title: Scrunching: a novel escape gait in planarians.
abstract: The ability to escape a predator or other life-threatening situations is central to animal survival. Different species have evolved unique strategies under anatomical and environmental constraints. In this study, we describe a novel musculature-driven escape gait in planarians, 'scrunching', which is quantitatively different from other planarian gaits, such as gliding and peristalsis. We show that scrunching is a conserved gait among different flatworm species, underlying its importance as an escape mechanism. We further demonstrate that it can be induced by a variety of physical stimuli, including amputation, high temperature, electric shock and low pH. We discuss the functional basis for scrunching as the preferential gait when gliding is impaired due to a disruption of mucus production. Finally, we show that the key mechanical features of scrunching are adequately captured by a simple biomechanical model that is solely based on experimental data from traction force microscopy and tissue rheology without fit parameters. Together, our results form a complete description of this novel form of planarian locomotion. Because scrunching has distinct dynamics, this gait can serve as a robust behavioral readout for studies of motor neuron and muscular functions in planarians and in particular the restoration of these functions during regeneration.
authors.affiliation: Physics Department, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
authors.forename: Olivier
authors.initials: O
authors.lastname: Cochet-Escartin
authors.forename: Keith J
authors.initials: KJ
authors.lastname: Mickolajczyk
authors.forename: Eva-Maria S
authors.initials: EM
authors.lastname: Collins
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D004924:Escape Reaction; D005684:Gait; D010932:Planarians / Q000502:physiology*; D012038:Regeneration