Sea snail is a common name for snails that normally live in saltwater, marine gastropod molluscs. (The taxonomic class Gastropoda also includes snails that live in other habitats, i.e. land snails and freshwater snails.)
Sea snails are marine gastropods that have shells. Those marine gastropods that have no shells, or have only internal shells, are variously known by other common names, including sea slug, sea hare, nudibranch, etc.
Many sea snails are edible and are exploited as food sources by humans. Some well-known kinds of edible sea snails are abalone, conch, limpets, whelks (such as the North American Busycon species and the North Atlantic Buccinum undatum) and periwinkles including Littorina littorea.
There is enormous diversity within sea snails; many very different clades of gastropods are either dominated by, or consist exclusively of, sea snails. Because of this great variability, it is not possible to generalize about the feeding, reproduction, habitat and so on of sea snails. Instead it is necessary to look at the articles about individual clades, families, genera or species.
A group of Patella vulgata limpets on a rock in PembrokeshireThe shell of Syrinx aruanus can be up to 91 cm longThe shells of most species of sea snails are spirally coiled; some however have shells that are conical, and these are often referred to by the common name of limpets.
The shells of living species of sea snails range in size from Syrinx aruanus, the largest living shelled gastropod species, to minute species whose shells are under 1 mm at adult size.
Because in many cases the shells of sea snails are strong and durable, as a group they are well represented in the fossil record.
Sea snails are a very large group of animals and a very diverse one. Most snails that live in saltwater respire using a gill or gills, a few species however 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 and another group of false limpets in the family Trimusculidae.
Many (but not all) sea snails have an operculum.
A number of species of edible whelks for sale at a fish market in JapanA number of species of sea snails are exploited by humans for food, including abalone, conch, limpets, whelks (such as the North American Busycon species and the North Atlantic Buccinum undatum) and periwinkles including Littorina littorea.
The shells of sea snails are often found by humans as one kind of seashell that washes up on beaches. Because the shells of many sea snails are attractive and durable, they have been used by humans to make necklaces and other jewelry from prehistoric times to the current day.
The shells of a few species of large sea snails within the Vetigastropoda have a thick layer of nacre and have been exploited as a source of mother of pearl. Historically the button industry relied on these species for a number of years.
A hermit crab which is occupying a shell of Acanthina punctulata has been disturbed, and has retracted into the shell, using its claws to bar the entrance in the same way that the snail used its operculum.The shells of sea snails are used for protection by many kinds of hermit crabs. A hermit crab carries the shell by grasping the central columella of the shell using claspers on the tip of its abdomen.
It is not always easy to decide whether some gastropods should be called sea snails. Some species that live in brackish water (such as certain neritids) can be listed as either freshwater snails or marine snails, and some species that live right at, or right above, the high tide level (for example species in the genus Truncatella), are sometimes considered to be sea snails and sometimes listed as land snails.
The following cladogram 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 (some of the highlighted taxa consist entirely of marine species, but some of them also contain freshwater or land species.)
- Clade Patellogastropoda
- Clade Vetigastropoda
- Clade Cocculiniformia
- Clade Neritimorpha
- Clade Cycloneritimorpha
- Clade Caenogastropoda
- Clade Heterobranchia
- Informal group Lower Heterobranchia
- Informal group Opisthobranchia
- Clade Cephalaspidea
- Clade Thecosomata
- Clade Gymnosomata
- Clade Aplysiomorpha
- Group Acochlidiacea
- Clade Sacoglossa
- Group Cylindrobullida
- Clade Umbraculida
- Clade Nudipleura
- Informal group Pulmonata
In the animated American TV series SpongeBob SquarePants, the main character SpongeBob has a pet sea snail called Gary. The character's eyes are well-developed and colorful, similar to the eyes of species in the sea snail family Strombidae.