Sea snails are slow-moving marine

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

molluscs Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

, usually with visible external shells, such as

whelk Whelks are any of several carnivorous sea snail species with a swirling, tapered shell. Many are eaten by humans, such as the common whelk of the North Atlantic. Most whelks belong to the family Buccinidae and are known as "true whelks." Othe ...

abalone Abalone ( or ; via Spanish , from Rumsen language, Rumsen ''aulón'') is a common name for any small to very large marine life, marine gastropod mollusc in the family (biology), family Haliotidae, which once contained six genera but now cont ...

. They share the taxonomic class

Gastropoda Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

with

slug Slug, or land slug, is a common name for any apparently shell-less Terrestrial mollusc, 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 ...

s, which are distinguished from

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

primarily by the absence of a visible

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses Science Biology * Seashell, a hard outer layer of a marine ani ...

Definition

Determining whether some gastropods should be called sea snails is not always easy. Some species that live in

brackish water Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuary ...

(such as certain neritids) can be listed as either

freshwater snails Freshwater snails are gastropod mollusks that 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 t ...

or marine snails, and some species that live at or just above the

high tide Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables ...

level (for example, species in the genus '' Truncatella'') are sometimes considered to be sea snails and sometimes listed as

land snail A land snail is any of the numerous species of snail that live on land, as opposed to the sea snails and freshwater snails. ''Land snail'' is the common name for terrestrial molluscs, terrestrial gastropod mollusks that have gastropod shell, shel ...

Anatomy

Sea snails are a very large and diverse group of animals. Most snails that live in salt water respire using a

gill A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow r ...

or gills; a few species, though, have a lung, are intertidal, and are active only at low tide when they can move around in the air. These air-breathing species include false limpets in the family

Siphonariidae Siphonariidae, also known as false limpets, are a taxonomic family of small to medium-sized air-breathing sea snails, marine and brackish water pulmonate gastropod molluscs. __TOC__ Shell description Empty siphonariid limpet shells can be di ...

and another group of false limpets in the family Trimusculidae. Many, but not all, sea snails have an operculum.

Shell

The shells of most species of sea snails are spirally coiled. Some, though, have conical shells, and these are often referred to by the common name of

limpet Limpets are a group of aquatic snails with a conical gastropod shell, shell shape (patelliform) and a strong, muscular foot. This general category of conical shell is known as "patelliform" (dish-shaped). Existing within the class Gastropoda, ...

s. In one unusual family ( Juliidae), the shell of the snail has become two hinged plates closely resembling those of a

bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...

; this family is sometimes called the "bivalved gastropods". Their shells are found in a variety of shapes and sizes, but are normally very small. Those living species of sea snails range in size from ''

Syrinx aruanus ''Syrinx aruanus'', common name the Australian trumpet or false trumpet, is a species of extremely large sea snail measuring up to 75 cm long and weighing up to 18 kg. It is a marine (ocean), marine gastropod mollusk in the family Turb ...

'', the largest living shelled gastropod species at , to minute species whose shells are less than 1 mm at adult size. Because the shells of sea snails are strong and durable in many cases, as a group they are well represented in the

fossil record A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

. The shells of snails are complex and grow at different speeds. The speed of growth is affected by a few variables such as the temperature of the water, depth of the water, food present for the snail, as well as isotopic oxygen levels. By looking at the composition of

aragonite Aragonite is a carbonate mineral and one of the three most common naturally occurring crystal forms of calcium carbonate (), the others being calcite and vaterite. It is formed by biological and physical processes, including precipitation fr ...

in the growth layers of

mollusks Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The num ...

you can predict the size the mollusk shell can reach.

Taxonomy

2005 taxonomy

The following

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

is an overview of the main clades of living gastropods based on the taxonomy of Bouchet & Rocroi (2005), with taxa that contain saltwater or brackish water species marked in

boldface In typography, emphasis is the strengthening of words in a text with a font in a different style from the rest of the text, to highlight them. It is the equivalent of prosody stress in speech. Methods and use The most common methods in We ...

