| Oyster, as a worldwilde distribution of shellfish, has been a main economical breed in almost coastal states, with tasty meat, nutrient rich and so on.The Pacific oyster (Crassostrea gigas) has come to the biggest breed scale. As the most worldwide distribution of oyster,determined the impact of the environmental salinity on both the low salinity and high salinity to promote the decelopment of the indust of oyster. with the expansion of the scale of farming, Hong kong giant oyster (Crassostrea hongkongensis),as the main economic shellfish in South China,had appared the shortcomings with a traditional breeding.Culthless oyster breeding technology gradually gains the attention,since the culthless oysters have some advantages in the aspect of both size and shell shaped.Therefore, the development of culthless oyster technology can not only improve quality of the oyster,but also increase the economic benefit. By studying the effect of environmental salinity, this research further verified the practical universality of triploid induction of shellfish by low and hig salinity.Meanwhile the study further confirmed the feasibility of inducing culthless Hong Kong giant oysters by EPI.1.Effect of environmental salinity on triploid oyster(Crassostrea gigas) by low salinity.The Crassostrea gigas were cultured at (25±2)℃and at different environmental salinity(22,26,30,34 and 38),and then made a study induced triploid on the effects of low salinity (4,6,8,10,12 and 14). The fertilized eggs were adopt different low salinity and duration time of 15 min when appeared 40%～50% of the PB1. Along with the increase of low salinity, cleavage rate and hatching rate were increased under the same environmental salinity. Compared with the other environmental salinity, when environment salinity was 38, both cleavage rate and hatching rate were significantly low. When environment salinity were 26,30,34 and 38, triploid rate was the highest under low salinity of 8.But when environment was 22, triploid rate was supreme under low salinity of 6. When environmental salinity was 22.26,30,34 and 38,Ie was the highest in low salinity of 8. And environmental salinity was 30 and low salinity was 8, both the triploid rate and the Ie were the highest, (81.27+4.68)% and 63.23% respectively.Through the factor analysis of variance,environmental salinity and low salinity had a significant impact on cleavage rate, hatching rate and the triploid rate (P <0.05).2. Effect of environmental salinity on triploid oyster (Crassostrea gigas) by high salinityThe Crassostrea gigas were cultured at (25±2)℃ and at different environmental salinity(22,26,30,34 and 38),and then made a study induced triploid on the effects of high salinity (45,50,55,60,65 and 70). The fertilized eggs was adopt different high salinity and duration time of 15 min when appeared 40%～50% of the PB1. Along with the increase of high salinity, both cleavage rate and hatching rate were increased under the same environmental salinity. Compared with the other environmental salinity, when environment salinity were both 22 and 38, cleavage rate and hatching rate were significantly lower. When environment salinity was 22 and 26,both triploid rate and Ie were highest under high salinity of 60.But when environment were 30,34 and 38,both triploid rate and Ie were supreme under high salinity of 65. Through the factor analysis of variance, environmental salinity and high salinity had a significant impact on the cleavage rate, the hatching rate and the triploid rate (P<0.05).3.Study on culthless oyster, Crassostrea hongkongensis induced by EPI.Culthless oyster of Crassostrea hongkongensis were induced by Epinephrine after the eye-spots were founded.The larvae group with 80%～90% of eyespot larvae was treated with different EPI solution (1.0×10-5mol/L,5×10-5 mol/L,1×10-4mol/L,5×10-4 mol/L,1.0×10-3 mol/L,5×10-3 mol/L) for 6h. The larvae group,in which the eyepots accounted of 20%～30%,50%～60%,80%～90% and 12h,24h,36h,48h after 80%～ 90% of eyespots larvae respectively,were treated by EPI concentration (5×10-4 mol/L) for 3h. The larvae group with 80%～90% of eyespot larvae were in-duced by the best solution of EPI for different duration time (lh,2h,3h,4h,5h,6h).After treatment,the culthless spats were cultured in a equipment of culturing culthless oyster for 24h.Spats of both the culthless and attachment were cultured in the same equipment.The result showed that, culthless oyster rate was the highest (53.5±4.0)%under the condition of 80%～90% eye-larvae, 5×10-4mol/L,durition time 3h. In the aspects of growth, compared with the attachment spats in the same desinty, the culthless spat had not an advantage. |
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