Sensory organs in Pila and their neural innervation

Pila has several well-developed sensory organs to navigate its freshwater environment and detect food, predators, and water quality.

• Osphradium: This is the most important chemosensory organ. It is a small, leaf-like structure (bipectinate) hanging from the mantle roof at the base of the incurrent siphon. 
  Function: It "tastes" or "smells" the incoming water, detecting chemicals and sediment. This allows Pila to check water quality before it passes over the gill. 
  Innervation: It is innervated by a nerve from the supra-intestinal ganglion (and sometimes also the left pleural ganglion).
• Tentacles: Pila has two pairs of tentacles on its snout. The first (anterior) pair are short, and the second (posterior) pair are long. 
  Function: They are highly mobile and act as tactile (touch) organs and chemoreceptors (taste/smell), constantly sampling the environment. 
  Innervation: Both pairs are innervated by nerves from the cerebral ganglia.
• Eyes (Ommatophores): A pair of simple eyes are located on short, stalk-like structures called ommatophores, at the base of the second pair of tentacles. 
  Function: These are simple photoreceptors, capable of detecting changes in light intensity and shadows, but not forming complex images. 
  Innervation: The optic nerve from each eye connects to the cerebral ganglion.
• Statocysts (Balance Organs): These are a pair of small, fluid-filled sacs located in the foot, one near each pedal ganglion. They contain tiny calcareous particles called statoliths. 
  Function: As the snail moves, the statoliths shift, stimulating sensory cells and providing information about gravity and the snail's orientation (balance). 
  Innervation: They are innervated by nerves from both the pedal ganglia and the cerebral ganglia.