Attachment performance of cuttlefish ( Sepia officinalis ) suckers depends on the interaction between papillae and substrate topography

Cephalopods are versatile predators, with many species using suckers to capture prey. These suckers attach to substrates ranging from the stiff, rough exoskeletons of crustaceans to the soft, smooth tissues of other cephalopods. Despite generating higher suction pressures than octopuses, less attention has been given to the biomechanics of cuttlefish suckers. Cuttlefish suckers exhibit a stiff, rough papillated rim that acts as a seal. We hypothesize that these papillae have evolved to attach to rough substrates, matching their rugosity to expel water at the contact interface. To test this hypothesis, we investigated the passive attachment performance of common cuttlefish (Sepia officinalis) suckers ex vivo on a variety of artificial substrates that differed in stiffness and roughness. We found that sucker attachment forces varied significantly with substrate roughness, with the highest forces occurring on roughnesses that coincided with the average sucker papillae height (root-mean-square, approx. 6.84 µm). Additionally, attachment forces were higher on stiffer substrates. We developed a mathematical model for predicting leakage across the sucker rim that qualitatively agrees with our experimental results. These findings indicate that the papillae may aid attachment performance, particularly to natural prey, and could inform the design and development of versatile bioinspired suction cups.