150
WILLIAM N. TAVOLGA
posteriorly. Two broad bands of muscle are firmly attached along the
lateral surfaces, with the fine, striated fibers running obliquely (Fig. 10a).
The interior of the bladder contains an extensive vascular network and a
pair of “red glands.” A thin transverse membrane with a small sphincter
separates the secretory and absorptive chambers. The remarkable gas
exchanging properties of this organ has been extensively investigated by
Fange ( 1966) and Fange and Wittenberg ( 1958).
The first experimental studies on the sonic function of the swim bladder of toadfish were those of Tower (1908). His observations, confirmed
by Tavolga (1964b), showed that the fundamental frequency of the
emitted sound is exactly equivalent to the vibration frequency of the
sonic muscles.
Thus far, although differences in the character of the cell exist among
populations and different species of toadfishes, no structural differences
in the swim bladder mechanism have been found to account for these
variations in pitch, duration, and quality ( Tavolga, 1958c, 196413). In
Porichthys, a genus of fish closely related to the toadfishes, the sonic
mechanism appears to be virtually identical ( Greene, 1924) (Fig. lob).
The sea robins (Triglidae) possess essentially the same mechanism
of sound production as the toadfishes except for the shape of the swim
bladder. In the sea robins (Trigla in Europe; Prionotus on our Atlantic
coast), the swim bladder is composed of two dirigible-shaped chambers
side by side, and attached to one another by a narrow passageway (Figs.
1Oc and 10d). The arrangement of the sonic muscles and their function
appears to be similar to that of the toadfish (Moulton, 1960a; Moreau,
1876). A family related to the sea robins is the Dactylopteridae-the flying gurnards. Although little is known of their ability for sound production, the mechanism seems to be identical to that of the sea robins
(Tower, 1908; Fish, 1954; Tavolga, 19641,) (Fig. log). Simultaneous electromyograms and sound recordings in the midshipman, Porichthys
notatus, showed that sound pulses and muscle potentials corresponded
in a one-to-one fashion (Cohen and Winn, 1967).
6. MECHANICS OF SWIM BLADDER SOUND PRODUCTION
If we consider the swim bladder and its associated skeletal and
muscular systems as an underwater loudspeaker, the energy source for
the emitted sound is the contraction of specialized muscles. In no case
is there a muscular antagonist to the action of the sonic muscles. In the
catfishes, the “elastic spring” maintains tension on the sonic muscles and
returns the fibers to their normal condition after each contraction
( Tavolga, 1962). In the squirrelfishes and groupers, the sonic muscles
WILLIAM N. TAVOLGA
posteriorly. Two broad bands of muscle are firmly attached along the
lateral surfaces, with the fine, striated fibers running obliquely (Fig. 10a).
The interior of the bladder contains an extensive vascular network and a
pair of “red glands.” A thin transverse membrane with a small sphincter
separates the secretory and absorptive chambers. The remarkable gas
exchanging properties of this organ has been extensively investigated by
Fange ( 1966) and Fange and Wittenberg ( 1958).
The first experimental studies on the sonic function of the swim bladder of toadfish were those of Tower (1908). His observations, confirmed
by Tavolga (1964b), showed that the fundamental frequency of the
emitted sound is exactly equivalent to the vibration frequency of the
sonic muscles.
Thus far, although differences in the character of the cell exist among
populations and different species of toadfishes, no structural differences
in the swim bladder mechanism have been found to account for these
variations in pitch, duration, and quality ( Tavolga, 1958c, 196413). In
Porichthys, a genus of fish closely related to the toadfishes, the sonic
mechanism appears to be virtually identical ( Greene, 1924) (Fig. lob).
The sea robins (Triglidae) possess essentially the same mechanism
of sound production as the toadfishes except for the shape of the swim
bladder. In the sea robins (Trigla in Europe; Prionotus on our Atlantic
coast), the swim bladder is composed of two dirigible-shaped chambers
side by side, and attached to one another by a narrow passageway (Figs.
1Oc and 10d). The arrangement of the sonic muscles and their function
appears to be similar to that of the toadfish (Moulton, 1960a; Moreau,
1876). A family related to the sea robins is the Dactylopteridae-the flying gurnards. Although little is known of their ability for sound production, the mechanism seems to be identical to that of the sea robins
(Tower, 1908; Fish, 1954; Tavolga, 19641,) (Fig. log). Simultaneous electromyograms and sound recordings in the midshipman, Porichthys
notatus, showed that sound pulses and muscle potentials corresponded
in a one-to-one fashion (Cohen and Winn, 1967).
6. MECHANICS OF SWIM BLADDER SOUND PRODUCTION
If we consider the swim bladder and its associated skeletal and
muscular systems as an underwater loudspeaker, the energy source for
the emitted sound is the contraction of specialized muscles. In no case
is there a muscular antagonist to the action of the sonic muscles. In the
catfishes, the “elastic spring” maintains tension on the sonic muscles and
returns the fibers to their normal condition after each contraction
( Tavolga, 1962). In the squirrelfishes and groupers, the sonic muscles