6. SOUND PRODUCTION AND DETECTION
167
swim bladder has anterior extensions which are either coupled directly
to the perilymphatic fluid (as in many clupeids) or attached to the
occipital region of the neurocranium (Froese, 1938; Grass&, 1958; Tracy,
1920). Wohlfahrt ( 1936, 1938) described long, thin anterior extensions
of the swim bladder in clupeids. These terminate in gas-filled capsules
enclosed in bone and coupled to the perilymph through an elastic
fenestra. Although auditory thresholds using psychophysical methods are
not yet available for any clupeid fishes, Enger (1967a) obtained action
potentials generated in the medulla in response to acoustic stimuli in the
herring, Clupea harengus. The tentative audiogram so generated showed
a rather flat frequency response over a range of 30-1200 Hz with a threshold of -20 to -25 dB pb, and a sharp increase to +35 dB pb at 4000 Hz.
In contrast to the neurophysiological technique used by Enger
(1967a), a number of workers have resorted to conditioning techniques
in which the fish are trained to make some behavioral response in the
presence of the test sound. By means of avoidance conditioning, Tavolga
and Wodinsky (1963) showed that the squirrelfish, Holocentrus ascensionis, has a low threshold and broad frequency response spectrum. It
is probable that this is related to the contiguity of the anterior end of the
swim bladder to the skull, as described by E. M. Nelson (1955).
Species with reduced or absent swim bladders should have poor hearing, but the evidence for this is sparse. Bull (1928) was unable to condition a blenny, Blennius, to respond to sound. In Gobius, Dijkgraaf (1949,
1952b) showed an upper frequency limit of only 800 Hz, and he
postulated that most sound reception in this species took place through
lateral line or cutaneous tactile senses.
On this basis, sharks and other elasmobranchs should be virtually deaf,
yet the studies of Kritzler and Wood ( 1961) and D. R. Nelson (1967a)
and the electrophysiological work of Lowenstein and Roberts (1951)
show this is not true. The validity of the statement that the fish is
acoustically transparent needs to be reexamined, and the possibilities that
the skull, vertebral column, and other portions of the body can act as
acoustic discontinuities should be investigated. Furthermore the contribution of the lateral line to hearing needs clarification.
3. LATERAL LINE AND HEARING
Fish possess two sensory modalities for the detection of underwater
vibrations. In addition to the inner ear, they possess a series of integumentary sense organs collectively known as the lateral line system (Fig.
18). This system will be covered in detail by Flock in Chapter 8
of this volume. Most of the anatomical studies on the lateral line in fishes
167
swim bladder has anterior extensions which are either coupled directly
to the perilymphatic fluid (as in many clupeids) or attached to the
occipital region of the neurocranium (Froese, 1938; Grass&, 1958; Tracy,
1920). Wohlfahrt ( 1936, 1938) described long, thin anterior extensions
of the swim bladder in clupeids. These terminate in gas-filled capsules
enclosed in bone and coupled to the perilymph through an elastic
fenestra. Although auditory thresholds using psychophysical methods are
not yet available for any clupeid fishes, Enger (1967a) obtained action
potentials generated in the medulla in response to acoustic stimuli in the
herring, Clupea harengus. The tentative audiogram so generated showed
a rather flat frequency response over a range of 30-1200 Hz with a threshold of -20 to -25 dB pb, and a sharp increase to +35 dB pb at 4000 Hz.
In contrast to the neurophysiological technique used by Enger
(1967a), a number of workers have resorted to conditioning techniques
in which the fish are trained to make some behavioral response in the
presence of the test sound. By means of avoidance conditioning, Tavolga
and Wodinsky (1963) showed that the squirrelfish, Holocentrus ascensionis, has a low threshold and broad frequency response spectrum. It
is probable that this is related to the contiguity of the anterior end of the
swim bladder to the skull, as described by E. M. Nelson (1955).
Species with reduced or absent swim bladders should have poor hearing, but the evidence for this is sparse. Bull (1928) was unable to condition a blenny, Blennius, to respond to sound. In Gobius, Dijkgraaf (1949,
1952b) showed an upper frequency limit of only 800 Hz, and he
postulated that most sound reception in this species took place through
lateral line or cutaneous tactile senses.
On this basis, sharks and other elasmobranchs should be virtually deaf,
yet the studies of Kritzler and Wood ( 1961) and D. R. Nelson (1967a)
and the electrophysiological work of Lowenstein and Roberts (1951)
show this is not true. The validity of the statement that the fish is
acoustically transparent needs to be reexamined, and the possibilities that
the skull, vertebral column, and other portions of the body can act as
acoustic discontinuities should be investigated. Furthermore the contribution of the lateral line to hearing needs clarification.
3. LATERAL LINE AND HEARING
Fish possess two sensory modalities for the detection of underwater
vibrations. In addition to the inner ear, they possess a series of integumentary sense organs collectively known as the lateral line system (Fig.
18). This system will be covered in detail by Flock in Chapter 8
of this volume. Most of the anatomical studies on the lateral line in fishes