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Learn about the comparison between nervous system of Unio and Pila.
Comparison # Unio:
1. The nervous system of Unio is symmetrically arranged on two sides of the body.
2. The ganglia are widely separated by long connectives in Unio.
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3. Cerebral ganglia are two in number. These ganglia are to be called cerebropleural ganglia. Each ganglion is formed by the fusion of cerebral and pleural ganglia of the side. The ganglia are roughly triangular in outline and situated on the antero-dorsal corners of the mouth at the base of labial palps. These ganglia are connected by the cerebral commissure.
4. Pedal ganglia is a bilobed ganglionic mass formed by the fusion of two separate pedal ganglia. It is located at the junction of the visceral mass with the foot.
5. Pleural ganglia have no separate existence and become fused with cerebral ganglia.
6. Visceral ganglia is a large bilobed ganglion formed by the fusion of two visceral ganglia. It is situated posteriorly on the ventral side of the posterior adductor muscles.
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7. Buccal ganglia is absent in Unio.
8. Intestinal gang-lion is absent in Unio.
9. Pedal commissure is absent in Unio.
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10. Connections between cerebral pleural and pedal ganglia:
A pair of cerebropedal connectives connects the cerebropleural ganglia with the pedal.
11. Chiastoneury is absent in Unio.
Comparison # Pila:
1. The nervous system of Pila assumes asymmetry due to torsion of visceral hump.
2. The ganglia, particularly at the anterior side, show the tendency towards concentration due to shortening of nerves between the ganglia.
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3. Cerebral ganglia are two in number. They are also roughly triangular in outline and are situated on the dorsolateral side of the buccal mass. The cerebral commissure is very thick.
4. The pedal ganglia have no separate existence. They become fused with the pleural ganglia. On each ventrolateral side of the buccal mass a large pleuropedal ganglion is present. The pedal and pleural ganglia are separated by an inconspicuous median constriction.
5. Pleural ganglia are present in Pila and each becomes fused with pedal ganglion of its side to form pleuropedal ganglion.
6. Visceral ganglia is a bilobed structure and formed by two visceral ganglia. It is placed posteriorly very close to the heart.
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7. Buccal ganglia are two in number, situated on the dorsal side of the buccal mass on the two sides of the oesophagus. These two ganglia are connected by buccal commissure and are connected with the cerebral by cerebrobuccal connectives.
8. Only supraintestinal ganglion is present on the left side of Pila. Infraintestinal ganglion is fused with the right pleuropedal ganglionic mass. The supraintestinal nerve has the normal position, but the infrainstestinal nerve is present connecting the two pleural ganglia.
9. Broad commissure connecting the pleuropedal ganglia is present in Pila and situated above the infraintestinal nerve.
10. Connections between cerebral pleural and pedal ganglia:
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Each cerebral ganglion is connected with the pleuropedal ganglionic mass by a pair of thick connectives—cerebropleural and cerebropedal connectives.
11. Chiastoneury with Zygoneury is present on the left side. Typical chiastoneurous configuration of the pleurovisceral nerves like the figure ‘8’ is not produced. This unusual chiastoneury is resulted due to gradual migration and fusion of the infraintestinal ganglion with the right pleuropedal ganglionic mass.
