香港巨牡蛎和长牡蛎幼虫及稚贝的表型性状

为了评估香港巨牡蛎和长牡蛎在北方沿海的早期表型性状,于2010年7月,以2009年6月在青岛繁育的两种牡蛎为材料,在大连研究了温度(Mt:(22±1.0)℃及Ht:(28±1.0)℃)、盐度(S₂₀:20±1.0及S₃₀:30±1.0)及中间育成环境(ID:室内及OD:室外)对两种牡蛎幼虫及稚贝表型性状的影响。结果表明:香港巨牡蛎壳宽显著大于长牡蛎(P<0.05),壳高及怀卵量显著小于长牡蛎(P<0.05),壳长、鲜重及壳重两者间无显著差异(P>0.05)。在温度和盐度相同情况下,长牡蛎卵径、受精率、孵化率及D形幼虫均大于香港巨牡蛎;香港巨牡蛎幼虫浮游前期生长较慢,而后快于长牡蛎。两种牡蛎幼虫存活能力在15日龄时高温组>中温组;相同温度下,香港巨牡蛎中盐组>高盐组,长牡蛎高盐组>中盐组。幼虫变态期间,较低的温度延迟了变态时间,降低了变态率,使得两种幼虫变态规格大型化。温度是影响幼虫生长、存活、变态的最主要因素,其次为盐度,交互作用几乎尚未起到作用。中间育成阶段,室外比室内培育效果更好,且香港巨牡蛎稚贝壳高在60日龄以后显著大于长牡蛎(P<0.05),环境是影响稚贝生长的最主要因素;无论室内还是室外两种牡蛎稚贝的存活率均在90%以上,且各实验组间无显著差异(P>0.05)。

Phenotypic traits of both larvae and juvenile Crasstrea hongkongensis and C. gigas

Two cupped oyster species,Crassostrea hongkongensis and Crassostrea gigas are economically and ecologically important species native to the Northern and Southern coasts of China,respectively.C.hongkongensis is one of the most important oyster species currently cultured due to its high market value in Southern China.The species is distributed from Fujian to Guangxi Provinces,with populations centered in Guangdong Province.C.gigas is the most commonly species of oyster cultured,owing to its worldwide distribution,rapid growth,and dominant position in commercial oyster cultures.In Northern China,they are farmed primarily farmed in Liaoning and Shandong Province.To determine the possibility of transplantation of C.hongkongensis from Southern to Northern China,the early phenotypic traits both larval and juvenile C.hongkongensis and C.gigas were determined under the identical environments,which include temperature(Mt:(22±1.0) and Ht:(28±1.0)℃),and salinity(S20:(20±1.0) and S30:(30±1.0)) for larvae,and culture conditions(ID: In door condition and OD: Out door condition) for juveniles,at in Dalian,Liaoning Provincein July,2007.The results showed that the shell width of C.hongkongensis was significantly larger than that of C.gigas(P<0.05),but the shell height of C.hongkongensis was significantly smaller than that of C.gigas(P<0.05).No significant differences in terms of shell length and fecundity(P>0.05) were found between the species.The egg-diameter,fertilization rate,hatchery successes,and the D larval size of C.gigas were all larger than those of C.hongkongensis.The larval growth of C.hongkongensis was smaller than that of C.gigas in during the early planktonic stage,but it was larger during the later planktonic stage under the same temperature and salinity.The order of two larval survival ability was: high temperature group > middle temperature group.The middle salinity group of C.hongkongensis larval size was larger than that of the high salinity group,and the high salinity group of C.gigas larval size was larger than that of the middle salinity group with at the same temperature.Larval metamorphosis was not only delayed,but it also larval metamorphosis was declined with decreasing temperature,the larval metamorphic size increased during the larval metamorphic stage under the same condition.Larval phenotypic characteristics were mainly affected by temperature,and the secondary factor was salinity,but mutual effects showed no positive action.The environment was the major factor for growth spurts during the juvenile stage and the phenotypic characteristics of spurts outdoors were better than those of indoors.The shell height of C.hongkongensis was significantly larger than that of C.gigas later on Day 60(P<0.05).The survival rates of the two species of oyster species were over 90% during the juvenile stage,and there were no significant difference between the experimental groups(P>0.05) was found.Our analysis explicitly demonstrates that seeds of C.hongkongensis were successfully achieved,and their transplantation to Northern China may yield considerable benefits.It is propitious to supply the resource of C.hongkongensis,and also provide the scientific base on the interspecific hybridization between two oyster species in China.