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Medium compensation in a spring-actuated system

ABSTRACT Mantis shrimp strikes are one of the fastest animal movements, despite their occurrence in a water medium with viscous drag. Since the strike is produced by a latch-mediated spring-actuated system and not directly driven by muscle action, we predicted that strikes performed in air would be faster than underwater as a result of reduction in the medium's drag. Using high-speed video analysis of stereotyped strikes elicited from Squilla mantis, we found the exact opposite: strikes are much slower and less powerful in air than in water. S. mantis strikes in air have a similar mass and performance to latch-mediated spring-actuated jumps in locusts, suggesting a potential threshold for the energetics of a 1–2 g limb rotating in air. Drag forces induced by the media may be a key feature in the evolution of mantis shrimp strikes and provide a potential target for probing the braking system of these extremely fast movements. Highlighted Article: Despite the forces of viscous drag underwater, mantis shrimp strike faster in water than they do in air.