My co-authors and I are pleased to provide the following information on
our recent publication:
Ketten DR, Simmons JA, Riquimaroux H, Simmons AM (2021) Functional
analyses of peripheral auditory system adaptations for echolocation in
air vs water. Frontiers in Ecology and Evolution, pp. 1-17.
The article provides a review and new data on comparisons of auditory
systems of bats and odontocetes.
It is open access:
https://www.frontiersin.org/article/10.3389/fevo.2021.661216
There are additional links in the article to supplemental videos of 3D
digital dissections of whole head and inner ear from microCTs of several
species.
ABSTRACT:
Similarities of acoustic tasks performed by odontocetes and
microchiropteran insectivorous bats suggest they have common auditory
ultrasonic signal processing mechanisms. However, there are also
significant differences among these earsrelated to operating in water
vs. air. We compared the anatomy of the peripheral auditory system of
two species of FM bat (big brown bat /Eptesicus fuscus/; Japanese house
bat /Pipistrellus abramus/) and tw odontocetes (harbor porpoise
/Phocoena phocoena/; bottlenose dolphin /Tursiops truncatus/) using
ultra high resolution (11–100 micron) isotropic voxel computed
tomography (helical and microCT). Significant differences were found for
the stapes-oval window location (the point of input of sound to the
inner ear) in these species compared to most mammals. Further, the
porpoise’s basilar membrane includes a “foveal” region with “stretched”
frequency representation and relatively constant membrane
thickness/width ratios similar to those previously reported for some bat
species. In the bats, the stapes is located above the hook which may
create bi-directional sound energy propagation. In the porpoise, there
is a narrow double hook which we hypothesize limits the penetration of
low frequency signals into the cochlea. Both bats and porpoises have low
ratios of cochlear radii, which also curtails low frequency
admission.These specializations result in an inner ear with the majority
of the hair cells and neurons devoted to high frequency transduction.
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