| Oyster is an important marine economic shellfish in the world.In recent years,the production of oysters in China has always been the first in the world.Fujian oyster(Crassostrea angulata),also known as the Portuguese oyster,is the main cultured oyster species in southern China,especially in Fujian Province.However,with the rapid development of industrialization,the heavy metal pollution in coastal areas of China is increasing day by day.Oysters are strong accumulator of heavy metals,especially for copper,zinc and cadmium,and they can still be alive with extremely high body metal concentration.In recent years,"blue-colored" and "green-colored"oysters have always been found in some contaminated oyster farms in China,and the total content of Cu and Zn in their body can reach up to 3%-7%of the whole-body tissue dry weight! The appearance of such "blue-" and "green-colored" oysters has undoubtedly posed great threat to the oyster industry and human seafood safety.However,it's impossible to alleviate the heavy metal contamination effectively in a short term in China.In view of this,based on the characteristics of Cu/Zn accumulation in oysters,as well as inspired by the researches about disease resistance of oysters,we focused on the genetic breeding of Cu and Zn enrichment capability,estimating the genetic parameters of Cu/Zn enrichment capability and growth traits,and carrying out a preliminary study on the relationship between Cu/Zn enrichment capability and glycogen content with our constructed C.angulata families.The main results are as follows:1.Study on the tissue distribution of Cu and Zn at different gonadal development stages of C.angulataIn order to find a tissue which can represent the Cu and Zn enrichment level of oysters during different gonadal development stages,Fujian oysters were collected at a same batch and dissected into mantle,gill,adductor,visceral mass and gonad after identifying the gonadal development stages,and then the Cu and Zn concentrations were determined separately.The results showed that gill has the highest Cu/Zn concentration which was followed by mantle,and the highest Cu/Zn content occurred in mantle(except for Cu content at gonadal maturation stage).Correlation analysis showed that Cu/Zn concentrations of mantle had the highest correlation coefficient with the concentrations of whole-body tissue(except for gonad).The results indicated that the Cu/Zn concentration of mantle can represent the whole-body Cu/Zn enrichment level of C.angulata,and is not affected by gonadal development.2.Estimation of the genetic parameters of Cu and Zn enrichment capability and growth traits in C angulataA nest design was carried out with 12 sires and 60 dams to produce 12 half-sib families and 60 full-sib families,of which 9 half-sib and 36 full-sib families were used to estimate the genetic parameters after one year.Results showed that,the CVs of Cu and Zn concentrations among different C.angulata individuals were 65.69%and 47.34%respectively,the values of narrow-sense heritability were 0.19±0.07 for Cu and 0.32±0.10 for Zn enrichment capability,the phenotypic and genetic correlation coefficient between Cu and Zn enrichment were 0.859 and 0.796 respectively.These indicated that the Cu and Zn enrichment capability in C.angulata has a high breeding potential,and the narrow-sense heritability for Cu enrichment is moderate while for Zn is medium-to-high,both the phenotypic and genetic correlation between Cu and Zn enrichment were positive and high,so they can be both effectively selected by pedigree breeding at the same time.The estimation for growth traits of C.angulata showed that,the CVs of live weight,dry meat weight and dry adductor weight were 40.28%,61.07%and 48.19%respectively,meaning high breeding potential.The narrow-sense heritability for live weight and shell length were 0.39±0.11 and 0.43±0.12,which were higher than Cu and Zn,Live weight showed high phenotypic and genetic correlation with shell length,shell width and shell depth(r>0.670).And both the phenotypic and genetic correlation among dry adductor weight,shell width and dry meat weight were high,too(r>0.610).Genetic parameters suggested that most of the growth traits of C.angulata can be improved by genetic breeding.The phenotypic and genetic correlation coefficients between Cu/Zn enrichment capability and growth traits were all below 0.436,means low correlation.Therefore,it is not possible to indirectly select the Cu/Zn enrichment capability of C.angulata by growth traits,but the selection for Cu/Zn enrichment capability will not affect these growth traits.3.Preliminary study on the relationship between Cu/Zn enrichment capability and glycogen content of C.angulataThe same materials of C.angulata as in chapter 2 were used to find a tissue which can best represent the glycogen content of oysters during different gonadal development stages.The results showed that mantle has both the highest glycogen concentration(content)and the highest correlation coefficient with the concentrations of whole-body tissue(except for gonad),indicating that the glycogen concentration of mantle can represent the whole-body glycogen level during different gonadal development stages.Based on this,six C.angulata families with differential Cu/Zn enrichment capability were selected to investigate the relationship between Cu/Zn enrichment and glycogen content.The results showed there was no specific regularity between Cu/Zn enrichment and glycogen content,and the correlation between them was low(except for family L2).As a result,we concluded that there is no significant relationship between Cu/Zn enrichment capability and glycogen content in C.angulata living in clean seawater. |
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