(some of the highlighted taxa consist entirely of marine species, but some of them also contain freshwater or land species.) * Clade

Patellogastropoda The Patellogastropoda, common name true limpets and historically called the Docoglossa, are members of a major phylogenetic group of marine (ocean), marine gastropods, treated by experts either as a clade or as a taxonomic Order (biology), order. ...

* Clade

Vetigastropoda Vetigastropoda is a major taxonomic group of sea snails, marine gastropod mollusks that form a very ancient lineage. Taxonomically the Vetigastropoda are sometimes treated as an order, although they are treated as an unranked clade in Bouch ...

* Clade Cocculiniformia * Clade

Neritimorpha Neritimorpha is a clade of gastropod molluscs that contains around 2,000 extant species of sea snails, limpets, freshwater snails, land snails and slugs. This clade used to be known as the superorder Neritopsina. Etymology The clade’s name, N ...

** Clade

Cycloneritimorpha Cycloneritida (nerites and false-limpets) is an order of land snails, freshwater snails, and sea snails.MolluscaBase eds. (2020). MolluscaBase. Cycloneritida. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/a ...

* Clade

Caenogastropoda Caenogastropoda is a taxonomic subclass of molluscs in the class Gastropoda. It is a large diverse group which are mostly sea snails and other marine gastropod mollusks, but also includes some freshwater snails and some land snails. The subcla ...

** Informal group Architaenioglossa ** Clade Sorbeoconcha ** Clade Hypsogastropoda *** Clade

Littorinimorpha Littorinimorpha is a large order of snails, gastropods, consisting primarily of sea snails ( marine species), but also including some freshwater snails ( limnic species) and land snails ( terrestrial species).Bouchet P. & Rocroi J.-P. (Ed.); Fr� ...

*** Informal group Ptenoglossa *** Clade Neogastropoda * Clade

Heterobranchia Heterobranchia, the heterobranchs (meaning "different gill"), is a taxonomic clade of snails and slugs, which includes marine, aquatic, and terrestrial gastropod molluscs. Heterobranchia is one of the main clades of gastropods. Currently Het ...

** Informal group

Lower Heterobranchia Lower Heterobranchia, also known as the Allogastropoda, is a group of rather specialized, highly evolved sea slugs and sea snails, marine (ocean), marine gastropod mollusc, mollusks within the Subclass (biology), subclass Heterobranchia.WoRMS (20 ...

** Informal group Opisthobranchia *** Clade

Cephalaspidea The order Cephalaspidea, also known as the headshield slugs and bubble snails, is a major taxon of sea slugs and bubble snails, marine (ocean), marine gastropod mollusks within the larger clade Euopisthobranchia. Bubble shells is another commo ...

*** Clade Thecosomata *** Clade Gymnosomata *** Clade Aplysiomorpha *** Group

Acochlidiacea Acochlidiacea, common name acochlidians, are a Taxonomy (biology), taxonomic clade of very unusual sea snails and sea and freshwater slugs, aquatic animal, aquatic gastropod mollusks within the large clade Heterobranchia. Acochlidia is a variant ...

*** Clade

Sacoglossa Sacoglossa are a superorder of small sea slugs and sea snails, marine gastropod mollusks that belong to the clade Heterobranchia known as sacoglossans. There are 284 valid species recognized within this superorder. Sacoglossans live by ingestin ...

*** Group Cylindrobullida *** Clade Umbraculida *** Clade Nudipleura **** Clade Pleurobranchomorpha **** Clade Nudibranchia ***** Clade Euctenidiacea ***** Clade

Dexiarchia The Dexiarchia are a suborder of sea slugs, shell-less marine gastropod molluscs in the order Nudibranchia. This classification is based on the study by Schrödl ''et al.,'' published in 2001, who recognized within this clade two clades Pseudo ...

****** Clade Pseudoeuctenidiacea ****** Clade

Cladobranchia The Cladobranchia are a taxonomic clade of nudibranchs, sea slugs, marine gastropod molluscs in the clade Dexiarchia. Taxonomy clade Metarminida * Superfamily Metarminoidea This name is not available as a Superfamily name as it is not based on ...

******* Clade Euarminida ******* Clade

Dendronotida Dendronotoidea is a taxonomic superfamily of small colorful sea slugs or nudibranchs, aeolid nudibranchs.MolluscaBase eds. (2022). MolluscaBase. Dendronotoidea Allman, 1845. Accessed through: World Register of Marine Species at: http://www.m ...

