Çommi of sex in Çypriids
181
carps
to
predict ovulation and reduce the risk of over—ripe eggs. Additional
precision may be gained from examining catheterized ova for the chronology of
germinal vesicle movement as reported for silver carp (Hypophthalmichthys
nmlitrix) (Duvarovas 1982), goldfish (Carassius auratus)_ÎÏaÎËËËËËÎ_197ËÎ and
carp
(Bieniarz and Epler,
One additional consideration in relation to induced ovulation involves
gamete storage. Application is particularly apropros to sperm treatment for
induced gynogenesis where short—term storage in needed. Consideration might
be given to cryopreservation of sperm for broodstock that are too important
to
transport to remote spawning sites but where milt shipment is plausible.
Fish gamete storage was recently reviewed by Stoss (l983).u8imple physiologie
salines
(Randall and Hear, 1971) and refrigeration are adequate for practical
use.
Quality of cyprinid sperm is affected seasonally and by various environ—
mental factors
(Belanova, 1981a,b ; Zhukinskiy and Alekseenko, 1983) and must
be a consideration for fertilization capability, either using normal or trea—
ted and stored milt.
Sex determination°
Reproductive diversity in fishes is unparalleled among other vertebrates;
virtually the complete range of sexuality is represented in fishes. Conse—
quently, it should not be surprising that no single explanation of sex deter—
mination is satisfactory° Some species appear to have polygenic sex determi—
nation, others may have functional sex chromosomes that are essentially auto—
somes
bearing sex—determining genes, while a few have heteromorphic sex chro—
mosomes
(Yamamoto, 1969 ; Gold, 1979). The evolutionary tendency among verte—
brates has been to aggregate sex determining genes on a single pair of
dm080mesêeasily discernible heteromorphic sex chromosomes have been demons—
trated in few fishes, yet heterosomal systems have been demonstrated by
genetic techniques (Vanyakina, 1969 ; Hunter and Donaldson, 1983 ; Reinboth,
1983). Chourrout (in press a) indicated that only 60 species (10 % of those
examined) have cytologically differentiated sex chromosomes. The determina—
tion of sex by chromosomes that differ in a few genes is characteristic of
fishes, including the cyprinids (Kirpichnikov, 1981). Apparently, modified
genes are also
located on autosomes but predominant control is by sex genes
on
seX(jmomosomes(Kallman, 1984). Male heterogamety has been established in
35 fishes while female heterogamety has been found in 14 (Kirpichnikov,
Reinboth (1983) and Yamazaki (1983) indicated that heterogamety is wellestab—
lished and the XX female system is the most widespread. Evidence for functio—
nal sex chromosomes without apparent dimorphism is found in various gynogene—
tic and sex inversion studies which will be discussed later. The general rule
for cyprinids is a homogametic female : common carp (Nagy et al., 1978,
golfish (Yamamoto and Kajishima, 1968), grass carp (Ctenopharyngodon idella)
(Stanley, 1976a ; Shelton in press a), silver carp (Mirza and Shelton, in
prep.) and bighead carp (Aristichthys nobilis) (Shelton, unpubl. data). The
generic sex of fish is determined at fertilization, whether solely through
the control
of
sex
chromosomes or with influence from autosomal factors
(Harrington, 1974). Fertilization determines the genetic sex and genetic
sex
is translated
consistently into gonadal sex (Reinb0th, 1982) ; therefore,
gonadal differentiation
is the phenotypic expression Of the
genotype,
but external and internal environmental influences may alter this sex deter—
mining pathway
1969)»
Gonadal differentiation (GaD.)a
_The process of gonadal development under
the control
Of the gen0typî969
is generally accepted, but the mechanism of induction is not. Yamamoto
(
)
reViewed the plausible hypothese for induction of
sexual differentiation:
_
&nŒer and Donaldson (1983) concluded that no Single
Of
sex determinî
ÜDn and sex differentiation is totally acceptable for fishes. Without imp y—
ùŒ that the steroid inductor model is the most acceptable one, lt ls cgmpa
re with the capability to redirect phenotypic
sexual development Wlt
181
carps
to
predict ovulation and reduce the risk of over—ripe eggs. Additional
precision may be gained from examining catheterized ova for the chronology of
germinal vesicle movement as reported for silver carp (Hypophthalmichthys
nmlitrix) (Duvarovas 1982), goldfish (Carassius auratus)_ÎÏaÎËËËËËÎ_197ËÎ and
carp
(Bieniarz and Epler,
One additional consideration in relation to induced ovulation involves
gamete storage. Application is particularly apropros to sperm treatment for
induced gynogenesis where short—term storage in needed. Consideration might
be given to cryopreservation of sperm for broodstock that are too important
to
transport to remote spawning sites but where milt shipment is plausible.
