AMER. ZOOL., 21:305-316 (1981)
Hormonal Regulation of Female Reproductive Behavior in Fish1
NORMAN EDWARD STACEY
m
Department of Zoology, University of Alberta,
Edmonton, Alberta T6G 2E9
SYNOPSIS. Fundamentally different mechanisms regulate female sexual behavior in the
ovoviviparous guppy and the oviparous goldfish. In the female guppy, ovarian estrogen
evidently synchronizes cycles of sexual receptivity with endogenous cycles of ovarian maturation and also increases female attractivity at the time of maximum receptivity by stimulating the release of a sexual pheromone. In the goldfish, it appears that prostaglandin,
released from the ovary or oviduct in conjunction with ovulation and the presence of
ovulated eggs, acts on the brain to stimulate spawning behavior. In contrast to the situation
in the guppy, steroid treatments alone (in the absence of ovulated eggs) fail to stimulate
spawning behavior in the goldfish. It is proposed that endocrine mechanisms regulating
female sexual behavior in the teleosts and in other vertebrates are less related to phylogeny
than to the mode of reproduction employed. In the goldfish and several other externally
fertilizing teleosts, where sexual behavior involves oviposition, female sexual behavior
apparently is synchronized with ovulation by mechanisms which respond to elevated plasma prostaglandin as an indicator of the presence of ovulated eggs. In internally fertilizing
species (guppy, reptiles, birds, mammals), where sexual behavior and fertilization are
temporally dissociated, female sexual behavior is synchronized with ovulation by mechanisms which anticipate either an imminent spontaneous ovulation, or the potential for
reflex ovulation, by responding to increases in plasma estrogen associated with follicular
development.
behavior occurs. For example, in female
goldfish and other externally fertilizing
vertebrates, sexual behavior and the release of oocytes are concurrent events. In
oviparous lizards and birds, and in ovoviviparous guppies and viviparous mammals, the advent of internal fertilization
has been accompanied by an advancement
in the occurrence of sexual behavior in relation to oocyte maturation and ovulation.
Thus, as the female role in reproduction
changed from donator of oocytes (external
fertilization) to recipient of sperm (internal fertilization), female sexual behavior
became temporally dissociated from both
fertilization and the expulsion of sexual
products. In contrast, the persistent role of
the male as gamete donator has necessitated a close temporal relation between sexual behavior and gamete release in all male
vertebrates.
As with the Amphibia, teleosts reproduce by both external and internal fertilization, and can be expected to present a
greater diversity of mechanisms regulating
female sexual behavior than is seen in reptiles,
birds or mammals. Although much is
1
From the Symposium on Social Signals—Compar- known of the reproductive physiology of
ative and Endocrine Aspects presented at the Annual
Meeting of the American Society of Zoologists, 27— teleosts (Billard and Marcel, 1978; Peter
and Crim, 1979), relatively little is under30 December 1979, at Tampa, Florida.
INTRODUCTION
The essential function of mechanisms
regulating female sexual behavior in vertebrates is to optimize the fertilization of
oocytes by synchronizing mating with the
appropriate stage of oocyte development.
How this synchrony is achieved likely will
be influenced by the stage of gamete development at which sexual behavior occurs. In the course of vertebrate evolution,
the presumed ancestral mode of reproduction, external fertilization, has given
rise a number of times to internal fertilization associated with oviparity, viviparity,
etc. However, regardless of the strategy
employed, formation and fate of the oocytes involves a similar series of stages: pituitary-stimulated development, ovulation,
a period of retention of oocytes or embryos within the body cavity or reproductive tract, and finally the expulsion of eggs
or fetuses. What has changed with the evolution of internal fertilization is the stage
at which the male intervenes and sexual
305
306
NORMAN EDWARD STACEY
stood of the endocrine control of female role of ovarian estrogen in inducing sexual
sexual behavior in this group. Liley (1969, responsiveness. In earlier work, the recov1979) and Crews and Silver (1979) have ery of receptivity in ovariectomized, but
reviewed the relevant literature in this area not in hypophysectomized, females led Liland I will not attempt to duplicate their ey (1968) to hypothesize that gonadotrowork. Rather, this paper considers in some pin or other pituitary hormones may pla£
detail studies of female sexual behavior in a direct role in stimulating sexual behavtwo teleosts, the goldfish (Carassius auratus) ior. Further studies (Liley and Donaldson,
and the guppy {Poecilia reticulata), and syn- 1969; Liley, 1972), although failing to conthesizes this information in view of endo- firm this hypothesis, demonstrated an uncrine mechanisms believed to regulate fe- expected aspect of the control of sexual
male sexual behavior in other teleosts and receptivity in the guppy.
in other vertebrate classes. I hope this apWhen first exposed to courting males, a
proach will encourage further study of the large proportion of naive virgin females
hormonal control of sexual behavior in fe- are highly receptive (Liley and Wishlow,
male teleosts and stimulate consideration 1974). Even when insemination is preof the evolution of the endocrine control vented by using gonopodectomized males,
of sexual behavior in female vertebrates.
receptivity declines rapidly after several
brief exposures. Furthermore, naive virgin
females first exposed to gonopodectomized males as late as 24 days after ovarHORMONAL CONTROL OF SEXUAL BEHAVIOR
iectomy also displayed initially high levels
IN FEMALE TELEOSTS
of receptivity which declined rapidly with
Receptivity and attractivity in the guppy
repeated courtship experience. However,
In the ovoviviparous female guppy, in in contrast to intact virgin females, there
which fertilization is intrafollicular and was no reappearance of receptivity in the
ovulation occurs just prior to parturition, habituated, ovariectomized virgin females.
sexual behavior involves approaching or From these results, it is apparent that the
gliding toward a displaying male, arching naive virgin female guppy displays an iniof the body in the vertical plane, and tially high level of receptivity which masks
wheeling in small circles as the male at- the cycle of receptivity regulated by the
tempts copulation (Liley and Wishlow, ovary (Liley and Wishlow, 1974). Evident1974). Successful copulation occurs when ly, this initial receptivity does not depend
the male deposits spermatophores in the on ovarian or pituitary hormones either
female's genital pore by means of the gon- for maintenance prior to, or habituation
following, exposure to male courtship.
opodium, a modified anal fin.
