Meeting Abstract
Animals have innovated a multitude of strategies to locomote over and in natural substrates. To develop principles of adaptive locomotion in complex, dynamic environments, we studied the Pacific Mole Crab ( Emerita analoga), a decapod crustacean capable of multimodal locomotion in the highly dynamic intertidal zone. E. analoga uses five pairs of multifunctional appendages to burrow rapidly into saturated, flowable intertidal substrate. We hypothesize that these controllable components can be represented as simple models (templates) that can be recruited in series or parallel towards robust and adaptive burrowing. Using granular particle image velocimetry (PIV) and refractive index matched substrates, we identified a set of potential control modules used by E. analoga to manipulate and make ingress into wet substrates. To further reveal the structure of these burrowing control modules, we measured limb kinematics as a function of depth. We found that limb cycle frequency of the anteriorly excavating appendages decreased from 3.7 ± 0.2 Hz at penetration to 2.2 ± 0.2 Hz at submersion. However, when the uropods were restricted, limb cycle frequency of the same appendages remained almost constant from penetration (3.1 ± 0.1 Hz) to submersion (3.0 ± 0.3 Hz), suggesting compensation. Finally, we propose a set of simple terradynamic template models that provide insight into the control affordances of the burrowing modules. Our findings begin to elucidate the structure and robustness of the burrowing control modules employed by mole crabs and suggest bioinspired design and control principles that may enable new burrowing behaviors in legged robots.
