盐度对菲律宾蛤仔幼虫生长、存活和附着变态的影响

Effects of Salinity on Growth,Survival,Settlement and Metamorphosis of Ruditapes philippinarum Larvae

为山东探究菲律宾蛤仔(Ruditapes philippinarum)人工苗种规模化繁育的最适环境条件,本文研究了不同盐度对菲律宾蛤仔幼虫生长、存活和附着变态的影响。实验设置4个盐度梯度(15、20、25、30),分别在第3、9、18、27天测量幼虫壳长和统计幼虫存活率,在第27天统计幼虫附着变态率。研究表明,培育至第18天时,盐度25组幼虫平均壳长最大,达到(0.164±0.003)mm,显著高于其他盐度组;盐度15组平均壳长最小,仅为(0.149±0.001)mm。盐度15组平均壳长与盐度20组无显著差异,与盐度25组和30组(对照组)有显著差异(P<0.05)。在存活率方面,盐度25组存活率最高,为51.40%,显著高于其他盐度组,但与盐度30组存活率(44.43%)无显著差异;盐度15组存活率最低,为25.75%。培育至第27天时,盐度25组幼虫存活率最高,为4.47%。在附着变态方面,盐度15组幼虫附着变态率最高,为21.56%,显著高于其他盐度组(P<0.01);盐度20组的附着变态率为11.14%,显著高于对照组和盐度25组(P<0.05)。研究结果表明,幼虫在盐度25时生长最快、存活率最高,而在盐度15时幼虫附着变态率最高。综上所述,在菲律宾蛤仔人工育苗过程中,盐度25是蛤仔幼虫生长和存活的最适盐度,附着变态前适当降低盐度有利于提高幼虫的附着变态率。

In order to explore the optimal environmental conditions for large-scale breeding of Manila clam(Ruditapes philippinarum)artificial seeds,the effects of different salinities on the growth,survival,settlement and metamorphosis were studied in R.philippinarum larvae.In this experiment,four salinity gradients(15,20,25,30)were set up,and larval shell length and survival rate were measured on days 3,9,18 and 27.Larval settlement and metamorphosis were calculated on day 27.The results showed that the average shell length of larvae at salinity 25 was the largest on day 18((0.164±0.003)mm),significantly higher than that at other salinities.The minimum shell length was observed at salinity 15((0.149±0.001)mm).There was no significant difference in the average shell length between the salinities 15 and 20.In comparison with salinity 20,salinities 25 and 30 showed the significantly higher average shell length(P<0.05).The salinity 25 had the highest survival rate(51.40)which was significantly higher than that at other salinities and similar to that at salinity 30(44.43%).The survival rate was the lowest at salinity 15(25.75%).After 27 days of culture,the maximum survival rate of larvae(4.47%)was found at salinity 25.In terms of settlement and metamorphosis,salinity 15 had the highest larval settlement and metamorphosis rate(21.56%)which was significantly higher than that at other salinities(P<0.01).The settlement and metamorphosis rate at salinity 20 was 11.14%which was significantly higher than that of control and at salinity 25(P<0.05).The findings indicated that larvae showed the rapid growth and high survival rate at salinity 25 while the highest settlement and metamorphosis rates were found at salinity 15.In summary,salinity 25 is the optimal salinity for growth and survival during the artificial cultivation of R.philippinarum larvae.The appropriate reduction of salinity before settlement and metamorphosis should aid to improve the settlement and metamorphosis rates of R.philippinarum larvae in clam hatcheries.