腹足類の這行運動に見る運動メカニズムと制御

This study aim to investigate the mechanism of adhesive locomotion in gastropod. It has been reported by previous study that the significant factors of locomotion mechanism are “propagation of muscular waves” and “interfacial friction against the ground”. Interfacial friction has been considered to be controlled by lifting the pedal up, or dynamic viscoelasticity of mucus. To lift pedal up in appropriate timing, complex signals from the center would be necessary although the mechanism of lifting is simple in kinetics. This study focused on the hypothesis of dynamic viscoelasticity of mucus reported by Denny from the point of view of automatic frictional control similar to the mechanism of locomotion in earthworm. Based on the matter of previous study, a simple mathematical model which captures essential factors obtained by qualitative observations is proposed, and the physical parameters in the model are estimated by quantitative results from careful experiments. It has been verified by numerical calculations with the model that the mutual interaction between flexible muscular contraction waves and nonlinear dynamic viscoelasticity of the mucus can achieve an efficient locomotion. The important result in this study is that two locomotion styles, direct wave and retrograde wave, which has been understood by different mechanism, can be realized by the same mechanism.