Shreyas Mandre

University Associate Professor of Fluid-Structure Interaction
Department of Engineering, University of Cambridge

Fish fins

Curvature-induced stiffening of fish fin

Biomechanics Fish fins

How fish modulate their fin stiffness during locomotive manoeuvres remains unknown. We show that changing the fin’s curvature modulates its stiffness. Modelling the fin as bendable bony rays held together by a membrane, we deduce that fin curvature is manifested as a misalignment of the principal bending axes between neighbouring rays. An external force causes neighbouring rays to bend and splay apart, and thus stretches the membrane. This coupling between bending the rays and stretching the membrane underlies the increase in stiffness.