Fish gamete storage was recently reviewed by Stoss (l983).u8imple physiologie
salines
(Randall and Hear, 1971) and refrigeration are adequate for practical
use.
Quality of cyprinid sperm is affected seasonally and by various environ—
mental factors
(Belanova, 1981a,b ; Zhukinskiy and Alekseenko, 1983) and must
be a consideration for fertilization capability, either using normal or trea—
ted and stored milt.
Sex determination°
Reproductive diversity in fishes is unparalleled among other vertebrates;
virtually the complete range of sexuality is represented in fishes. Conse—
quently, it should not be surprising that no single explanation of sex deter—
mination is satisfactory° Some species appear to have polygenic sex determi—
nation, others may have functional sex chromosomes that are essentially auto—
somes
bearing sex—determining genes, while a few have heteromorphic sex chro—
mosomes
(Yamamoto, 1969 ; Gold, 1979). The evolutionary tendency among verte—
brates has been to aggregate sex determining genes on a single pair of
dm080mesêeasily discernible heteromorphic sex chromosomes have been demons—
trated in few fishes, yet heterosomal systems have been demonstrated by
genetic techniques (Vanyakina, 1969 ; Hunter and Donaldson, 1983 ; Reinboth,
1983). Chourrout (in press a) indicated that only 60 species (10 % of those
examined) have cytologically differentiated sex chromosomes. The determina—
tion of sex by chromosomes that differ in a few genes is characteristic of
fishes, including the cyprinids (Kirpichnikov, 1981). Apparently, modified
genes are also
located on autosomes but predominant control is by sex genes
on
seX(jmomosomes(Kallman, 1984). Male heterogamety has been established in
35 fishes while female heterogamety has been found in 14 (Kirpichnikov,
Reinboth (1983) and Yamazaki (1983) indicated that heterogamety is wellestab—
lished and the XX female system is the most widespread. Evidence for functio—
nal sex chromosomes without apparent dimorphism is found in various gynogene—
tic and sex inversion studies which will be discussed later. The general rule
for cyprinids is a homogametic female : common carp (Nagy et al., 1978,
golfish (Yamamoto and Kajishima, 1968), grass carp (Ctenopharyngodon idella)
(Stanley, 1976a ; Shelton in press a), silver carp (Mirza and Shelton, in
prep.) and bighead carp (Aristichthys nobilis) (Shelton, unpubl. data). The
generic sex of fish is determined at fertilization, whether solely through
the control
of
sex
chromosomes or with influence from autosomal factors
(Harrington, 1974). Fertilization determines the genetic sex and genetic
sex
is translated
consistently into gonadal sex (Reinb0th, 1982) ; therefore,
gonadal differentiation
is the phenotypic expression Of the
genotype,
but external and internal environmental influences may alter this sex deter—
mining pathway
1969)»
Gonadal differentiation (GaD.)a
_The process of gonadal development under
the control
Of the gen0typî969
is generally accepted, but the mechanism of induction is not. Yamamoto
(
)
reViewed the plausible hypothese for induction of
sexual differentiation:
_
&nŒer and Donaldson (1983) concluded that no Single
Of
sex determinî
ÜDn and sex differentiation is totally acceptable for fishes. Without imp y—
ùŒ that the steroid inductor model is the most acceptable one, lt ls cgmpa
re with the capability to redirect phenotypic
sexual development Wlt