盐度突降对拟穴青蟹大眼幼体生长发育和Na~+/-K~+-ATPase活性的影响

研究了盐度突降对拟穴青蟹(Scylla paramamosain)大眼幼体生长发育和Na+/-K+-ATPase活性的影响。实验用水由海水和淡水配制成20%、40%、60%、80%和100%SW,其盐度分别为6.4、12.8、19.2、25.6和32.0。在不同环境盐度突降条件下,盐度6.4处理组拟穴青蟹大眼幼体在24 h内全部死亡;盐度12.8、19.2、25.6和32.0处理组拟穴青蟹大眼幼体的存活率无显著差异(P≥0.05),各处理组幼体蜕皮持续时间分别为2、2、3和4 d;当发育至C1期第2天时,盐度12.8处理组体重平均增量低于盐度19.2、25.6和32.0处理组,且差异显著(P<0.05)。盐度6.4处理组酶活性从实验开始即急速增加,至6 h时与其它各组呈显著差异(P<0.05);盐度32.0处理组酶活性从实验开始就下降,至72 h后变化趋于平缓;盐度12.8、19.2和25.6处理组酶活性在6 h内逐渐上升,之后迅速下降,于72 h时降至最低,之后酶活性变化趋于平缓。在96~120 h内,盐度12.8处理组酶活性始终显著高于25.6和32.0处理组(P<0.05)。结果表明,拟穴青蟹大眼幼体生长的最适盐度为19.2,适宜生长盐度下限在12.8~19.2之间,生存盐度下限在6.4~12.8之间。

Survival, development and Na+/-K+ -ATPase activity of Scylla paramamosain megalopa in low salinities

Effects of low salinities on development and Na+/-K+-ATPase activity of Scylla paramamosain megalopa were analyzed by two experiments.Five different levels of salinity conditions,20%,40%,60%,80% and 100% seawater(SW) were used in the two experiments.In Experiment 1,all larvae reared in 20% SW died within 24 hours,while survival rates in 40%,60%,80% and 100% SW were 80.0%,96.7%,93.3% and 90.0%,respectively.It also revealed that salinity affected duration of molt.There was rapid and synchronous development in 40% and 60% SW,but it was delayed and extended in 100% SW.In Experiment 2,megalopa was sampled for 0,6,24,48,96 and 120 h.Na+/-K+-ATPase activity changed when megalopa was transferred from full-strength(100%) SW(32 ppt) directly to different salinity conditions of 20%,40%,60%,80% and 100% SW.After megalopa were transferred to 20% SW,Na+/-K+-ATPase activity increased dramatically during the first 6 h,while Na+/-K+-ATPase activity under the salinity conditions of 40%,60%,80% SW increased a little during the first 6 h.As to megalopa transferred to 100% SW,Na+/-K+-ATPase activity decreased significantly between 0 h and 24 h,increased a little from 24 h to 48 h,then tended to be stable from 48 h to 120 h.Na+/-K+-ATPase activity of megalopa in 40%,60%,80% SW decreased significantly from 6 h to 72 h and reached the minimum at 72 h.After that it increased a little,but no significant differences were found with the time going on regardless salinity conditions.Na+/-K+-ATPase activity also showed significant differences under various salinity conditions at the same time.Especially,megalopa in 20% SW had a significantly higher activity than those in the other four salinity conditions at 6 h.Megalopa in 40% SW had a significantly higher activity than those in 80% and 100%SW at 96 h and 120 h,respectively.No significant activity difference in Na+/K+-ATPase was observed in 60% SW as compared to those in 80% and 100% SW at 96 h and 120 h.Based on the above,it is suggested that the optimum salinity condition recommended for the megalopa nursery rearing of S.paramamosain is 60% SW.A lower limit of acceptable salinity for megalopa was between 40% and 60% SW.