The

sensory organs A sense is a biological system used by an organism for sensation, the process of gathering information about the world through the detection of stimuli. (For example, in the human body, the brain which is part of the central nervous system rec ...

of gastropods (

snail A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class G ...

s and slugs) include olfactory organs, eyes,

statocyst The statocyst is a balance sensory receptor present in some aquatic invertebrates, including bivalves, cnidarians, ctenophorans, echinoderms, cephalopods, and crustaceans. A similar structure is also found in '' Xenoturbella''. The statocyst c ...

s and mechanoreceptors. Gastropods have no sense of hearing.Chase R.: ''Sensory Organs and the Nervous System''. in Barker G. M. (ed.): ''The biology of terrestrial molluscs''. CABI Publishing, Oxon, UK, 2001, . 1–146, cited pages: 179–211.

Olfactory organs

In terrestrial gastropods the most important sensory organs are the olfactory organs which are located on the tips of the 4

tentacle In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work ma ...

s. Some terrestrial gastropods can track the odor of food using their

tentacles In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work mainl ...

( tropotaxis) and the wind ( anemotaxis). In opisthobranch marine gastropods, the chemosensory organs are two protruding structures on top of the head. These are known as

rhinophore A rhinophore is one of a pair of chemosensory club-shaped, rod-shaped or ear-like structures which are the most prominent part of the external head anatomy in sea slugs, marine gastropod opisthobranch mollusks such as the nudibranchs, sea ha ...

s. An opisthobranch sea slug ''

Navanax inermis ''Navanax inermis'', common name the California aglaja, is a large species of predatory sea slug, a marine opisthobranch gastropod mollusk in the family Aglajidae. ''Navanax'' is not a nudibranch, even though it somewhat resembles one; it belo ...

'' has chemoreceptors on the sides of its mouth to track

mucopolysaccharides Glycosaminoglycans (GAGs) or mucopolysaccharides are long, linear polysaccharides consisting of repeating disaccharide units (i.e. two-sugar units). The repeating two-sugar unit consists of a uronic sugar and an amino sugar, except in the case o ...

in the

slime Slime may refer to: Biology * Slime mold, a broad term often referring to roughly six groups of Eukaryotes * Biofilm, an aggregate of microorganisms in which cells adhere to each other and/or to a surface * Slimy (fish), also known as the pony ...

trails of prey, and of potential mates. The freshwater snail '' Bithynia tentaculata'' is capable of detecting the presence of molluscivorous (mollusk-eating)

leeches Leeches are segmented parasitic or predatory worms that comprise the subclass Hirudinea within the phylum Annelida. They are closely related to the oligochaetes, which include the earthworm, and like them have soft, muscular segmented bo ...

through

chemoreception A chemoreceptor, also known as chemosensor, is a specialized sensory receptor which transduces a chemical substance (endogenous or induced) to generate a biological signal. This signal may be in the form of an action potential, if the chemorecept ...

, and of closing its operculum to avoid predation. The deepwater snail '' Bathynerita naticoidea'' can detect mussel beds containing the mussel '' Bathymodiolus childressi'', because it is attracted to water that has cues in it from this species of mussel.

Eyes

In terrestrial pulmonate gastropods, eye spots are present at the tips of the tentacles in the Stylommatophora or at the base of the tentacles in the Basommatophora. These eye spots range from simple

ocelli A simple eye (sometimes called a pigment pit) refers to a form of eye or an optical arrangement composed of a single lens and without an elaborate retina such as occurs in most vertebrates. In this sense "simple eye" is distinct from a multi-l ...

that cannot project an image (simply distinguishing light and dark), to more complex pit and even lens eyes. Vision is not the most important requirement in terrestrial gastropods, because they are mainly nocturnal animals. Some gastropods, for example the freshwater apple snails (family

Ampullariidae Ampullariidae, commonly known as the apple snails, is a family of large freshwater snails, aquatic gastropod mollusks with a gill and an operculum. These snails simultaneously have a gill and a lung as functional respiratory structures ...

) and marine species of genus ''

Strombus ''Strombus'' is a genus of medium to large sea snails, marine gastropod molluscs in the family Strombidae, which comprises the true conchs and their immediate relatives. The genus ''Strombus'' was named by Swedish Naturalist Carl Linnaeus in 1 ...

'' can completely regenerate their eyes. The gastropods in both of these families have lens eyes. Morphological sequence of different types of multicellular eyes exemplified by gastropod eyes:

Lens eyes

another drawing of eye of ''Helix pomatia''

Statocysts

In the

s of ''

Haliotis asinina ''Haliotis asinina'', common name the ass's-ear abalone, is a fairly large species of sea snail, a tropical gastropod mollusk in the family Haliotidae, the abalones, also known as ormers or paua. Both the common name and the scientific nam ...

'' was found the

expression Expression may refer to: Linguistics * Expression (linguistics), a word, phrase, or sentence * Fixed expression, a form of words with a specific meaning * Idiom, a type of fixed expression * Metaphorical expression, a particular word, phrase, o ...

of a conserved gene ( Pax-258 gene), which is also important for forming structures for balance in eumetazoans.

Mechanoreceptors

The mechanoreceptors are very crucial to the snail's sensory.

References

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External links

{{DEFAULTSORT:Sensory Organs of Gastropods Gastropod anatomy Sensory organs in animals