Effects of Ionic Environment on Viscosity of Catch Connective Tissue in Holothurian Body Wall

Abstract

The effects of cations (H+, Na+, K+, Ca2+, Mg2+) on the mechanical properties of the catch connective tissue in the dermis of a sea cucumber, Holothuria leucospilota Brandt, were studied. The manipulation of the ionic environment caused rapid (apparent in minutes) and reversible viscosity change. Artificial sea water (ASW) with a high concentration of Ca2+ (50 mmol 1−’) increased the normal viscosity 9 times; Ca2+-free ASW decreased it to one-tenth. Ca2+ was the only ion which caused a viscosity change whose range was as large as the range of the viscosity distribution of the dermis in ASW. Manipulation of the concentration of other ions caused an increase in viscosity. An increase of more than five-fold was observed in the following solutions: ASW with acidic (pH 4) or basic (pH 9, 10) pH ; Na+-free ASW whose Na+ was replaced by either sucrose or choline; ASW with high (100mmoll−1) concentration of K+; ASW with low (0 mmol 1−1) or high (250 mmol 1−1) concentrations of Mg2+. The dermis contracted in distilled water, although this tissue contained no muscle cells.