A genetic linkage map of Pacific abalone(Haliotis discus hannai) was constructed using AFLP markers based on a two-way pseudo-testcross strategy in a full-sib family. With 33 primer combinations,a total of 455 markers(225 from the female parent and 230 from the male parent) segregated in a 1:1 ratio,corresponding to DNA polymorphism:heterozygous in one parent and null in the other. The female framework map consisted of 174 markers distributed in 18 linkage groups,equivalent to the H. discus hannai haploid chromosome number,and spanning a total length of 2031.4 cM,with an average interval of 13.0 cM between adjacent markers. The male framework map consisted of 195 markers mapped on 19 linkage groups,spanning a total length of 2273.4 cM,with an average spacing of 12.9 cM between adjacent markers. The estimated coverage for the framework linkage maps was 81.2% for the female and 82.1% for the male,on the basis of two estimates of genome length. Fifty-two markers(11.4%) remained unlinked. The level of segregation distortion observed in this cross was 20.4%. These linkage maps will serve as a starting point for linkage studies in the Pacific abalone with potential application for marker-assisted selection in breeding programs.
Microsatellite DNA technique was used to detect the genetic variation between five hatchery populations of the Pacific oyster from China and two wild populations from Japan. Seven microsatellite loci screened in this study showed high polymorphism in both hatchery and wild populations, as observed in an average number of allele per locus （19.1-29.9） and average expected heterozygosity （0.916-0.958）. No significant difference in average allelic richness or expected heterozygosity was observed between Chinese hatchery populations and Japanese wild populations. Pairwise Fsr values and heterogeneity tests of allele frequencies showed significant genetic differentiation between all populations. According to the neighbor-joining tree constructed on the basis of the Dc distance, the seven populations fell into three groups showing a clear division between hatchery and wild populations, and between the northern and southern hatchery populations. Assignment tests correctry assigned high percentages （97%-100%） of individuals to their original populations and demonstrated the feasibility of microsatellite analysis for discrimination between populations. The information obtained in this study is useful for designing suitable management guidelines and selective breeding programs for the Pacific oyster in China.
The inheritance mode of seven microsatellite markers was investigated in Patinopecten yessoensis larvae from four con-trolled crosses,and the feasibility of using these markers for kinship estimation was also examined. All the seven microsatellite loci were compatible with Mendelian inheritance. Neither sex-linked barriers to transmission nor major barriers to fertilization between gametes from the parents were evident. Two of the seven loci showed the presence of null alleles in two families,suggesting the need to conduct comprehensive species-specific inheritance studies for microsatellite loci used in population genetic studies. However,even if the null allele heterozygotes were considered as homozygotes in the calculation of genetic distance,offspring from four families were all unambiguously discriminated in the neighbor-joining dendrogram. This result indicates that the microsatellite markers used may be capable of discriminating between related and unrelated scallop larvae in the absence of pedigree information,and of investigating the effective number of parents contributing to the hatchery population of the Japanese scallop.
Genetic diversity and differentiation of the oyster Crassostrea plicatula populations from China’s coast were studied based on seven microsatellite loci. All loci showed high polymorphism for all five C. plicatula populations,with an average number of allele per locus of 19.3-27.9 and an average expected heterozygosity of 0.889-0.952. Significant departures from Hardy-Weinberg equilib-rium and deficits of heterozygotes were observed over most populations at each locus,which were fully explained by null alleles. Microsatellite analysis revealed significant subdivision in the C. plicatula populations. According to the neighbor-joining tree con-structed on the basis of the DA distance,the five populations fell into three regional groups,showing a relatively homogeneous genetic structure in geographically close populations. Assignation tests correctly assigned high percentages of individuals to their original populations and groups,and also confirmed the existence of genetic differentiation among C. plicatula populations. The results ob-tained in this study will facilitate the formulation of appropriate fisheries management programs,stock identification and conservation of biodiversity for the species.
Five full-sib families of the Pacific oyster(Crassostrea gigas) larvae were used to study the mode of inheritance at eight microsatellite loci,and the feasibility of these markers for kinship estimate was also examined.All eight microsatellite loci were compatible with Mendelian inheritance.Neither evidence of sex-linked barriers to transmission nor evidence of major barriers to fertilization between gametes from the parents was shown.Three of the eight loci showed the presence of null alleles in four families,demonstrating the need to conduct comprehensive species-specific inheritance studies for microsatellite loci used in population genetic studies.Although the null allele heterozygotes were considered as homozygotes in the calculation of genetic distance,offspring from five full-sib families were unambiguously discriminated in the neighbor-joining dendrogram.This result indicates that the microsatellite markers may be capable of discriminating between related and unrelated oyster larvae in the absence of pedigree information,and is applicable to the investigation of the effective number of parents contributing to the hatchery population of the Pacific oyster.
研究了利用6-二甲基氨基嘌呤（60μg／mL；6-DMAP）抑制第1卵裂诱导栉孔扇贝[Chlamys farreri（Jones et Preston）]雄核发育二倍体的条件。雄核发育单倍体是将强度为2．8mW／（cm^2·s）的紫外线照射20s的卵子与正常精子受精后得到的。6-DMAP不仅可以有效地抑制减数分裂，还可以有效地抑制有丝分裂；抑制第1卵裂的适宜起始时间为受精后80min,诱导率为21．0％～22．6％。细胞学观察显示，6-DMAP抑制第1卵裂产生的雄核发育二倍体主要来源于第1卵裂中期的受精卵，由于阻止了染色体分离和原核移动，导致一个融合的二倍性雌性原核的形成；经紫外线照射的卵核在第1卵裂中期没能形成染色体，而是形成1个浓缩的染色质小体，没有参与第1卵裂后期的核分裂。尽管倍化率和D形幼虫发生率较低，但本研究证实了栉孔扇贝雄核发育二倍体人工诱导的可行性。[中国水产科学，2006，13（4）：585—590]
