What is a gastropod's primary sense?

Gastropods have no hearing and most gastropods have simple eyes that merely distinguish light from dark.  However, some have more sophisticated eyes, even some with lenses.  Terrestrial gastropods generally use olfactory organs as their main sense system.  These organs are generally located on the tips of the four tentacles.  Marine and fresh water gastropods are mainly olfactory and some also use taste.  Gastropods also use statocysts for balance and mechanoreceptors that are used to “feel” their environment.