Ellers O
Biol Bull. 1995 Oct;189(2):120-127. doi: 10.2307/1542462.
Clams of the species Donax variabilis migrate shoreward during rising tides and seaward during falling tides. These clams spend most of the time in the sand, emerging several times per tidal cycle to ride waves. Migration is not merely a passive result of waves eroding clams out of the sand; rather clams actively jump out of the sand and ride specific waves. Such active migration is experimentally demonstrated during a falling tide by comparing the motion of dead and live clams; live clams emerge from the sand and move seaward even when dead ones do not. As low tide approaches, live clams become progressively less active. They cease migrating for 2 hours around low tide and resume jumping to migrate shoreward after the tide has turned. During the rising tide, far from being passive, the clams jump out to ride only the largest 20% of waves. Specifically, they choose swash that have the largest excursion, i.e., those swash that move furthest on the beach.
多变多彩海螂在涨潮时向岸迁移，落潮时向海迁移。这些海螂大部分时间都埋在沙子里，每个潮汐周期会出现几次以乘浪前行。迁移不仅仅是海浪将海螂从沙子中冲刷出来的被动结果；相反，海螂会主动跳出沙子并搭乘特定的海浪。通过比较死海螂和活海螂的运动，在落潮期间通过实验证明了这种主动迁移；即使死海螂不会，活海螂也会从沙子中出来并向海移动。随着低潮临近，活海螂的活动逐渐减少。它们在低潮前后停止迁移2小时，潮水转向后又恢复跳跃向岸迁移。在涨潮期间，海螂远非被动，它们只会跳出搭乘最大的20%的海浪。具体来说，它们选择具有最大偏移量的冲流，即那些在海滩上移动最远的冲流。
