184
W.L. She/fon
Silver carp have been treated using a similar protocol (Mirza and Shelton,
in prep.). Oral treatment of the filterfeeding silver carp would have been
futile since they rarely take a prepared diet. The 5—mg implant was administe—
red in the same general size range as for the grass carp because of the simi—
larity in G.D., but was difficult because of their sensitivity. Most of those
treated between 65 and 105 mm died but 20—37 % of the fish treated between
110 and
135 were sex inverted.
The
injectable suspension of MT was again in
ineffective. No sex—inverted fish were retained for breeding ; however, based
on
gynogenesis we can suggest that the silver carp females are homegametic
(XX) .
Successful sex inversion is directly related to knowledge of the particu—
lar
fish. We need more information on growth in relation to G.D. and the
effect on sex inversion.
Stocking density is important in oral hormone treat—
ments
ascompetitionnæy'prevent some fish from receiving an adequate food/hor—
mone
allowance
;
this can be related to the shoot—carp phenomenon (Wohlfarth,
1977). Growth management is vital for maintenance of an optimal physiologica1
hormone
level as a function of the diffusion from an implant. Measurement of
circulating, exogenous steroid from feeding or implant studies would suggest
rates
and exposure times necessary to effect sex inversion.
Residual androgen
and tissue clearance rates will be needed if treated fish are to be eaten.
Delivery systems, such as the implant or liquid carrier, need further development.
GYNOGENËSIS.
Gynogenesis is the development of an individual with only maternal inheri—
tance
and most frequently involves the retention of the second polar body as
the mechanism for restoration of diploidy. Diploidization can also be induced
by interference with the first mitotic division of developing haploids. The
incidence of diploidization by either means is low but can by increased by a
variety of physical shocks or chemical treatment, if applied at the appropri—
ate
time. Most larvae develop as haploids and survive only briefly beyond
hatching
(Cherfas, 1981). To eliminate the sperm genome,they are treated with
either Cobalt 60, x—rays or ultraviolet radiation. The latter is the most
convenient and safest, and recent studies indicate that it is the cleanest
treatment
because no chromosome fragmenŒ;remain (Chourrout, in press b ;
Streisinger et al., 1981). Thorgaard (1983) reviewed gynogenesis and other
ploidy manipulations. Gynogenesis has several direct applications, 1) chromosome
mapping (Nagy and Csanyi, 1978 ; Nagy et al., 1979 ; Gervai and
Csanyi, 1984), 2) inbreeding or increasing homozygosity
(Stanley and Sneed:
1974
;
Nagy and Csanyi 1982 ; Nagy et al., 1983) and 3) production of monoseX
populations (Stanley, 1976a, 1981 ; Stanley et al., 1975). In purpose
of monosexing, gynogenesis may be used to develop a pool of known females for subse—
quent breeding programs (Stanley, 1976c,d ; Shelton, 1982 ; Shelton et al.,
1982 ; Nagy and Csanyi, 1984). Gynogenesis by polar body retention rapidly
increases
the homozygosity but some heterozygous loci are retained because
of
crossing over between chromosome segments. Nevertheless, polar body gynogenes15
results in rapid inbreeding for several generations ; in carp
each
generation
is rough1y equivalent to 10—12 sibling crosses (Nagy et al., 1979)°
Gyn0g8neSis through mitotic interference can produce absolute homozygoSity—
Gynogenesis has been investigated rather extensively in common carp.
Golov1nskaya(1968’ 1969) reported occurrence in carp with a frequency of about
0-1—3 Z.
Makino and Ozima (1943) induced second polar body retention by coding
fertilized eggs to 0.5—3C during the first 30 minutes of development. They
related the action to the completion of meiosis at 17—18C ; telophase ocureed
1Q—15
minutes after insemination and the second polar body formed at 25—30
minutes.
Cherfas
(1975) increased gynogenesis by cold shock from 0.1—1 % in
the control
to
8—22 %
;
shock temperature was 8—9C for 210—330 minutes.
Taniguchi et al.
(in press) produced 25 % diploids by treating Koi carp 6385
12
to
15 minutes after insemination at 0.5C for 60 minutes. Nagy et.
