71
the jaws). These motions stimulate the adjacent swim bladder to produce a pulsed
sound with peak frequency in the range of 100–200 Hz (Boyle and Tricas 2011 ;
Boyle et al. 2013 ; Tricas and Boyle 2014 , 2015a ). The anal fi n retract sound is also
produced by F. fl avissimus and has a much lower peak frequency (27 Hz) (Fig. 6 ;
Tricas and Boyle 2015a ). These two acoustic behaviors in Forcipiger are not yet
reported for the other bannerfi sh genera studied so far.
In contrast, the bannerfi shes Hemitaurichthys polylepis and H. thompsoni produce loud pulse sounds that do not involve a head bob motion, but instead produce
sounds that are associated with a buckling of the anterior body wall caused by contraction of the hypaxial musculature lateral to the anterior portion of the swim bladder (Boyle and Tricas 2010 ; Tricas and Boyle 2014 ). This mechanism is similar to
that demonstrated in Heniochus chrysostomus , which likely involves the contraction
of the lateral subdivision of the hypaxial musculature (Parmentier et al. 2011 ). Thus
the head bob sound in Forcipiger is produced by the action of the epaxial, adductor
mandibula and sternohyoideus muscles, and their musculoskeletal linkages. The
anal-fi n spine-retraction sound is produced by the action of the anal fi n erector and
retractor muscles and their associated linkages. The pulsed sounds of Heniochus
and Hemitaurichthys are driven primarily by the action of the hypaxial
musculature.
Several acoustic behaviors of Chaetodon (including some for which the sound
production mechanisms are not yet confi rmed) clearly vary among species and
clades, and span a wider range of frequencies than those produced by the bannerfi shes (Table 2 ; Tricas and Boyle 2015a ). A prominent head bob behavior that is
similar to that seen in Forcipiger occurs in both C. unimaculatus (Clade 2) and C.
auriga (Clade 4), but also includes a prominent and active protrusion of the jaws
(Fig. 6 ). In comparison, pulsed sounds produced by the blacklip butterfl yfi sh, C.
kleinii , (Clade 2) involves jaw protrusion without a prominent head bob motion. The
possibility that the jaw motion found among Clade 2 species causes the relatively
high average peak frequency pulsed sounds (e.g., C. kleinii = 516 Hz, C. unimaculatus = 1031 Hz) needs to be tested and examined in more species. In addition, the
causal factors for the head-bob jaw-protrusion sound in C. auriga and its lower peak
frequency (23 Hz) need to be resolved. Furthermore, the common sound produced
by C. multicinctus (also in Clade 2) does not involve a visible head bob or jaw protrusion, but instead is a body motion pulse sound (average peak frequency = 137 Hz)
similar to that described for Hemitaurichthys and Heniochus . Additional detailed
electromyographic studies are needed to confi rm or reject the presence of similar
internal kinematic patterns (see Tricas and Boyle 2015a ). A similar body motion
acoustic behavior occurs in C. ornatissimus (Clade 3), but that pulsed sound has a
much lower peak frequency (10 Hz). Collectively, the head bob, jaw protrusion, and
body motion sounds produced by Chaetodon species studied thus far span a greater
frequency range than sounds produced by members of other butterfl yfi sh genera,
and involve several sound production mechanisms.
Several species of Chaetodon also produce a very low frequency hydrodynamic
stimulus known as the tail slap, which has peak frequencies that range from <1 to
69 Hz and a signifi cant component in the infrasound (<20 Hz) range (sensu Sand
Acoustic Communication in Butterfl yfi shes…
the jaws). These motions stimulate the adjacent swim bladder to produce a pulsed
sound with peak frequency in the range of 100–200 Hz (Boyle and Tricas 2011 ;
Boyle et al. 2013 ; Tricas and Boyle 2014 , 2015a ). The anal fi n retract sound is also
produced by F. fl avissimus and has a much lower peak frequency (27 Hz) (Fig. 6 ;
Tricas and Boyle 2015a ). These two acoustic behaviors in Forcipiger are not yet
reported for the other bannerfi sh genera studied so far.
In contrast, the bannerfi shes Hemitaurichthys polylepis and H. thompsoni produce loud pulse sounds that do not involve a head bob motion, but instead produce
sounds that are associated with a buckling of the anterior body wall caused by contraction of the hypaxial musculature lateral to the anterior portion of the swim bladder (Boyle and Tricas 2010 ; Tricas and Boyle 2014 ). This mechanism is similar to
that demonstrated in Heniochus chrysostomus , which likely involves the contraction
of the lateral subdivision of the hypaxial musculature (Parmentier et al. 2011 ). Thus
the head bob sound in Forcipiger is produced by the action of the epaxial, adductor
mandibula and sternohyoideus muscles, and their musculoskeletal linkages. The
anal-fi n spine-retraction sound is produced by the action of the anal fi n erector and
retractor muscles and their associated linkages. The pulsed sounds of Heniochus
and Hemitaurichthys are driven primarily by the action of the hypaxial
musculature.
Several acoustic behaviors of Chaetodon (including some for which the sound
production mechanisms are not yet confi rmed) clearly vary among species and
clades, and span a wider range of frequencies than those produced by the bannerfi shes (Table 2 ; Tricas and Boyle 2015a ). A prominent head bob behavior that is
similar to that seen in Forcipiger occurs in both C. unimaculatus (Clade 2) and C.
auriga (Clade 4), but also includes a prominent and active protrusion of the jaws
(Fig. 6 ). In comparison, pulsed sounds produced by the blacklip butterfl yfi sh, C.
kleinii , (Clade 2) involves jaw protrusion without a prominent head bob motion. The
possibility that the jaw motion found among Clade 2 species causes the relatively
high average peak frequency pulsed sounds (e.g., C. kleinii = 516 Hz, C. unimaculatus = 1031 Hz) needs to be tested and examined in more species. In addition, the
causal factors for the head-bob jaw-protrusion sound in C. auriga and its lower peak
frequency (23 Hz) need to be resolved. Furthermore, the common sound produced
by C. multicinctus (also in Clade 2) does not involve a visible head bob or jaw protrusion, but instead is a body motion pulse sound (average peak frequency = 137 Hz)
similar to that described for Hemitaurichthys and Heniochus . Additional detailed
electromyographic studies are needed to confi rm or reject the presence of similar
internal kinematic patterns (see Tricas and Boyle 2015a ). A similar body motion
acoustic behavior occurs in C. ornatissimus (Clade 3), but that pulsed sound has a
much lower peak frequency (10 Hz). Collectively, the head bob, jaw protrusion, and
body motion sounds produced by Chaetodon species studied thus far span a greater
frequency range than sounds produced by members of other butterfl yfi sh genera,
and involve several sound production mechanisms.
Several species of Chaetodon also produce a very low frequency hydrodynamic
stimulus known as the tail slap, which has peak frequencies that range from <1 to
69 Hz and a signifi cant component in the infrasound (<20 Hz) range (sensu Sand
Acoustic Communication in Butterfl yfi shes…