There is good evidence that the female
Female guppies display cycles of sexual
receptivity which are correlated with cycles guppy releases a pheromone which atof ovarian activity. Maximum receptivity tracts males and stimulates male courtship
occurs shortly after parturition at a time of (Crow and Liley, 1979). Given a choice beactive steroidogenesis associated with vitel- tween water in which females have been
logenesis in the next crop of oocytes (Liley, kept and water in which either male gup1966; Liley and Wishlow, 1974; Lambert, pies or no fish have been kept, male gup1970). Partially purified salmon gonado- pies prefer "female water"; no preference
tropin (SG-G100) restores receptivity in is shown for water from ovariectomized
hypophysectomized but not in hypophy- females. As males are more attracted to
sectomized-ovariectomized females, sug- water from early postpartum females than
gesting ovarian involvement in the regu- to water from ovariectomized or midgeslation of sexual responsiveness (Liley and tation females, Crow and Liley suggest that
Donaldson, 1969). The finding that estra- a pheromone produced in the ovary, or
diol restores receptivity in hypophysec- under ovarian control, synchronizes maxtomized and ovariectomized females (Lil- imum attractivity with maximum receptivey, 1972) further supports this suggested ity. This suggestion is supported by the
HORMONES AND SEX BEHAVIOR IN FEMALE FISH
finding that addition of water from hypophysectomized females treated with
either gonadotropin or estradiol increased
courtship by males of ovariectomized females, whereas water from estrogen-treat0 d , ovariectomized females was ineffective
(H. Meyer and N. R. Liley, unpublished
results).
In summary, cycles of ovarian estrogen
production appear to stimulate and synchronize cycles of sexual receptivity and
attractivity in the female guppy. Cycles of
receptivity are not evident in naive virgin
females which respond to male courtship
regardless of the stage of the ovarian cycle.
Whether ovarian steroids normally initiate
receptivity in naive virgin females is not
known; however, it is clear that naive fish
remain in a receptive state following ovariectomy. Repeated courtship experience
reduces the sexual responsiveness of naive
virgins, allowing expression of a cycle of
receptivity regulated by an endogenous
cycle of ovarian activity.
Female spawning behavior in the goldfish
In goldfish, spawning behavior (behavior associated with oviposition) usually extends over several hours and involves persistent chasing of an ovulated female by
the male(s), interspersed with as many as
several hundred spawning acts. A spawning act is initiated when the female approaches floating vegetation in a head-up
position, the male in contact with the female but slightly behind and below. As
they enter the vegetation, both fish turn
on their sides and then swim rapidly
through a short arc, usually breaking the
water surface. Eggs and milt are released
at this time and the fertilized eggs adhere
to the vegetation.
Spawning behavior in the female goldfish is closely linked with ovulation. During
spontaneous ovulation at 20°C on a
16L:8D photoperiod, serum gonadotropin
levels increase rapidly during the latter
part of the light phase and remain high
through the time of follicular rupture,
which occurs during the latter half of the
dark phase. Within several hours of the
onset of light, levels of serum gonadotropin have decreased markedly from those
307
at the time of ovulation (Stacey et al.,
1979). Females that have ovulated begin to
spawn at the onset of light provided a sexually active male and aquatic vegetation
are present.
The close temporal correlation between
ovulation and the onset of spawning behavior is due to the stimulatory effect of
ovulated eggs within the ovarian lumen
and oviduct. Female spawning behavior,
which normally ceases when all ovulated
eggs have been shed, may be terminated
prematurely by hand-stripping the ovulated eggs (Yamazaki, 1965), and restored in
stripped females by injecting ovulated eggs
through the ovipore and into the oviduct
and ovarian lumen (Stacey and Liley,
1974). Females injected with ovulated eggs
often fail to spawn if water has entered the
ovipore (Stacey, 1977); the eggs in this case
become hard and adhesive, changes which
normally occur within seconds of oviposition. Substitutes for ovulated eggs (gelatin,
petroleum jelly), though less effective than
ovulated eggs, do induce spawning behavior in some females (Stacey, 1977).
Female goldfish with ovaries in any stage
of vitellogenesis begin to spawn within several hours of an injection of ovulated eggs.
However, females with regressed ovaries
containing only previtellogenic oocytes fail
to spawn following egg injection; high doses of estradiol (Stacey and Liley, 1974) and
other steroids (Stacey, 1977) restore responsiveness to ovulated eggs in these regressed fish. The spawning response to injection of ovulated eggs is abolished by
hypophysectomy, and restored in hypophysectomized fish by treatment with
salmon gonadotropin (SG-G100). In contrast, estradiol and other steroids are completely ineffective in restoring responsiveness to egg injection in hypophysectomized
fish (Stacey, 1977). Thus, while there is evidence that steroids may play a role in inducing responsiveness to ovulated eggs,
the nature of this role remains to be determined.
