Control of ovulation
141
dissolved in freshwater
teleost
physiological saline (PS; Burnstock, 1958),
whereas PIM and RES were
suspended in a vehicle (VEH) of
NaCl with
sodium metabisulphite°
Dosages of
PIM and RES
utilized, and the
injection schedules, are provided in the results sectiono
Control fish
received injections of PS and
Blood
samples were obtained at various times by puncture of the caudal
vasculature with a 25—gauge needle attached to a 1 ml syringe.
Blood was
allowed
to
clot, serum collected following centrifugation, and then stored
at
—20°C°
Serum GtH
levels
in common carp
and
bream were determined by
radioimmunoassay using the protocol and reagents described by Peter et al°
(1984).
Ovulation was
assessed by abdominal massage°
GtH
data
analysed by one way analysis of variance and Duncan's multiple range test°
Fisher's exact probability test was used to compare the number of fish which
ovulate between treatment
groupse
RESULTS
Common Carp
The
results
of
a
study testing the influence of males and floating
vegetation as a spawning substrate on serum GtH levels and ovulation in
common
carp
are
shown in Figo la
Addition of males
and vegetation to the
holding pond at 18:00 resulted in ovulation the following morning of 60% (24
of 40) of the fish tested; no fish ovulated in the absence of males and
vegetation°
Serum GtH
levels remained low during the course of sampling in
control fish and
fish which failed
to
ovulate in response to added males
and
vegetation°
A pronounced surge of GtH was found in fish which ovulate; the
ovulatory GtH surge in common carp lasts at least 12 hours, during which GtH
levels increase about lO—fold above basal levels…
Figure 2 shows the effects of LHRH—A alone and in cOmbination with PIM
or
RES
on
serum
GtH
levels and ovulation in common carp°
Injections of
LHRH—A, PIM or RES alone caused only a modest increase in serum GtH levels
when compared to control fish; combined injections of either PIM or RES with
LHRH—A resulted in high serum GtH levels.
Injections of RES and LHRH—A had
a
very prolonged action, resulting in higher serum GtH levels than
injections of PIM and LHRH—A at 38 hours.
LHRH—A, PIM and RES when injected
alone failed to induce ovulation—within 38
Injections of PIM
LHRH—A were also ineffective whereas injections of RES and LHRH—A resulted
in a significant increase in the number of fish which ovulate.
A second
experiment, conducted when water temperature was elevated
(24—28°C), reexamined the effects of PIM
8 alo e and in combination
With LHRH—A on ovulation in common carp (Table 1). ,In this experiment, PIM,
RES and LHRH—A alone caused ovulation within 38 hours in_a small proportion
Of the fish.tested, but did not differ from the ovulatory…rate in control
fi$h—
Combined injections of PIM and LHRH—A were highly effective, causing
°Y“lation in 8 of 10 fish; however this did not differ-significantly from
response to PIM alohe (3 of 10 fish) or LHRH“A
Of 8
Combined injections of RES and LHRH—A caused ovulation in 9 of 10 fish which
Was
significantly higher than the response to RES alone and LHRH—A alone.
141
dissolved in freshwater
teleost
physiological saline (PS; Burnstock, 1958),
whereas PIM and RES were
suspended in a vehicle (VEH) of
NaCl with
sodium metabisulphite°
Dosages of
PIM and RES
utilized, and the
injection schedules, are provided in the results sectiono
Control fish
received injections of PS and
Blood
samples were obtained at various times by puncture of the caudal
vasculature with a 25—gauge needle attached to a 1 ml syringe.
Blood was
allowed
to
clot, serum collected following centrifugation, and then stored
at
—20°C°
Serum GtH
levels
in common carp
and
bream were determined by
radioimmunoassay using the protocol and reagents described by Peter et al°
(1984).
Ovulation was
assessed by abdominal massage°
GtH
data
analysed by one way analysis of variance and Duncan's multiple range test°
Fisher's exact probability test was used to compare the number of fish which
ovulate between treatment
groupse
RESULTS
Common Carp
The
results
of
a
study testing the influence of males and floating
vegetation as a spawning substrate on serum GtH levels and ovulation in
common
carp
are
shown in Figo la
Addition of males
and vegetation to the
holding pond at 18:00 resulted in ovulation the following morning of 60% (24
of 40) of the fish tested; no fish ovulated in the absence of males and
vegetation°
Serum GtH
levels remained low during the course of sampling in
control fish and
fish which failed
to
ovulate in response to added males
and
vegetation°
A pronounced surge of GtH was found in fish which ovulate; the
ovulatory GtH surge in common carp lasts at least 12 hours, during which GtH
levels increase about lO—fold above basal levels…
Figure 2 shows the effects of LHRH—A alone and in cOmbination with PIM
or
RES
on
serum
GtH
levels and ovulation in common carp°
Injections of
LHRH—A, PIM or RES alone caused only a modest increase in serum GtH levels
when compared to control fish; combined injections of either PIM or RES with
LHRH—A resulted in high serum GtH levels.
Injections of RES and LHRH—A had
a
very prolonged action, resulting in higher serum GtH levels than
injections of PIM and LHRH—A at 38 hours.
LHRH—A, PIM and RES when injected
alone failed to induce ovulation—within 38
Injections of PIM
LHRH—A were also ineffective whereas injections of RES and LHRH—A resulted
in a significant increase in the number of fish which ovulate.
A second
experiment, conducted when water temperature was elevated
(24—28°C), reexamined the effects of PIM
8 alo e and in combination
With LHRH—A on ovulation in common carp (Table 1). ,In this experiment, PIM,
RES and LHRH—A alone caused ovulation within 38 hours in_a small proportion
Of the fish.tested, but did not differ from the ovulatory…rate in control
fi$h—
Combined injections of PIM and LHRH—A were highly effective, causing
°Y“lation in 8 of 10 fish; however this did not differ-significantly from
response to PIM alohe (3 of 10 fish) or LHRH“A
Of 8
Combined injections of RES and LHRH—A caused ovulation in 9 of 10 fish which
Was
significantly higher than the response to RES alone and LHRH—A alone.