63
external wall (tunica externa) of the swim bladder (Webb et al. 2006 ; Fig. 4 ). Only
one LC variant is found in each of the 11 Chaetodon subgenera, with the exception
of the subgenus Citharoedus in which two short horn variants (Ind3 and Ind4) are
found.
2.2 The Swim Bladder
Butterfl yfi shes have a euphysoclistous swim bladder that sits just below the vertebral column and is typically 30 % of the length of the body. The swim bladder wall
is composed of a thicker collagenous tunica externa and a thinner, epithelial tunica
interna (Woods 2006 ; Woods et al. 2006 ). The gas exchange structures in the tunica
interna (the secretory rete mirabile and resorptive oval) are well developed. A transverse diaphragm pierced by a central opening is formed by the infolding of the
tunica interna and divides the swim bladder into anterior and posterior chambers
(in Chaetodon and Forcipiger , and presumably other chaetodontid genera). The
morphology of the diaphragm tissue suggests that the size of the opening can be
changed, perhaps in order to control relative gas pressure in the two compartments
Fig. 4 Schematic representation of the six LC variants in dorsal view (rostral to top) among
Chaetodon species (see Table 2 for more information). ( a ) Dir1 —direct LC with mucoid connective tissue ( pink ) deep to opening in supracleithral lateral line canal containing neuromast ( blue ),
wide horns, and one-chambered swim bladder (e.g., Chaetodon auriga ). ( b ) Dir2 —direct LC without mucoid connective tissue, with narrow horns, and a two-chambered swim bladder (e.g., C. plebeius ). ( c ) Ind1 —indirect LC with mucoid connective tissue ( pink ) deep to opening in supracleithral
lateral line canal, with muscle ( green ) lateral to wide horns, and one-chambered swim bladder (e.g.,
C. kleinii ). ( d ) Ind2 —indirect LC without mucoid connective tissue, with muscle ( green ) lateral to
wide horns, and one-chambered swim bladder (e.g., C. multicinctus ). ( e ) Ind3 —indirect LC with
short horns (which do not reach the level of the opening in the supracleithral canal, and a
one-chambered swim bladder (e.g., C. ornatissimus ). ( f ) Ind4 —indirect LC with short horns, a onechambered swim bladder, and a medial anterior extension of swim bladder (e.g., C. meyeri ).
d diaphragm (transverse) in tunica interna, h swim bladder horn, hc sensory macula, e ear in otic
capsule, kt kidney tissue, ll 1st lateral-line scale, m muscle, mct mucoid connective tissue, nm neuromast, s supracleithrum, te tunica externa of swim bladder ( solid line ), ti tunica interna of swim
bladder ( dotted line ). (From Webb et al. 2006 , reprinted with permission of John Wiley & Sons)
Acoustic Communication in Butterfl yfi shes…
external wall (tunica externa) of the swim bladder (Webb et al. 2006 ; Fig. 4 ). Only
one LC variant is found in each of the 11 Chaetodon subgenera, with the exception
of the subgenus Citharoedus in which two short horn variants (Ind3 and Ind4) are
found.
2.2 The Swim Bladder
Butterfl yfi shes have a euphysoclistous swim bladder that sits just below the vertebral column and is typically 30 % of the length of the body. The swim bladder wall
is composed of a thicker collagenous tunica externa and a thinner, epithelial tunica
interna (Woods 2006 ; Woods et al. 2006 ). The gas exchange structures in the tunica
interna (the secretory rete mirabile and resorptive oval) are well developed. A transverse diaphragm pierced by a central opening is formed by the infolding of the
tunica interna and divides the swim bladder into anterior and posterior chambers
(in Chaetodon and Forcipiger , and presumably other chaetodontid genera). The
morphology of the diaphragm tissue suggests that the size of the opening can be
changed, perhaps in order to control relative gas pressure in the two compartments
Fig. 4 Schematic representation of the six LC variants in dorsal view (rostral to top) among
Chaetodon species (see Table 2 for more information). ( a ) Dir1 —direct LC with mucoid connective tissue ( pink ) deep to opening in supracleithral lateral line canal containing neuromast ( blue ),
wide horns, and one-chambered swim bladder (e.g., Chaetodon auriga ). ( b ) Dir2 —direct LC without mucoid connective tissue, with narrow horns, and a two-chambered swim bladder (e.g., C. plebeius ). ( c ) Ind1 —indirect LC with mucoid connective tissue ( pink ) deep to opening in supracleithral
lateral line canal, with muscle ( green ) lateral to wide horns, and one-chambered swim bladder (e.g.,
C. kleinii ). ( d ) Ind2 —indirect LC without mucoid connective tissue, with muscle ( green ) lateral to
wide horns, and one-chambered swim bladder (e.g., C. multicinctus ). ( e ) Ind3 —indirect LC with
short horns (which do not reach the level of the opening in the supracleithral canal, and a
one-chambered swim bladder (e.g., C. ornatissimus ). ( f ) Ind4 —indirect LC with short horns, a onechambered swim bladder, and a medial anterior extension of swim bladder (e.g., C. meyeri ).
d diaphragm (transverse) in tunica interna, h swim bladder horn, hc sensory macula, e ear in otic
capsule, kt kidney tissue, ll 1st lateral-line scale, m muscle, mct mucoid connective tissue, nm neuromast, s supracleithrum, te tunica externa of swim bladder ( solid line ), ti tunica interna of swim
bladder ( dotted line ). (From Webb et al. 2006 , reprinted with permission of John Wiley & Sons)
Acoustic Communication in Butterfl yfi shes…