Biaiegy of gameäes, eggs, embryos
157
(1982) have proposed ovum size,
protein and energy content as quality parame—
ters
of
eggs;
one
ova
should
be
1.45—1.51
mm
in diameter
(700—900 ova per g)
and should contain more than 0.25 mg of protein (Statova et al., 1982). However
Tomita et al.
(1980) reported that there was no difference in the percentage of
eyed—eggs in carp of various ages,
although the ovum diameter was smaller in
the
2—year group than in the older group.
Amino
acid
content
also
has
to
be
taken
into
account
according to these
authors.
Zhukinskiy and Kim
(1980) have shown that amino acid content changes
as
the ova
age
and
become overripe.
In carp,
Konovalov
(1979) has positively
correlated the
total
protein,
SH groups
of protein and non—protein thiol com—
pounds found at mid—gastrulation stage with the rate of fertilization,
hatched
embryos
and
exogenously
feeding larvae.
In
roach
and
bream,
Konovalov
and
nMinskiy
(1978)
reported
that
these
compounds
in
ripe
ova
decrease
as
the
females
age
and
Konovalov
(1982)
studied
their
dynamics in muscle,
liver
and
sexual
products during spawning.
In
roach,
ovum
weight decreases when food
supply and fecundity increase (Lyagina, 1975).
The
effects
of
temperature
on
females
and
oocytes
have
been
stressed
by
some
authors.
At
the
end
of
vitellogenesis,
the
thermal
regime must be kept
below spawning temperature (18—20°C for carp),
and once
this
level
is reached,
the
oocyte started to regress after 10 days at 20°C
(Statova et al.,
1982).
These authors
also showed
that
cytological images of ova can serve as an index
of
quality
:
changes
such
as
the
fusion
of
the
cortical
granules
and
their
incorporation into
the
vitellus
were
correlated
with
poor
embryonic survival,
although the percentage of fertilization may still remain high.
During ovula—
tion the optimal temperature is 22°C (Horvath and Peteri,
1980). These authors
also
showed
that
the
oxygen
requirement was high and that water concentration
must be
above
6
mg/l.
The
season
at
which the
induced spawning takes place is
of
importance;
Statova
et
al.
(1982) using heated water to warm the females
early in the season
(April)
obtained
variable
results
(26 to 80% hatching).
This was attributed to the heterogeneous physiological state of the females and
to
differences
in
the
degree
of‘
ovarian
maturation
due
'ü3
the
asynchronous
development of the oocytes.
In addition,
ovum
protein and lipid contents were
lower in mid—April than in the high spawning season in early May.
Ovarian
fluid
also
seems
to
be
an
important
factor
determining egg fer—
tilizability,
Plouidy (1982) carried out artificial insemination with carp ova
exposed or deprived of ovarian fluid.
The
same
percentage of fertilization was
first observed in both groups,
but embryonic loss became significant later (P <
0.05 at
90h) in the group fertilized with ovarian fluid,
also
noted
that
the
percentage of fertilization was positively correlated with the calcium concen—
tration of the ovarian fluid in silver carp (r = 0.78; P < 0.05) and negatively
correlated with potassium in carp (r = 0.69;
P
<
0.05). Such a negative effect
was
due
to
the
direct
deleterious
effect
of
potassium on fertilization (Saad,
unpublished data).
In the goldfish, the ovarian fluid originates from the epithelial cells of
the ovarian
cavity which
become
ciliated
and
seoretory at the time of sexual
maturation, probably under the influence of sex steroids (Takahashi and Takano,
1971). The composition of the fluid and possibly egg quality may thus depend on
endocrine balance. Dysfunction in hormone secretion has already been related to
low egg fertility in coho salmon (Morrisson et al., 1985).
157
(1982) have proposed ovum size,
protein and energy content as quality parame—
ters
of
eggs;
one
ova
should
be
1.45—1.51
mm
in diameter
(700—900 ova per g)
and should contain more than 0.25 mg of protein (Statova et al., 1982). However
Tomita et al.
(1980) reported that there was no difference in the percentage of
eyed—eggs in carp of various ages,
although the ovum diameter was smaller in
the
2—year group than in the older group.
Amino
acid
content
also
has
to
be
taken
into
account
according to these
authors.
Zhukinskiy and Kim
(1980) have shown that amino acid content changes
as
the ova
age
and
become overripe.
In carp,
Konovalov
(1979) has positively
correlated the
total
protein,
SH groups
of protein and non—protein thiol com—
pounds found at mid—gastrulation stage with the rate of fertilization,
hatched
embryos
and
exogenously
feeding larvae.
In
roach
and
bream,
Konovalov
and
nMinskiy
(1978)
reported
that
these
compounds
in
ripe
ova
decrease
as
the
females
age
and
Konovalov
(1982)
studied
their
dynamics in muscle,
liver
and
sexual
products during spawning.
In
roach,
ovum
weight decreases when food
supply and fecundity increase (Lyagina, 1975).
The
effects
of
temperature
on
females
and
oocytes
have
been
stressed
by
some
authors.
At
the
end
of
vitellogenesis,
the
thermal
regime must be kept
below spawning temperature (18—20°C for carp),
and once
this
level
is reached,
the
oocyte started to regress after 10 days at 20°C
(Statova et al.,
1982).
These authors
also showed
that
cytological images of ova can serve as an index
of
quality
:
changes
such
as
the
fusion
of
the
cortical
granules
and
their
incorporation into
the
vitellus
were
correlated
with
poor
embryonic survival,
although the percentage of fertilization may still remain high.
During ovula—
tion the optimal temperature is 22°C (Horvath and Peteri,
1980). These authors
also
showed
that
the
oxygen
requirement was high and that water concentration
must be
above
6
mg/l.
The
season
at
which the
induced spawning takes place is
of
importance;
Statova
et
al.
(1982) using heated water to warm the females
early in the season
(April)
obtained
variable
results
(26 to 80% hatching).
This was attributed to the heterogeneous physiological state of the females and
to
differences
in
the
degree
of‘
ovarian
maturation
due
'ü3
the
asynchronous
development of the oocytes.
In addition,
ovum
protein and lipid contents were
lower in mid—April than in the high spawning season in early May.
Ovarian
fluid
also
seems
to
be
an
important
factor
determining egg fer—
tilizability,
Plouidy (1982) carried out artificial insemination with carp ova
exposed or deprived of ovarian fluid.
The
same
percentage of fertilization was
first observed in both groups,
but embryonic loss became significant later (P <
0.05 at
90h) in the group fertilized with ovarian fluid,
also
noted
that
the
percentage of fertilization was positively correlated with the calcium concen—
tration of the ovarian fluid in silver carp (r = 0.78; P < 0.05) and negatively
correlated with potassium in carp (r = 0.69;
P
<
0.05). Such a negative effect
was
due
to
the
direct
deleterious
effect
of
potassium on fertilization (Saad,
unpublished data).
In the goldfish, the ovarian fluid originates from the epithelial cells of
the ovarian
cavity which
become
ciliated
and
seoretory at the time of sexual
maturation, probably under the influence of sex steroids (Takahashi and Takano,
1971). The composition of the fluid and possibly egg quality may thus depend on
endocrine balance. Dysfunction in hormone secretion has already been related to
low egg fertility in coho salmon (Morrisson et al., 1985).