Question

Nacre or mother of pearl is secreted by mantle's
A) Cubical epithelial cells
B) Columnar epithelial cells
C) Columnar endothelial cells
D) Cubical endothelial cells

Answer 1

Hint:Let us first understand what is nacre.The inner alternating layers of molluscan shells composed of organic materials and aragonite platelet films is called Nacre.

Complete answer:
>Mollusca belongs to kingdom Animalia and is considered as the second largest phylum in the world.
>Nacre also called mother of pearl is produced as an inner shell layer by some molluscs.
>It is also the composition of a pearl layer. It is strong, flexible and exhibits the phenomenon of iridescence.
>It is formed by the secretions of mantel's columnar epithelial cells.

Additional information:
>The layer of tissues present between the shell and the body of molluscs is called as mantel.
>The shell is formed by the secretion of calcium carbonate and it forms a cavity between body and mantle called mantel cavity.
>The epithelial cells of mantel secretes the shell material.
>Both columnar and cuboidal cells are called glandular epithelial cells. The main function of these cells is secretion.
>Molluscs have an open circulatory system where the blood is directly pumped from gills to other tissues with the help of heart that are made up of cuboidal or columnar endothelial cells.

Therefore the correct answer is (b) columnar epithelial cells.

Note:The epithelial cells that create nacre are formed by germ layer ectoderm. Apart from pearl oysters (Pteriidae), that are found in freshwater, other molluscs family that have the layer of nacre includes marine gastropods such as Turbinidae, Haliotidae and Trochidae.