Induction Of Meiotic Gynogenesis And Sex Reversal In Diploid Misgurnus Anguillicaudatus

The loach(Misgurnus anguillicaudatus)is an important freshwater aquaculture fish in China with tender meat and high nutritional value.However,at present most loach seedlings are produced from wild species that are not selected,and the advantage of its potential improvement has not been fully mined yet.The female loach grows larger and faster than the males,so monosex cultivation is beneficial to increase the economic and yield benefit.This study aims at establishing a technique system for all-female breeding of loach.The main results and conclusions are as follows:According to the releasing time of the second polar body,the efficient artificial gynogenesis technology of loach was established.The fertilization cytology observation confirmed that the second polar body was released at 3-5 minute after artificial insemination.The eggs of loach were activated by the UV-inactivated sperm of yellow river carp(Cyprinus carpio).After 3.5 min,the meiotic gynogenesis was induced by heat shock treatment at 41 °C for 2 min,and several first-generation gynogenetic populations of the loach were obtained.In the gynogenesis experiment,the average fertilization rate and survival rate of loach was 21.33% and 10.26%.Diploidy of gynogenetic offspring was confirmed by flow cytometry and karyotype analysis.The homozygosity of gynogenetic loach was significantly improved.Through microsatellite marker analysis,the average effective number of alleles(Ne),average polymorphism information content(PIC),average observed heterozygosity(Ho)and average expected heterozygosity(He)of three gynogenetic population were significantly lower than those of wild type control group,and the genetic homozygosity was significantly higher than that of wild type.The number and proportion of homozygotes in each gynogenetic population were significantly higher than those in the wild-type population.The genetic distance between gynogenetic populations increased and the genetic identity decreased.The loach reversal technology was established.Through the treatment of30mg/kg 17α-Methyltestosterone(MT),gynogenetic loach and wild loach had been successfully transformed into the fish that the phenotype were male and the heredity is female.We used pseudo-male fish as male parent and the wild loach as female parent to breed all-female loach.The normal development of gonads was determined by histological observation of gonads.The results showed that the techniques of artificial induction of meiosis gynogenesis and sex reversal in loach were established in this paper,the genetic homozygosity of the first-generation gynogenetic offspring of loach increased,which provided important breeding materials for the cultivation of new varieties of loach.