FEMINIZATION and PROGENY TESTING OF CONVERTED MATERNAL (C-ZZ) GENOTYPE AFTER SEX REVERSE TO PRODUCE SUPER MALE (ZZ) IN OREOCHROMIS AUREUS EXPERIMENTALLY
Mohamed E. Farag1 and Ahmed Said Diab2
1Genetics Department.
2fish diseases departemnt. Central Laboratory for Aquaculture Research, Agriculture Research Center, Ministry of Agriculture, Egypt
Received 15/ 10/ 2011 Accepted 9/ 11/ 2011
Abstract
The present study represents a first step in program for producing “supermales” of Oreochromis aureus in Egypt as a practical solution for the unwanted reproduction of tilapia in ponds and for increases the fish production. A trial of sex reversal for feminization of sexually undifferentiated progeny from Oreochromis aureus was conducted using 17-β ethynylestradiol as a feminizing stimulating agent. Oral administration of powdered feed containing 500 and 1000 mg/kg-1 were tested for 30 days.
Upon termination of the experiment, average weight and length on higher doses were generally higher (103±0.006 mg & 22.3±0.306 mm respectively) than those fed on lesser amounts (101±0.003mg & 22±0.153 mm respectively) indicating the effectiveness of the hormone for enhancement of fish growth. Through 2009 experiments hormone effect was highly detectable among fry that were orally fed on 1000 mg/kg hormone-treated feed for 30 days (mean percentage of phenotypic females (MPF) was 94.33 ± 2.08%). While, fry consumed the 500-mg/kg hormone-treated feeds for 30 days was 83.67 ± 4.04%. Fry was feeding with hormone 17-β ethynylestradiol treated-feed 500 mg/kg showed that male, inter sex and non differential percentages were 11.2±4.39, 3±1 & 2.33±0.58 % respectively, while, this percentage decreased in fry treated-feed 1000 mg/kg showed that male, inter sex and non differential percentages were 3.33±1.53, 1.67±0.58 & 0.67±0.58 % respectively. From the 2010 experiments, the pseudofemales (C-zz) could be differentiated form the normal ones (wz) using pair-mating of normal genotypic males to the mixed females with normal males separately. Progeny testing of their offspring proved that the majority of females were originally genotypic females from the moment of fertilization and their offspring had a normal sex ratio of 1:1. Forty remaining females generated progeny including mean percentage of phenotypic males (MPM) was 70 ± 5.2% while female, inter sex and non differential percentages were 25 ± 4.3, 3 ± 1.9 & 2 ± 0.8 % respectively. Pseudofemales (C-zz) produce low number of male (70±5.2%) in first generation for estrogen-treated
females. Also it is hypothetically supposed that one third of these males are super males of the “C-zz” genotype and two thirds should be normal males “N-zz”. Further research by crossing these males after sexual maturation to normal females and testing their progeny will prove or disprove this hypothesis.
Key words: Sex reversal, Oreochromis, aureus, Feminization and Progeny testing.