The stimulatory effect of ovulated eggs
on spawning behavior appears to be mediated by prostaglandin (PG). Indomethacin, an inhibitor of PG synthesis, completely inhibits spawning behavior in
308
NORMAN EDWARD STACEY
females which have ovulated (unpublished
results) and in unovulated females injected
with ovulated eggs (Stacey, 1976). In females injected with ovulated eggs and indomethacin, a high dose of prostaglandin
F2a (PGF2a) restores normal spawning behavior, while PGE2 is less effective and
PGE, is ineffective (Stacey, 1976). PG also
induces spawning behavior in fish which
do not have ovulated eggs in the ovaries,
suggesting that ovulated eggs stimulate the
synthesis of PG which in turn induces
spawning behavior. In unanesthetized
fish, intramuscular PGF2a injection can induce spawning in several minutes, and
doses as low as 1 ng/g body weight can be
effective (unpublished results).
Removal of the ovipore, oviduct, and
posterior portions of the ovaries failed to
influence the behavioral response to
PGF 2a , demonstrating that these peripheral sites do not mediate PG stimulation of
spawning behavior. Furthermore, injection of 10 ng/g PGF2a into the preoptic recess of the third ventricle induced a much
greater spawning response with a shorter
latency than did the same dose of PGF2a
given intramuscularly or intraperitoneally
(Stacey and Peter, 1979). These findings
indicate that PG acts within the brain to
stimulate female spawning behavior.
The source of PG involved in spawning
behavior is not known; however, indirect
evidence suggests it may be produced by
the ovaries or oviduct. Both in hCG-treated females (Stacey and Pandey, 1975) and
in females undergoing a spontaneous, preovulatory gonadotropin surge (N. E. Stacey, A. F. Cook, and R. E. Peter, unpublished results), follicular rupture is blocked
by indomethacin. PG overcomes indomethacin blockade of ovulation only when
given just prior to the expected time of
follicular rupture, suggesting that PG synthesis may normally increase at this time
(Stacey and Pandey, 1975). Direct support
for this idea has been provided by Bouffard (1979) who has found that at ovulation in hCG-treated goldfish plasma levels
of PGF 2 Q increased about sixfold (to approximately 1.8 ng/ml) over those prior to
ovulation. At the same time, the concentration of PGFo_ in the ovarian fluid bath-
ing the ovulated eggs was much higher
than in the plasma, suggesting the ovaries
or oviduct may have been the source of the
increased plasma PGF2a levels. In contrast
to the females which ovulated, hCG-treated females which did not ovulate showe^
no changes in plasma PGF2a levels. By 12
hr after ovulation, plasma PGF2n levels increased further in fish retaining ovulated
eggs, but decreased to preovulatory levels
in fish from which ovulated eggs had been
removed, suggesting postovulatory retention of ovulated eggs maintains PG synthesis. Of the three PGs (PGF2n, PGE,, PGB,)
measured by Bouffard, only PGF2n increased in the plasma at ovulation. PGE,,
which is less potent than PGF2a in stimulating spawning behavior (Stacey, 1976;
Stacey and Peter, 1979), decreased in the
plasma following hCG injection.
Partridge et al. (1976) showed clearly
that male goldfish placed with one ovulated and one unovulated female spend more
time courting the ovulated fish. My work
confirms this finding and also demonstrates that males preferentially court PGtreated females. Pairs of female goldfish
were placed in 60-liter aquaria containing
one sexually active male and the total
amount of male courtship directed toward
each female was recorded for 40 min following the onset of male sexual activity.
Five treatment groups were used: one ovulated and one unovulated female placed in
the male's aquarium when vegetation was
present (group 1) or absent (group 2); one
PGF2a-treated (0.1 Mg/g) and one salinetreated female placed with the male with
(group 3) or without (group 4) vegetation;
one PGF2a-treated and one ovulated female placed with the male when vegetation
was absent (group 5). All males courted
actively for at least ninety percent of the
test period. As in the study of Partridge et
al. (1976), males presented with one ovulated and one unovulated female showed
a significant preference for the ovulated
female when vegetation was present and
spawning occurred (Fig. 1). Even when
vegetation was absent and the ovulated female therefore did not spawn, males still
preferred the ovulated fish. In the same
test situations (with and without vegeta-
309
HORMONES AND SEX BEHAVIOR IN FEMALE FISH
75'
T
T
I
20-
•
MALES
T
S
2 50'
5
-
o
S
" \
H
(A
o 10-|
<0
25
O)
c
'c
i
8 | |10
—
Q.
V)
V NV
"*V NV
A3
E
male courts - • OV
vs
^
PG
vs
PG
vs
OV
UNOV
SAL
FIG. 1. Courtship behavior of male goldfish exposed
to pairs of females for 40 min. Data expressed as
percentage (mean ± SE) of total courtship time males
courted female indicated by arrow. V (vegetation
present during test), NV (vegetation absent), OV
(ovulated female), UNOV (unovulated female), PG
(female injected with 100 ng/g PGF2<)), SAL (saline
injected female). Number of tests shown in each bar.
•kP < .05, -k-kP < .01 (Mest using transformed percentages).
tion), males presented with one PGF2cr-injected and one saline-injected female
showed significant preference for the PGtreated females. When tested in the absence of vegetation with two sexually active
females, one ovulated and one PG-treated,
males showed no preference. In all five
treatment groups, males almost always terminated courtship of one female by initiating courtship of the second, and thus
directed similar numbers of courtship
bouts toward each female of a pair. Male
preference was therefore due to a greater
tendency to maintain, rather than to initiate, a bout of courtship. Partridge et al.
(1976) reported similar results.
Their findings that males in a Y-maze
respond positively to water in which either
ovulated females or ovulated eggs have
been kept, and that anosmic males show
greatly reduced courtship of ovulated females, led Partridge et al. (1976) to conclude that an ovarian pheromone released
at ovulation plays the major role in the
PG
4)
_
20-|
FEMALES
E
•i
3
C
C
(0
10-
•o
Xi
A
E
\
PG
30
I
90
150
minutes post-injection
FIG. 2. Median number of female spawning acts
performed by male (n = 12) and female (n = 12)
goldfish following intramuscular injection of 4
(•—•), 20 (A—A), and 100 (•—•) ng/g PGF2(I.
male's ability to distinguish females that
have ovulated from those that have not.
