Study on sex ratio and comparison of morphological variation between genders of cultured half-smooth tongue sole(Cynoglossus semilaevis)

Studies were conducted to reveal the changes in sex ratio of juvenile half-smooth tongue sole(Cynoglossus semilaevis)in cultured group by identified genetic sex and phenotypic sex with SSR marker and histological section,respectively.Meanwhile,further comparative analysis of growth and morphological characteristics among female,male,and sex reversal male(neo-male)were carried out.The results were as follows.Genetically,there was no significant difference between females and males with the sex ratio 45.5% to 54.5%; however,only 53.5% of genetic females had ovaries,while 46.5% of them had testes.The genetic males all had testes,no sex reversal happened.As a whole,the ratio of males was 75.2% and significantly higher than the ratio of females 24.8% morphologically(P<0.05).The growth of neo-male half-smooth tongue sole was higher than the normal males,while lower than the phenotypic females between 6 months post hatching(mph)to 8 mph,but no significant difference was found(P>0.05).Interestingly,the body height of the phenotypic females was higher than the phenotypic males when they had the same total length.In general,the average ratio of total length to body height of phenotypic males was 4.05,however,the phenotypic females was 3.89.This ratio would be useful for discrimination of the gender of juvenile half-smooth tongue sole.