An Electron Microscope Study on the Calcification of the Exoskeleton in a Shore Crab

Abstract

The early phase of calcification of the endocuticle newly formed after molting in the shore crab, Gaetice depressus, was studied by electron microscopy. In endocuticle matrix near the outer surface of the epidermal cell in which the calcification has begun, a number of small or large granular crystallites, 2-150 mμ in diameter, were found to be deposited in the fibrils. The fibrils, about 30-80mμ thick, are dispersed randomly in the ground substance. In each elliptical border of the pore canals situated between the fibrils, the small granular crystallites, 2-26 mμ in diameter, are often deposited in minute spaces. With the advancement of calcification, small or large granular crystallites deposited in the fibrils begin to join with one another and gradually form the band-shaped clusters of crystallites. On the other hand, the small granular crystallites deposited in each border of the pore canals do not form any crystallite clusters even with the advancement of calcification.