Biology of gamei‘es, eggs, embryos
158
rences
in
carp
(Kudo,
1982).
The
enter half
of this
layer is rich in protein
and contains acid—phosphatase activity,
while the lower part is rich in carbo—
hydrates and has no acid phosphatase activity. This composite external layer is
responsible for the great stickiness of carp eggs which occurs after eggs are
immersed in fresh water but not in saline solutions.
In Chinese carp,
such as
silver carp,
grass
carp,
bighead and black carp,
the
VE
is
8—11
um
and also
includes 4
layers (Mikodina and Makayeva,
1980).
The
outermost layer is much
less
sticky than in common carp and very thin
(Yemelyanova,
1979).
There
is
usually only one micropyle in the eggs of cyprinids as in other fish;
its mor—
phology varies according to species (Mikodina and Makayeva,
1980). After acti—
vation,
the
VE
shows
considerable
morphological changes.
The
content
of
the
cortical
organelles is released into the perivitelline space;
from
there
it
reaches
the
VE
which
undertake
hardening.
The
thickness
of
the
VE
decreases
while the
perivitelline space increases within a few min after activation.
In
carp it
increases
5
times
(Kudo,
1982) and reaches 200 nm within
min in
water
and
25
min
in
a
saline
solution;
the
surface of
the
outermost
layer is
initially slightly
folded
but
flattens
after
activation
(Renard et al.,
see
summary this volume).
The
total diameter
of the
egg increases
from 1.0
to
1.4
um according to Rubson
(1981).
The
increases
in
diameter
is
much
higher in
Chinese carp:
from
O.7—1.5 to
6 mm
in diameter
(Horvath and Luckowicz,
1982)
and from 3—8 to
30—8O mm2 in surface
(Mikodina and Makeyeva,
1980). Tench eggs
are
smaller:
O.4—O.5
mm
before
activation and
0.6—0.7 afterwards
(Horvath and
Lukowicz, 1982). However, Brylinska and Dlugosz (1978) reported larger—sized (>
1 mm) follicular oocytes.
The material
from the
cortical reaction
blocks the
micropyle within a few
minutes and prevents any more sperm from entering. Theref0re, the percentage of
fertilization decreases very rapidly after dilution (Yamamoto,
1961;
Mikodina
and Makayeva, 1980; Sjafei, 1985).
,
II.
COMPOSITION OF GAMETE COMPANION FLUIDS
A.
Seminal fluid
The
mineral
composition of the seminal
fluid
in
cyprinids varies widely
(Clemens and Grant,
1965;
Grant
et
al.,
1969;
Plouidy and Billard,
1982;
Morizawa et al.,
1983; Kruger et al., 1984; Gaty et al., unpublished data) re—
examined this point and,
like Mori2awa et al.
(1983), showed that the concen—
tration of carp seminal fluid was 74 t 23 mM Na
and 77 i 10 mM K
;
Kurager et
al.
(1984) found lower Na values in the spring (59 mM).
In the
same
species,
Ménêzo et al.
(1983) found large amounts of amino aCids (36 mM).
The osmotic
pressure
is around 300
mOms/kg.
The
lipid content of the seminal fluid of va—
rious cyprinids was studied by Belova (1982, 1983) who showed differences among
species and after pituitary extract stimulation of spermiation.
The pH of the
seminal
fluid
measured
in
a
large number of cÿprinids by Zhukinsky and Bilko
(1984) was in the range of 7.6—8.6.
B. Ovarian fluid
Only a few data are available on the composition of ovarian fluid.
The
osmotic pressure is 306
mOsm for carp and 218 for silver carp.
Plouidy (1982)
and
Gosh
(1985)
reported
large differences in mineral and organic contents
between common carp and grass Carp. Plouidy (1982) found a concentration of 4.1
8l(carp and 2.7 g/l (silver carp) of total protein and 10—5 PM/ml
Of
æMno
acids
and
urea.
Hydrolases and dehydrogenases,
glucose and lactic
and
acids were
identified
in
carp
ovarian
fluid.
An
interesting feature
18
the