• Journal of Aquaculture
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• v.13 no.4
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• pp.331-338
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• 2000

To establish an alternate technology for all male seed production of Nile tilapia, Oreochromis niloticus at hatchery scale, the performance of progenies produced by crossing superfemale with sex reversed male was evaluated. Free crossings between 21 superfemales and 7 sex reversed males stocked in an aquarium for 60 days resulted in the production of 93.5 % male progenies, compared to 53.2 % males produced by an equal number of normal females and normal males. Spawning frequency was lower (19 times) in the experimental cross including superfemales than that (24 times) in the control including normal females. Seed production in the experimental aquarium was (3,085) significantly lower than that (3,797) of the control. Both in terms of seeds per female per day or seeds per g female per day, seed productivity did not significantly differ between these groups. The alternate technology involving crossing between superfemale and sex reversed male has proven to be an efficient alternate technology for mass production of all male seeds at the hatchery scale.

• Journal of Aquaculture
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• v.9 no.1
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• pp.101-106
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• 1996

Gynogenetic males induced from sex reversed female (${\Delta}XY$) were crossed with normal female (XX) for analysing their genotypes. The fish tested produced a high percentage of male progenies (93.3 to $100\%$) and were considered as supermales (YY). Superfemales (${\Delta}YY$) were also produced by combination of sex reversal and chromosome manipulation techniques. Superfemale fish can be produced approximetly $90\%$ of male when the fish were crossed with normal male. Chi-square values against an expected 1 : 1 (male : female) ratio were highly significant for both YY males${\times}$ normal females (P<0.01 or P<0.001) and ${\Delta}YY$ females${\times}$normal males (P<0.005 or P<0.001). All male progenies were produced consistently when crossed supermales (YY) with superfemales (${\Delta}YY$).

• Journal of Aquaculture
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• v.13 no.4
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• pp.325-330
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• 2000

For development of all male seed production at hatchery scale, a comparative study was made on the seed production traits of supermale (IT - t) and superfemale (IT - L1 ~) Nile tilapia, Oreochromis niloticus. Supermales were crossed with normal females (XX- f) and the superfemales with normal males (XY - t ) or sex reversed males (XX- L1 t); progeny survival of these crossings and sex ratio were evaluated. Hatching success of the eggs, fertilized by the supermale was significantly lower than that by the normal male. Over 95-99 % progenies sired by crossing supermales with normal females were males, while 52-55 % progenies alone were males with the cross of normal males and normal females. Hatching success and survival of alevins were significantly higher for the progenies of the crosses between superfemales and sex reversed males than those resulting from the crosses between superfemales and normal males. However, there was no significant difference in the sex ratio among the progenies of these crosses. Therefore, crossings of superfemales with sex reversed males provide the highest percentage of survival and male progenies.

• Journal of Aquaculture
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• v.8 no.4
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• pp.295-306
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• 1995

The present study was performed to produce supermales and superfemales in Oreochromis niloticus by combination of induced sex reversal and diploid gynogenesis. More than $95\%$ of female was obtained by oral administration of $17\beta-estradiol$ (480 mg/kg diet) to the eutheroembryonic larvae of this species. The result of progeny tests with XY pseudofemales showed that incidences of male progeny were ranged from $71.4\%\;to\;73.7\%$. p.opo.lion of male from XY pseudofemale was not significantly different (P>0.05) from that of $\chi^2$ (1:3), but it was significantly different (P<0.01) from that of $\chi^2$(1:1) Gynogenetic diploids were produced by applying cold shocks 3 min after insemination to the eggs of XY pseudofemale sperms were genetically inactivated by ultraviolet rays of 4,050 $erg/mm^2$. Fertilization rates of gynogenetic diploids were not different from that of their controls, however, hatching rates and early survival rates were silghtly lower than those of controls. In the cytogenetic studies, there was no difference in the size of cell and nucleus between the gynogenetic diploids and the controls. At 80 days after hatching, frequencies of gynogenetic male were higher than those of gynogenetic female (P<0.01) in their population.