Studies On Morphological And Genetic Sexualdifferences Of Large Yellow Croaker (Larimichthys Crocea)

In this study,we measured morphological characteristics and visceral organ parameters of gender of large yellow croaker(Larimichthys crocea),analyzed main morphological indexes,and compared the differences of external morphology,growth traits and visceral organ between female and male.Moreover,preliminary analyzed the differences of genome on female and male by using genome re-sequencing method,screened the gender specific candidate markers.The main results as follows:1.Principal Component Analysis(PCA)of 23 morphological characteristics of 554 large yellow croaker,we obtained 5 principal components that eigenvalue more than 1.5,whose cumulative contribution rate is 82.56%.They are the overall framework structure,the level of obesity,the head and snout length,the trunk and caudal peduncle and the size of chest longitudinal section.2.The comparison results of external characteristics of 554 large yellow croaker showed that the difference of 9 quantitative characteristics reach significant level(P<0.05)except snout length,eye diameter and caudal fin length between female and male,and 5 standard characteristics including fatness,body length to body height,body length to body thickness,head length to eye diameter and caudal peduncle length to caudal peduncle height have extremely significant difference(P<0.01).Of them fatness,body length to body thickness,body length to body height have greatest differences,and this three value would be useful for the sex discrimination.Comprehensive analysis indicated that body height,body thickness and caudal peduncle height of female are larger than male,while the eye diameter,caudal peduncle length of male are longer than female,the body configuration of female is much fatter,and its type is thick and fat,while the type of male is flat and thin.3.We compared the growth of quantitative characteristics of gender of 10 large yellow croaker families.There are 9 quantitative characteristics are significant different(P<0.05)in growth except snout length,eye diameter and caudal fin length between female and male.Discriminant analysis was performed at the level of population and family.we found the best discriminant accuracy of population is 76.83% and the best discriminant accuracy of family is 97.1%,which indicates that discriminant analysis based on family is more accurate.4.By the comparision of eight organs and seven visceral index differences of the large yellow croaker between male and female,some differences were observed: except for the heart and maw index difference being not significant,the rest of differences in the internal organ parameters are extremely significant(P < 0.01).The difference of the gonads,liver,stomach and intestine length is the largest,and these organs are closely related to the reproductive system and digestive system.The result reveals that the shape difference in large yellow croaker male and female is relative to different reproductive energy configuration and the functional strength of digestive system.5.Here,we used NGS based re-sequencing method to analysis the differences in the level of genetic between male and female.By preliminary analysis,we found out 3 long potential fragments for the X-chromosome candidate and 1448 short underlying fragments for Y-chromosome by the use of bioinformatics.The length of 3 long fragments are 21.6K,30.8K and 47.4K,respectively.