盐度骤变和渐变对三疣梭子蟹幼蟹发育和摄食的影响

Effect of Abrupt and Gradual Changes in Salinity on Development and Feeding in Juvenile Swimming Crab(Portunus trituberculatus)

为探讨三疣梭子蟹幼蟹对盐度的适应性,设置盐度骤变和渐变2组试验。骤变试验以27为基础盐度,幼蟹直接转入7、11、15、19、23、31、35、39、43、47、51盐度水体中;渐变试验盐度从27开始,以4/d的日变幅逐渐升至51和降至7,分析不同处理下幼蟹存活率、变态率及摄食量的变化。试验结果表明,I期幼蟹盐度从27骤变为11～23后,120 h存活率≥50%,骤变为35～47,72 h存活率均降至10%,96 h内幼蟹全部死亡。Ⅱ期幼蟹盐度骤变为7、47、51后,96 h存活率分别为40%、20%、0%,其他处理存活率≥50%。I期幼蟹盐度骤变为11～31时,变态率≥40%,其他处理均为0%;Ⅱ期幼蟹盐度骤变为11～39时,变态率≥40%,其他变态率为10%～30%(51处理组除外,为0%)。盐度骤变试验组存活幼蟹平均摄食卤虫成体1～3.17个。盐度突降<16或突升<8时,幼蟹的摄食量高于其他盐度骤变组。盐度渐变对幼蟹存活率、变态率和摄食量的影响均小于相应盐度下的骤变组。幼蟹适应盐度渐变的能力强于骤变;在盐度的降低或升高变化中,幼蟹能较好的适应盐度降低;幼蟹的盐度适应能力随发育呈增强趋势。15～31为三疣梭子蟹幼蟹生长发育的适宜盐度。

The survival rate,metamorphosis rate and the daily mean food intake of swimming crab（Portunnus trituberculatus） juveniles under abrupt and gradual changes in salinities were determined to evaluate the tolerance of juveniles Swimming crab to salinity.The abrupt changes in salinity mean that the salinity was changed to 7,11,15,19,23,31,35,39,43,47 and 51 from 27,respectively.The gradual changes in salinity mean that the salinity was raised and reduced 4 every day for five days from 27.The results showed that,in the treatments of abrupt changes,the survival rate of the crab instar 1 juveniles in the salinity of from 11 to 23 was higher than 50% 120 h after salinity changing;in the salinity from 35 to 47,the survival rates were 10% and 0% at 72 h and 96 h,respectively;at the salinity from 11 to 31,the rate was higher than 40%,those of other treatments were 0%.For crab instar 2 juveniles,the survival rates were 40,20 and 0% at salinity 7,47 and 51 at 96 h,respectively.At salinity from 11 to 39,the metamorphosis rates were higher than 40%.The daily mean food intake was 1～3.17 adult Artemia per juvenile.The daily mean food intake was significant higher at the salinity from 11 to 35 than that in others.Gradual treatments had higher survival rate,metamorphosis rate and the daily mean food intake than those in abrupt treatments.The results indicated that juveniles could better acclimatize themselves to gradual change than abrupt change salinities.Salinity tolerance increaseds with juvenile development.Therefore,the optimum growth and development of the swimming crab juveniles was found at a salinity from 15 to 31.