Meeting Abstract
Mechanical redundancy allows mechanical systems to vary overall morphology while retaining similar outputs, as exemplified by the 4-bar linkage system in fishes. However, even in mechanically redundant systems, mechanical output may be particularly sensitive to variation in individual components. We define mechanical sensitivity as the process by which small changes in some components may have larger effects on output than similar changes in other components. Here we test whether mantis shrimp (Stomatopoda) 4-bar linkages are mechanically redundant while also exhibiting mechanical sensitivity to variation in the component links. While the overall linkage system showed a classic pattern of mechanical redundancy, it also presented distinct mechanical sensitivity to a single component of the system (carpus link), which was tightly correlated with output (kinematic transmission; KT). Analyses of trait evolution indicated that the mechanically sensitive component (carpus link) evolved in tandem with KT, while insensitive components (other links) evolved independently. Our results illustrate the connections between mechanical redundancy, mechanical sensitivity and constraint: mechanically insensitive components vary freely, creating mechanical redundancy in the whole system, while mechanically sensitive components act as structural constraints that play a significant role in the function and evolutionary variability of the system.
