| Chinese mitten crab(Eriocheir sinensis),also known as river crab or hairy crab,is mainly distributed in the eastern coastal areas of China.Its rapid growth and delicious meat make this crab as one of the important economic crustaceans in China.As a muscle suppressor hormone,MSTN gene is involved in the regulation of muscle growth and development in animals.In order to further explore the influence of different MSTN genotypes on the growth of Eriocheir sinensis,and whether the related SNP genotypes are correlated with growth traits,and whether there is breeding potential.In this paper,the correlation analysis of MSTN genotypes and growth phenotype of Eriocheir sinensis under the two modes of individual recirculating aquaculture system and pond colony culture was carried out,and the morphological changes of muscle during molting in different genotypes were observed and compared.The main research contents are as follows:1.Differences in molting and growth of Eriocheir Sinensis with different MSTN genotypesIn order to explore the effects of different MSTN genotypes on the growth of Eriocheir Sinensis under the individual cultivation condition.In this chapter,the individual recirculating aquaculture system was used to observe the molting and growth characters of 99 individuals of Eriocheir Sinensis in two molting cycles,and the association analysis were conducted between the MSTN genotypes,their combinations and growth traits.The results showed that there were 5 SNP synonymous mutations in MSTN genotype,and the dominant genes were C,T,C,A,A and genotypes were CC,TT,CC,AA,TT,respectively.After two cycles of molting,the weight gain rate of TC genotype at SNP2 site decreased from 49.46%to 39.29%,and the average molting interval increased from 49.09 days to 69.83 days.The weight gain rate of TT genotype decreased from 48.09%to 38.71%,and the average molting interval increased from 51.11 days to 72.38 days.The weight gain rate of CC genotype decreased from 52.29%to 42.21%,and the average molting interval increased from 49.33 days to 68.55 days.There were no significant differences in body weight,shell length,conditional factor,weight gain rate and molting interval among the three SNP2 genotypes(P>0.05).After the first molting,CC/TT/CC/AA/TG genotype accounted for the highest proportion(23.23%),and the average body weight and shell length were higher than other genotypes,but there was no significant difference(P>0.05).The results of this study showed that different MSTN genotypes had certain effects on the growth and molting of Eriocheir Sinensis,which could further expand the sample size and explore the breeding potential of CC/TT/CC/AA/TG genotypes and TT genotypes in future.2.Population growth comparison of Eriocheir sinensis with different MSTN genotypes in pond culture conditionTo explore growth differences aomong different MSTN genotypes in Eriocheir Sinensis in pond culture condition,the adult crab of 1195 individuals were collected from three ponds,and associated analysis were conducted between the MSTN genotypes,their combination and growth traits.Tt was found that the coefficient of variation were the highest in body weight and the lowest in carapace length;and there were some differences in genotypes and phenotypic traits between female and male crabs.The genotypes of CC/TT/CC/AA/TT and CC/TT/CC/AA/TG accounted for the highest proportion in female and male crabs,and the growth phenotypes of the CC/TT/CC/AA/TG genotype were higher than those of the CC/TT/CC/AA/TT genotype.By analyzing genotypes in percentile range,the CC/TT/CC/AA/TT displayed a positive selection signal and the CC/TT/CC/AA/TG showed a negative selection signal,and the two genotypes showed the stronger selection pressures in d female than in male.In scatter plot curve fitting,the relationship between carapacel length and body weight of the genotypes of CC/TT/CC/AA/TT and CC/TT/CC/AA/TG were power functions,and the K value of fitting curve of male crabs was larger than that of female crabs,but R~2of fitting curve of female crabs was larger than that of male crabs.The results of this study showed that the genotypes of CC/TT/CC/AA/TT and CC/TT/CC/AA/TG were the dominant genotypes,and would have breeding potential in future.3.Muscle histological observation of Eriocheir Sinensis with different MSTN genotypesIn order to explore the change characteristics of muscle tissue of different genotypes of Eriocheir sinensis,histological observation and calculation of basic morphological indexes of muscle fibers were conducted by paraffin section,HE staining and electron microscope section in this chapter.The results showed that the morphological characteristics of muscle tissue in different parts of Eriocheir sinensis were different.Abdominal muscle fibers are irregular in shape,pointed at both ends,mostly diamond shaped and closely arranged.Chelate muscle fibers are oval in shape,arranged loosely and separated,and do not form muscle fiber bundles.Through the observation of microstructure,the pectoralis muscle segments of the TT genotype(M breeding strain)and TC/CC genotype(non-M control)and stripper muscle segments were short,with no significant difference in length,but the thickness of pectoralis muscle segments of M strain was significantly greater than that of non-M strain.The morphological characteristics of muscle tissues in different parts at different molting stages were different:the diameter and variation range of chelate muscle fibers were significantly larger than that of stepper muscle fibers and pectoral muscle fibers.The average diameter of muscle fiber was significantly higher in M strain(205.04±6.64μm)than that in non-M strain(186.05±5.35μm)(P<0.05).The results of this study showed that there were significant morphological changes in the claw muscle before and after molting,and muscle parameters were significantly different between the M strain and non-M strain of Eriocheir Sinensis with significantly larger,of muscle fiber diameter in the M stain than in the non-M strain. |
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