However, as anosmia also drastically reduces the male's tendency to court either
unovulated females or other males (neither of which is likely to produce an ovulation pheromone), it is questionable
whether the reduced courtship behavior
displayed by anosmic males is good evidence for a pheromone specific to ovulated females (N. E. Stacey and A. L. Kyle,
unpublished results).
Male preference for PG-treated females
may result from PG-stimulated release of
an olfactory stimulant, or from some PGinduced change in female behavior. Al-
310
NORMAN EDWARD STACEY
160
In three tests on alternate days, sexually
mature male and female goldfish were injected intramuscularly (without anesthesia)
•5
Q)
with 20, 4, and 100 ng/g PGF2a, placed im3 120
mediately in 60-liter test aquaria contain3
females
males
ing one sexually active stud male an<^
u
aquatic vegetation, and observed for feco
O)
male spawning behavior for 150 min. Both
E 80
males and females performed significantly
c
more female spawning acts with each ineg
a
crement in PG dosage (Figs. 2, 3), and at
co
each dose the number of female spawning
* 40
acts performed by males was similar to that
co
performed by females. However, at the
a> 2 0 '
high dose, 9 of 12 males, but only 3 of 12
females, were spawning at the end of the
4 20 100 4 20 100 test period, suggesting that had a longer
test been used, males would have shown a
significantly
greater response than fePGF
(ng/g)
2a
males.
At
all
three
doses, males performed
FIG. 3. PGF2a-induced female spawning behavior in
male and female goldfish. Incompleted female significantly more incomplete female
spawning acts (median) shown in clear bars. Com- spawning acts (partial entries into the
pleted acts (median) shown in shaded bars.
vegetation, accompanied by the stud male,
which did not lead to a spawning act) than
did the females (Fig. 3). Whether this difthough the former possibility has not been ference resulted from inappropriate beinvestigated, it is clear that both ovulated havior of the test male, stud male, or both
females and PG-treated females exhibit is not known.
behaviors which may advertise their recepIn summary, PG appears to play an estivity and thereby increase their attractive- sential role in female spawning behavior in
ness to males. First, in situations where the goldfish. Indirect evidence indicates
males perform little courtship behavior, that PG, perhaps synthesized by the ovaovulated and PG-treated females often ac- ries or oviduct in conjunction with ovulatively solicit male courtship (Partridge et tion and the presence of ovulated eggs,
al., 1976; Stacey, 1977). This proceptive enters the circulation and then acts on the
behavior did not contribute to the prefer- brain to trigger spawning behavior. Alences reported in Figure 1 as all males though the possibility remains that genital
were highly active; however, it may have tract distension at ovulation also might
contributed to the preference of anosmic generate neural input stimulating spawnmales for ovulated females reported by ing behavior, it is clear that even in the
Partridge et al. Second, unreceptive fe- absence of ovulated eggs spawning behavmales (females which have neither ovulat- ior can be induced by doses of injected PG
ed nor received PG treatment) generally which apparently are within the physiologdisplay more vigorous escape behavior in ical range. Estradiol restores responsiveresponse to male courtship and for this ness to injection of ovulated eggs in intact
reason may be involved in shorter court- females with regressed ovaries. However,
ship bouts. An increase in evasiveness as steroid treatments are ineffective in reoften is seen at the conclusion of normal storing the spawning response to injection
spawning when a female has released all of eggs or PG in hypophysectomized fish
ovulated eggs (Stacey, 1977).
(Stacey, 1976, 1977), it is uncertain whether
steroids play any direct role in spawning
Injection of PGF2a in male goldfish induces female spawning behavior which ap- behavior. The demonstration of PG-inpears indistinguishable from that per- duced female spawning behavior in male
formed by females (unpublished results). goldfish provides exciting possibilities for
c
n>
1
HORMONES AND SEX BEHAVIOR IN FEMALE FISH
further research into the regulation of sexual behavior in this species.
The spawning reflex in cyprinodonts
In the oviparous cyprinodont fishes, inc l u d i n g Fundulus heteroclitus (Wilhelmi et
al., 1955), Oryzias latipes (Egami, 1959),
and Jordanella floridae (Crawford, 1975),
injection of a variety of neurohypophyseal
hormones (NHHs) induces a spawning reflex. It should be noted, however, that
NHHs do not have this effect in several
other teleost species (Liley, 1969, 1979).
The spawning reflex in Fundulus has been
compared to the flexures of body and fins
serving to lock a pair together during gamete release. As described by Macey et al.
(1974), the response in Fundulus involves
"an S-shaped flexure, and quivering of the
body, with dorsal and anal fins flattened to
one side and ending with a 'kick' that results from a flick of the tail, propelling the
fish forward in a quick dart movement."
In addition, treated fish may show behaviors (egg-eating, clinging to vertical surfaces) usually associated with natural
spawning. In Fundulus, the response to injection of NHHs usually commences within 30 min, is similar in males and females,
and is unaffected by gonadectomy or hypophysectomy (Wilhelmi et al., 1955).
Early studies of the spawning reflex in
Fundulus demonstrated that teleost pituitary preparations induced the response,
but that only pharmacological doses of the
mammalian peptides arginine vasopressin
and oxytocin were effective (Wilhelmi et
al., 1955). Pickford and Strecker (1977),
using intraperitoneal injections, have
shown that the potency of arginine vasotocin is equivalent to that of vasopressin,
while isotocin is the least effective of the
four NHHs tested. Macey et al. (1974) hypothesized that an action of NHHs on the
brain could account for the pharmacological systemic doses required to elicit the
spawning reflex; their finding that electrolytic lesion of the nucleus preopticus in
Fundulus abolished the spawning reflex induced by NHH injection provided indirect
support for this suggestion. However, apparently even if arginine vasotocin is administered centrally, the effective dose is
similar to that required peripherally (Pick-
311
ford and Knight, unpublished results cited
in Peter, 1977).
