盐度突降对拟穴青蟹仔蟹生长发育和Na＋／K＋-ATP酶活性的影响

研究了盐度（6、13、20、27和33）对拟穴青蟹仔蟹（Scylla paramamosain）生长发育和Na＋/K＋-ATP酶活性的影响。结果表明，盐度对拟穴青蟹仔蟹特定生长率（甲宽和体重）、C3蜕壳间期、甲宽增量（C1至C2和C2至C3）及Na＋/K＋-ATP酶活性有显著影响（P〈0．05），但对仔蟹存活率、C2蜕壳间期及C3至C4甲宽增量无显著影响（P〉0．05）.盐度13处理组特定生长率最高、蜕壳间期最短，盐度69．1：理组特定生长率最低，但与盐度20、27和33处理组无显著差异（P〉0．05），而盐度33处理组蜕壳间期的延长降低了其生长速度；除C1蜕壳为C2的甲宽增量以盐度20处理组最大外，C2、C3蜕壳后的甲宽增量均为盐度13处理组最大；不同盐度条件下，仔蟹Na＋／K＋-ATP酶活性在实验开始后12h、48h、168h和264h时分别表现为盐度6〉13〉20〉27〉33、6〉13〉27〉20〉33、6〉13〉20〉27〉33和6〉13〉33〉20〉27的趋势，低盐环境下酶活性的升高可能有助于拟穴青蟹仔蟹对低渗环境的调节。试验结果表明，拟穴青蟹C1～C3的适宜盐度下限为13以上，C3后对低盐环境的适应能力明显增强，可在盐度6以上的低盐度环境中正常生长。

Growth, Survival and Na＋/K＋-ATPase Activity of Early Juvenile Mud Crabs （ Scylla paramamosain ） in Low Salinities

The effects of low salinities on development and Na＋/K＋-ATPase activity of early juvenile mud crabs （Scylla paramamosain ） were studied. The salinities tested for the experiment were 6, 13, 20, 27 and 33. Each salinity experiment was triplicated. Each replicate consisted of 10 crab instar 1 （ Cl ） juveniles for development test. Carapace width measured during each molt, while juvenile mortality recorded daily. The juveniles were sampled at 0.5, 4, 7 and 11 d for Na＋/K＋-ATPase activity test. Results demonstrate that salinity significantly affects the specific growth rates （ SGR ） for carapace length or weight, C3 intermoh duration, carapace width increase at C1 to C2 or C2 to C3 stages and Na＋/K＋-ATPase activity of early juvenile mud crabs（ P〈O.05 ）. There was no significant difference in survival, C2 intermoh duration and carapace width increase at C3 to C4 stages among salinities tested （P〉0.05 ）. There was delayed and extended development at 33, and then the growth was inhibited. At 13, maximum SGR for carapace length or weight was achieved, and at the same time, intermolt duration was relatively shortest for all salinities tested at C2 and C3 stages. At 6, the carapace width increase at the first molt and C2 to C3 stages was the least among salinities tested. In each time point, the enzyme activity became elevated in order to accommodate to low salinities. Base on the above, it is suggested that early juvenile S. paramamosain tolerate a broad range of salinity, and the low salinity （ 13 ） can result in the best growth and shortest duration. However, from an aquaculture point of view, a salinity range of 13-27 was recommended at C1 to C3 stages for early juvenile S. paramamosain, which widened （ 6-27 ） in the later stages for the culture.