Sensory organs of gastropods

[1] Some terrestrial gastropods can track the odor of food using their tentacles (tropotaxis) and the wind (anemotaxis).

[2] In opisthobranch marine gastropods, the chemosensory organs are two protruding structures on top of the head.

An opisthobranch sea slug Navanax inermis has chemoreceptors on the sides of its mouth to track mucopolysaccharides in the slime trails of prey, and of potential mates.

[3] The freshwater snail Bithynia tentaculata is capable of detecting the presence of molluscivorous (mollusk-eating) leeches through chemoreception, and of closing its operculum to avoid predation.

[1] Some gastropods, for example the freshwater apple snails (family Ampullariidae)[7] and marine species of genus Strombus[8] can completely regenerate their eyes.

Rhinophores of Aplysia californica .
The upper pair of tentacles on the head of the edible snail Helix pomatia have eyes, but the main sensory organs are sensory neurons for olfaction in the epithelium of the tentacles.
Eye pit of Patella sp.
Scheme of pit eye .
Eye cup of Pleurotomaria sp.
Pinhole eye of Haliotis sp.
Closed eye of Turbo coronatus .
Lens eye of Bolinus brandaris .
Lens eye of Nucella lapillus .
Scheme of lens eye .
Eye of a snail.
1 - anterior chamber,
2 - lens,
3 - retina,
4 - optic nerve.
Drawing of cross section of the eye of Helix pomatia .
1 - lens
2 - olfactory epithelium
3 - corneal epithelium
4 - corneal endothelium
5 - retina
6 - layer with rod cells
7 - fibrous connective tissue layer
8 - nerve of the eye
Drawing of cross sections of the extracted tentacle (left) and constricted tentacle (right) with and eye of Helix pomatia .
1 - nerve of an eye
2 -
3 -
4 - eye
5 - tentacle ganglion
6 - epidermis
7 -
8 - nerve of an tentacle
9 - retractor muscle
10 -
Well-developed lens eye of Eustrombus gigas on eyestalk has a black iris . There is a small tentacle on the eyestalk also.
Statocysts (ss) and statolith (sl) inside the head of Gigantopelta chessoia .