Question

What is radula?

Answer 1

Hint: Molluscs are triploblastic, coelomate(schizocoelic) organisms with organ system level of organization. The body is soft and unsegmented, divisible into the head with sensory tentacles, foot, and visceral hump. Mollusks contain a rasping organ called radula for feeding.

Complete answer: Mollusca is the second-largest animal phylum. Mollusks are triploblastic, coelomate(schizocoelic) organisms with organ system level of organization. They have bilateral symmetry, but some are asymmetrical due to torsion as they grow. The body is soft and unsegmented, divisible into the head with sensory tentacles, foot, and visceral hump( contain digestive tract and other visceral organs). The soft body is covered by a fleshy fold called mantle/pallium. The mantle cavity is present between the visceral hump and mantle. Mantle secretes a calcareous shell(conchiolin matrix and calcite and aragonite) on its outer surface in some species. The respiration is carried out by feather-like gills(ctenidia) in the mantle cavity or pulmonary chamber. Gills also help in excretion. The digestive system is well developed.

Mollusks contain a rasping organ called radula for feeding. The radula is a ribbon-like structure that has transverse rows of chitinous teeth and helps in cutting of food before it enters into the stomach. The sensory organs include the eyes, statocyst, and osphradia. The excretory organ is one or two pairs of kidneys. The nervous system consists of paired ganglia. Development is indirect in Molluscs.

Note: Some representative animals are-
-Neopilina is a living fossil and connecting link between Annelida and Mollusca.
-Unio is a freshwater mussel.
-Aplysia is commonly known as Sea hare.
-Pinctada(pearl oyster): best quality pearls are obtained from P. vulgaris and P. margaritifera.