A puzzling aspect of the spawning reflex
is the absence of behavioral coordination
between the sexes that is typical of normal
spawning. Assuming NHHs play a physiological role in cyprinodont spawning behavior, several explanations could account
for this finding. First, NHHs may normally
function only to induce a spawning reflex
in a pair brought together through performance of prespawning behaviors; injection of NHHs, by bypassing the behaviors
necessary for coordinating the activities of
male and female, might thus induce the
spawning reflex out of context. Second,
NHHs might induce only male behavior.
During normal spawning in Fundulus, the
body flexures of male and female are similar, while the positions of the fins in the
two sexes apparently are different. In the
male, the dorsal and anal fins are deflected
laterally so as to embrace the female, while
in the female the anal fin "extends at nearly right angles from the belly" (Newman,
1907); Able and Castagna (1975) also observed this orientation of the anal fin in
spawning female Fundulus. Thus, the lateral deflection of dorsal and anal fins by
both sexes in response to NHH injection
(Macey et al., 1974) suggests that both male
and female may be showing male spawning behavior, a situation in which lack of
coordination of injected fish might be expected.
In Jordanellafloridae,sexual behaviors of
male and female differ both in the prespawning period and during the spawning
act (Foster et al., 1969; Crawford, 1975).
Thus, it is interesting that whereas female
Jordanella injected with PGF2n or oxytocin
exhibited caudal and anal fin flexures similar to those seen in female spawning behavior, males injected with oxytocin displayed a rigid S-shaped body flexure
similar to that shown when clasping a female (Crawford, 1975). As in Fundulus injected with NHHs, male or ovulated female Jordanella injected with oxytocin or
PGF2a showed no behavioral coordination
with appropriate spawning partners.
Sexual behavior in female cyprinodonts
normally is seen only after ovulation (Newman, 1907; Egami, 1959; Crawford, 1975).
312
NORMAN EDWARD STACEY
Whether the presence of ovulated eggs induces sexual behavior in these species, as
in the goldfish, is not known; however,
Crawford's work with Jordanella (see following section) indicates this is likely. The
behavioral effects of NHHs on cyprinodonts cannot be ignored. However, the
pharmacological doses required to elicit
the spawning reflex and the failure of
treated fish to coordinate their behaviors
with sexual partners raise questions as to
the relationship of the spawning reflex to
normal spawning behavior. Hopefully,
further studies will follow Crawford's lead
by attempting to manipulate female sexual
behavior in the normal spawning situation.
Comparison of mechanisms regulating female
sexual behavior in teleosts
plasma PGF2a levels increase at ovulation.
In contrast, the female guppy is either sexually unreceptive, during much of the
ovarian cycle, or sexually receptive, in the
immediate postpartum period.
It is not known whether endocrine con^
trol of female sexual behavior in the guppy^
is typical of live-bearing teleosts. However,
Carlson (1969) reports a cycle of receptivity in Gambusia which corresponds roughly
to the gestation cycle. On the other hand,
in several oviparous teleosts two aspects of
the regulation of female sexual behavior—
the temporal relation between ovulation
and spawning, and the role of PG—may
be similar to the goldfish system.
In oviparous, externally fertilizing teleosts, ovulation necessarily precedes
spawning or oviposition behavior. This
temporal relationship has been emphasized by Liley (1969, 1979); however, with
the exception of studies on the goldfish, a
causal relationship between these two
events has received little attention. Crawford (1975) suggests that in Jordanella ovulated eggs in the ovarian lumen stimulate
the female's positive responses to male
courtship which quickly lead to T-circling,
a prespawning behavior; passage of oocytes from ovarian lumen to oviduct during T-circling may then induce nudging of
the male by the female, a behavior which
usually induces the male to clasp the female. In the three-spine stickleback (Gasterosteus aculeatus), preliminary components of female reproductive behavior
(head-up, following) may be shown prior
to ovulation and after oviposition (Wooton, 1974). However, entering the male's
nest, a behavior which normally occurs
only in fish containing ovulated eggs, apparently may still be shown shortly after
egg release. In several cichlids, discrete behavioral changes in the female associated
with the onset of oviposition occur at the
time of ovulation (Polder, 1971).
PG may mediate the effect of ovulated
eggs on sexual behavior of several oviparous teleosts in addition to the goldfish.
