induced spawning
125
6 hours
followed by a decrease to reach by 24 hours levels which are higher
than those
oberved
just before the injection and those previously described
for androgens
(about
3ng/ml)
in a study conducted all the year round with
males
held
in
a
concrete
tank and which
released a small quantity of milt
(WEIL 1981).
After hypophysation collectable milt volume increased conside—
rably during
the
ZH
hour
experimental
period (from 0,190ml to 9,5ml/ 6)
while spermatocrit
was
declining from 75 % to 53 % indicating a sperm dilu—
tion.
This
increase
in GtH and
11—ketotestosterone confirms the role of GtH
via steroid
synthesis in spermiation (see above). These data and works from
KIME and
MANNING
(summary this volume) and from TAKASHIMA et al. 1984 indi—
cate
that
in carp
11—Ketotestosterone is closely associated with male repro—
ductive
development,
The technique of hypophysation has certain disadvantages as :
—
its
relatively high cost due to the unpredictable supply of pituitary
and the necessity to maintain water temperature above 18°C.
—
its
partial
success.
Only
about
70 % of the animals ovulate and
unspawned fish
undergo
oocyte
atresia leading to an increase in mortality
even
under ideal conditions
(good oxygenation of the water and food supply).
2)
Use
of mammalian hormones.
HCG
(Human
Chorionic gonadotropin) and Synahorin (mammalian pituitary
extract) can
be
reliably
supplied and attempts have been made to use them
instead of hypophysation. HCG efficiency depends on the species. It's effec—
tive in inducing ovulation in goldfish (YAMAMOTO and YAMAZAKI 1967). Chinese
studies report
that
it
is weakly effective in grass carp and mud carp but
more
efficient in silver
carp
and bighead. However it has harmful effects on
unspawned fish
leading to the death of the animals. In indian carp, the re—
latively low
efficiency
of HCG and Synahorin can be improved by using them
in combination with a lower dose of pituitary extract (CHAUDHURI 1976).
C — Discharge of endogenous gonadotropin hormone.
1)
Administration of gonadotropin releasing hormone (GnRH)As mentionned
above
LHRH
or
LHRH analogues (LHRHa) evoke the release of en—
dogenous pituitary
gonadotropin
supplies. A seasonal pituitary sensitivity
to GnRH have
been demonstrated but at
the
time of inducing spawning the Sen—
sitivity is
maximal
in carp
(WEIL et al. 1975) and in goldfish (SOKOLOWSKA
et al.
1985).
Action in female
In goldfish, spontaneous ovulation does not occur at 12°C when fish are
held in
aquaria
without vegetation. Relatively high doses of LHRH given in
one
injection
administered
either
by
intraperitoneal (1ug/g) or by intra
cranial
injection
(200ng/g)
were
partially effective in inducing ovulation
(PESPeCtively 50
%
and
33
% of ovulation, LAM et al. 1975 —1976). A weak
percentage of
ovulation was also recorded with
the
total
dose of 200ng/g of
a
Potent
LHRHa when given in two injections 12 hrs apart at 12 —14°C (CHANG
et PETER
1983)
or
3
hrs
apart at 18 —ZO°C (SOKOLOWSKA et al.
198U). Sus—
tained GnRH
release
allowed
by the implantation of pellets containing 25ug
°F
125ug
of
LHRHa
were
also
partially effective (20 — 50 % of ovulation
SOKOLOWSKA et
al.
1984). Both treatments with LHRHa induced high plasma GtH
levels which were in the range of those reached during spontaneous ovulation
bUt were of longer duration.
In
carp,
nine
daily LHRH intrahypophseal injections at 1ug/kg stimula—
ted oocyte
maturation
(germinal
vesicle
migration and breakdown) at 18 —
20°C but
the
same
dosage
given
by
intracardiac.
or
intraventricular
injection produced
any
effect
(SOKOLOWSKA et al.
