Germplasm Resource Excavation,Culture Performance,and Nutritional Evaluation Of Mitten Crab In China

Mitten crab?Eriocheir sensu stricto?is an indigenous and economically important species in East Asia.However,it is unclear whether there are any differences in wild germplasm genetic characteristics,culture performance,and quality of artificial breeding.Hence,this paper was conducted to compare the genetic diversity from four wild Eriocheir sensu stricto populations,culture performance,nutritional composition,and flavor quality under similar pond-reared conditions,which will provide basic data for germplasm resource excavation,and reasonable utilization.The contents and results are as follows:1. Genetic diversity and population structure of native mitten crab?Eriocheir sensu stricto?derived from Yangtze,Oujiang,Minjiang,and Nanliujiang River basins.Genetic diversity and population structure of Eriocheir sensu stricto from four rivers were studied by microsatellite and mitochondrial cytochrome oxidase subunits I?COI?markers.The polymorphism information content?PIC?values ranged from 0.7827 to0.8580 and Shannon Wiener index?I?values varied from 2.0722 to 2.4088,according to microsatellite markers analysis.The haplotype diversity?h?values ranged from 0.52101to 0.87097,while the values of nucleotide diversity???varied from 0.00139 to 0.02796based on mitochondrial COI gene sequence.Four wild Eriocheir s.s.populations all showed high genetic diversity.As microsatellite analysis results,pair-wise F_ST values of Yangtze?YZ?,Oujiang?OJ?,Minjiang?MJ?and Nanliujiang?NLJ?populations were0.1347,0.1103 and 0.0943 respectively,which indicated that they were in medium genetic differentiation(0.05<F_ST<0.15).This result was consistent with mitochondrial COI gene's conclusion.The bottleneck analysis was a hint that Eriocheir s.s.experienced bottleneck effect under SMM models of Sign Test and Wilcoxon Sign-rank Test.Based on genetic structure,YZ,OJ and MJ populations were in the same cluster separated from NLJ population.In summary,by microsatellite and mitochondrial COI markers analysis,all four Eriocheir s.s.populations had high genetic diversity,and genetic differentiation was consistent with geographical distance.Populations OJ and MJ were closer to population YZ genetically,and they had large genetic distance with NLJ population.This study provides a particularly important basis for mitten crab resources conservation and utilization in south China.2. Culture performance of first-generation mitten crabs produced from Liaohe,Yangtze,Oujiang,and Minjiang RiversThrough pond-reared experiment and dissection,this study systematically evaluated the growth,precocious rate,survival rate,yield,and feed conversion ratio?FCR?of first-generation mitten crabs produced from Liaohe?LH?,Yangtze?YZ?,Oujiang?OJ?,Minjiang?MJ?Rivers during juvenile culture stage.This paper was also conducted to compare the growth,puberty molting,gonadal development,survival rate,yield,and FCR during adult culture stage.The results illustrated that:?1?There was no statistically significant difference in mean body weights of each month juveniles from four river basins?P>0.05?.Significant differences were observed between WGR and SGR of juveniles from four river basins during the periods of August-October and October-November?P<0.05?.No precocious individuals were finally discoverd from LH populations,however,the precocity of other three populations were observed,and there were significant differences among them?P<0.05?.LH crab had the highest survival rate,yield,and the lowest FCR,but MJ crab was on the contrary.?2?YZ crab had the largest final mean body weight in the late culture period?September-November?,although the mean body weight of LH crab was higher than YZ and MJ crab did in the early stage?March-July?.The WGR and SGR of MJ crab were slightly higher than LH and YZ crabs did during the periods of March-May and July-September.Females all completed puberty molting in September,whereas males did until October.MJ crab had significantly higher increase in gonadosomatic index?GSI?from September to November than LH and YZ crabs,while YZ crab had significantly higher GSI in November?P<0.05?.YZ crab had the highest survival rate,final yield,and lowest FCR,respectively.For the final body weight distribution,YZ crab had the highest proportion of large body weight female individuals??150.00 g/crab?followed by LH and MJ crabs.LH crab had the largest body weights of male individuals??200.00 g/crab?followed by YZ and MJ crabs,but no significant difference was observed?P>0.05?.In conclusion,YZ crab showed the best culture performance in the Yangtze delta.It was a little late for MJ crab to develop gonad,but rapid gonadal developmental rate was observed.The findings provide a