The glycerinated body wall of the sea cucumber as a suitable preparation for electron microscopic and physiological studies of ‘catch mechanism’

The body wall of the sea cucumber changes its stiffness by ionic environments. The stiff state can be held for a long time, and the mechanism concerned is known as ‘catch mechanism’. In the present study, the direct effects of ions on the mechanism using the glycerinated body wall treated with 50% glycerin to clarify how the ions effect changes of stiffness were examined. The glycerinated body walls contained collagen fibers and some broken cells in the connective tissue ultrastructurally. Cell membranes were not clearly present in the broken cells, and cell organelles were dispersed around the cells. The glycerinated body walls went into a limp state during addition of 10 mM ethylenediaminetetraacetic acid (EDTA), and showed height elongation rate in this study’s experimental system. In contrast, the elongation rate decreased by the addition of 10 mM CaCl2, that is, the body wall came to a stiff state. This stiff state could be considered as equivalent to ‘catch state’ of glycerinated body wall. Collagen fibers in those samples showed more compact arrangements at 10 mM CaCl2 treatment than the one of 10 mM EDTA ultrastructurally. These features and physiological results suggested that EDTA and/or CaCl2 from outside affect directly to the main part of the ‘catch’ mechanism in the glycerinated body wall.