8£@!@gy af gameäes, eggs, embwos
159
V1 — INCUBATION
'
The
duration of embryogenesis varies according to the species:
in degree—
days:
60—70 for carp,
24—30 for grass carp and silver carp,
30—50 for bighead
carp,
and
60—70 for
tench.
The
optimal incubation temperature is 20—22°C for
carp
and
22—25°C
for
the
Chinese
carp
and
the
tench
(Horvath
and
Lukowicz,
1982) and 10—12°C for roach (Gulidov and Popova, 1979). According to Kokurewicz
(1970),
the range was wider:
19—24°C
for tench and 12—24°C for reach.
The size
of the
hatched larvae
is
also
influenced by the temperature during incubation;
for Idus
idus
the lenght was shorter at 9 than at 13°C. Usually eggs will stand
a
short—term temperature change. For instance, during synchronous segmentation,
carp eggs
support 1h of thermal fluctuation within a range of 8 to 28°C (Jaoul
and
Roubaud,
1982).
Carp eggs are fragile after degumming (Rubstov,
1973),
although the
metabolic
process
was
not
altered
neither
during embryonic nor
post—embryonic development (Moroz and Luzhin,
1976).
The eggs of Chinese carp
are
also
very
fragile and any injury during handling may result in an altera—
tion of the structure of the
swollen chorion
(Mikodina and Malayeva, 1980).
During incubation, the water should be filtered, the phosphate content low
(< 0.12 mg/l) (TOOR et al., 1983), exempt of zooplankton such as cyclopids, and
saturated with oxygen.
In 8—liter Zugg jars containing 250—300 g of fertilized
carp eggs,
the
flow rate should be limited to 1.5 1/min during the first hours
to
avoid
shocking the
eggs
and
to
3
1/min afterwards.
Larger incubators are
used
for
Chinese
carp
eggs.
A
wide
variety of incubators and other hatchery
equipment are described by Woynarovich and Horvath (1981).
CONCLUSION
Work
on
gametes and
fertilization
in
cyprinids
has
been
limited
in
the
past few years.
The
actual
information
available
does
not
allow
a
good pre—
diction of gamete quality which seems to depend on various environmental fac—
tors, especially the feeding rate and temperature for females. The loss of ovum
fertilizability after ovulation and autoactivation after dilution limits the
possibilities of storage and handling.
On the contrary,
carp spermatozoa show
good intratesticular survival and can be stored for a few days in the refrige—
rator.
The
improved technique of artificial insemination results in a better
utilization of gametes which are mixed in a well—defined diluent but an impro—
vement of the technique for degumming eggs is still needed.
Aknowledgements.
The manuscript was translated by A.
Daifuku and
reviewed by
R.E. Peter and Z.
Yaron.
159
V1 — INCUBATION
'
The
duration of embryogenesis varies according to the species:
in degree—
days:
60—70 for carp,
24—30 for grass carp and silver carp,
30—50 for bighead
carp,
and
60—70 for
tench.
The
optimal incubation temperature is 20—22°C for
carp
and
22—25°C
for
the
Chinese
carp
and
the
tench
(Horvath
and
Lukowicz,
1982) and 10—12°C for roach (Gulidov and Popova, 1979). According to Kokurewicz
(1970),
the range was wider:
19—24°C
for tench and 12—24°C for reach.
The size
of the
hatched larvae
is
also
influenced by the temperature during incubation;
for Idus
idus
the lenght was shorter at 9 than at 13°C. Usually eggs will stand
a
short—term temperature change. For instance, during synchronous segmentation,
carp eggs
support 1h of thermal fluctuation within a range of 8 to 28°C (Jaoul
and
Roubaud,
1982).
Carp eggs are fragile after degumming (Rubstov,
1973),
although the
metabolic
process
was
not
altered
neither
during embryonic nor
post—embryonic development (Moroz and Luzhin,
1976).
The eggs of Chinese carp
are
also
very
fragile and any injury during handling may result in an altera—
tion of the structure of the
swollen chorion
(Mikodina and Malayeva, 1980).
During incubation, the water should be filtered, the phosphate content low
(< 0.12 mg/l) (TOOR et al., 1983), exempt of zooplankton such as cyclopids, and
saturated with oxygen.
In 8—liter Zugg jars containing 250—300 g of fertilized
carp eggs,
the
flow rate should be limited to 1.5 1/min during the first hours
to
avoid
shocking the
eggs
and
to
3
1/min afterwards.
Larger incubators are
used
for
Chinese
carp
eggs.
A
wide
variety of incubators and other hatchery
equipment are described by Woynarovich and Horvath (1981).
CONCLUSION
Work
on
gametes and
fertilization
in
cyprinids
has
been
limited
in
the
past few years.
The
actual
information
available
does
not
allow
a
good pre—
diction of gamete quality which seems to depend on various environmental fac—
tors, especially the feeding rate and temperature for females. The loss of ovum
fertilizability after ovulation and autoactivation after dilution limits the
possibilities of storage and handling.
On the contrary,
carp spermatozoa show
good intratesticular survival and can be stored for a few days in the refrige—
rator.
The
improved technique of artificial insemination results in a better
utilization of gametes which are mixed in a well—defined diluent but an impro—
vement of the technique for degumming eggs is still needed.
Aknowledgements.
The manuscript was translated by A.
Daifuku and
reviewed by
R.E. Peter and Z.
Yaron.