Question

Osphradium of Pila/mollusca is
A. Chemoreceptor
B. Photoreceptor
C. Tangoreceptor
D. Phonoreceptor

Answer 1

Hint: Pila has a single gill-like osphradium located on the left side of the pulmonary area. It hangs from the roof of the mantle cavity next to the left nuchal lobe. It is used to detect materials entering the gills.

Complete Answer:
Molluscs constitute the second largest animal phylum. Molluscs are land or marine (water or freshwater) organisms with an organ-system level of organisation. The body is enclosed by a calcareous shell and has a distinct head, a muscular foot and a visceral hump.

The nervous system is composed of several pairs of ganglia and their associated nerve cords. The nervous system in molluscs, particularly cephalopods (squid and octopus), is well developed. The tentacles and the foot of the pila are generously supplied with nerves, which are sensory for touch. Tentacles contain both tactile and chemoreceptors cells, and presumably even taste cells.

Osphradium is a single or paired sensory organ attached to one of the visceral ganglias and located near the gill of most marine molluscs that is meant to be olfactory or to measure the quality of the water flowing through the gills.

In pila, the statocysts receive the nerves of the pedal and cerebral ganglia, and are the organs of balance and control the position of the snail. They are located at the foot of each pedal ganglion. It is a round capsule lined with epithelial cells and covered by connective tissues. There is a thin calcareous statoconia in the cavity of the capsule.

Thus, the correct answer is option A i.e., Chemoreceptor.

Note: Many molluscs, other than bivalves, possess sensory organs, including pairs of eyes and tentacles. Mussels lack both, but they may have statocysts and sensory osphradia that are chemoreceptors found next to gills.