Age-dependent effects of water striders moving on perturbed water surfaces

Surface roughness is a ubiquitous phenomenon in both oceanic and terrestrial waters. For insects that live at the air-water interface, such as water striders, non-linear and multi-scale perturbations produce dynamic surface deformations which may impair locomotion. We studied escape jumps of adults, juveniles, and first-instar larvae of the water strider Aquarius remigis on smooth, wave-dominated, and bubble-dominated water surfaces. Effects of substrate on takeoff jumps were substantial, with significant reductions in take-off angles, peak translational speeds, attained heights, and power expenditure on more perturbed water surfaces. Age effects were similarly pronounced, with the first-instar larvae experiencing the greatest degradation in performance; age-by-treatment effects were also significant for many kinematic variables. Although commonplace in nature, perturbed water surfaces thus have significant and age-dependent effects on water strider locomotion, and on behavior more generally of surface-dwelling insects.