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TOSHIAKI J. H A M
factors was described in the courtship behavior of the catfish Ameiurm
by Breder ( 1935), and of gobiid fish Bathygobius by Tavolga (1956).
Bathygobius males showed courtship behavior in response to the introduction of a small amount of the water in which a gravid female had
been placed for a few minutes. Of various internal body fluids tested only
the ovarian fluid elicited a courtship response at extreme dilutions.
Whether the stimulating ovarian substance is secreted by the eggs or the
ovary has not been determined. The male detected the rapidly diffusing
substance by the olfactory sense, since anosmic males whose nostrils were
plugged failed to respond to any amount of the courtship-stimulating
substance ( Tavolga, 1956).
Furthermore, it was demonstrated that anosmic males tended to show
fighting behavior and that castrated males never exhibited such behavior
(Tavolga, 1956). These results may indicate that the olfactory stimulus
by the ovarian substance not only elicits courtship but inhibits fighting.
It is also possible that the male sex hormone affects the sensitivity of the
olfactory organs in some ways. In this connection, it has been shown that
aff erent-evoked bulbar electrical responses produced by NaCl infusion
into the olfactory sac and by electrical stimulation of the olfactory
epithelium in goldfish were markedly influenced by administrations of
sex hormones (Hara, 196713; Oshima and Gorbman, 1968, 1969).
C. Discrimination of Body Odors and Schooling
Wrede (1932) apparently was the first to demonstrate that a minnow
has an individual body odor recognizable by other members of the same
species. GO, (1941) later trained the blinded minnow to discriminate
the body odor of the catfish Ameiurus and proved that minnows could
no longer discriminate the odor after the olfactory lobes were removed.
The minnows could be trained to discriminate the body odors of 15 different species of fish from eight families; they could also recognize odors
of different individuals of their own species. Furthermore, they could
specifically discriminate olfactorily between two different species of frogs
( R a m esculenta and R. temporaria) and between two species of salamanders ( Triturus and Salamandra) , but they could not discriminate between
two individuals within the same amphibian species. Yellow bullheads,
Ictalurus notatus, also recognized individuals of their own species by
means of intraspecific chemical stimuli (Todd et al., 1967). Through
conditioning, blinded bullheads were able to discriminate between the
odors of two donor fish, but they lost this ability when deprived of their
sense of smell. The main source of the intraspecific chemical stimuli in-
TOSHIAKI J. H A M
factors was described in the courtship behavior of the catfish Ameiurm
by Breder ( 1935), and of gobiid fish Bathygobius by Tavolga (1956).
Bathygobius males showed courtship behavior in response to the introduction of a small amount of the water in which a gravid female had
been placed for a few minutes. Of various internal body fluids tested only
the ovarian fluid elicited a courtship response at extreme dilutions.
Whether the stimulating ovarian substance is secreted by the eggs or the
ovary has not been determined. The male detected the rapidly diffusing
substance by the olfactory sense, since anosmic males whose nostrils were
plugged failed to respond to any amount of the courtship-stimulating
substance ( Tavolga, 1956).
Furthermore, it was demonstrated that anosmic males tended to show
fighting behavior and that castrated males never exhibited such behavior
(Tavolga, 1956). These results may indicate that the olfactory stimulus
by the ovarian substance not only elicits courtship but inhibits fighting.
It is also possible that the male sex hormone affects the sensitivity of the
olfactory organs in some ways. In this connection, it has been shown that
aff erent-evoked bulbar electrical responses produced by NaCl infusion
into the olfactory sac and by electrical stimulation of the olfactory
epithelium in goldfish were markedly influenced by administrations of
sex hormones (Hara, 196713; Oshima and Gorbman, 1968, 1969).
C. Discrimination of Body Odors and Schooling
Wrede (1932) apparently was the first to demonstrate that a minnow
has an individual body odor recognizable by other members of the same
species. GO, (1941) later trained the blinded minnow to discriminate
the body odor of the catfish Ameiurus and proved that minnows could
no longer discriminate the odor after the olfactory lobes were removed.
The minnows could be trained to discriminate the body odors of 15 different species of fish from eight families; they could also recognize odors
of different individuals of their own species. Furthermore, they could
specifically discriminate olfactorily between two different species of frogs
( R a m esculenta and R. temporaria) and between two species of salamanders ( Triturus and Salamandra) , but they could not discriminate between
two individuals within the same amphibian species. Yellow bullheads,
Ictalurus notatus, also recognized individuals of their own species by
means of intraspecific chemical stimuli (Todd et al., 1967). Through
conditioning, blinded bullheads were able to discriminate between the
odors of two donor fish, but they lost this ability when deprived of their
sense of smell. The main source of the intraspecific chemical stimuli in-