induced spawning
121
Recently
experiments of brain lesioning (PETER and PAULENCU 1980) have
demonstrated the presence of a gonadotropin release—inhibiting factor (GRIF)
in the
anterior—ventral
preoptic
region.
CHANG et PETER
1983a found that
dopamine has GRIF activity in goldfish modulating spontaneous release of GtH
as
well as
LHRHa—stimulated release of GtH.
Finally, sexual steroids, which are under the control of GtH, act locally on
the gonad
to
trigger
gametogenesis. In the present paper we will focus on
the regulation of the final aspects of oogenesis and spermatogenesis. Oocyte
maturation
(resumption of meiosis and structural and biochemical transforma—
tions which
develop
simultaneously)
is
induced
in vitro
by carp pituitary
extracts
or
carp
gonadotropic
hormone
in goldfish (JALABERT et al.
1973,
JALABERT
1976,
EPLER
et
al.
1979)
and
in carp
(EPLER 1978, EPLER et al.
1979,
1982a).
These
in vitro study techniques have shown that gonadotropic
action of
the
pituitary
is
probably mediated by direct steroid action on
oocyte maturation
in goldfish and in carp. Progestins and particularly 17Œ—
hydroxy, BOB—dihydroprogesterone (17e 208 OH P) are active in inducing matu—
ration in
goldfish
(JALABERT et al.
1976) and in carp EPLER et al.
(1980).
Corticosteroids are
also active
in goldfish (JALABERT et al. 1973, JALABERT
1976, EPLER
et
al.
1979)
and
in carp
(EPLER et al.
1980). Since cortisol
increases
the
potency of carp pituitary extracts in in vitro goldfish matu—
ration
(JALABERT
1976),
and
desoxycorticosterone that of 17ŒZOBOH P (EPLER
et al.
1980) and that of carp hypophysial homogenate (EPLER et al. 1982b) in
carp,
it is
evident
that
corticosteroids may have some synergistic action in
the process
of oocyte maturation. Other glands such as the thyroid may have
&
synergistic
action
in
oocyte
maturation as
suggested by the results of
EPLER and
BIENIARZ
(1983) in carp. Triiodothyronine (T3) influences positi—
vely the maturational effect of gonadotropic and steroid hormones. Ovulation
consists
in
follicular
rupture and expulsion of the mature oocyte from the
follicule. In
goldfish
ovulation
was
induced
in
vivo by prostaglandins
(STACEY and
PANDEY
1975)
and
in
vitro
in
carp
(EPLER 1978, EPLER et al.
1985) as well as by adrenaline (EPLER 1978). The action of prostaglandins is
temperature independant
(EPLER et al.
1985) while in vivo ovulation is tem—
perature dependant (HORVATH 1978).
Spermiation
in carp and related species (thinning of the semen) is pi—
tuitary dependant
(CLEMENS
and GRANT
1965). In goldfish hypophysectomy and
replacement therapy
studies
indicate
that
spermiation seems to depend on
androgen via
GtH.
Different
steroids
are
active
:
11—ketotestosterone, tes—
tosterone, methyltestosterone,
testosterone
propionate,
progesterone
(reviewed in BILLARD et al.
1982).
Il — HORMONAL TECHNIQUES USED FOR INDUCING SPAWNING.
The use of hormones
to
induce
fish spawning has been reviewed many times and
recent reviews
dealing
with
this
topic include those of CHAUDHURI
(1976)
HARVEY and HOAR (1979) and LAM (1982).
À — Selection of breeders
Induced
spawning
is
always performed on mature animals and fully ripe
animals are selected for treatments.
Ripe
males
are
selected
based
upon the possibility of collectin8 a
small quantity
of
sperm
by hand stripping. For females different criteria
have been
adopted and most depend upon external characteristics such as the
sWelling, softness
and
elasticity of the abdomen, colour and state of swel—
ling Of
the cloacal
region and body girth. However these are only pough ln—
dications of
the
stage
of development of the ovary and attempts have been
121
Recently
experiments of brain lesioning (PETER and PAULENCU 1980) have
demonstrated the presence of a gonadotropin release—inhibiting factor (GRIF)
in the
anterior—ventral
preoptic
region.
