Schematic drawing and photograph of the region of the oyster including the pearl sac.

(A) The position of the pearl sac formed in the distal region of the oyster. (B) Schematic drawing of a vertical section of the pearl sac epithelium surrounding the pearl. (C) Dissection of the pearl sac tissue from the whole pearl sac for ISH. (D) After dissection of the pearl sac samples for ISH, we scratched the surface of pearl with a scalpel as a reference for SEM observation.