All types of oysters (and, indeed, many other shelled molluscs) can secrete pearls, but those from edible oysters have no market value.

所有种类的牡蛎(实际上也包括其他许多有壳的软体动物)都能分泌出珍珠，但是可食用的牡蛎出产的珍珠没有市场价值。