******* Clade

Aeolidida The Aeolidida is a taxonomic clade of sea slugs, specifically aeolid nudibranchs, marine gastropod molluscs in the clade Cladobranchia. They are distinguished from other nudibranchs by their possession of cerata containing cnidosac A cnidosac ...

** Informal group Pulmonata *** Informal group Basommatophora *** Clade

Eupulmonata Eupulmonata is a taxonomic clade of air-breathing gastropod molluscs. The great majority of this group are land snails and slugs, but some are intertidal or inhabit coastal saltmarshes and mangroves. Possible synapomorphy of the group are gl ...

**** Clade

Systellommatophora The Systellommatophora (synonym Gymnomorpha) is a clade of primitive, air-breathing slugs, according to the taxonomy of the Gastropoda (Bouchet & Rocroi, 2005). They are marine and terrestrial pulmonate gastropods within the Heterobranchia. T ...

**** Clade Stylommatophora ***** Clade Elasmognatha ***** Clade Orthurethra ***** Informal group

Sigmurethra Sigmurethra is a taxonomic category of air-breathing land snails and slugs, terrestrial pulmonate gastropod molluscs. This is an informal group which includes most land snails and slugs. The two strong synapomorphies of Sigmurethra are a long ...

Uses

By humans

A number of species of sea snails are harvested in

aquaculture Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. Nelu ...

and used by humans for food, including

conch Conch ( , , ) is a common name of a number of different medium-to-large-sized sea snails. Conch shells typically have a high Spire (mollusc), spire and a noticeable siphonal canal (in other words, the shell comes to a noticeable point on both ...

s (such as the North American '' Busycon'' species and the North Atlantic ''

Buccinum undatum ''Buccinum undatum'', the common whelk or the waved buccinum, is a large, edible Marine (ocean), marine gastropod in the family (biology), family Buccinidae, the "true whelks".Fraussen, K.; Gofas, S. (2014). Buccinum undatum Linnaeus, 1758. Acces ...

'') and periwinkles including '' Littorina littorea''. The shells of sea snails are often found washed up on

beach A beach is a landform alongside a body of water which consists of loose particles. The particles composing a beach are typically made from Rock (geology), rock, such as sand, gravel, shingle beach, shingle, pebbles, etc., or biological s ...

es. Because many are attractive and durable, they have been used to make necklaces and other

jewelry Jewellery (or jewelry in American English) consists of decorative items worn for personal adornment such as brooches, ring (jewellery), rings, necklaces, earrings, pendants, bracelets, and cufflinks. Jewellery may be attached to the body or the ...

since prehistoric times. The shells of a few species of large sea snails within the

have a thick layer of

nacre Nacre ( , ), also known as mother-of-pearl, is an organicinorganic composite material produced by some molluscs as an inner shell layer. It is also the material of which pearls are composed. It is strong, resilient, and iridescent. Nacre is ...

and have been used as a source of

mother of pearl Nacre ( , ), also known as mother-of-pearl, is an organicinorganic composite material produced by some molluscs as an inner shell layer. It is also the material of which pearls are composed. It is strong, resilient, and iridescent. Nacre is ...

. Historically, the

button A button is a fastener that joins two pieces of fabric together by slipping through a loop or by sliding through a buttonhole. In modern clothing and fashion design, buttons are commonly made of plastic but also may be made of metal, wood, or ...

industry relied on these species for a number of years.

By non-human animals

The shells of sea snails are used for protection by many kinds of

hermit crab Hermit crabs are anomuran Decapoda, decapod crustaceans of the superfamily (taxonomy), superfamily Paguroidea that have adapted to occupy empty scavenged mollusc shells to protect their fragile exoskeletons. There are over 800 species of hermit c ...

s. A hermit crab carries the shell by grasping the central

columella Lucius Junius Moderatus Columella (, Arabic: ) was a prominent Roman writer on agriculture in the Roman Empire. His in twelve volumes has been completely preserved and forms an important source on Roman agriculture and ancient Roman cuisin ...

of the shell using claspers on the tip of its abdomen.

References

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