Collecting differently sized particles on water surface by maneuvering pedal waves on the foot of the water snail Pomacea canaliculata.

Abstract

The water snail (Pomacea canaliculata) features both broad dietary scope and high feeding rate, possibly making it one of the most successful mollusc invaders globally. The water snail can collect differently sized food particles on the air-water interface by generating pedal waves on the foot surface, such as granular duckweed and animal carrion in wild aquatic environment. While foraging by pedal waves, the biomechanical challenges by manipulating the differently sized particles might be overcome by mediating the waveform for optimized energy costs, the physics and the function of which have not been uncovered yet. Herein, we study the two-dimensional topographic features of the snail foot in the pedal wave feeding pattern by a laser sensor. Feeding on differently sized particles, the average wavelength of the pedal waves remains nearly constant, whereas the amplitude increases while transporting larger particles. We develop a hydrodynamical model and discover that applying a larger amplitude to transport the particle can shorten the transport time, facilitating the food transport rate. However, to maintain a relatively constant mass uptake rate, the water snail exhibits a flexible strategy of collecting larger particles with increased amplitudes. This work demonstrates that the water snail implements a strategy by generating varying waveforms on the foot surface to take up the floating food at an optimized feeding rate. This feeding fashion may open up a new way for developing bio-inspired solid waste collectors at the gas-liquid interface.