Exposure to herring milt rapidly induces
spawning in ovulated Pacific herring (Clu-
Basic differences in the mode of reproduction likely account for differences in
the regulation of female sexual behavior
in the goldfish and guppy. In the goldfish,
an abrupt physiological change, the elevation of plasma PGF2a at ovulation (Bouffard, 1979), appears to function as a shortlatency, short-duration stimulus acting on
the brain to synchronize spawning behavior with the presence of ovulated eggs (Stacey and Liley, 1974; Stacey, 1976; Stacey
and Peter, 1979). However, in the guppy,
where development of the potential for
fertilization of the oocytes may not be accompanied by abrupt endocrine changes,
ovarian estrogen acts as a relatively longlatency stimulus synchronizing receptivity
with oocyte maturation (Liley, 1972). The
female goldfish experiences three states of
sexual responsiveness: (1) an unresponsive
state in which the absence of some hypophysial-gonadal priming effect renders females with regressed ovaries unresponsive
to the presence of ovulated eggs or elevated plasma PG, (2) a potentially responsive
state in which females with maturing ovaries exhibit spawning behavior when injected with ovulated eggs or PG, and (3) a
responsive or receptive state in which ovulation leads to the synthesis of PG which
acts on the brain to trigger spawning. Female goldfish are naturally in a state of
potential sexual responsiveness for much pea harengus pallasi), a response which is
of the year, becoming sexually active when blocked by indomethacin (N. E. Stacey and
HORMONES AND SEX BEHAVIOR IN FEMALE FISH
A. S. Hourston, unpublished results). Indomethacin also inhibits nest-digging and
spawning of ovulated rainbow trout (Salmo
gairdneri), indicating PG stimulates these
behaviors (N. R. Liley, unpublished re£sults). In vitro ovulation of rainbow trout
oocytes can be induced both by PG (Jalabert and Szollosi, 1975) and by coelomic
fluid from ovulated trout (Jalabert et al.,
1972), suggesting that, as in the goldfish
(Bouffard, 1979), fluid bathing the ovulated eggs contains PG. Further evidence of
increased PG synthesis at ovulation in teleosts is provided by Ogata et al. (1979)
who have demonstrated a sevenfold increase in ovarian PGF2a concentration in
hCG-treated Misgurnus anguillicaudatus.
In ovulated sticklebacks treated with indomethacin, nest-entering and oviposition
were almost completely inhibited while
head-up and following, behaviors occurring earlier in the spawning sequence,
were less affected (T. J. Lam, unpublished
results); injection of PGF2a restored headup, following and nest-entering but not
oviposition in some of these ovulated, indomethacin-treated fish. If ovulated sticklebacks are prevented from spawning for
several days, the ovulated eggs become
overripe (hard and translucent); females
in this condition show only escape behavior in response to male courtship (Lam et
al., 1978). Lam's unpublished findings that
PGF 2 Q injection restored following behavior in some of these females suggest loss of
receptivity in fish with overripe eggs may
be due to reduced PG synthesis.
The generality of mechanisms proposed
to regulate female sexual behavior in the
goldfish and guppy cannot be assessed
without additional research. While female
sexual behavior in a number of oviparous
species is associated with the presence of
ovulated eggs, investigation of the physiological link(s) between ovulation and sexual activity has only begun. Hopefully further studies will examine the action of PG
on sexual behavior in other oviparous
species and clarify the role of NHHs. The
findings that steroid treatment alone (in
the absence of ovulated eggs) fails to induce spawning behavior in goldfish and
other oviparous fishes (Liley, 1969, 1979)
313
should not discourage research into possible roles of steroids in female reproductive behaviors in these species. Estradiol
(Stacey and Liley, 1974) and other steroids
(Stacey, 1977) restore responsiveness to
ovulated eggs in female goldfish with regressed ovaries. Furthermore, the possibility should not be overlooked that female
reproductive behaviors preceding ovulation {e.g., pair formation and nest-building
in cichlids) may be influenced by steroids.
HORMONES AND FEMALE SEXUAL BEHAVIOR:
A COMPARATIVE PERSPECTIVE
Females of externally and internally fertilizing species encounter different problems in attempting to synchronize sexual
behavior with the appropriate stage of oocyte development. Females which utilize
external fertilization must release ovulated
oocytes if sexual behavior is to be successful. In these species, female sexual behavior would be activated effectively by an endogenous signal that ovulated eggs are
ready for release. In goldfish, and perhaps
in some other oviparous teleosts, PG may
serve this function by increasing in the
plasma at ovulation and remaining high
until the ovulated oocytes have been shed.
Such a PG-mediated mechanism appears
designed simply to detect the occurrence of
ovulation by responding rapidly to the
presence of ovulated eggs and ceasing to
function when oviposition has been completed and plasma PG levels decrease.
Whether PG synchronizes sexual behavior
with ovulation in amphibians which use
external fertilization is not known (Diakow
and Raimondi, 1981); however, injection
of PGE2 rapidly induces receptivity both in
intact and in ovariectomized Xenopus laevis
(D. B. Kelley, unpublished results). In the
female guppy (Liley, 1979) and in female
lizards (Crews and Silver, 1980), birds
(Crews and Silver, 1980) and mammals
(Morali and Beyer, 1979), where fertilization is internal, sexual behavior and fertilization are temporally dissociated. In order that sperm reach the ovulated oocyte(s)
during the brief period when fertilization
is possible, sexual behavior in these species
is synchronized with ovulation by mechanisms which anticipate either an imminent
314
NORMAN EDWARD STACEY
spontaneous ovulation, or the potential for
reflex ovulation, by responding to increases in circulating estrogen associated
with follicular development.
Recent studies in the rat (Hall et al,
1975; Rodriguez-Sierra and Komisaruk,
1977; Hall and Luttge, 1978) and hamster
(Buntin and Lisk, 1979) demonstrate that,
as in the goldfish, PG exerts potent, shortlatency stimulatory effects on female sexual behavior. However, in contrast to the
situation in goldfish, where indomethacin
rapidly inhibits spawning behavior, indomethacin treatment of rats (RodriguezSierra and Komisaruk, 1977; Hall and
Luttge, 1978) and hamsters (Buntin and
Lisk, 1979) fails to inhibit steroid-induced
receptivity. These findings raise the possibility that female sexual behavior in the
rat and hamster may be regulated by two
mechanisms: (1) a steroid-mediated mechanism responsible for initiating sexual behavior, and (2) a PG-mediated mechanism,
independent of steroids and capable of
short-term modulation of receptivity. How
such a PG-mediated mechanism might
normally be activated is not known, although this may occur in response to coitus. Significantly, in female guinea pigs in
which steroid-induced receptivity has been
abbreviated by coitus, plasma levels of PGF
metabolites are elevated (S. M. Irving, R.
