88
accompanied by modifi cation of the ear or otic capsule. Thus, the evolution of
acoustic anatomy, physiology, and behavior has a complex and interesting history
that deserves more study. Future studies on sound production in other chaetodontid
genera and outgroups are needed to better understand the evolution of butterfl yfi sh
acoustic behaviors.
2. The sounds produced by butterfl yfi shes are diverse in form, frequency and with
respect to their correlated kinematic (motor) patterns. This indicates that a variety of sound production mechanisms are present that are open for more investigation. In addition, the production of very low frequency sounds (<1–30 Hz)
requires that the role and reception of “infrasound” for social communication be
further considered in butterfl yfi shes and other fi sh taxa.
3. All butterfl yfi shes are sensitive to the hydrodynamic fl ow component of an
acoustic fi eld. In Chaetodon , the swim bladder horns also respond to sound pressure stimuli that enhances their auditory sensitivity from 100 to 600 Hz and
extends their absolute hearing range up to 2 kHz. Studies on sound pressure
sensitivity are needed on more species to defi ne the potential roles of LC types
and variants in the enhancement of hearing.
4. The physical motion of the wall of the swim bladder horns at the medial opening
of the supracleithrum (which defi nes the LC) and the resultant activation of adjacent canal neuromasts (hypothesized by Webb 1998 ; Webb et al. 2006 ) remain to
be determined.
5. The importance of the swim bladder horns in affecting auditory sensitivity and
frequency range in Chaetodon begs the question of what other groups of fi shes,
and coral reef fi shes in particular, may have evolved adaptations for the enhancement of auditory capabilities in noisy reef habitats.
6. The coral reef environment is replete with abiotic and biotic noise that overlaps
with the spectrum of butterfl yfi sh sounds and their auditory sensitivity. The close
affi liative social behaviors demonstrated by most butterfl yfi shes facilitate acoustic communication in these noisy coral reef environments and indicate that the
non-visual sensory environment may infl uence the evolution of behavior in these
fi shes.
7. Studies are needed to determine the amplitude of sound pressure and hydrodynamic stimuli in the many sub-habitats of the coral reef, which are occupied by
different butterfl yfi sh species, in order to better understand the constraints on
acoustic communication imposed by the soundscape.
8. The relative contributions of the ear and lateral line in the detection of different
components of hydrodynamic and acoustic stimuli generated at close range
(especially at low frequencies, <1–100 Hz) need to be determined. In addition,
neuroanatomical and neurophysiological analyses of the central neural pathways
that integrate diverse auditory (direct or via the swim bladder) and lateral line
(direct or via the laterophysic connection) inputs will likely to provide novel
insights into the function of these complementary acoustic modalities.
Acknowledgments The authors would like to thank Drs. Arthur Popper and Richard Fay for
intellectual inspiration, scientifi c and editorial advice and collaboration, for their mentorship, and
in their roles as luminaries in the fi eld of fi sh bioacoustics. Art Popper told JFW, then a young
T.C. Tricas and J.F. Webb
accompanied by modifi cation of the ear or otic capsule. Thus, the evolution of
acoustic anatomy, physiology, and behavior has a complex and interesting history
that deserves more study. Future studies on sound production in other chaetodontid
genera and outgroups are needed to better understand the evolution of butterfl yfi sh
acoustic behaviors.
2. The sounds produced by butterfl yfi shes are diverse in form, frequency and with
respect to their correlated kinematic (motor) patterns. This indicates that a variety of sound production mechanisms are present that are open for more investigation. In addition, the production of very low frequency sounds (<1–30 Hz)
requires that the role and reception of “infrasound” for social communication be
further considered in butterfl yfi shes and other fi sh taxa.
3. All butterfl yfi shes are sensitive to the hydrodynamic fl ow component of an
acoustic fi eld. In Chaetodon , the swim bladder horns also respond to sound pressure stimuli that enhances their auditory sensitivity from 100 to 600 Hz and
extends their absolute hearing range up to 2 kHz. Studies on sound pressure
sensitivity are needed on more species to defi ne the potential roles of LC types
and variants in the enhancement of hearing.
4. The physical motion of the wall of the swim bladder horns at the medial opening
of the supracleithrum (which defi nes the LC) and the resultant activation of adjacent canal neuromasts (hypothesized by Webb 1998 ; Webb et al. 2006 ) remain to
be determined.
5. The importance of the swim bladder horns in affecting auditory sensitivity and
frequency range in Chaetodon begs the question of what other groups of fi shes,
and coral reef fi shes in particular, may have evolved adaptations for the enhancement of auditory capabilities in noisy reef habitats.
6. The coral reef environment is replete with abiotic and biotic noise that overlaps
with the spectrum of butterfl yfi sh sounds and their auditory sensitivity. The close
affi liative social behaviors demonstrated by most butterfl yfi shes facilitate acoustic communication in these noisy coral reef environments and indicate that the
non-visual sensory environment may infl uence the evolution of behavior in these
fi shes.
7. Studies are needed to determine the amplitude of sound pressure and hydrodynamic stimuli in the many sub-habitats of the coral reef, which are occupied by
different butterfl yfi sh species, in order to better understand the constraints on
acoustic communication imposed by the soundscape.
8. The relative contributions of the ear and lateral line in the detection of different
components of hydrodynamic and acoustic stimuli generated at close range
(especially at low frequencies, <1–100 Hz) need to be determined. In addition,
neuroanatomical and neurophysiological analyses of the central neural pathways
that integrate diverse auditory (direct or via the swim bladder) and lateral line
(direct or via the laterophysic connection) inputs will likely to provide novel
insights into the function of these complementary acoustic modalities.
Acknowledgments The authors would like to thank Drs. Arthur Popper and Richard Fay for
intellectual inspiration, scientifi c and editorial advice and collaboration, for their mentorship, and
in their roles as luminaries in the fi eld of fi sh bioacoustics. Art Popper told JFW, then a young
T.C. Tricas and J.F. Webb