Mollusca Nervous System

Molluscan neural systems exhibit a wide range of variations. It demonstrates the steady development of complexity from simple to complex that may be gathered into a single perspective by the nervous system’s coordination. Here, let us learn more about the components that make up the molluscan nervous system.

Table of Contents

• Phylum Mollusca – Nervous System
• Nervous System in Different Classes of Molluscs
• Frequently Asked Questions

Phylum Mollusca – Nervous System

Basic Plan of Nervous System

The pedal, cerebral and pleural ganglia are the three pairs of ganglia that make up the central nervous system in molluscs. Connectives and commissures bind these ganglia together. The cerebro-pleural, cerebro-pedal and pleuro-pedal are the connectives.

The components of the nervous system in molluscs are as follows:

• It has connectives, nerves and paired ganglia.
• The head, mouth and related sensory organs are innervated by a pair of cerebral ganglia, which are large collections of nerve cell bodies.
• Two pairs of longitudinal nerve cords arise from the dorsal cerebral ganglia – a ventral pair of pedal cords that frequently produce pedal ganglia (which innervate the foot) and a pair of lateral cords that frequently form pleural ganglia (which innervate the mantle).
• Typically the radular apparatus of the head is innervated by a buccal nerve loop containing paired ganglia.
• The viscera are innervated by posterior paired visceral ganglia if they are present.
• The osphradium, a chemoreceptive sensory organ supplied by the most posterior part of the lateral nerve cords, maintains track of the water currents approaching the mantle cavity.

See more: Difference between Crustaceans and Molluscs

Nervous System in Different Classes of Mollusca

The complexity of nervous system components might not be the same in all classes of Mollusca. Let’s have a look at the nervous system in each class separately.

• Monoplacophora – They have the simplest form of nervous system with cerebral commissure surrounding their mouth. One pair each of lateral and pedal nerve cords forms the commissure.
• Gastropoda – They have unique nerve arrangements as a result of torsion, or the body being twisted while it is developing. Here, the ganglia that make up the central nervous system are linked by nerve cells. The cerebral ganglia, osphradial ganglia, parietal ganglia, pleural ganglia, pedal ganglia and visceral ganglia are among the paired ganglia that make up this region. Buccal ganglia are also present at times.
• Polyplacophora – Four anteroposterior nerve cords and a large number of transverse nerves make up the ladder-like neural system. The oesophagus is encircled by a nerve ring. Examples of sensory structures include tactile receptors on the mantle margin, osphradia, chemoreceptors in the mouth, and statocysts in the foot. In some chitons, the shell’s surface is covered in photoreceptors.
• Cephalopoda – They have enormous brains and the ganglia combine to produce the brain. A cartilaginous capsule encloses the concentrated mass of ganglia. Significant quantities of their brain space are dedicated to sensory perception, sensory control, and mental functions including memory and decision-making.
• Scaphopoda – One pair of cerebral and pleural ganglia each lay close to the oesophagus and effectively compose the animal’s brain. Two visceral ganglia are located further back in the body and connect to the pavilion ganglia via lengthy connectives, while a separate set of pedal ganglia are located in the foot. Moreover, statocysts with staticonia and sub-radular and radular ganglia are seen. No eyes, osphradia, or other distinctive sensory organs are present in scaphopods.
• Bivalves – They have only 3 pairs of ganglia – cerebral, visceral and pedal, with the visceral being the largest and most essential of the three, and serving as the primary centre of thinking. Some animals, like scallops, have eyes along the edges of their shells that are connected to two looped nerves and enable them to distinguish between shadow and light.

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Also Check:

• Pila globosa (Apple Snail) – Diagram and Description
• Difference between Cephalopods and Gastropods
• Snail – Skeletal System