W. Goy, R. V. Haning, and G. A. Davis,
unpublished results). As physical stimulation of the cervix inhibits receptivity in the
guinea pig (Goldfoot and Goy, 1970), and
facilitates receptivity in the rat (RodriguezSierra et al., 1975), the fact that PG also
exerts the same differential effects on female sexual behavior in these species (Marrone et al., 1979) suggests that PG mediates these behavioral effects of cervical
stimulation.
In summary, I propose the following
hypotheses in the hope of stimulating a
more broadly comparative approach to the
study of female sexual behavior. In ancestral, externally fertilizing female vertebrates, where sexual behavior necessarily
involves oviposition, an "ovulation-detector," rapidly activated by PG synthesized
in conjunction with ovulation and the presence of ovulated eggs, synchronizes sexual
behavior and egg release with ovulation.
Ovarian steroids may prime the ovulation
detector but appear not to be involved directly in stimulating sexual behavior. With
the evolution of internal fertilization and
the temporal dissociation of fertilization^
and sexual behavior, the mechanism triggering female sexual behavior has become
an "ovulation-anticipator" by acquiring responsiveness to a preovulatory endocrine
stimulus, the increase in circulating estrogen. However, there is evidence that at
least in some rodents the ancestral sex behavior responsiveness to PG has been
maintained and modified to mediate shortterm effects of coital stimuli on receptivity.
ACKNOWLEDGMENTS
This work was funded by a Killam Postdoctoral Scholarship to N.E.S. and National Research Council grant A6371 to R. E.
Peter. My sincere thanks to R. E. Peter, A.
L. Kyle, N. R. Liley, D. B. Kelley, and M.
S. Krieger for their comments on the
manuscript, to the Upjohn Company for
generous gifts of prostaglandins, and to all
those who have allowed me to refer to
their unpublished findings.
REFERENCES
Able, K. W. and M. Castagna. 1975. Aspects of an
undescribed reproductive behavior in Fundulus
heteroditus (Pisces: Cyprinodontae) from Virginia. Chesapeake Science 16:282-284.
Billard, R. and J. Marcel. 1978. International symposium on reproductive physiology of fish. Ann.
Biol. Anim. Bioch. Biophys. 18:759-1 106.
Bouffard, R. E. 1979. Role of prostaglandins during
sexual maturation, ovulation, and spermiation in
the goldfish, Carassius auratus. M.Sc. Thesis,
Univ. British Columbia.
Buntin, J. D. and R. D. Lisk. 1979. Prostaglandin H^induced lordosis in estrogen-primed female
hamsters: Relationship to progesterone action.
Physiol. Behav. 23:569-575.
Carlson, D. R. 1969. Female sexual receptivity in
Gambusia affinis (Baird and Girard). Texas J. Sci.
21:167-173.
Crawford, S. 1975. An analysis of the reproductive
behavior of the female American flagfish, Jordanellafloridae (Pisces: Cyprinodontidae), including preliminary studies of the histology of the
reproductive tract and of the internal factors
regulating spawning behavior. B.Sc. Thesis,
Univ. British Columbia.
Crews, D. and R. Silver. 1980. Reproductive physiology and behavior interactions in nonmammalian vertebrates. In R. \V. Goy and D. W. Pfaff
HORMONES AND SEX BEHAVIOR IN FEMALE FISH
315
grams. In J. E. Bardach (ed.), The physiological
and behavioral manipulation of food fish as production
Press, New York.
and management tools. ICLARM, Manila.
Crow, R. T. and N. R. Liley. 1979. A sexual pheromone in the guppy, Poecilia reticulata (Peters). Liley, N. R. and E. M. Donaldson. 1969. The effects
of salmon pituitary gonadotropin on the ovary
Can. J. Zool. 57:184-188.
and the sexual behavior of the female guppy,
Diakow, C. and D. Raimondi. 1981. Physiology of
Poecilia reticulata. Can. J. Zool. 47:569-573.
Rana pipiens reproductive behavior: A proposed
mechanism for inhibition of the release call. Liley, N. R. and W. VVishlow. 1974. The interaction
Amer. Zool. 21:295-304.
of endocrine and experiential factors in the regulation of sexual behavior in the female guppy
Egami, N. 1959. Preliminary note on the induction
Poecilia reticulata. Behaviour 48:185-214.
of the spawning reflex and oviposition in Oryzias
latipes by the administration of neurohypophy- Macey, M. J., G. E. Pickford, and R. E. Peter. 1974.
seal substances. Annot. Zool. Japon. 32:13-17.
Forebrain localization of the spawning reflex response to exogenous neurohypophyseal horFoster, N. R., J. Cairns, and R. L. Maisler. 1969. The
mones in the killifish, Fundulus heteroditus. J.
flagfish, Jordanellafloridae, as a laboratory animal
Exp. Zool. 190:269-280.
for behavioral bioassays. Proc. Acad. Nat. Sci.
Phil. 121:129-152.
Marrone, B. L., J. F. Rodriguez-Sierra, and H. H.
Feder. 1979. Differential effects of prostaglanGoldfoot, D. W. and R. W. Goy. 1970. Abbreviation
dins on lordosis behavior in female guinea pigs
of behavioral estrus in guinea pigs by coital and
and rats. Biol. Reprod. 20:853-861.
vagino-cervical stimulation. J. Comp. Phys. PsyMorali, G. and C. Beyer. 1979. Neuroendocrine conchol. 72:426-434.
trol of mammalian estrous behavior. In C. Beyer
Hall, N. R. and W. G. Luttge. 1978. Effects of the
(ed.), Endocrine control of sexual behavior, pp. 3 3 prostaglandin synthesis inhibitor, indomethacin,
75. Raven Press, New York.
on estrogen- and estrogen plus progesterone-induced sexual receptivity in ovariectomized rats. Newman, H. H. 1907. Spawning behavior and sexual dimorphism in Fundulus heteroditus and allied
Pharmac. Biochem. Behav. 8:597-602.
fish. Biol. Bull. 12:314-339.
