Light and Scanning Electron Microscopic Observations on Shell Chamber Formation in the Japanese Oyster Crassostrea gigas

Abstract

The growth front of paper shell obtained from a chambered oyster, Crassostrea gigas, was observed with light and scanning electron microscopes. In the very early stage of paper shell growth, many small, granular shell materials are randomly distributed in the membrane-like materials on the jelly-like material which is observed to be present on the interior surface of the shell. These small, granular shell materials are covered with a layer of larger circular disc shell materials. These circular disc shell materials which keep separate, gradually bind together, and make a thin brittle paper shell. Then, as it is covered with some structures such as comb, cracker, foliated and chalky deposits, the thin paper shell becomes thicker and harder, and makes a wall of the shell chamber. It is remarkable that the process of paper shell formation occurs on soft jelly-like material. It seems to be a new type of shell formation. Use of this early stage of paper shell as a material for the study of shell formation may be promising.