60
JERALD J. BERNSTEIN
innervating the palatal organ into seven groups, one group responding
only to acetic acid, but other types responding to two or more different
taste solutions (i.e., type 1 responded to acetic acid and sodium chloride,
type 3 responded to acetic acid and sucrose, etc.).
In addition to the palatine nerve preparation, preparations of the
facial nerve (Cr.N.VI1) innervating the lips and barbels of fresh- and
saltwater catfish have been used to test the taste responses (Konishi
et al., 1966; Tateda, 1961, 1964). Following physiological stimulation of
the barbel of the freshwater catfish, Ameiurus melas, with sodium
chloride solutions, the chemoreceptors responded with a train of summated spikes which continued for the duration of stimulation. In the
catfish, potassium chloride produced larger responses in the nerve fibers
than sodium chloride (Tateda, 1961). Hydrochloric acid resulted in a
large initial burst of impulses which declined rapidly (10-20 sec). Several nerve fibers within the isolated barbel of Parasilurus asotus responded to hydrochloric acid alone but not to other taste solutions. Most
fibers responded to two or more taste solutions (Tateda, 1964), the majority responding to both acid and salt. Recordings from the facial ncrve
of sea catfish, Plotosus anguillaris, demonstrated a response to hypertonic
sodium chloride solution, to quinine and to acid, but not to sugar
(Konishi et al., 1966). This insensitivity to sugar solutions was also
demonstrated by Bardach and Case (1965) behaviorally (on the sea
robin) and physiologically (on the fin preparations from the hake).
There appears then to be differences in the chemoreceptive response
patterns to sapid substances by different animals. In addition, the difference between animals which lived in saltwater and animals which lived
in freshwater are quite apparent.
Comparisons between the reaction of chemoreceptors to sapid substances in freshwater catfish, Ictaluris natalis and 1. nebulosus (innervation to taste buds, facial nerve only), the chemoreceptors of the tomcod,
Microgadus tomcod (cranial and spinal innervation to taste buds), and
the chemoreceptors of the sea robin Prionotus carolinus with modified
fins (innervation to taste buds on these fins, spinal nerve 3 ) were carried
out by Bardach et al. ( 1967). The animals were classificd according to
whether they lived in freshwater or saltwater. Rccordings were made
from the chemoreceptors of isolated barbels or fin rays. A larger concentration of acetic acid was required for the stimulation of the marine
animals than freshwater animals. However, it was pointed out ( Bardach
et al., 1967) that the presence of acid in seawater can result in the binding
of hydrogen ions on the substance upon which the stimulation depends.
Therefore, although freshwater fish did seem more sensitive in reality, t b y
may not be, since more acid must be added to the marine medium in
JERALD J. BERNSTEIN
innervating the palatal organ into seven groups, one group responding
only to acetic acid, but other types responding to two or more different
taste solutions (i.e., type 1 responded to acetic acid and sodium chloride,
type 3 responded to acetic acid and sucrose, etc.).
In addition to the palatine nerve preparation, preparations of the
facial nerve (Cr.N.VI1) innervating the lips and barbels of fresh- and
saltwater catfish have been used to test the taste responses (Konishi
et al., 1966; Tateda, 1961, 1964). Following physiological stimulation of
the barbel of the freshwater catfish, Ameiurus melas, with sodium
chloride solutions, the chemoreceptors responded with a train of summated spikes which continued for the duration of stimulation. In the
catfish, potassium chloride produced larger responses in the nerve fibers
than sodium chloride (Tateda, 1961). Hydrochloric acid resulted in a
large initial burst of impulses which declined rapidly (10-20 sec). Several nerve fibers within the isolated barbel of Parasilurus asotus responded to hydrochloric acid alone but not to other taste solutions. Most
fibers responded to two or more taste solutions (Tateda, 1964), the majority responding to both acid and salt. Recordings from the facial ncrve
of sea catfish, Plotosus anguillaris, demonstrated a response to hypertonic
sodium chloride solution, to quinine and to acid, but not to sugar
(Konishi et al., 1966). This insensitivity to sugar solutions was also
demonstrated by Bardach and Case (1965) behaviorally (on the sea
robin) and physiologically (on the fin preparations from the hake).
There appears then to be differences in the chemoreceptive response
patterns to sapid substances by different animals. In addition, the difference between animals which lived in saltwater and animals which lived
in freshwater are quite apparent.
Comparisons between the reaction of chemoreceptors to sapid substances in freshwater catfish, Ictaluris natalis and 1. nebulosus (innervation to taste buds, facial nerve only), the chemoreceptors of the tomcod,
Microgadus tomcod (cranial and spinal innervation to taste buds), and
the chemoreceptors of the sea robin Prionotus carolinus with modified
fins (innervation to taste buds on these fins, spinal nerve 3 ) were carried
out by Bardach et al. ( 1967). The animals were classificd according to
whether they lived in freshwater or saltwater. Rccordings were made
from the chemoreceptors of isolated barbels or fin rays. A larger concentration of acetic acid was required for the stimulation of the marine
animals than freshwater animals. However, it was pointed out ( Bardach
et al., 1967) that the presence of acid in seawater can result in the binding
of hydrogen ions on the substance upon which the stimulation depends.
Therefore, although freshwater fish did seem more sensitive in reality, t b y
may not be, since more acid must be added to the marine medium in