The Asian brush-clawed shore crab Hemigrapsus takanoi has high tolerance for environmental changes facilitated the establishment of non-native populations along the Atlantic European coast. The self-maintenance and potential spread of this invasive crab will partially depend on its ability to disperse during the larval period. Larvae are not equipped with efficient osmoregulatory mechanisms to tolerate low salinity conditions; therefore, they evolved specific swimming behavior that facilitates exportation offshore for development in more stable and higher salinity conditions. To study the salinity tolerance, we quantified the survival of newly hatched larvae subjected to salinities ranging from 2 to 35 over a 24 h period. We observed that more than 50% of larvae could survive 24 h only at salinities higher than 20, and that shorter incubation periods of 2–6 h could produce high mortality at salinities lower than 10. We used video-tracking techniques to quantify swimming in newly hatched larvae at different levels of salinity, and under starvation or food availability conditions. The results showed that apparent swimming speed increases as salinity increases, and that upward trajectories are faster than downward ones. When food was available, the larvae reduced the frequency of helical swimming trajectories, turned out to be faster, straighter and more vertical. At salinities lower than 20, the swimming trajectories became more random, and the described patterns tended to disappear. Our results indicate that lower survival and reduced swimming performance may constrain the dispersal capacity of the non-native populations located at low salinity habitats.

亚洲刷爪岸蟹Hemigrapsus takanoi对环境变化具有高度的耐受性，促进了欧洲大西洋沿岸非本地人口的建立。这种侵入性螃蟹的自我维持和潜在传播将部分取决于其在幼体期的分散能力。幼虫没有配备有效的渗透调节机制来耐受低盐度条件。因此，他们进化出特定的游泳行为，从而促进了在更稳定和更高盐度条件下向海外出口以进行发育。为了研究盐度耐受性，我们对新孵化的幼虫在24小时内的盐度范围为2至35的存活情况进行了定量。我们观察到，只有在盐度高于20时，才有超过50％的幼虫能够存活24小时，而且较短的潜伏期2–6 h可以在盐度低于10时产生很高的死亡率。我们使用视频跟踪技术来量化在不同盐度，饥饿或食物供应条件下刚孵出的幼虫的游泳情况。结果表明，表观游泳速度随着盐度的增加而增加，并且向上运动比向下运动更快。当有食物时，幼虫减少了螺旋形游泳轨迹的频率，结果是更快，更直和更垂直。在低于20的盐度下，游泳轨迹变得更加随机，并且所描述的模式趋于消失。我们的结果表明，较低的生存率和降低的游泳表现可能会限制低盐度栖息地的非本地人口的扩散能力。