title: The advantage of mucus for adhesive locomotion in gastropods.
abstract: For many gastropods, locomotion is driven by a succession of periodic muscular waves (contractions and relaxations) moving along the foot. The force generated by these waves is coupled to the substratum by a thin layer of pedal mucus. Gastropod pedal mucus has unusual physical properties: the mucus is a viscoelastic solid at small deformation and shows a sharp yield point; then, at greater strains, the mucus is a viscous liquid, although it will recover its solidity if allowed to heal for a certain period. In this paper, to clarify the role of the mucus and the flexible muscular waves in adhesive locomotion, we use a simple mathematical model to verify that directional migration can be realized through the interaction between the periodic muscular waves and the specific physical features of mucus. Our results indicate that the hysteresis property of mucus is essential in controlling kinetic friction for the realization of crawling locomotion. Furthermore, our numerical calculations show that both the hysteresis property of mucus and the contraction ratio of muscle give rise to two styles of locomotion, direct waves and retrograde waves, which until now have been explained by different mechanisms. The biomechanical effectiveness of mucus in adhesive locomotion is also discussed.
authors.affiliation: Department of Mathematical Modeling, Analysis and Simulation, Graduate School of Advanced Mathematical Sciences, Meiji University, 4-21-1 Nakano, Nakano-ku, Tokyo 164-8525, Japan. Electronic address: m093666@gmail.com.
authors.forename: Mayuko
authors.initials: M
authors.lastname: Iwamoto
authors.affiliation: Department of Mathematical Modeling, Analysis and Simulation, Graduate School of Advanced Mathematical Sciences, Meiji University, 4-21-1 Nakano, Nakano-ku, Tokyo 164-8525, Japan; Meiji Institute for Advanced Study of Mathematical Sciences, 4-21-1 Nakano, Nakano-ku, Tokyo 164-8525, Japan; Department of Mathematical Sciences Based on Modeling and Analysis, Faculty of Interdisciplinary Mathematical Sciences, Meiji University, 4-21-1 Nakano, Nakano-ku, Tokyo 164-8525, Japan.
authors.forename: Daishin
authors.initials: D
authors.lastname: Ueyama
authors.affiliation: Meiji Institute for Advanced Study of Mathematical Sciences, 4-21-1 Nakano, Nakano-ku, Tokyo 164-8525, Japan; Department of Mathematical and Life Sciences, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashihiroshima, Hiroshima 739-8526, Japan; JST CREST, 5 Sanbancho, Chiyoda-ku, Tokyo 102-0075, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Kobayashi
mesh_terms: D000269:Adhesives / Q000378:metabolism*; D000818:Animals; D049851:Gastropoda / Q000502:physiology*; D008124:Locomotion / Q000502:physiology*; D008954:Models, Biological; D009093:Mucus / Q000378:metabolism*; D009132:Muscles / Q000502:physiology; D009716:Numerical Analysis, Computer-Assisted; D013312:Stress, Physiological; D013997:Time Factors
chemical_list: D000269:Adhesives
keywords: Hysteresis loop; Mathematical model; Muscular wave; Viscoelasticity; Yield point