GLYCOSAMINOGLYCAN INVOLVED IN THE CATION-INDUCED CHANGE OF BODY WALL STRUCTURE OF SEA-CUCUMBER STICHOPUS-JAPONICUS

The body wall of sea cucumber Stichopus japonicus was treated with various concentrations of several cations, and examined for changes in toughness, taking punch force as parameter. Toughness of the body wall tended to decrease with increasing concentration of each cation, but in different modes depending mainly upon the valency of cation: e.g., the body wall completely lost toughness in 0.3 M Na± or 0.4 M K±, whereas it retained more than half the initial toughness even in 0.4 M Ca2± or Mg2±. Glycosaminoglycan (GAG) from the body wall was dissolved in water, and examined for viscosity changes as caused by those cations. Specific viscosity (ηsp) decreased from 0.71 (without cation) to 0.47-0.57 in the presence of 0.1 M monovalent and divalent cations. At 0.4 M, monovalent cations reduced ηsp to 0.38-0.46, but divalent cations increased ηspto 0.56-0.63. Electron microscopy demonstrated that GAG matrix was clearly observed in the absence of cation, but disappeared in 0.4 M NaCl, forming wide free spaces in the body wall. These results all suggested that GAG is closely involved in the change of toughness of sea cucumber body wall. © 1990 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.