Influence of ionic environment of the stress relaxation behavior of an invertebrate connective tissue

The rheological properties of an invertebrate connective tissue were measured in three different ionic environments. Short-term stress relaxation tests were conducted on sections of holothurian (Echinodermata) body wall immersed in isotonic monovalent and divalent salt solutions and deionized water. Using a reduced modulus format, the viscoelastic behavior over the experimental time scale was described by a two term Maxwell equation with empirically determined spring constants and relaxation times. In addition, equilibrium relaxation moduli (Ge) were estimated from the empirical relationship of Chasset and Thirion (1965, in Physics of Non Crystalline Solids, ed. Prins, North Holland). The experiments indicated that both relaxation times and equilibrium moduli decreased in the presence of monovalent and divalent inorganic ions whereby the effect of the Na+ was greater than that of the Ca++. The present findings are compared with those reported for vertebrate connective tissue.