(1978)
W.L. She/fon
Silver carp have been treated using a similar protocol (Mirza and Shelton,
in prep.). Oral treatment of the filterfeeding silver carp would have been
futile since they rarely take a prepared diet. The 5—mg implant was administe—
red in the same general size range as for the grass carp because of the simi—
larity in G.D., but was difficult because of their sensitivity. Most of those
treated between 65 and 105 mm died but 20—37 % of the fish treated between
110 and
135 were sex inverted.
The
injectable suspension of MT was again in
ineffective. No sex—inverted fish were retained for breeding ; however, based
on
gynogenesis we can suggest that the silver carp females are homegametic
(XX) .
Successful sex inversion is directly related to knowledge of the particu—
lar
fish. We need more information on growth in relation to G.D. and the
effect on sex inversion.
Stocking density is important in oral hormone treat—
ments
ascompetitionnæy'prevent some fish from receiving an adequate food/hor—
mone
allowance
;
this can be related to the shoot—carp phenomenon (Wohlfarth,
1977). Growth management is vital for maintenance of an optimal physiologica1
hormone
level as a function of the diffusion from an implant. Measurement of
circulating, exogenous steroid from feeding or implant studies would suggest
rates
and exposure times necessary to effect sex inversion.
Residual androgen
and tissue clearance rates will be needed if treated fish are to be eaten.
Delivery systems, such as the implant or liquid carrier, need further development.
GYNOGENËSIS.
Gynogenesis is the development of an individual with only maternal inheri—
tance
and most frequently involves the retention of the second polar body as
the mechanism for restoration of diploidy. Diploidization can also be induced
by interference with the first mitotic division of developing haploids. The
incidence of diploidization by either means is low but can by increased by a
variety of physical shocks or chemical treatment, if applied at the appropri—
ate
time. Most larvae develop as haploids and survive only briefly beyond
hatching
(Cherfas, 1981). To eliminate the sperm genome,they are treated with
either Cobalt 60, x—rays or ultraviolet radiation. The latter is the most
convenient and safest, and recent studies indicate that it is the cleanest
treatment
because no chromosome fragmenŒ;remain (Chourrout, in press b ;
Streisinger et al., 1981). Thorgaard (1983) reviewed gynogenesis and other
ploidy manipulations. Gynogenesis has several direct applications, 1) chromosome
mapping (Nagy and Csanyi, 1978 ; Nagy et al., 1979 ; Gervai and
Csanyi, 1984), 2) inbreeding or increasing homozygosity
(Stanley and Sneed:
1974
;
Nagy and Csanyi 1982 ; Nagy et al., 1983) and 3) production of monoseX
populations (Stanley, 1976a, 1981 ; Stanley et al., 1975). In purpose
of monosexing, gynogenesis may be used to develop a pool of known females for subse—
quent breeding programs (Stanley, 1976c,d ; Shelton, 1982 ; Shelton et al.,
1982 ; Nagy and Csanyi, 1984). Gynogenesis by polar body retention rapidly
increases
the homozygosity but some heterozygous loci are retained because
of
crossing over between chromosome segments. Nevertheless, polar body gynogenes15
results in rapid inbreeding for several generations ; in carp
each
generation
is rough1y equivalent to 10—12 sibling crosses (Nagy et al., 1979)°
Gyn0g8neSis through mitotic interference can produce absolute homozygoSity—
Gynogenesis has been investigated rather extensively in common carp.
Golov1nskaya(1968’ 1969) reported occurrence in carp with a frequency of about
0-1—3 Z.
Makino and Ozima (1943) induced second polar body retention by coding
fertilized eggs to 0.5—3C during the first 30 minutes of development. They
related the action to the completion of meiosis at 17—18C ; telophase ocureed
1Q—15
minutes after insemination and the second polar body formed at 25—30
minutes.
Cherfas
(1975) increased gynogenesis by cold shock from 0.1—1 % in
the control
to
8—22 %
;
shock temperature was 8—9C for 210—330 minutes.
Taniguchi et al.
(in press) produced 25 % diploids by treating Koi carp 6385
12
to
15 minutes after insemination at 0.5C for 60 minutes. Nagy et.
(1978)