Lungfish Hearing: Implications for the evolution of the tetrapod middle ear

Christian Bech Christensen, Peter Teglberg Madsen, Jakob Christensen-Dalsgaard

Research output: Contribution to conference without publisher/journalConference abstract for conferenceResearch


Recent research has shown that tympanic middle ears
evolved independently in the major vertebrate groups and
represent independent experiments in terrestrial hearing.
Furthermore, the tympanic ear emerged quite late – ap
proximately 120 mya after the origin of the tetrapods and
approximately 70 my after the first truly terrestrial tetrapods
emerged. One of the major challenges is to understand the
transitional stages from tetrapod ancestors to the tympanic
tetrapod ear, for example how a non-tympanic ear functions
in terrestrial hearing. Lungfish are the closest living relatives
of the tetrapods, and the ear of lungfish may be similar to the
ear of theearly tetrapods.
We have studied the sensitivity of African lungfish to air-borne
sound, underwater sound and vibrations. We show that lung
fish detect underwater sound pressure via pressure-to-par
ticle motion transduction by air volumes in their lungs and
that lungfish detect air-borne sound by sound-induced head
vibrations, resulting in a limited sensitivity to low-frequen
cy sound (lowest thresholds from 80 dB SPL). Adiditionally,
lungfish are sensitive to substrate vibration with a sensitivity
comparable to anurans and urodeles.
Based on ABR and vibration measurements also on amphib
ians, lizards, snakes and alligators we can outline scenarios
for the initial adaptations of the middle ear to non-tympanic
hearing and assess the selection pressures later adapting the
middle ear for tympanic hearing. Hearing by bone conduc
tion, sound induced vibrations of the skull, is found in snakes
and some earless frogs, whereas urodeles and other earless
frogs are more sensitive than predicted from sound-induced
skull vibrations and may have specialized pathways to the
inner ear. We propose four stages : 1) the unspecialized cros
sopterygian ear with immobile middle ear bone, 2) increased
inner ear frequency ranges, 3) mobile middle ear structures
and 4) the tympanic middle ear.
Original languageEnglish
Publication date21. Feb 2015
Publication statusPublished - 21. Feb 2015
Event38th Annual Midwinter Meeting of the Association for Research in Otorhinolaryngology - Baltimore Marriott Waterfront, Baltimore, Denmark
Duration: 21. Feb 201525. Feb 2015


Conference38th Annual Midwinter Meeting of the Association for Research in Otorhinolaryngology
LocationBaltimore Marriott Waterfront

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