Study On Gynogenesis And Sex Control In Four Flounder Fish

The majority of marine fishes have a difference at growth rate between female and male. It was conducted by sex control and mono-sex culture to greatly increase yield and improve the efficiency of breeding according to the difference of growth rate. Recently, the rise of factory farming in flatfishes gave birth to the fourth aquaculture wave, especially the culture of tarbot and half-smooth tongue sole. Thus, the development of all-female group is very important to high-efficiency factory farming.Gynogensis technology is a well sex control technology, combined with the sex reversal make the product of all-female group possible. Here we report the methods of gynogenesis on the four important marine fishes and all-female production were attained by sex reversal. At the same time, the flow cytometry and microsatellite analysis were used to identification on the offspring of the gynogenesis.The following results were received:1. Summer flounder, Paralichthys dentatus, is an important commercial and recreational fish. In this study, diploid gynogenesis was induced by activating egg development with UV irradiated summer flounder sperm or sea perch sperm (80 mJ/cm2) for 5 min in seawater, and then subjecting the eggs to coldshock in 3℃seawater for 45 min. The hybrid of could not survive to hatching, thus the offspring was allogynogenesis only. The normal temperature of cultivation to one years later, the total survival is 228 and 100 randomly selected to identify the sex ratio. The result show that the female were 38 while the male were 62. Sex ratio are not comply the presumed 1:1 by the chi-square test. The 2700 individuals were dealt with using different methods of hormone treatment, 30 to 100 fishes from each treatment group randomly selected after one year cultivation and were determined the sex ratio. The results of all treatment groups were male and the male ratio was 100%.2. Southern flounder, Paralichthys lethostigma, is one member of a large family of distinctive benthic flatfishes with a high economic values. Effective methods for induction of diploid gynogenesis of the southern flounder, Paralichthys lethostigma, are needed to initiate monosex culture, which will allow growers to take advantage of the more rapid growth and larger size attained by females. The results of experiments showed that gynogenetic diploid and triploid can be induced by inactivated homologous sperm and noninactivated, respectively; and only gynogenetic diploid were obtained using inactivated heterologous sperm because that hybrid would be died before hatching. Diploid gynogenesis was induced by activating egg development with UV irradiated homologous sperm (80 mJ/cm2) for 4~5 min in seawater, and then then 65MPa pressure treatment for 6min. Flow cytometry and microsatellite DNA analysis were used to demonstrate diploidy. These results indicate that the use of UV irradiated sperm from Lateolabrax japonicas for activation of flounder eggs and pressure shock for polar body retention is an effective method to produce gynogenetic offspring.subjecting the eggs to coldshock in 3℃seawater for 45 min. The offspring of gynogensis were identified by morphologically examination after one year. The result show that the rate of male was 42.8%. After the Androgen immersion and the feeding, the rate of male can reach to 95.3% and 97.5%, respectively.3. Barfin flounder, Verasper moseri is an important economical marine fish. Since females grow faster than males, the production of all-female populations is highly desirable. To test methods for inducing diploid gynogenesis in barfin flounder using homologous sperm, The Cryopreservative sperm of Lateolabrax japonicas was used to active eggs and cool shock was used to prevent extrusion of the second polar body. Four treatments, named for their expected outcome, were employed: hybrid, haploid, triploid, and gynogenetic diploid to prove the ability of Lateolabrax japonicas sperm activing flounder eggs. Diploid gynogenesis was induced by activating egg development with UVirradiated sperm (80 mJ/cm2) for 7~9 min in seawater, and then subjecting the eggs to cold shock in -1~1.5℃seawater for 60–90 min. The hybrid of could not survive to hatching, thus the offspring was allogynogenesis only and the result of microsatellite markers analysis proved this result. This work provides procedures for induction of diploid gynogenesis in barfin flounder using heterologous sperm.4. Half-smooth tongue sole (Cynoglossus semilaevis) is a newly exploited and commercially important cultured marine fish in China. In order to attain the all-female and elucidation the sex mechanism of tongue sole, a set of experiments were carried out for developing artificial gynogenesis technique in the tongue sole. First of all, the effects of different sperms on gynogenesis induction were examined. The sea perch (Lateolabrax japonicus) sperm was considered to be effective sperm in inducing gynogenesis in the tongue sole. Secondly, iradiation conditions for sea perch spermatozoa were developed. Thirdly, the optimal iniation time for cold shock of gynogenetic eggs was determined, the optimal temperature and treatment time were determined. Chromosomes from gynogenetic haploid, diploid were analyzed, WW chromosomes were discovered in some gynogenetic diploid embryos. Microsatellite marker technique was applied to analyze gynogenetic diploid fry. Among the 30 gynogenetic diploid fry, 11 fry contained only one allele, 19 contained two alleles which had same genetype as their mother. Finally, female-specific DNA marker for half-smooth tongue sole was observed in four individuals of ten gynogenetic diploid fry. Thus, a set of techniques for induction of artificial gynogenesis was developed for the first time in half smooth tongue sole, and more than 6600 gynogenetic diploid tongue sole fry were successfully produced by using this technique.In this study, the method of gynogenesis was established by sperm of the sea bass for four marine fishes and the flow cytometry and microsatellite were involved in the identification of offspring of gynogenesis. Moreover, the fishes of sex reversal were also achieved. Therefore it was a foundation for the gynogenesis and all-female production in practice. ?...