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 ...

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

s (

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 Gastro ...

s and

slug Slug, or land slug, is a common name for any apparently shell-less terrestrial gastropod mollusc. The word ''slug'' is also often used as part of the common name of any gastropod mollusc that has no shell, a very reduced shell, or only a smal ...

s) include olfactory organs,

eye Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conv ...

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 cons ...

s and

mechanoreceptor A mechanoreceptor, also called mechanoceptor, is a sensory receptor that responds to mechanical pressure or distortion. Mechanoreceptors are innervated by sensory neurons that convert mechanical pressure into electrical signals that, in animals, ...

s. 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 main ...

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 main ...

( tropotaxis) and the wind ( anemotaxis). In

opisthobranch Opisthobranchs () is now an informal name for a large and diverse group of specialized complex gastropods which used to be united in the subclass Opisthobranchia. That taxon is no longer considered to represent a monophyletic grouping. Euopisth ...

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 har ...

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 belong ...

'' 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 ...

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 Freshwater snails are gastropod mollusks which live in fresh water. There are many different families. They are found throughout the world in various habitats, ranging from ephemeral pools to the largest lakes, and from small seeps and springs ...

Bithynia tentaculata ''Bithynia tentaculata'', common names the mud bithynia or common bithynia, or faucet snailKipp R. M. & Benson A. (2008). ''Bithynia tentaculata''. USGS Nonindigenous Aquatic Species Database, Gainesville, FL. https://nas.er.usgs.gov/queries/Fac ...

'' is capable of detecting the presence of molluscivorous (mollusk-eating)

leeches Leeches are segmented parasitism, parasitic or Predation, predatory worms that comprise the Class (biology), subclass Hirudinea within the phylum Annelida. They are closely related to the Oligochaeta, oligochaetes, which include the earthwor ...

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 ''Bathynerita naticoidea'' is a species of small sea snail, a marine gastropod mollusc in the family Neritidae, the nerites. This species is endemic to underwater cold seeps (oil seeps and gas seeps) in the northern Gulf of Mexico and in the Ca ...

'' can detect mussel beds containing the mussel ''

Bathymodiolus childressi ''Bathymodiolus childressi'' is a species of deepwater mussel, a marine bivalve mollusk species in the family Mytilidae, the mussels. Although this species has been known since 1985,Childress J.J., Fisher C.R., Brooks J.M., Kennicutt M.C., II, B ...

'', 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 Stylommatophora is an orderPhilippe Bouchet, Jean-Pierre Rocroi, Bernhard Hausdorf, Andrzej Kaim, Yasunori Kano, Alexander Nützel, Pavel Parkhaev, Michael Schrödl and Ellen E. Strong. 2017. Revised Classification, Nomenclator and Typification ...

or at the base of the tentacles in the

Basommatophora Basommatophora was a term that was previously used as a taxonomic informal group, a group of snails within the informal group Pulmonata, the air-breathing slugs and snails. According to the taxonomy of the Gastropoda (Bouchet & Rocroi, 2005), w ...

. 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, wh ...

) 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 175 ...

'' 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 name a ...

'' 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

eumetazoa Eumetazoa (), also known as diploblasts, Epitheliozoa, or Histozoa, are a proposed basal animal clade as a sister group of the Porifera (sponges). The basal eumetazoan clades are the Ctenophora and the ParaHoxozoa. Placozoa is now also seen as a ...

ns.

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