CHANG et PETER
1983a found that
dopamine has GRIF activity in goldfish modulating spontaneous release of GtH
as
well as
LHRHa—stimulated release of GtH.
Finally, sexual steroids, which are under the control of GtH, act locally on
the gonad
to
trigger
gametogenesis. In the present paper we will focus on
the regulation of the final aspects of oogenesis and spermatogenesis. Oocyte
maturation
(resumption of meiosis and structural and biochemical transforma—
tions which
develop
simultaneously)
is
induced
in vitro
by carp pituitary
extracts
or
carp
gonadotropic
hormone
in goldfish (JALABERT et al.
1973,
JALABERT
1976,
EPLER
et
al.
1979)
and
in carp
(EPLER 1978, EPLER et al.
1979,
1982a).
These
in vitro study techniques have shown that gonadotropic
action of
the
pituitary
is
probably mediated by direct steroid action on
oocyte maturation
in goldfish and in carp. Progestins and particularly 17Œ—
hydroxy, BOB—dihydroprogesterone (17e 208 OH P) are active in inducing matu—
ration in
goldfish
(JALABERT et al.
1976) and in carp EPLER et al.
(1980).
Corticosteroids are
also active
in goldfish (JALABERT et al. 1973, JALABERT
1976, EPLER
et
al.
1979)
and
in carp
(EPLER et al.
1980). Since cortisol
increases
the
potency of carp pituitary extracts in in vitro goldfish matu—
ration
(JALABERT
1976),
and
desoxycorticosterone that of 17ŒZOBOH P (EPLER
et al.
1980) and that of carp hypophysial homogenate (EPLER et al. 1982b) in
carp,
it is
evident
that
corticosteroids may have some synergistic action in
the process
of oocyte maturation. Other glands such as the thyroid may have
&
synergistic
action
in
oocyte
maturation as
suggested by the results of
EPLER and
BIENIARZ
(1983) in carp. Triiodothyronine (T3) influences positi—
vely the maturational effect of gonadotropic and steroid hormones. Ovulation
consists
in
follicular
rupture and expulsion of the mature oocyte from the
follicule. In
goldfish
ovulation
was
induced
in
vivo by prostaglandins
(STACEY and
PANDEY
1975)
and
in
vitro
in
carp
(EPLER 1978, EPLER et al.
1985) as well as by adrenaline (EPLER 1978). The action of prostaglandins is
temperature independant
(EPLER et al.
1985) while in vivo ovulation is tem—
perature dependant (HORVATH 1978).
Spermiation
in carp and related species (thinning of the semen) is pi—
tuitary dependant
(CLEMENS
and GRANT
1965). In goldfish hypophysectomy and
replacement therapy
studies
indicate
that
spermiation seems to depend on
androgen via
GtH.
Different
steroids
are
active
:
11—ketotestosterone, tes—
tosterone, methyltestosterone,
testosterone
propionate,
progesterone
(reviewed in BILLARD et al.
1982).
Il — HORMONAL TECHNIQUES USED FOR INDUCING SPAWNING.
The use of hormones
to
induce
fish spawning has been reviewed many times and
recent reviews
dealing
with
this
topic include those of CHAUDHURI
(1976)
HARVEY and HOAR (1979) and LAM (1982).
À — Selection of breeders
Induced
spawning
is
always performed on mature animals and fully ripe
animals are selected for treatments.
Ripe
males
are
selected
based
upon the possibility of collectin8 a
small quantity
of
sperm
by hand stripping. For females different criteria
have been
adopted and most depend upon external characteristics such as the
sWelling, softness
and
elasticity of the abdomen, colour and state of swel—
ling Of
the cloacal
region and body girth. However these are only pough ln—
dications of
the
stage
of development of the ovary and attempts have been