Question

Which mollusk gives black pearls?

A. Pinctada maxima
B. Tridacna noae
C. Pinctada fucata
D. Pinctada margaritifera

Answer 1

Hint: The real pearl oyster belongs to the family Pteriidae, order Dysodonta, and the genus Pinctada (Roding). Members of the Pteriidae family have a straight hinge with \[1-2\] tiny tooth-like thickening, a cavity for the byssus below the anterior angle, and generally a scaly surface on the outer shell valves. Pearl oysters of the genus Pinctada are members of this family.

Complete solution:
Option A - Pinctada maxima produces white, silver, champagne and gold color pearls.
Thus, option A is not correct.
Option B – Large white pearls with an undulating, porcelain-like surface are produced by Tridacna clams and are known as "non-nacreous pearls."
Thus, option B is not correct.
Option C – Pinctada fucata produces white and yellowish colored pearls of high quality which are called Akoya pearls.
Thus, option C is also not correct.
Option D – Pinctada margaritifera is a saltwater mollusk which produces black colored pearls and thus is commonly known as black lip pearl oyster.
Thus, option D is the correct answer.

Hence, Option D Pinctada margaritifera is the correct answer.

Additional information:
When a foreign particle enters the gap between the oyster's mantle and shell by mistake, it clings to the mantle. As a protective strategy, the mantle epithelium encloses it like a sac and begins to secrete concentric layers of nacre around it. The mantle's epithelial layer secretes nacre on a constant basis, which is deposited around the foreign particle, and the hard and lustrous pearl is formed over time by the creation of successive layers of calcium carbonate.

Note:
The calcareous secretion of the nacre (mother of pearl) found in the glandular mantle of pearl oysters is produced in concentric layers around a centre made of foreign item causing irritation, forming a spherical or irregular mass. The form, size, and colour of pearls vary depending on the type of pearl. The form of the pearls is usually uneven.