing sensitivity on a literature review summarized in Taylor et al. Indeed, species with both low and high emphasized frequencies in their calls tend to have tuning in each papilla that matches each emphasized frequency. The tuning of the basilar papilla is always higher in frequency than the amphibian papilla, and often corresponds quite closely to the dominant frequency of the males’ courtship call. Thus, frogs typically have two peaks in hearing sensitivity at both a low and a high frequency. Hair cells within each organ are responsible for detecting sound, and the amphibian papilla contains more hair cells which are tuned to lower frequencies compared to the hair cells in the basilar papilla. From there, sound is transmitted through the middle ear to the inner ear where it is perceived by two distinct sensory organs: the basilar papilla and the amphibian papilla. (Interestingly, the tympanum may also help transmit calls from males ). The primary pathway for sound perception in frogs involves sound waves first impinging on tympanic membranes (or tympana), which are situated externally on the side of the frog’s head just posterior to the eyes in most species. Indeed, there is a large body of research comparing brain and body size evolution that explores what factors can account for deviations in allometric scaling between the brain and body size across taxa. To understand phenotypic evolution, it is necessary to account for both differences in body size as well as evolutionary relationships amongst taxa being compared. Therefore, such functional correlations that appear to evolve together may in fact emerge as a byproduct of changes to body size. Thus, similarities in morphology of related species arising from correlated changes with body size could contribute to maintaining functional correlations of traits within a specific domain. These data provide foundational results regarding constraints imposed by body size on communication systems and motivate further data collection and analysis using comparative approaches across the numerous anuran species.Īllometry, the scaling relationships between body size and aspects of morphology, physiology, and behavior, is one mechanism that could facilitate coordination of communication systems and has long been of interest to biologists. Furthermore, after accounting for body size, we find preliminary evidence that morphological evolution beyond allometry can correlate with hearing sensitivity and dominant frequency. We find robust, phylogenetically independent scaling effects of body size for all features measured. Here, we compile and compare data on various aspects of auditory morphology, hearing sensitivity, and call-dominant frequency across 81 species of anurans. Anurans constitute one of the most speciose groups of vocalizing vertebrates, and females typically rely on vocalizations to localize males for reproduction. The acoustic communication of anurans (“frogs”) offers an excellent system to ask when and how such coordination is maintained, and to allow researchers to dissociate allometric effects from independent correlated evolution. This is especially important for communication systems, in which these structures must remain coordinated both within and between senders and receivers for successful information transfer. As species change through evolutionary time, the neurological and morphological structures that underlie behavioral systems typically remain coordinated. ![]()
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