Ramshorn Snails

Gyraulus, Helisoma, Menetus, Micromenetus, Planorbula spp.

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Photo of a ramshorn snail on a wet rock.
The shell of a ramshorn snail is a flat, disklike coil, similar to a ram's horn.
Other Common Name
Wheel Snails; Planorbids
Family

Planorbidae (ramshorn snails) in the class Gastropoda (snails, slugs)

Description

Ramshorn snails, a group of freshwater snails, are easy to identify at a glance, because the shell is a flat, disklike coil, similar to a ram’s horn. (In most other freshwater snails, the shell forms with a strong twist toward one side, with a spire at the apex pointing to left or right — as with a common land snail.)

Ramshorn snails are grouped with the lunged, or “pulmonate” snails, for they breathe air by means of a lunglike organ, and do not breathe water via gills. Like other pulmonate snails, they lack an operculum, the hard horny “trapdoor” that other types of aquatic snails possess that closes when the animal retracts into the shell.

Size

Adult shell diameter: from about 1/8 to 3/4 inch (varies with species).

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Photo of a ramshorn snail crawling in a water-filled petri dish.
Ramshorn Snail
Ramshorn snails are easy to identify at a glance, because the shell is a flat, disklike coil. Like other pulmonate aquatic snails, they lack the hard horny “trapdoor” possessed by other types of aquatic snails.

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Photo of a ramshorn snail, held in a hand, showing aperture of shell.
Ramshorn Snail Showing Aperture
The shape of the shell's aperture ("mouth opening") is helpful when identifying snails to species.

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Photo of a ramshorn snail held in hand, showing underside of shell.
Ramshorn Snail Shell, Underside
Rough ramshorn snail, underside.
Habitat and conservation

Various species are found in all types of aquatic habitats.

Foods

Most ramshorn snails are herbivorous. Like other snails, they have a radula, sometimes called a “rasping tongue,” that scrapes rhythmically against the substrate they are crawling across. Algae and other plant materials form the bulk of the diet.

image of Ramshorn Snails Wheel Snails Planorbids Distribution Map
Distribution in Missouri

Statewide.

Status

There are about 10 species of ramshorn snails in Missouri. One of them, the Sampson sprite (Menetus sampsoni or Micromenetus samsoni) occurs only in the Ozark region and is a Species of Conservation Concern in Missouri. It is vulnerable to becoming extirpated from our state.

Life cycle

Pulmonate snails, including ramshorns, are hermaphroditic, meaning that each individual functions as both female and male, and a pair of mating snails typically fertilize each other, with both individuals laying eggs afterward. Pulmonate snails typically lay gelatinous masses of eggs underwater on the surfaces of plants or rocks.

Human connections

The many types of snail shells, including the incredible diversity of saltwater snails such as conchs, abilones, and more, are interesting and beautiful. A biologist who studies mollusks (including snails) is called a malacologist. One who specializes in the shells is a conchologist.

Ecosystem connections

Ramshorn snails are unusual mollusks because their blood contains the iron-containing protein hemoglobin, which is excellent for carrying oxygen. This molecule is also the primary component of human red blood cells. As a result of their own hemoglobin, ramshorn snail bodies are usually reddish.