Nervous system of Pila: An Apple Snail.

Nervous system of the Pila:

The nervous system of Pila consists of paired ganglia, commissures, and connectives uniting them. The nerves running from the central organs to all parts of the body.

1. Ganglia:

These are paired ganglia, which are an aggregation of a nerve cell. These nerve cells consist of following parts.

• Cerebral ganglia.
• Buccal ganglia.
• Pleuro-pedal ganglia.
• Supra-intestinal ganglia.
• Visceral ganglia.

(a) Cerebral ganglia:

These are the pair of roughly triangular ganglia, situated anteriorly on the dorsolateral sides of the buccal mass.

(b) Buccal ganglia:

These are a pair of small, triangular ganglia, lying dorsolaterally one on either side at the junction of the buccal mass and oesophagus. These ganglia are partially embedded in the muscles.

(c) Pleuro-pedal ganglia:

These ganglia are large somewhat triangular ganglionic masses present one on the ventrolateral side of the buccal mass.Right, pleuro-pedal ganglionic mass also consists of the infra-intestinal ganglia fused with it.These ganglia are formed by the fusion of outer pleural and inner pedal ganglia.

(d) Supra-intestinal ganglia:

Behind the left pleuro-pedal ganglionic mass there is an unpaired fusiform ganglion, lying in a sinus called as supra-intestinal ganglia.

(e) Visceral ganglia:

At the lower end of the visceral mass, there is present a single ganglionic mass called visceral ganglia.The visceral ganglia are represented by two fused ganglia.

2.Commissures:

The nerves which establish a connection between two similar ganglia are commissures. It consists of following three parts.

1. Cerebral commissures.
2. Buccal commissure.
3. Pedal commissures.

1. Cerebral commissures:

It lying dorsally to the buccal mass. A thick hand of nerve connective two cerebral ganglia are called cerebral commissures.

2. Buccal commissures:

It lies transversely on the ventral side of the oesophagus.A fine nerve which connects the two buccal ganglia is called buccal commissures.

3. Pedal commissure:

Pedal commissure connects the two pedal ganglia together.Two thick nervous bands that lie one above the other underneath the buccal mass are called pedal commissure.

3. Connectives:

Connectives are those nerve which connects two different ganglia. In the nerve system of pila, it consists of following parts.

1. Two Cerebro-buccal connectives.
2. Two Cerebro-pleural connectives.
3. Two Cerebro-pedal connectives.
4. Pleuro-infra intestinal connectives.
5. Infra-intestinal visceral connectives.
6. Supra-intestinal visceral connective.
7. Supra-intestinal-pleural connectives.

1. Two Cerebro-buccal connectives.

These connect, on either side, the cerebral ganglion and buccal ganglia together.

2. Two Cerebro-pleural connectives.

These connect, on either side, the cerebral and outer pleural ganglion of the pleuro-pedal ganglionic mass.

3. Two Cerebro-pedal connectives.

These connect, on either side, the cerebral and inner pedal ganglion of the pleuro-pedal ganglionic mass.

4. Pleuro-infra intestinal connectives.

It connects infra-intestinal nerve, it is a nerve connection between the pleural ganglion of the left pleural –pedal mass and the infra- intestinal ganglion which is fused with the right pleuro-pedal mass.

5. Infra intestinal visceral connective.

It is a long nerve running below the intestine , that connects the visceral ganglion with the infra-intestinal part of the right pleuro-pedal-infra-intestinal ganglionic mass.

6. Supra-intestinal visceral connective.

It is a slender nerve running above the intestine, that connects the visceral ganglion with the supraintestinal ganglion.

7. Supra-intestinal –pleural connective.

It is also called supra-intestinal nerve. It connects the supraintestinal ganglion with the pleural part of the right pleuro-pedal-infra-intestinal ganglionic mass.

8. Zygoneury.

It is a nerve that connection between the pleural part of the left pleuro pedal ganglionic mass and supraintestinal ganglion.

4. The nerve to different parts of the body.

Various ganglia send nerves to innervate different parts of the body.

1.Each cerebral ganglion gives off nerves, supplying the snout, skin, tentacles and buccal mass anteriorly and the tentacles, eye, and statocyst, posteriorly.

2. Buccal ganglia, of each side, send nerves to innervate the buccal mass, radius sac, salivary gland, oesophagus and oesophagal pouches.
3. Pedal ganglia give off nerves, anteriorly as well as posteriorly , to innervate the foot.
4. Left pleural ganglion innervates the parietal wall, mantle, osphradium, left nuchal lobe, columellar muscle and the anterior part of the gills.
5. Right pleural ganglion innervates the parietal wall, epithelia,right nuchal lobe, copulatory organ, columellar muscle and the rectum.
6. Supra-intestinal ganglion gives off a stout nerve to innervate the mantle and the anterior part of the ctenidium, while its connectives with the left pleural ganglion send a few nerve to the parietal wall.
7. Nerves from the visceral ganglion supply the renal organ, genital organs, pericardium, stomach, intestine, digestive gland,etc.

Reference:

Bhamrah, H.S., and Kavita, Juneja. A Text Book of Invertebrates, New Delhi: Anmol Publications Pvt Ltd, 2011.

Jordan E.L. and P. S., Verma. Invertebrate Zoology, New Delhi,: S. Chand and Company Pvt. Ltd., 2011.

Kotpal, R. L.,Modern Text Book of Zoology: Invertebrates, New Delhi, India: Rastogi Publications,2011.

http://www.biologydiscussion.com/

https://en.wikipedia.org/wiki/Pila_(gastropod)