theoretical and practical foundation for further excavation of excellent germplasm resources and breeding.3. A comparative study between culture performance and total edible yield of first-generation Chinese mitten crabs produced from inbred families and hybrid familiesTo understand the impact of one-year precocious traits of Eriocheir sinensis on its offspring,one-year precocious inbred families?PI?and hybrid families?PHN?comprising one-year precocious crabs and two-year normally mature crabs were constructed to comprehensively evaluate the culture performance and total edible yield of the offspring.The results illustrated that during the juvenile E.sinensis culture stage,the mean body weight of F₁in PI was always higher than in PHN.The WGR,SGR,and precocious rate of F₁females from PI were higher than F₁ females from PHN?P>0.05?.The survival rate of F₁ females from PI was significantly lower than F₁ females from PHN?P<0.05?,and the F₁ male survival rate was also slightly lower than in PHN.Although the total yield of F₁ from PHN was higher,there was no statistically significant difference?P>0.05?.The final body weight of juveniles was normally distributed,and highest proportion of final body weights were between 3.00 and 8.99 g.The results also showed that during the adult E.sinensis culture stage,the mean body weight of PI individuals was lower than those from PHN in the pre-growth period?March-May?,and that the mean body weight of PHN individuals was higher than PI individuals in the late growth stage?July-September?.The WGR and SGR values of PHN individuals were higher than those of PI individuals in the March-May and July-September periods.Puberty molting and gonad development was slightly earlier in PI crabs than in PHN individuals,but no statistically significant difference was observed?P>0.05?.Overall,the survival rate and yield were higher for PI than PHN,but FCR was significantly lower in PI individuals?P<0.05?.A greater number of PHN crabs had final body weights of<125.00 g and?250.00 g.There was significant difference between the number of individuals in the two groups with body weights<125.00 g?P<0.05?.In terms of TEY,TEY of PI was higher regardless of gender.The female TEY for PI was higher than for PI males,but there was no statistically significant difference?P>0.05?.In summary,PI of E.sinensis produce individuals with larger mean body weights,slightly higher precocious rates during the juvenile culture stage,and early puberty molting,and also produce higher survival rates,and higher yields during the adult culture stage.However,PHN of E.sinensis produce higher survival rates and yields during the juvenile culture stage,and produce individuals with late puberty molting and lower feed conversion ratios.4. Quality Comparison of Adult mitten crab pond-reared in the Yangtze delta from Liaohe,Yangtze and Minjiang RiversPond-reared experiments,dissection,and biochemical composition analysis were carried out to systematically compare CF?TEY,fatty acids?FAs?and free amino acids?FAAs?of mitten crabs from Liaohe,Yangtze,and Minjiang River basins.The results are presented as follows:?1?Significant differences were found in female GSI and male CF?P<0.05?,however,no significant differences were observed between HSI and MY?P>0.05?.?2?The proximate composition of adult individuals from three river basins was similar.Except for significant differences in crude protein of female hepatopancreas,moisture and total lipid of male gonad,total lipid of male hepatopancreas?P<0.05?,there was no significant difference?P>0.05?.?3?DHA,EPA,HUFA,and n-3/n-6 PUFA contents in female hepatopancreas and gonads of LH population were significantly higher than those of other two populations under similar pond-reared conditions?P<0.05?.Male muscle of YZ population had significantly higher levels of C18:2n6?C20:2n6,andPUFA than that of other two populations?P<0.05?.The muscles of MJ population had higher percentage of DHA in females,EPA,and HUFA in males?P<0.05?.?4?Tau,and Trp contents in male gonad,and Thr content in female muscle of LH population were significantly higher than those of YZ and MJ populations?P<0.05?.The muscle of YZ females had significantly higher contents of Ala than that of other two populations?P<0.05?.Higher contents of Asn,Ser,Ile in female gonad,and Gln in male muscle were observed from MJ population?P<0.05?.Glu and Arg were major flavor amino acids in gonad of three populations,while Glu,Gly,Ala,and Arg were major flavor amino acids in muscle among three populations.In summary,the three populations have similar FAs and FAAs composition.However,there are significant differences in DHA,EPA and free amino acids such as Tau,Trp,and Thr among three populations?P<0.05?,which may be related to genetic characteristics of germplasm.