1978). Germinal vesicle
125
6 hours
followed by a decrease to reach by 24 hours levels which are higher
than those
oberved
just before the injection and those previously described
for androgens
(about
3ng/ml)
in a study conducted all the year round with
males
held
in
a
concrete
tank and which
released a small quantity of milt
(WEIL 1981).
After hypophysation collectable milt volume increased conside—
rably during
the
ZH
hour
experimental
period (from 0,190ml to 9,5ml/ 6)
while spermatocrit
was
declining from 75 % to 53 % indicating a sperm dilu—
tion.
This
increase
in GtH and
11—ketotestosterone confirms the role of GtH
via steroid
synthesis in spermiation (see above). These data and works from
KIME and
MANNING
(summary this volume) and from TAKASHIMA et al. 1984 indi—
cate
that
in carp
11—Ketotestosterone is closely associated with male repro—
ductive
development,
The technique of hypophysation has certain disadvantages as :
—
its
relatively high cost due to the unpredictable supply of pituitary
and the necessity to maintain water temperature above 18°C.
—
its
partial
success.
Only
about
70 % of the animals ovulate and
unspawned fish
undergo
oocyte
atresia leading to an increase in mortality
even
under ideal conditions
(good oxygenation of the water and food supply).
2)
Use
of mammalian hormones.
HCG
(Human
Chorionic gonadotropin) and Synahorin (mammalian pituitary
extract) can
be
reliably
supplied and attempts have been made to use them
instead of hypophysation. HCG efficiency depends on the species. It's effec—
tive in inducing ovulation in goldfish (YAMAMOTO and YAMAZAKI 1967). Chinese
studies report
that
it
is weakly effective in grass carp and mud carp but
more
efficient in silver
carp
and bighead. However it has harmful effects on
unspawned fish
leading to the death of the animals. In indian carp, the re—
latively low
efficiency
of HCG and Synahorin can be improved by using them
in combination with a lower dose of pituitary extract (CHAUDHURI 1976).
C — Discharge of endogenous gonadotropin hormone.
1)
Administration of gonadotropin releasing hormone (GnRH)As mentionned
above
LHRH
or
LHRH analogues (LHRHa) evoke the release of en—
dogenous pituitary
gonadotropin
supplies. A seasonal pituitary sensitivity
to GnRH have
been demonstrated but at
the
time of inducing spawning the Sen—
sitivity is
maximal
in carp
(WEIL et al. 1975) and in goldfish (SOKOLOWSKA
et al.
1985).
Action in female
In goldfish, spontaneous ovulation does not occur at 12°C when fish are
held in
aquaria
without vegetation. Relatively high doses of LHRH given in
one
injection
administered
either
by
intraperitoneal (1ug/g) or by intra
cranial
injection
(200ng/g)
were
partially effective in inducing ovulation
(PESPeCtively 50
%
and
33
% of ovulation, LAM et al. 1975 —1976). A weak
percentage of
ovulation was also recorded with
the
total
dose of 200ng/g of
a
Potent
LHRHa when given in two injections 12 hrs apart at 12 —14°C (CHANG
et PETER
1983)
or
3
hrs
apart at 18 —ZO°C (SOKOLOWSKA et al.
198U). Sus—
tained GnRH
release
allowed
by the implantation of pellets containing 25ug
°F
125ug
of
LHRHa
were
also
partially effective (20 — 50 % of ovulation
SOKOLOWSKA et
al.
1984). Both treatments with LHRHa induced high plasma GtH
levels which were in the range of those reached during spontaneous ovulation
bUt were of longer duration.
In
carp,
nine
daily LHRH intrahypophseal injections at 1ug/kg stimula—
ted oocyte
maturation
(germinal
vesicle
migration and breakdown) at 18 —
20°C but
the
same
dosage
given
by
intracardiac.
or
intraventricular
injection produced
any
effect
(SOKOLOWSKA et al.
1978). Germinal vesicle