336
bladder. In the silver perch Bairdiella chrysoura the anterior chamber of the swim
bladder surrounds the otic capsule and terminates lateral to the saccules (Ramcharitar
et al. 2004 ). B. chrysoura detects sound up to 4 kHz and has thresholds almost as
low as goldfi sh (74 dB at 600 Hz). In contrast, Horodysky et al. ( 2008 ) found no
signifi cant difference in hearing thresholds in species with ( Cynoscion regalis ,
Cynoscion nebulosus , Micropogonias undulatus ) and without swim bladder specializations ( Sciaenops ocellatus , Leiostomus xanthurus ). Surprisingly, the authors
found that sensitivities in the Northern kingfi sh Menticirrhus saxatilis , a species
which has a reduced swim bladder in adults, were among the highest above 0.6 kHz.
Furthermore the Mediterranean brown meagre Sciaena umbra , which lacks specialization, has a broader hearing bandwidth (3 kHz) than all other species except B.
chrysoura (Wysocki et al. 2009 ) (for a comparison of all sciaenid audiograms see
fi gures 21 and 22 in Ladich and Fay 2013 ). Again, swim bladder size has not been
investigated in sciaenids except for the above report on M. saxatilis . In summary,
the form–function relationship in the Sciaenidae is not as consistent as in catfi shes,
holocentrids, and cichlids. Ramcharitar et al. ( 2006 ) found a relationship between
maximum frequency detected and minimum swim bladder-otic capsule distance (in
millimeters). This correlation cannot be confi rmed by the data from Horodysky
et al. ( 2008 ) because the latter did not measure frequencies beyond 1.2 kHz. The
swim bladder–inner ear distance does not seem to affect the absolute auditory sensitivity in this family, particularly at higher frequencies, as expected from numerous
other studies.
6 Conclusions
One of the most interesting aspects in fi sh audition is the tendency in numerous taxa
(genera, families, orders) to exploit vibrations of gas-fi lled cavities or bladders in a
sound fi eld for improvement of hearing. Sound pressure fl uctuations in a sound fi eld
create volume changes and subsequently oscillations of the walls of gas cavities
(swim bladders, air-breathing organs) which can be transmitted to the inner ear.
These oscillating walls may then function as tympana (ear drums), similar to tympana in tetrapods (anurans, reptiles, birds, mammals) (Ladich 2010 ). While sound
pressure hearing via tympana has become the standard pattern of sound detection in
tetrapods (with a few exceptions such as whales), this was not the case in fi shes.
Among fi shes, “tympana” and connections to the inner ears evolved in all otophysines, anabantoids (labyrinth fi shes), and mormyrids. Several other families such as
cichlids, holocentrids, and sciaenids exhibit diversity in peripheral structures for
hearing and subsequently in hearing sensitivities. Interestingly, diversity in swim
bladders and auditory sensitivities is also found in otophysines, particularly in
catfi shes.
Earlier intrafamilial studies investigating the effects of swim bladder morphology on hearing concentrated on the distance to the inner ears but did not study swim
F. Ladich
bladder. In the silver perch Bairdiella chrysoura the anterior chamber of the swim
bladder surrounds the otic capsule and terminates lateral to the saccules (Ramcharitar
et al. 2004 ). B. chrysoura detects sound up to 4 kHz and has thresholds almost as
low as goldfi sh (74 dB at 600 Hz). In contrast, Horodysky et al. ( 2008 ) found no
signifi cant difference in hearing thresholds in species with ( Cynoscion regalis ,
Cynoscion nebulosus , Micropogonias undulatus ) and without swim bladder specializations ( Sciaenops ocellatus , Leiostomus xanthurus ). Surprisingly, the authors
found that sensitivities in the Northern kingfi sh Menticirrhus saxatilis , a species
which has a reduced swim bladder in adults, were among the highest above 0.6 kHz.
Furthermore the Mediterranean brown meagre Sciaena umbra , which lacks specialization, has a broader hearing bandwidth (3 kHz) than all other species except B.
chrysoura (Wysocki et al. 2009 ) (for a comparison of all sciaenid audiograms see
fi gures 21 and 22 in Ladich and Fay 2013 ). Again, swim bladder size has not been
investigated in sciaenids except for the above report on M. saxatilis . In summary,
the form–function relationship in the Sciaenidae is not as consistent as in catfi shes,
holocentrids, and cichlids. Ramcharitar et al. ( 2006 ) found a relationship between
maximum frequency detected and minimum swim bladder-otic capsule distance (in
millimeters). This correlation cannot be confi rmed by the data from Horodysky
et al. ( 2008 ) because the latter did not measure frequencies beyond 1.2 kHz. The
swim bladder–inner ear distance does not seem to affect the absolute auditory sensitivity in this family, particularly at higher frequencies, as expected from numerous
other studies.
6 Conclusions
One of the most interesting aspects in fi sh audition is the tendency in numerous taxa
(genera, families, orders) to exploit vibrations of gas-fi lled cavities or bladders in a
sound fi eld for improvement of hearing. Sound pressure fl uctuations in a sound fi eld
create volume changes and subsequently oscillations of the walls of gas cavities
(swim bladders, air-breathing organs) which can be transmitted to the inner ear.
These oscillating walls may then function as tympana (ear drums), similar to tympana in tetrapods (anurans, reptiles, birds, mammals) (Ladich 2010 ). While sound
pressure hearing via tympana has become the standard pattern of sound detection in
tetrapods (with a few exceptions such as whales), this was not the case in fi shes.
Among fi shes, “tympana” and connections to the inner ears evolved in all otophysines, anabantoids (labyrinth fi shes), and mormyrids. Several other families such as
cichlids, holocentrids, and sciaenids exhibit diversity in peripheral structures for
hearing and subsequently in hearing sensitivities. Interestingly, diversity in swim
bladders and auditory sensitivities is also found in otophysines, particularly in
catfi shes.
Earlier intrafamilial studies investigating the effects of swim bladder morphology on hearing concentrated on the distance to the inner ears but did not study swim
F. Ladich