Question

In pearl oyster, the pearl is formed by secretion of
a) Shell
b) Mantle
c)Digestive gland
d)None of these

Answer 1

Hint: The formation of pearl is the characteristic feature of the phylum mollusca. In them, the pearl is formed when a foreign particle enters inside the shell and the mantle. There is a secretion done on the foreign particle which makes it shiny and glossy in nature.

Complete answer:
The pearls are formed when an irritant called the foreign particle enters the body of the oyster. It uses the defence mechanism against the foreign particle and the mantle secretes a fluid that coats the material. These layers of fluid which are deposited are called nacre and they lead to the formation of the pearl. Pearl appears to be shiny in texture and is used in the making of jewelry. The pearls that are produced in the saltwater are rounder in shape and have good texture when compared to the pearl produced in the freshwater. The pearls are also cultured and reared from the mussels which are first grown into adults and then the foreign particle is implanted on them in order to produce pearls from them. The formation of good quality pearls usually takes three to four years. There are also artificial pearls which are the glass beads made to dip in the solution made from the scales of the fishes. The artificial or the fake pearls have a very soft texture but the real pearls feel a little gritty in texture.
So, the answer is ‘mantle’.

Note: The mantle secretes substances that are responsible for the formation of the pearls and shells. The shell provides the protective covering to an organism and the pearl is formed due to the presence of the foreign particle on the body of the organism.