lnterspecific hybridization can generate heterosis, which is proven to be a useful tool in selective breeding programs for oyster culture. Crassostrea angulata and C. ariakensis are two important economic shellfish sp...lnterspecific hybridization can generate heterosis, which is proven to be a useful tool in selective breeding programs for oyster culture. Crassostrea angulata and C. ariakensis are two important economic shellfish species in China. We conducted 2 × 2 reciprocal crosses to determine whether these two species can cross-fertilize and their hybrids can hatch, survive and perform hetero- sis. Fertilization was found symmetrical without delay. The rate of fertilization success of C. angulata ♀× C. ariakensis ♂ was lower than that of C. ariakensis ♀ x C. angulata ♂, and the success rate of both hybridizations was lower than that of two intraspecific crosses each. During the planktonic period, survival rate of the progeny was lower in the hybrid crosses than in the intraspecific crosses. On day 360, mean shell height of the progeny of C. angulata ♀ x C. angulata ♂ was highest, which was followed by that of C. angulata ♀ × C. ariakensis ♂, C. ariakensis ♀x C. ariakensis ♂ and C. ariakensis ♀× C. angulata ♂ in a descending order. Mor- phology of adults produced by the hybrid crosses was similar to that of C. angulata. Both hybrids underwent normal gonad devel- opment and produced mature gametes in the mating season. This study provided new insights into the quantitative traits in interspeci- fic crosses of Crassostrea species, thus being of guidance value for selective breeding of oyster.展开更多
The accession of an African-American Obama to the U.S. Presidency in 2008 is an epoch-making event. The thesis focuses on the current situation of the blacks in U.S. to highlight the prophetic nature of Faulkner, the ...The accession of an African-American Obama to the U.S. Presidency in 2008 is an epoch-making event. The thesis focuses on the current situation of the blacks in U.S. to highlight the prophetic nature of Faulkner, the Nobel Prize winning American novelist＇s exploration of the blacks throughout his career, namely, the miserable living states of the blacks, racial segregation against the blacks in the sphere of education and religion, racial discrimination against the blacks with regard to civil rights, racial persecution against the blacks in legal cases, and the dependency upon the black leadership to salvage the multi-ethnic nation and so on. The paper comes up with the conclusion that Faulkner is accurate in his prophecy that the savior of the nation, the blacks shall suffer and lead.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.31172403)the National Key Basic Research Development Planning Project(Grant No.2010CB126406)
文摘lnterspecific hybridization can generate heterosis, which is proven to be a useful tool in selective breeding programs for oyster culture. Crassostrea angulata and C. ariakensis are two important economic shellfish species in China. We conducted 2 × 2 reciprocal crosses to determine whether these two species can cross-fertilize and their hybrids can hatch, survive and perform hetero- sis. Fertilization was found symmetrical without delay. The rate of fertilization success of C. angulata ♀× C. ariakensis ♂ was lower than that of C. ariakensis ♀ x C. angulata ♂, and the success rate of both hybridizations was lower than that of two intraspecific crosses each. During the planktonic period, survival rate of the progeny was lower in the hybrid crosses than in the intraspecific crosses. On day 360, mean shell height of the progeny of C. angulata ♀ x C. angulata ♂ was highest, which was followed by that of C. angulata ♀ × C. ariakensis ♂, C. ariakensis ♀x C. ariakensis ♂ and C. ariakensis ♀× C. angulata ♂ in a descending order. Mor- phology of adults produced by the hybrid crosses was similar to that of C. angulata. Both hybrids underwent normal gonad devel- opment and produced mature gametes in the mating season. This study provided new insights into the quantitative traits in interspeci- fic crosses of Crassostrea species, thus being of guidance value for selective breeding of oyster.
文摘The accession of an African-American Obama to the U.S. Presidency in 2008 is an epoch-making event. The thesis focuses on the current situation of the blacks in U.S. to highlight the prophetic nature of Faulkner, the Nobel Prize winning American novelist＇s exploration of the blacks throughout his career, namely, the miserable living states of the blacks, racial segregation against the blacks in the sphere of education and religion, racial discrimination against the blacks with regard to civil rights, racial persecution against the blacks in legal cases, and the dependency upon the black leadership to salvage the multi-ethnic nation and so on. The paper comes up with the conclusion that Faulkner is accurate in his prophecy that the savior of the nation, the blacks shall suffer and lead.
