Zhang Yuehuan

Studies on establishment of families and their early growth and development for surf clam Mactra chinensis Philipi.

A total of 7 half-sib families and 21 full-sib families(A1,A2,A3…G1,G2,G3) of sunray surf clam Mactra chinensis Philipi were established by using the method of unbalanced nest design in Sept.2007.Phenotypic traits of different families,such as egg-diameter,fertilization rates,hatching rates,and larval and juvenile growth,survival and metamorphosis were analyzed.The results showed that egg-diameter,fertilization rates,hatching rates,and D larval size were non-significantly different among families(P0.05).Considering growth,growth was varied at different development stages for each family and was influenced by maternal effect,paternal effect and male within female effect.G1 had the largest shell length with the growth rate of(10.04 ± 1.67) μm/d;whereas A2 had the smallest shell length with(6.07 ± 1.32) μm/d during pelagic period of larvae.B3 grew fastest in filial generation of family with(29.93 ± 3.67) μm/d;whereas D1 grew slowest in filial generation of family with(16.72 ± 2.73) μm/d during plantigrade period.G3 had the largest shell length with the growth rate(83.14 ± 5.85) μm/d;whereas A2,A3 of juvenile indoor period had the smallest shell length with growth rate of(57.78 ± 5.44) μm/d,(55.86 ± 4.48) μm/d respectively.Considering survival,A2,C1,E3,F2,G1 and G2 had higher survival rate( 85%) in filial generation of family,whereas B2,D1 had lower survival rate( 35%) in filial generation of family during pelagic period of larvae.G1 had the highest survival rate(70.40%) in filial generation of family,whereas A1(23.40%),C2(20.90%),F1(19.30%) had lower survival rate in filial generation of family during juvenile indoor period.Considering metamorphosis,growth rate was varied for each family,the growth rate of G1and G3 was(7.94 ± 1.53) μm/d,and(7.96 ± 1.52) μm/d respectively,but the growth of D1 was only(5.23 ± 0.75) μm/d.B1,E1 and G2 had higher metamorphosis( 80%) in filial generation of family,whereas E2(41.24%),and F1(43.25%) had lower metamorphosis in filial generation of family.However,as the metamorphic time prolonged,the metamorphic size decreased.G1,G2,G3 had the largest metamorphic size(240 μm) with the shortest metamorphic time(13 d),whereas D1 had the lowest metamorphic size[(226.65 ± 5.65) μm]with the longest metamorphic time(17 d).By summarizing the early phenotypic traits of families,G3,F2 and G1 respectively inherited the excellent traits such as fast growth,strong stress resistance,and high yield,and could further be used as the breeding material for rearing of new sunray surf clam strains.

Preliminary study of establishment of families and their early growth and development for manila clam(Ruditapes philippinarum)

A total of 11 half-sib families and 33 full-sib families were generated by using the method of unbanlanced nest design,in Sept. 2007. Phenotypic traits of different families,such as egg sizes,fertilization rates,embryonic hatching rates,larval and juvenile growth,survival and metamorphosis were analyzed. The results showed that the differences in egg sizes and fertilization rates among the full-sib families were not significant,but those in embryonic hatching rates were significant(P0.05,n=90). The growth of each family was not the same at different stages.The fastest growth family named C2 was significantly larger than the slowest growth family named F2 by 28.24% in average shell length (P0.05,n=90)at 9 days of larval stage. D3 whose Absolute growth was the largest of all families was bigger than the average Absolute growth by 37.24%.The fastest growth family I1 at 40 days of nursing stage was significantly larger than the slowest growth family B3 by 78.29% in average shell length(P0.05,n=90). Moreover,I1 was the largest of all families in Absolute growth,and it was bigger than the average Absolute growth by 87.61%,the distributions of shell length between 400-500 μm and above 500 μm accounted for 30% and 53.33% of total shell length among I1 ,respectively. However,the growth trait depression families B1 and B3 involved in miniaturization,the distributions of shell length below 300 μm accounted for 83.33% and 90% of total shell length of B1 and B3 ,respectively. The survival of each family was different at the same stage. The highest suevival family I2 was significantly larger than the average survival by 94.14%,and the lowest growth suevival family F2 was obviously smaller than the average survival by 72.65% at 9 days of larval stage. The survivals of all families at 40 days of nursing stage were higher than 85%. The study of full-sib families at metamorphosis stage presented some phenomena,such as metamorphism time delay and metamorphism individual miniaturization. The metamorphosis time was delayed from 15 to 22 days. The average metamorphic size was (193.18±12.15) μm. The smallest metamorphic size family was K1 with(183.00±14.42) μm of shell length,and the metamorphic sizes of three families which were generated through each female mated with the same male named K were generally smaller than other families,and this was mainly due to paternal effect.The metamorphosis rates were significantly different among the full-sib families.The highest metamorphic rate family was E3 with the rate of (94.33%±0.58%),and the lowest metamorphic rate family was B2 with the rate of (7.33%±2.08%). These results suggest that I1 is a family with the best early growth and development traits,and it could be used to produce high-quality seed which presents short culture cycle,and higher production in artificial selection breeding.