Hall, N. R., W. G. Luttge, and R. B. Berry. 1975.
Intracerebral prostaglandin E2: Effects upon Ogata, H., T. Nomura, and M. Hata. 1979. Prostaglandin F2o changes induced by ovulatory stimuli
sexual behavior, open field activity, and body
in the pond loach, Misgurnus anguillicaudatus.
temperature in ovariectomized rats. ProstaglanBull. Jap. Soc. Sci. Fish. 45:929-931.
dins 10:877-888.
Jalabert, B., B. Breton, and C. Bry. 1972. Matura- Partridge, B. L., N. R. Liley, and N. E. Stacey. 1976.
tion et ovulation in vitro des ovocytes de la truite
The role of pheromones in the sexual behavior
of the goldfish. Anim. Behav. 24:291-299.
arc-en-ciel Salmo gairdneri. C. R. Acad. Sci. Paris
Peter, R. E. 1977. The preoptic nucleus in fishes: A
275:1139-1142.
comparative discussion of function-activity relaJalabert, B. and D. Szollosi. 1975. In vitro ovulation
tionships. Amer. Zool. 17:775-785.
of trout oocytes: Effect of prostaglandins on
smooth muscle-like cells of the theca. Prostaglan- Peter, R. E. and L. W. Crim. 1979. Reproductive
endocrinology of fishes: Gonadal cycles and godins 9:765-778.
nadotropin in teleosts. Ann. Rev. Physiol.
Lam, T. J., Y. Nagahama, K. Chan, and W. S. Hoar.
41:323-335.
1978. Overripe eggs and post-ovulatory corpora
lutea in the threespine stickleback, Gasterosteus Pickford, G. E. and E. L. Strecker. 1977. The spawning reflex response of the killifish, Fundulus hetaculeatus L., form trachurus. Can. J. Zool.
eroditus: Isotocin is relatively inactive in compar56:2029-2036.
ison with arginine vasotocin. Gen. Comp.
Lambert, J. G. D. 1970. The ovary of the guppy
Endocrinol. 32:132-137.
Poecilia reticulata. The granulosa cells as sites of
steroid biosynthesis. Gen. Comp. Endocrinol. Polder, J. J. W. 1971. On gonads and reproductive
15:464-476.
behavior in the cichlid fish Aequidens portalegrensis
(Hensel). Netherlands J. Zool. 21:265-365.
Liley, N. R. 1966. Ethological isolating mechanisms
in four sympatric species of poeciliid fishes. Be- Rodriguez-Sierra, J. F., W. R. Crowley, and B. R.
hav. Suppl. 13:1-197.
Komisaruk. 1975. Vaginal stimulation in rats induces prolonged lordosis responsiveness and
Liley, N. R. 1968. The endocrine control of reprosexual receptivity. J. Comp. Physiol. Psychol.
ductive behavior in the female guppy Poecilia re89:79-85.
ticulata Peters. Anim. Behav. 16:318-331.
Liley, N. R. 1969. Hormones and reproductive be- Rodriguez-Sierra, J. F., and B. R. Komisaruk. 1977.
Effects of prostaglandin E,, and indomethacin on
havior in fishes. In W. S. Hoar and D. J. Randall
sexual behavior in the female rat. Horm. Behav.
(eds.), Fish physiology, Vol. 3, pp. 73—116. Aca9:281-289.
demic Press, New York.
Liley, N. R. 1972. The effects of estrogens and other Stacey, N. E. 1976. Effects of indomethacin and
prostaglandins on the spawning behavior of festeroids on the sexual behavior of the female
male goldfish. Prostaglandins 13:113-124.
guppy, Poecilia reticulata. Gen. Comp. EndocriStacey, X. E. 1977. The regulation of spawning benol. Suppl. 3:542-552.
havior in the female goldfish, Carassius auratus.
Liley, N. R. 1979. Patterns of hormonal control in
Ph.D. Thesis, Univ. British Columbia.
the reproductive behavior of fish, and their relevance to fish management and culture pro- Stacey, N. E., A. F. Cook, and R. E. Peter. 1979.
(eds.), Handbook of behavioral neurobiology. Plenum
316
NORMAN EDWARD STACEY
Ovulatory surge of gonadotropin in the goldfish,
Carassius auratus. Gen. Comp. Endocrinol.
37:246-249.
Stacey, N. E. and N. R. Liley. 1974. Regulation of
spawning behavior in the female goldfish. Nature 247:71-72.
Stacey, N. E. and S. Pandey. 1975. Effects of indomethacin and prostaglandins on ovulation of
goldfish. Prostaglandins 9:597-607.
Stacey, N. E. and R. E. Peter. 1979. Central action
of prostaglandins in spawning behavior of female goldfish. Physiol. Behav. 22:1191-1196.
Wilhelmi, A. E., G. E. Pickford, and W. H. Sawyer.
1955. Initiation of the spawning reflex response
in Fundulus by administration of fish and mammalian neurohypophyseal preparations and synthetic oxytocin. Endocrinology 57:243-252.
Wooton, R. J. 1974. Changes in the courtship behavior of female three-spined sticklebacks between spawnings. Anim. Behav. 22:850-855.
Yamazaki, F. 1965. Endocrinological studies on the
reproduction of the female goldfish, Carassius
auratus L., with special reference to the function
of the pituitary gland. Mem. Fac. Fish. Hokkaido
Univ. 13:1-64.