Echolocation is the primary sense used by most bats to navigate their environment. However, the influence of echolocating behaviors upon the morphology of the auditory apparatus remains largely uninvestigated. While it is known that middle ear ossicle size scales positively with body mass across mammals, and that peak call frequency scales negatively with body mass among bats, there are still large gaps in our understanding of the degree to which allometry or ecology influences the morphology of the chiropteran auditory apparatus. To investigate this, we used μCT datasets to quantify three morphological components of the inner and middle ear: ossicle size, ossicle shape, and cochlear spirality. These data were collected across 27 phyllostomid species, spanning a broad range of body sizes, habitats, and dietary categories, and the relationships between these variables and ear morphology were assessed using a comparative phylogenetic approach. Ossicle size consistently scaled with strong negative allometry relative to body mass. Cochlear spirality was significantly (
Vibroacoustic Response of the Tympanic Membrane to Hyoid-Borne Sound Generated during Echolocation in Bats
The hyoid apparatus in laryngeally echolocating bats is unique as it forms a mechanical connection between the larynx and auditory bullae, which has been hypothesized to transfer the outgoing echolocation call to the middle ear during call emission. Previous finite element modeling (FEM) found that hyoid-borne sound can reach the bulla at an amplitude likely heard by echolocating bats; however, that study did not model how or if the signal could reach the inner ear (or cochlea). One route that sound could take is via stimulation of the eardrum—similarly to that of air-conducted sound. We used micro computed tomography (μCT) data to build models of the hyoid apparatus and middle ear from six species of bats with variable morphology. Using FEM, we ran harmonic response analyses to measure the vibroacoustic response of the tympanic membrane due to hyoid-borne sound generated during echolocation and found that hyoid-borne sound in all six species stimulated the eardrum within a range likely heard by bats. Although there was variation in the efficiency between models, there are no obvious morphological patterns to account for it. This suggests that hyoid morphology in laryngeal echolocators is likely driven by other associated functions.
more » « less- NSF-PAR ID:
- 10398529
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Integrative Organismal Biology
- Volume:
- 5
- Issue:
- 1
- ISSN:
- 2517-4843
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract p = .025) associated with wing aspect ratio (a proxy for habitat use) but was not associated with body mass. From a morphological perspective, the malleus and incus exhibited some variation in kind with diet and call frequency, while stapes morphology is more closely tied to body size. Future work will assess these relationships within other chiropteran lineages, and investigate potential morphological differences in the middle and inner ear of echolocating‐vs‐non‐echolocating taxa. -
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