Three way crosses between two-band red and white zebra strains of Manila clam, Ruditapes philippinarum.

In order to improve the phenotypic character of Manila clam Ruditapes philippinarum,three way crosses between Two-band Red ( R:fast growth) and White Zebra strains ( WZ:obvious heterosis) were conducted in August 2009.The generation F2 of White Zebra strain was from two way crosses between Pearl White and Zebra strains.The experiments consisted of two self-fertilized groups( RR,WZWZ) and two hybrid groups( RWZ,WZR) .Then the growth,survival,heterosis and shell color genetic mechanism were investigated in the study.The results showed that the single-parental heterosis was asymmetrical between two reciprocal crosses,and the growth and survival were clearly improved in RWZ group,whereas only survival heterosis was observed in another group.Considering growth,the value of mid-parental heterosis was-0.68,and that of single-parental heterosis was + 1.70 for RWZ,and-2.92 for WZR,respectively.It was mainly affected by the interaction between egg origin and mating strategy,next is maternal effect during planktonic stage.The value of mid-parental heterosis was only + 0.90,and that of single-parental heterosis was + 9.71 for RWZ,and-6.57 for WZR during juvenile stage.Considering survival,the value of mid-parental heterosis was + 3.60,and that of single-parental heterosis was + 4.47 for RWZ,and + 3.05 for WZR,respectively.It was mainly affected by the mating strategy,next that is maternal effect during planktonic stage.The value of mid-parental heterosis was + 9.00,and that of single-parental heterosis was + 13.09 for RWZ,and + 7.30 for WZR during juvenile stage.The shell color of generation for R × R,R × WZ,WZ × R,WZ × WZ were two band red,two band red with white zebra,two band red with white zebra and white zebra,respectively.The generation of white zebra was still white zebra on the outer shell color,that is,no shell color separated for two way hybrids.These results indicated that coloring was linked to sex and was not of sex-linked inheritance.

Studies on phenotypic traits of different shell color strains F2 of Manila clam (Ruditapes philippinarum).

The study on phenotypic traits of different shell color strains F1 and F2(C:the control strains;Tr;two-band red strain;Tw:two-band white strain;Ab:agate-black strain;Or:ocean-red strain;Pw:pearl-white strain;Z:zebra strain;W:wave strain.) of Manila clam was conducted in September 2007.The results showed that the shell length of Pw F1 was the greatet,and significantly greater than others except Tr(P0.05),the shell length of Z was the smallest,and significantly smaller than others(P0.05),there were no obvious differences in shell length among C,Or,W,between Tr and Tw,among Tw,Ab,Or,among Ab,Or,W(P0.05).Both fresh weight and fecundity of Pw F1 were the greatet,that of Tr were the second greatet and significantly greater than others(P0.05),those of Z were the smallest,and significantly smaller than others(P0.05),there were no remarkable differences between C and W,among Tw,Ab,Or in fresh weight and between C and Z,among Tr,Ab,Or,W in fecundity(P0.05).No significant differences in egg-diameter,the fertilized rates and size of D larvae were observed among all strains(P0.05),the hatching rate of C was significantly lower than those of other strains except Tw(P0.05).By end of pelagic period(9 d),the shell lengths of W and Z were significantly greater than those of other strains(P0.05),there were no remarkable differences in shell length among Tw,Ab,Or,Pw,Z,W(P0.05) ;the sequences of survival rates were following:Ab,ZOr,WTw,PwTrC,there were significant differences among them(P0.05).No remarkable difference in both metamorphic time and metamorphic size among all strains was observed(P0.05).There were such a sequence in metamorphic rates as follows:AbZTwOrPwWTrC,there were significant differences among them(P0.05).By the end of indoor rearing period(240 d),the shell length of Ab were significantly greater than those of other strains except Or,Tr(P0.05),the shell length of Z were significantly smaller than those of other strains except C,W(P0.05),there were no remarkable differences in shell length between C and Pw,W,Tr,Tw,Or,and between Tw and Pw;the survival rate of Z was remarkably higher than those of other strains except Ab(P0.05),the survival rate of C was remarkably lower than those of other strains except Tr,Tw(P0.05).On day 360,both shell length and fresh weight were the greatet and remarkably greater than those of other strains(P0.05),the shell length of Ab and Z were significantly smaller than those of other strains(P0.05),the survival rate of Ab and Z were significantly higher than those of other strains except Or,Pw(P0.05),the survival rate of Or was significantly higher than that of C(P0.05),there was no remarkable difference in survival rate among other strains(P0.05).The order of relative yields was as follows:Z(678.63%±56.80%)Ab(554.88%±69.42%)Or(527.23%±76.21%)W(475.97%±90.25%)Pw(405.90%±55.19%)Tw(224.89%±47.85%)Tr(178.50%±34.50%)C(100.00%±22.10%).