69
eight have an Indirect LC (Webb et al. 2006 ). Thus, LC type is not correlated with
corallivory, which is thought to be a major ecological factor in the evolution of
Chaetodon species. The drivers of the evolutionary diversifi cation of the LC have
yet to be identifi ed, but it has been shown experimentally that the presence of long
swim bladder horns enhances auditory capabilities (threshold, frequency range) in
Chaetodon species regardless of other defi ning features of LC variation (Sect. 3 ).
3 Diversity and Evolution of Sound Production
in Butterfl yfi shes
The discovery of the LC in Chaetodon led to the hypothesis that these highly social
fi shes produce sounds for acoustic communication during social interactions.
Subsequent fi eld and laboratory investigations on several species show that sound
production is used by Chaetodon and representatives of other genera during their
social interactions.
3.1 Acoustic Behavior and Sound Production Mechanisms
Sound production is now known for eight Chaetodon species and for all of the species of Forcipiger , Heniochus , and Hemitaurichthys studied so far. The names for
most acoustic behaviors (and sound types) are derived from the most prominent
observable motor pattern that occurs during the sound production event (Table 2 ).
Lab and fi eld studies show that as a group, these fi shes produce a large repertoire of
pulsed sounds and pulse trains that are generated by: (1) multiple sound production
mechanisms associated with subtle movements of various body parts (e.g., head
bob, jaw protrusion, body motion, buckling of the anterior body wall), and (2)
hydrodynamic stimuli generated by movement of the whole body during a stereotyped locomotor tail slap in Chaetodon . Several sound production mechanisms
appear to be shared among species studied, which generate sounds across a broad
range of frequencies (Table 2 ).
Kinematic and electromyographic analyses indicate the presence of at least three
sound production mechanisms in non- Chaetodon bannerfi sh species, which produce sounds with peak frequencies of 27–170 Hz (Table 2 ). The head bob sound is
produced by the two known species of Forcipiger and is associated with a rapid and
prominent vertical motion of the head (Fig. 6 ). The head bob acoustic behavior is
driven by epaxial muscle action on the skull and a ventral linkage between the head
and pectoral girdle, which is maintained by simultaneous activity of the adductor
mandibulae and sternohyoideus muscles (Boyle and Tricas 2011 ). This results in the
anterior motion of the pectoral girdle, ribs, and rostral swim bladder before the head
is released and rotated dorsally (and also contributes to apparent passive motions of
Acoustic Communication in Butterfl yfi shes…
eight have an Indirect LC (Webb et al. 2006 ). Thus, LC type is not correlated with
corallivory, which is thought to be a major ecological factor in the evolution of
Chaetodon species. The drivers of the evolutionary diversifi cation of the LC have
yet to be identifi ed, but it has been shown experimentally that the presence of long
swim bladder horns enhances auditory capabilities (threshold, frequency range) in
Chaetodon species regardless of other defi ning features of LC variation (Sect. 3 ).
3 Diversity and Evolution of Sound Production
in Butterfl yfi shes
The discovery of the LC in Chaetodon led to the hypothesis that these highly social
fi shes produce sounds for acoustic communication during social interactions.
Subsequent fi eld and laboratory investigations on several species show that sound
production is used by Chaetodon and representatives of other genera during their
social interactions.
3.1 Acoustic Behavior and Sound Production Mechanisms
Sound production is now known for eight Chaetodon species and for all of the species of Forcipiger , Heniochus , and Hemitaurichthys studied so far. The names for
most acoustic behaviors (and sound types) are derived from the most prominent
observable motor pattern that occurs during the sound production event (Table 2 ).
Lab and fi eld studies show that as a group, these fi shes produce a large repertoire of
pulsed sounds and pulse trains that are generated by: (1) multiple sound production
mechanisms associated with subtle movements of various body parts (e.g., head
bob, jaw protrusion, body motion, buckling of the anterior body wall), and (2)
hydrodynamic stimuli generated by movement of the whole body during a stereotyped locomotor tail slap in Chaetodon . Several sound production mechanisms
appear to be shared among species studied, which generate sounds across a broad
range of frequencies (Table 2 ).
Kinematic and electromyographic analyses indicate the presence of at least three
sound production mechanisms in non- Chaetodon bannerfi sh species, which produce sounds with peak frequencies of 27–170 Hz (Table 2 ). The head bob sound is
produced by the two known species of Forcipiger and is associated with a rapid and
prominent vertical motion of the head (Fig. 6 ). The head bob acoustic behavior is
driven by epaxial muscle action on the skull and a ventral linkage between the head
and pectoral girdle, which is maintained by simultaneous activity of the adductor
mandibulae and sternohyoideus muscles (Boyle and Tricas 2011 ). This results in the
anterior motion of the pectoral girdle, ribs, and rostral swim bladder before the head
is released and rotated dorsally (and also contributes to apparent passive motions of
Acoustic Communication in Butterfl yfi shes…