3. FISH PROLACTIN AND GROWTH HORMONE
221
cated in brood patch production, pigeon crop sac development (for feeding the young), promotion of broodiness, and suppression of gonadal
activity (see Parkes and Marshall, 1960; Lehrman, 1961, 1963; Riddle,
1963a); in general, it seems to promote parental care and behavior in
mammals ( Riddle, 1963a,b), including, of course, lactation ( Meites and
Nicoll, 1966). Because of this background information from work on
higher vertebrates, many investigators have been predisposed to expect
that prolactin might promote parental behavior in lower vertebrates. One
result of this predisposition was the incorrect interpretation that Noble
et al. (1936, 1938) had shown prolactin to promote parental behavior in
a cichlid mouthbrooding fish, Hemichromys (see Pickford and Atz, 1957).
More recent investigators have reported that prolactin protects the embryos of the viviparous cyprinodont Gambusiu from the deleterious effects
of injected estradiol benzoate (Ishii, 1961; Egami and Ishii, 1962). Contrary to the statement by Egami and Ishii (1962), Ishii (1960) did not
demonstrate the importance of prolactin in the maintenance of gestation
in the viviparous embiotocid fish, Neoditrema; this is just one out of several possible interpretations of his data. It is premature to argue from
these observations on intact fish that fish prolactin plays some physiological role in gestation in viviparous teleosts, since it is possible that the
results actually reveal peripheral interactions between estrogen and exogenous prolactin rather than pointing up any normal role of fish prolactin. The pituitary is certainly not necessary to maintain gestation in
P. htipinnu and P. fomnosa (Ball, 1962, 1968), nor, apparently, in
Gum(Chambolle, 1966, 1967a), despite earlier claims to the contrary ( Chambolle, 1964).
A distinct stimulation of a component of parental behavior by prolactin has been reported by Fiedler ( 1962) and Bliim and Fiedler ( 1965).
Certain cichlid fishes exhibit characteristic parental care behavior in
which they fan their eggs by movements of the pectoral fins; during this
phase, the tendency to fight is depressed and the appetite reduced. Injections of ovine prolactin at low doses, in the absence of eggs, elicited
fanning behavior in intact fish, directed toward a definite point as though
toward eggs. Prolactin simultaneously inhibited fighting behavior and
feeding. These effects of prolactin were opposed by gonadotropins (FSH,
LH, and HCG), and higher doses of prolactin actually inhibited fanning
behavior. In contrast to this work on cichlids, the similar parental egg
fanning in Gasterosteus was not induced by prolactin treatment (R. J. F.
Smith and Hoar, 1967). However, R. J. F. Smith and Hoar (1967) emphasize the possibility raised by work from their laboratory on prolactin
and ionic regulation (Section I, B, Gasterosteus) that fish prolactin codd
be a causal in promoting the movement of this fish from the sea to fresh-
221
cated in brood patch production, pigeon crop sac development (for feeding the young), promotion of broodiness, and suppression of gonadal
activity (see Parkes and Marshall, 1960; Lehrman, 1961, 1963; Riddle,
1963a); in general, it seems to promote parental care and behavior in
mammals ( Riddle, 1963a,b), including, of course, lactation ( Meites and
Nicoll, 1966). Because of this background information from work on
higher vertebrates, many investigators have been predisposed to expect
that prolactin might promote parental behavior in lower vertebrates. One
result of this predisposition was the incorrect interpretation that Noble
et al. (1936, 1938) had shown prolactin to promote parental behavior in
a cichlid mouthbrooding fish, Hemichromys (see Pickford and Atz, 1957).
More recent investigators have reported that prolactin protects the embryos of the viviparous cyprinodont Gambusiu from the deleterious effects
of injected estradiol benzoate (Ishii, 1961; Egami and Ishii, 1962). Contrary to the statement by Egami and Ishii (1962), Ishii (1960) did not
demonstrate the importance of prolactin in the maintenance of gestation
in the viviparous embiotocid fish, Neoditrema; this is just one out of several possible interpretations of his data. It is premature to argue from
these observations on intact fish that fish prolactin plays some physiological role in gestation in viviparous teleosts, since it is possible that the
results actually reveal peripheral interactions between estrogen and exogenous prolactin rather than pointing up any normal role of fish prolactin. The pituitary is certainly not necessary to maintain gestation in
P. htipinnu and P. fomnosa (Ball, 1962, 1968), nor, apparently, in
Gum(Chambolle, 1966, 1967a), despite earlier claims to the contrary ( Chambolle, 1964).
A distinct stimulation of a component of parental behavior by prolactin has been reported by Fiedler ( 1962) and Bliim and Fiedler ( 1965).
Certain cichlid fishes exhibit characteristic parental care behavior in
which they fan their eggs by movements of the pectoral fins; during this
phase, the tendency to fight is depressed and the appetite reduced. Injections of ovine prolactin at low doses, in the absence of eggs, elicited
fanning behavior in intact fish, directed toward a definite point as though
toward eggs. Prolactin simultaneously inhibited fighting behavior and
feeding. These effects of prolactin were opposed by gonadotropins (FSH,
LH, and HCG), and higher doses of prolactin actually inhibited fanning
behavior. In contrast to this work on cichlids, the similar parental egg
fanning in Gasterosteus was not induced by prolactin treatment (R. J. F.
Smith and Hoar, 1967). However, R. J. F. Smith and Hoar (1967) emphasize the possibility raised by work from their laboratory on prolactin
and ionic regulation (Section I, B, Gasterosteus) that fish prolactin codd
be a causal in promoting the movement of this fish from the sea to fresh-