Evolutionary adaptations of cochlear function in Jamaican mormoopid bats

Mormoopid bat species have their echolocation system adapted to different hunting strategies. To study the corresponding mechanical properties of their inner ear, we measured distortion-product otoacoustic emissions to assess cochlear sensitivity and tuning. Mormoops blainvillii, Pteronotus macleayi...

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Bibliographic Details
Published in:Journal of Comparative Physiology 1999-09, Vol.185 (3), p.217-228
Main Authors: Kössl, M., Mayer, F., Frank, G., Faulstich, M., Russell, I. J.
Format: Article
Language:English
Subjects:
Adaptation
Auditory system
Bats
Biological evolution
Cochlea
Deoxyribonucleic acid
Distortion
DNA
Echolocation
Evolution
Frequency dependence
Hunting
Inner ear
Mechanical properties
Mitochondrial DNA
Mormoops blainvillii
Narrowband
Otoacoustic emissions
Phylogeny
Pteronotus macleayii
Pteronotus parnellii
Pteronotus quadridens
Redesign
Sensitivity analysis
Tuning
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Summary:Mormoopid bat species have their echolocation system adapted to different hunting strategies. To study the corresponding mechanical properties of their inner ear, we measured distortion-product otoacoustic emissions to assess cochlear sensitivity and tuning. Mormoops blainvillii, Pteronotus macleayii and P. quadridens use frequency-modulated echolocation signals, sometimes preceded by a short narrowband signal component. Their distortion-product otoacoustic emission-threshold curves are most sensitive between 30 and 50 kHz and show no adaptation to the narrowband echolocation components. In contrast, the constant-frequency bat P. parnellii always uses long constant-frequency call components. Its inner ear is maximally sensitive at 62 kHz, the echo-frequency of the dominant constant-frequency component, and pronounced insensitivities at 61 and 93 kHz (CF2 and CF3 call frequency) are the major evolutionary change in comparison to its relatives. Furthermore, in P. parnellii, the optimum cochlear frequency separation is minimal at 62 and 93 kHz, associated with enhanced cochlear tuning, while for the other mormoopids there is no indication of enhanced tuning. The phylogeny of mormoopids, assessed by mitochondrial DNA analysis, shows a close relationship between the Pteronotus species. This suggests that major cochlear redesign, associated with the acquisition of echolocation-call specific cochlear processing in P. parnellii, has occurred within a relatively short evolutionary time scale.
ISSN:0340-7594
1432-1351
DOI:10.1007/s003590050381