Induced meiogynogenesis in Japanese flounder (Paralichthys olivaceus) by sperm of red sea bream (Pagrus major)

Japanese flounder(Paralichthys olivaceus) is a commercially important marine finfish in China.The growth rate of Japanese flounder is significantly faster in females than in males.Effective methods for gynogenetic inducement in this species are important for all-female population construction.Meiogynogenesis was induced in Japanese flounder(P.olivaceus) by using UV irradiated sperm of red sea bream(Pagrus major).The sperm of red sea bream exhibited a significant Hertwig effect after irradiating by UV.The embryo had the lowest hatching rate(2.0% ± 0.1%) when UV dosage was 3.4 mJ/cm2,and recovered with the increase of UV dosage.It reached the highest hatching rate(57.7% ± 3.1%) when UV dosage was 73 mJ/ cm2,and ploidy analysis by flow cytometer showed that the embryos were all haploids.After a series of tests for initiation and duration at water temperature of(0 ± 0.5) ℃,the best parameters for meiogynogenesis inducing in Japanese flounder were determined that cold shock begun at 3 min after insemination and continued for 45 min.The fertilization rate and hatching rate at this scenario were 80.7% ± 1.1% and 57.3% ± 2.3%,respectively,which were significantly higher than all the other treatment groups(P 0.05).Fries of gynogenesis were confirmed to be diploids via flow cytometer.Further analysis of RAPD analysis showed that genetic material of red sea bream sperm was destroyed after UV irradiation and was not transmitted to progenies.This study provided an effective method to induce meiogynogenesis for all female population construction in Japanese flounder.