Surface movement mechanism of abalone and underwater adsorbability of its abdominal foot

The abalone, a marine mollusk, inhabits fast-flowing rocky reefs. Its predation and crawling abilities strongly depend on the adhesion capacity of its abdominal foot. Here, the macroscopic and microscopic morphology of the abalone foot was observed. The foot is divided into four main regions, each having a large number of folds on the surface. The extensional ability of the folds is the source of the abalone’s locomotory power. A high-speed camera was used to photograph the movement of an abalone. It was found that two to three deep-yellow round fold areas appear and disappear periodically on the surface of the foot. The folds move forward with the movement of the abalone. This results in a crawling motion that ensures efficiency of movement and adaptability of the wide abdominal foot to adsorptive surfaces. According to underwater tensile testing of an abalone, the adhesion force of the foot is composed of suction force, capillary force, friction and an interlocking structure. Among them, suction force is the most important component of the adhesion force, and the other factors play an auxiliary and reinforcing role. The strong adhesivity and adhesion-based crawling motion of the abalone may inspire new design ideas and mechanisms for underwater suckers.