Compare Pila nervous system with other gastropods

The nervous system of Pila is a classic example of a "prosobranch" (a group of gastropods) but shows differences when compared to other groups like opisthobranchs (sea slugs) and pulmonates (land snails).

• Pila (Prosobranch): Pila's nervous system is defined by streptoneury (or chiastoneury). This is a "twisted" condition where the pleuro-visceral connectives form a figure-eight, a direct result of the 180-degree torsion of the visceral mass in its larval stage. The ganglia are distinct but show some fusion (e.g., pleuro-pedal).
• Opisthobranchs (e.g., Sea Slugs): Many sea slugs have undergone detorsion—a secondary evolutionary "untwisting" of the body. As a result, their nervous system is euthyneurous (untwisted). The visceral loop is short and symmetrical, and there is no figure-eight crossing. They also show a much higher degree of ganglionic concentration, with many ganglia fused around the oesophagus to form a "nerve ring."
• Pulmonates (e.g., Land Snails): Land snails are also euthyneurous (untwisted) and show a very high degree of ganglionic fusion. All the main ganglia (cerebral, pleural, pedal, and visceral) are concentrated in a single large nerve ring around the oesophagus, making their nervous system appear much more centralized and compact than that of Pila.

In summary, Pila represents the classic "twisted" gastropod nervous system, while other groups like sea slugs and land snails have evolved a "secondarily untwisted" and more concentrated (fused) nervous system.