| Pinctada fucata martensii is the main species cultured for marine pearls.Pearl oyster farming is facing several problems in recent years,such as high mortality,high rate of nucleus spitting.P.f.martensii itself is rich in protein and has a high proportion of flavor amino acids,which has a high edible value.Therefore,some farmers choose not to insert nucleus and sell the pearl oysters as edible shellfish.However,as an edible shellfish,pearl oyster farming also faces several prominent problems,such as slow growth,long breeding cycle and low meat yield.It is necessary to carry out the breeding of P.f.martensii for edible.In this study,we compared the differences in economic traits of three populations of P.f.martensii,aiming to explore the trait advantages of different populations.Then,we compared the differences in nutritional components of P.f.martensii in different harvesting seasons.Also,we explored the rapid growth mechanism from the perspective of physiological and metabolic.Finally,through family breeding,we estimated the heritability and breeding value of important economic traits such as growth rate and meat yield of P.f.martensii.All of these studies will provide reference for the genetic improvement of edible P.f.martensii.(1)The economic traits comparison of the Haiyou NO.1,cultured populations and wild populations were carried out.The average meat yield of cultured population was the highest(0.26),which was significantly higher than Haiyou NO.1(0.23)and the wild population(0.14)(P<0.05).The shell width coefficient of Haiyou No.1 was the largest(0.154),which was larger than the cultured population(0.150)and wild population(0.150)(P<0.05).The correlation coefficients of shell height(X1),shell length(X2)and shell width(X3)with live body weight(WL)and tissue weight(WM)were significant(P<0.05).For Haiyou NO.1,shell width was the main factor affecting live weight,while shell height was the main factor affecting tissue weight.Shell height was the most important factor affecting weight traits in both cultured and wild populations.The regression equations between morphological and weight traits were established by introducing the traits gradually.Haiyou NO.1 WL:y=-23.324+0.254X1+0.634X2+0.306X3(R~2=0.833)WM:y=-6.044+0.016X1+0.213X3(R~2=0.614)Cultured population WL:y=-37.893+0.926X1+0.094X2+0.183X3(R~2=0.812)WM:y=-14.230+0.312X1+0.041X2+0.051X3(R~2=0.675)Wild population WL:y=-154.107+0.990X1+0.718X2+3.740X3(R~2=0.899)WM:y=-27.035+0.258X1+0.643X3(R~2=0.401)(2)The differences in nutrients and taste substances of Haiyou No.1 and the cultured population were compared.The contents of glycogen and crude fat in February were significantly higher than those in June(P<0.05);there was no significant difference in the contents of glycogen and crude fat between the two populations(P>0.05).For crude protein content,the highest was in the cultured population in February,and the lowest was the cultured population in June.The total amount of amino acids(TAA),essential amino acids(EAA)and non-essential amino acids(NEAA)in February were significantly higher than those in June(P<0.05).For the two populations,EAA of Haiyou No.1 was significantly higher than that of cultured population in February(P<0.05).In June,the content of TAA,EAA and taste amino acids in Haiyou No.1 was higher than the cultured population,but the difference was not significant(P>0.05).The highest total free amino acid was in February,which was significantly higher than that in June(P<0.05).The taurine content of cultured population in February was the highest.The content of free amino acids(Gly,Ala,Glu and Arg)in Haiyou No.1 was significantly higher than cultured population(P<0.05).In February,C18:2n-6,C20:5n-3,EPA,DHA and other polyunsaturated fatty acids and the total amount of unsaturated fatty acids∑PUFA were significantly higher than those in June(P<0.05).For the different populations,the total amount of polyunsaturated fatty acids andΣn-3 in Haiyou No.1 were significantly higher than those of the cultured population in February(P<0.05).The total amount of taste nucleotides in June was significantly higher than that in February(P<0.05).The taste nucleotide of Haiyou No.1 was significantly higher than cultured population(P<0.05).The TAV values of guanylate GMP and adenylate AMP in February were significantly higher than June(P<0.05).The content of malic acid in June was higher than February(P<0.05).The contents of succinic acid and betaine in February were significantly higher than those in June(P<0.05),no significant difference was found between different populations(P>0.05).For organic acid TAV values,it was significant difference between months(P<0.05),such as malic acid,the TAV value was greater than 1in June but lower than 1 in February.The betaine TAV value in February was significantly higher than June(P<0.05),and the Haiyou No.1 was significantly higher than cultured population(P<0.05).The EUC value of Haiyou No.1 was the largest in February.In both seasons,the EUC of Haiyou No.1 was higher than that of the cultured population(P<0.05).(3)We compared the growth characteristics between Haiyou No.1 and a cultured population.Large size(SL)and small size(SS)individuals of Haiyou No.1 were selected,the differences of physiological and metabolic indexes,such as feeding,respiration,excretion,and enzyme activities between SL and SS and cultured population(CL)were also compared.The results showed that at the age of 6 months,pearl oysters of Haiyou No.1 were14.61%larger than CL,and the proportion of SL(30-40 mm)was 59%,which was two times higher than CL(28%).SL with a rapid growth rate had a high clearance rate(CR),and the CR of SL was about 1.8 times higher than that of CL and 5 times higher than that of SS.In addition,the activities of digestive enzymes(amylase,pepsin,and lipase)and growth-related carbonic anhydrase enzymes in SL were higher than those in the other two groups(P<0.05).SS with a slow growth rate had higher oxygen consumption(OCR)and ammonia excretion(AER)rates than SL and CL(P<0.05).Our results suggest that the rapid growth of the Haiyou No.1 can be attributed to increased energy intake and reduced energy consumption.(4)Ten half-sib male families and 30 full-sib female families were established;the growth and production performance of different families were compared.The fertilization rates of different families ranged from 29.24%to 73.05%,and there were significant differences among different families(P<0.05).Families such as E3,D1,D3 grew fast in larval and nurturance stage,while families G3,F2 showed inferior growth all the time.During larval stage,the families with D,H and A as fathers had higher survival rate,while the families with F and I as fathers had the lowest survival rate.At 360 days of age,live body weight varies greatly between different families(3.88-21.58g);C1 with the largest mean body weight,it was 5.6 times that the smallest(J3).The meat yield was 16.80-28.53%;families E1(26.25%),G3(27.93%),I1(28.53%)and A3(28.94%)with higher meat yield than their parents,and E3,D1 and D3 with the fastest growth rate.(5)The heritability of P.f.martensii was estimated by the whole sibling inter-group correlation method.The Kung breeding value and comprehensive evaluation value Pi of different families were calculated.The results showed that the heritability of shell height was0.101-0.656.The estimated heritability of body weight at 360 days was 0.273-0.446.The heritability of meat yield at 360 days was 0.222-0.815,which were all significant or extremely significant.Kung breeding value and the comprehensive evaluation value Pi of C1,D1 and E3 rank are all ahead,showing the obvious comprehensive superiority. |
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