Quantitative real-time polymerase chain reaction(q RT-PCR) is a rapid and reliable technique which has been widely used to quantifying gene transcripts(expression analysis). It is also employed for studying heterosis, hybridization breeding and hybrid tolerability of oysters, an ecologically and economically important taxonomic group. For these studies, selection of a suitable set of housekeeping genes as references is crucial for correct interpretation of q RT-PCR data. To identify suitable reference genes for oysters during low temperature and low salinity stresses, we analyzed twelve genes from the gill tissue of Crassostrea sikamea(SS), Crassostrea angulata(AA) and their hybrid(SA), which included three ribosomal genes, 28 S ribosomal protein S5(RPS5), ribosomal protein L35(RPL35), and 60 S ribosomal protein L29(RPL29); three structural genes, tubulin gamma(TUBγ), annexin A6 and A7(AA6 and AA7); three metabolic pathway genes, ornithine decarboxylase(OD), glyceraldehyde-3-phosphate dehydrogenase(GAPDH) and glutathione S-transferase P1(GSP); two transcription factors, elongation factor 1 alpha and beta(EF1α and EF1β); and one protein synthesis gene(ubiquitin(UBQ). Primers specific for these genes were successfully developed for the three groups of oysters. Three different algorithms, ge Norm, Norm Finder and Best Keeper, were used to evaluate the expression stability of these candidate genes. Best Keeper program was found to be the most reliable. Based on our analysis, we found that the expression of RPL35 and EF1α was stable under low salinity stress, and the expression of OD, GAPDH and EF1α was stable under low temperature stress in hybrid(SA) oyster; the expression of RPS5 and GAPDH was stable under low salinity stress, and the expression of RPS5, UBQ, GAPDH was stable under low temperature stress in SS oyster; the expression of RPS5, GAPDH, EF1β and AA7 was stable under low salinity stress, and the expression of RPL35, EF1α, GAPDH and EF1β was stable under low temperature stress in AA oyster. Furthe
This study examined the effects of salinity on embryonic development, survival, and growth of the Hong Kong oyster Crassostrea hongkongensis. The embryos, larvae, and juveniles of C. hongkongensis were held in artificial seawater at three different salinities(low, 15; medium, 23; and high, 30) to determine the optimum hatchery and nursery conditions for mass production of the seeds. Results showed that the percentage production of straight-hinged larvae from fertilized eggs was significantly lower at the high salinity than at the low- and medium-salinities(P < 0.05). The survival rates of larvae and juveniles differed significantly among the three salinity trials, with the highest survival rate observed at the low salinity(P < 0.05). The shell height of larvae was significantly larger at the low salinity than at the high and medium salinities from days 9 to 15(P < 0.05), whereas that of juveniles was significantly larger at the low salinity than at the high and medium salinities on day 70(P < 0.05). These results indicate that the larvae and juveniles of C. hongkongensis are tolerant to a wide range of salinities(15 to 30), but show better growth and survival at relatively low salinities. Thus, it is recommended to use relatively low salinities in hatchery and nursery systems for improved yields of C. hongkongensis.
HUO ZhongmingWANG ZhaopingLIANG JianZHANG YuehuanSHEN JianpingYAO TuoSU JiaqiYU Ruihai
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.
YAO TuoZHANG YuehuanYAN XiwuWANG ZhaopingLI DongchunSU JiaqiYU Ruihai
