4. CHEMORECEPTION
105
movements; this resulted in continuous and characteristic courses in the
form of figure eight. Dogfish with one nostril occluded found the food by
predominant movements toward the side of the open nostril. Their movements were essentially circular in such a way that the open nostril is
toward the center of the circle. Parker explained these movements on the
basis of the osmotropotaxis as in the circus movements of invertebrates.
Gilbert et al. (1964) reported that electrical potential recorded from the
forebrain reflected olfactory processes in three species of sharks ( N e -
gaprion, Sphyrw, and Ginglymostom) . Both the amplitude and frequency of the potential clearly increased during chemical stimulation of
the olfactory sac with extracts of crabs and tuna.
Blinded bluntnose minnows, Hyborhynchus notatus, were able to
discriminate odors of aquatic plants at extreme dilutions. They also could
discriminate between odors of certain aquatic invertebrates ( Hasler,
1957). These findings support the view that aquatic plants may play an
important role in the life of fish.
Juvenile sockeye salmon, Oncorhynchus nerka, responded by evoking
exploratory and feeding behavior to aqueous extracts of foods to which
they had been previously conditioned but failed to respond to similar
foods which had not previously been in their diet ( McBride e t al., 1962).
Responses were characterized by breaking up of the school, increased
swimming speeds, and swimming into lighted areas. Fish probably became conditioned to some component( s ) of their foods, but they might
be attracted by extracts of foods that they had not previously ingested.
As already mentioned, such a complicated feeding behavior is accomplished by successively separated individual behaviors. For instance, once
a fish has found food by visual, mechanical, or chemical clues, it may
still have to test before eating it. Various environmental stimuli are
integrated in the central nervous system, probably hypothalamus, and
subsequently organized into a unified expression of the behavior. Electrical stimulation of olfactory areas in the central nervous system of goldfish elicited stereotyped feeding activity indistinguishable from normally
induced behavior ( Grimm, 1960). Stimulation of vagal lobes produced
no feeding arousal. It is suggested that the olfactory rather than the
peripheral gustatory system plays the predominant role in the arousal of
feeding activity. Further studies of the central integration of feeding behavior are to be encouraged.
B. Reproductive Behavior and Chemical Senses
In contrast to work with visual cues, the role of chemical senses in
reproductive behavior has been poorly investigated. The role of chemical
105
movements; this resulted in continuous and characteristic courses in the
form of figure eight. Dogfish with one nostril occluded found the food by
predominant movements toward the side of the open nostril. Their movements were essentially circular in such a way that the open nostril is
toward the center of the circle. Parker explained these movements on the
basis of the osmotropotaxis as in the circus movements of invertebrates.
Gilbert et al. (1964) reported that electrical potential recorded from the
forebrain reflected olfactory processes in three species of sharks ( N e -
gaprion, Sphyrw, and Ginglymostom) . Both the amplitude and frequency of the potential clearly increased during chemical stimulation of
the olfactory sac with extracts of crabs and tuna.
Blinded bluntnose minnows, Hyborhynchus notatus, were able to
discriminate odors of aquatic plants at extreme dilutions. They also could
discriminate between odors of certain aquatic invertebrates ( Hasler,
1957). These findings support the view that aquatic plants may play an
important role in the life of fish.
Juvenile sockeye salmon, Oncorhynchus nerka, responded by evoking
exploratory and feeding behavior to aqueous extracts of foods to which
they had been previously conditioned but failed to respond to similar
foods which had not previously been in their diet ( McBride e t al., 1962).
Responses were characterized by breaking up of the school, increased
swimming speeds, and swimming into lighted areas. Fish probably became conditioned to some component( s ) of their foods, but they might
be attracted by extracts of foods that they had not previously ingested.
As already mentioned, such a complicated feeding behavior is accomplished by successively separated individual behaviors. For instance, once
a fish has found food by visual, mechanical, or chemical clues, it may
still have to test before eating it. Various environmental stimuli are
integrated in the central nervous system, probably hypothalamus, and
subsequently organized into a unified expression of the behavior. Electrical stimulation of olfactory areas in the central nervous system of goldfish elicited stereotyped feeding activity indistinguishable from normally
induced behavior ( Grimm, 1960). Stimulation of vagal lobes produced
no feeding arousal. It is suggested that the olfactory rather than the
peripheral gustatory system plays the predominant role in the arousal of
feeding activity. Further studies of the central integration of feeding behavior are to be encouraged.
B. Reproductive Behavior and Chemical Senses
In contrast to work with visual cues, the role of chemical senses in
reproductive behavior has been poorly investigated. The role of chemical