Viscoelasticity of Holothurian Body Wall

Abstract

Stress-relaxation tests and creep tests were performed on the bodywall dermis of two sea cucumbers, Actinopyga echinites (Jäger) and Holothuria leucospilota Brandt. These viscoelastic connective tissues had mechanical properties which agreed well with those of a four-element mechanical model composed of two Maxwell elements connected in parallel. The elastic stiffness of the dermis of Actinopyga was 1·7 MPa and that of Holothuria was 0·42 MPa. The viscosity of the dermis showed great variation of more than two orders. Chemical stimulation with artificial sea water containing 100 mm potassium increased the viscosity but not elasticity. The viscosity change is suggested to be caused by the change in weak (non-covalent) bonds between macromolecules which constitute the dermis.