Freshwater snail feeding: lubrication-based particle collection on the water surface

The means by which aquatic animals such as freshwater snails collect food particles distributed on the water surface are of great interest for understanding life at the air-water interface. The apple snail Pomacea canaliculata stabilizes itself just below the air-water interface and manipulates its foot such that it forms a cone-shaped funnel into which an inhalant current is generated, thereby drawing food particles into the funnel to be ingested. We measured the velocity of this feeding current and tracked the trajectories of food particles around and on the snail. Our experiments indicated that the particles were collected via the free surface flow generated by the snail's undulating foot. The findings were interpreted using a simple model based on lubrication theory, which considered several plausible mechanisms depending on the relative importance of hydrostatic pressure, capillary action and rhythmic surface undulation.

淡水螺等水生动物收集分布在水面的食物颗粒的方式对于理解气 - 水界面的生命活动具有重大意义。福寿螺（Pomacea canaliculata）在气 - 水界面下方稳定自身，并操控其足部，使其形成一个锥形漏斗，在其中产生吸入水流，从而将食物颗粒吸入漏斗以便摄取。我们测量了这种进食水流的速度，并追踪了食物颗粒在螺体周围及上方的轨迹。我们的实验表明，颗粒是通过螺体波动的足部所产生的自由表面流收集的。研究结果通过一个基于润滑理论的简单模型进行解释，该模型根据静水压力、毛细作用和有节奏的表面波动的相对重要性考虑了几种可能的机制。