Question

The glandular fold enclosing the visceral mass of most of the molluscs , secreting shells is called as
(a)Atrium
(b)Peritoneum
(c)Mantle
(d)None of the above.

Answer 1

Hint: Molluscs are a clade of organisms that all have soft bodies which typically have a "head" and a "foot" region. It is a significant part of the anatomy of molluscs: it is the dorsal body wall which covers the visceral mass and usually protrudes in the form of flaps well beyond the visceral mass itself.

Complete answer:
Molluscs are soft-bodied organisms with a hard skeleton. The skeleton is made up of a hard calcareous shell-like structure. The mantle is an important part of the body of molluscs. It forms the dorsal body wall. The mantle covers the organs of digestion, reproduction and movement. The mantle leads to the formation of a mantle cavity. This cavity is formed by the mantle skirt. The mantle skirt is the result of the double fold of mantle, which encloses a water space. This is the space which contains the visceral mass. This space contains the gills, anus and organs for taste, excretion and reproduction organs. This is the space which contains the tissues which secrete the shell.

Additional Information: The mantle cavity may be a central feature of molluscan biology. This cavity is made by the mantle skirt, a double fold of mantle which encloses a water space. This space contains the other parts of molluscs like gills, anus, osphradium, nephridiopores, and gonophores.

The mantle cavity performs the activity of the respiratory chamber in most molluscs. In bivalves, it's usually a part of the feeding structure. In some molluscs, the mantle cavity may be a brood chamber, and in cephalopods and a few bivalves like scallops, it's a locomotory organ.

So, the correct answer is, “Mantle.”

Note: The mantle is very muscular. In cephalopods, the contraction of the mantle is employed to force water through a tubular siphon, the hypostome, and this propels the animal very rapidly through the water. In gastropods, it's used as a sort of "foot" for locomotion over the surface. In Patella, the foot includes the whole ventral surface of the animal. The foot of the Bivalvia may be a fleshy process adopted by its form to digging instead of to locomotion.