| In this research the heritability of growth-related traits of 23-month aged Paralichthys olivaceus was estimated by means of intra-group correlation of full-sibs, casual variance components of phenotypic variants were dissected as paternal half-sibs variance component, maternal half-sibs variance component and full-sibs variance component. The used parent population, of 3-5 year aged healthy wild Paralichthys olivaceus in this analysis, were collected from different sites of Shandong peninsula and induced into normal breeding stage by means of artifical light induction in April, 2007. Eight sires and twenty six dams were mated by an unbalanced nest design. Eight half-sib families and 26 full-sib families were produced by artificial fertilization. 21～44 23-month aged individuals were randomly selected from each half-sib family and measured for growth-related traits of body weight, body length and full length. Causal component s of phenotypic variance were calculated with the GLM procedure of the SAS software. The result of analysis indicated that the heritability of body weight was between 0.474 and 0.707, the heritability of body length was between 0.397 and 0.398, the heritability of full length was between 0.481 and 0.605. Only the t test of heritability estimated by full-sibs variance component was significant. The estimation of heritability of body weight was bigger compared to former research, which maybe due to the increasing trend of the CV of phenotypic variants with increasement of age or the genetic difference of parent population. The estimation of heritabilities of body length and full lenth were basically consistent with former research. These three traits have a big potential of selection breeding. Duing to the insufficiency of measured number of families in this research, the heritabilities estimated by paternal half-sibs and maternal half-sibs variance component were insignificant. It is necessary to increase the sample content, makesure the minimal number of family and increase content of family to improve the veracity of heritability estimation and provide important genetic parameter for the establishment of selection breeding plan of Paralichthys olivaceus.100 3-month aged and 131 23-month aged Paralichthys olivaceus , from the families built in Apr. 2007 , were randomly sampled for measuring five morphometric traits including body length (X1), full length (X2), head length (X3), body width (X4), body height (X5) and body weight (Y). By path analysis and multiple linear regression through SAS 8.2 software , this study estimated the path coefficients and determination coefficients of each morphometric trait to body weight and dissected effect of each morphometric trait on body weight as direct effect and indirect effect. This study also confirmed the main morphometric traits influencing the body weight of 3-month aged and 23-monthe aged Paralichthys olivaceus and provided theoretical evidence and optimal measuring indexes for selection breeding of Paralichthys olivaceus. The results showed that the correlation coefficients between all morphometric traits and body weight were extremely significant (P<0.01). The path coefficients of body length,body width and body height of 3-month aged Paralichthys olivaceus to body weight were all extremely significant (P<0.01). Whilst, the degree of determination of body length and body width to body weight were big enough to be chosen as optimal measuring indexes for selection breeding of Paralichthys olivaceus in this stage. The path coefficients of full length of 3-month aged Paralichthys olivaceus to body weight were significant (P<0.05), and that of body width and head length to body weight were both extremely significant. Whilst, the degree of determination of this three morphometric traits to body weight were all big enough to be chosen as optimal measuring indexes in this stage. The total determination coefficient of all selected morphometric traits in 3-month and 23-month aged Paralichthys olivaceus to body weight (R2) were 0.9448 and 0.8650 respectively, which means the main morphometric traits influencing body weight in both 3-month and 23-month aged Paralichthys olivaceus were included in this study. The insignificant morphometric traits were excluded through coefficient test of partial regression, and then the optimal multiple linear regression equation was established respectively. The optimal multiple linear regression equation of 3-month aged Paralichthys olivaceus was: Y=-4.98829+0.76291X2+2.99686X4+1.08878X5, of which the determination coefficient was 0.9426, and in which all included partial regression coefficients are extremely significant (P<0.01). The optimal multiple linear regression equation of 3-month aged Paralichthys olivaceus was: Y=-815.57935+1.60448X2+3.86923X3+3.09831X4 , of which the determination coefficient was 0.8611, and in which all included partial regression coefficients are extremely significant (P<0.01).The estimation of upper thermal tolerance of different families in different month-aged Paralichthys olivaceus by average tolerance time of tested individuals , which come from the built families in May 2008, was firstly conducted in two different speed of heating up, acute heat up by 1.6℃/h and chronic heat up by continuous 1.6℃/h for 2℃and kept for two days, at 1-month, 4-month and 11-month aged respectively. The results showed that there was a significant difference of acute and chronic upper thermal tolerance in different mont-aged Paralichthys olivaceus between different families, which indicates possible potential to improve both traits. Also, this research mensurated the phenotypic parameters of upper thermal tolerance in different month-aged Paralichthys olivaceus for the first time, and made the estimation of tolerance time more exact through eliminating the effect of body length on tolerance time by covariance analysis. Whilst, this research confirmed two effective heat up approaches, acute heat up and chronic heat up, and made an elementary evaluation of parental upper thermal tolerance ability, which provides basic data and methodological reference for the estimation of heritability for upper thermal tolerance in different month-aged Paralichthys olivaceus.
|
PDF Full Text Request