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

Cephalopods are highly versatile predators, with many species using suckers to capture their prey. These suckers attach to substrates ranging from the stiff, rough exoskeletons of crustaceans to the soft, smooth mucosal 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 when in contact with a substrate. We hypothesise that these rim papillae have evolved to attach to rough substrates that match their own rugosity and to prevent the trapping of water at the contact interface, which occurs for soft interfaces underwater. 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 both stiffness and roughness. We found that suckers generated larger attachment forces on stiffer substrates. Furthermore, sucker attachment forces varied significantly with substrate roughness, where highest attachment forces occurred on substrate roughnesses that coincided with the average sucker papillae size ([~]6.33 m RMS). These findings indicate that the papillae morphology may be associated with attachment performance, and could inform the design and development of versatile, bioinspired suction cups. Summary StatementCuttlefish suction cups have microscopic pillars that may interact with rough or soft surfaces to improve adhesion. We systematically examine this hypothesis using a pull-off experiment and a mathematical model.