SENSE ORGANS IN PILA (SNAIL)

Pila is an amphibian. It shows many sense organs. They are ospharadium, eyes, statocyst and tentacles

1. Ospharadium

Near the left pseudepipodium attached to the pulmonary sac a leaf like ospharadium is present. It is leaf like. It is 6 to 7 mm. in length. It isbipectinate. It bears a median axis. From this axis 22-28 lamellae will arise in two rows. This structure is innervated by a nerve coming from left pleural ganglion. This will test the purity of water.

2. Eye

On the head of Pila two stalks are present. They are called ommatophores.They bear eyes. Each eye is black and round. In the section of the eye a central sac like structure is present. It is called optic vesicle Eye is derived from ectoderm. Optic nerve is connected to the eye. In the sac of the eye a lens is present. The inner surface of the sac shows retina. In this retina visual cells and supporting cells are present.

This eye of Pila cannot form image of the object.

3. Statocyst

On either side of the Pedal ganglion two statocysts are present. Each statocyst is pear shaped. Each statocyst is hollow bag like structure.vIt is covered by connective tissue. It is derived from ectoderm. In the sac of this statocyst watery fluid is present. In this fluid calcareous particles are present called statoconia. This is connected with a nerve coming from Pedal ganglion. This will maintain equilibrium.

4. Tentacles

On the head of Pila two tentac'es are present.

• The first pair of tentacles are called cephalic tentacles.
• The second pair of tentacles are t.ue tentacles. They are tactile sense organs.