RT Journal Article SR Electronic T1 Medium compensation in a spring-actuated system JF The Journal of Experimental Biology JO J. Exp. Biol. FD The Company of Biologists Ltd SP jeb208678 DO 10.1242/jeb.208678 VO 223 IS 4 A1 Feller, Kathryn D. A1 Sutton, Gregory P. A1 Gonzalez-Bellido, Paloma T. YR 2020 UL http://jeb.biologists.org/content/223/4/jeb208678.abstract AB 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.