• Nervous system in mollusca has a well developed nervous system. It also bears paired ganglia, nerves and connectives. One important aspect is there that a Circumentric ring is formed by ganglia.
  • A pair of cerebral ganglia (masses of nerve cell bodies) innervate the head, mouth, and associated sense organs. From the dorsal cerebral ganglia, two pairs of longitudinal nerve cords arise: a pair of lateral (pleural) nerve cords, often forming pleural ganglia (which innervate the mantle), and a ventral pair of pedal nerve cords, often forming pedal ganglia (which innervate the foot). In primitive forms both cords are interconnected by lateral branches of nerve fibres.
  • A buccal nerve loop with paired ganglia generally supplies the radular apparatus in the head. Posterior paired visceral ganglia, when present, innervate the viscera. Other mollusks have various grades of ganglia, all of which may be concentrated anteriorly. Because of torsion (that is, a twisting of the body during development), special nerve configurations are found in gastropods; in cephalopods a cartilaginous capsule encloses the concentrated mass of ganglia.

Nervous system in Pila

As described above the nervous system of Pila bears paired ganglia, commissures and the connectives connects them. Nerves in form of branches are supplied to all body organs.

1.The ganglia : there are paired ganglia which are the mass of nerve cells as well. The following type of ganglia are present in Pila:

  • Cerebral ganglia : It is present on dorso-lateral side of buccal cavity. Two (right & left) cerebral ganglia are present, which are triangular in shape.
  • Ganglionic mass : this is composed of pedal ganglion, pleural ganglion and other nerves. There are to pleural-pedal (right & left) are Present in Pila.
  • Buccal ganglia : It is present dorso-laterally near the joint of esophagus and buccal mass.
  • Supra instinal ganglion : this is present near pleura-pedal gangionic mass.
  • Viceral ganglia : present at the end of visceral mass; two fused ganglia are there.

2.Commissures : the commissures always connects similar ganglia. There are three commissures are present in pila.

  1. Cerebral Commissure; connects cerebral ganglia. 
  2. Pedal commissure; connects pedal ganglia.
  3. Buccal commissure; connects buccal ganglia

3. Connectives : the connectives always connect two different ganglia. Following conectives are present in pila.

  • Two cerebral-buccal connective 
  • Two cerebral-pedal connective 
  • Two cerebral-pleural connective 
  • Pleuro-infra intestinal connective
  • Supra-intestinal visceral connective
  • Infra-intestinal visceral connective
  • Supra-intestinal pleural connective 
  • Zygoneury

Various nerves are supplied to different part of body from the different ganglia.


The nervous system is the part of an animal’s body that coordinates the animal’s voluntary and involuntary functions. It is also responsible for transmission of signals between different parts of the body. The nervous system has evolved from primitive form to an advance form in animals as there is diffuse nerve net in Coelentrates and there is an advance central nervous system in Arthropoda. Ventral nerve system is present in Invertebrates; ganglia play an important role in the group. In Mollusca Commissures: connects similar ganglia, Connectives: connect two different ganglia, Ganglia: Mass of nerve cells.

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