How do gastropods move

The locomotion of the snails

Although gastropods are the most diverse and species-rich group of molluscs, their locomotion can be traced back to a specialized organ that most of them have in common in terms of their basic structure.

The foot

The arduous path of a Roman snail through the
Undergrowth here reveals the sight of the sole of the foot.
Image: Robert Nordsieck.

The so-called foot is essentially the largest part of the body that is visible outside the shell of the active animal. In most snails the ventral side (ventral) is also formed into a flat crawling sole, which indicates the most common and proverbial method of locomotion for snails: they crawl.


Of course, we know this method of locomotion best from land snails, which we can observe most frequently, at least when the weather is appropriate. Using the example of the Roman snail (Helix pomatia) we have also described how this movement process takes place: The snail sets the sole of its foot in undulating movements that carry it forward.

Since snails, in contrast to their relatives, the mussels (bivalvia), move in a certain direction, the head has formed at the front end of the foot as the center of most sensory cells and organs, with antennae and eyes. It is impossible to tell where the head ends and the foot begins and therefore both are referred to as cephalopodium, a characteristic feature of snails.

Locomotion of a land snail (Roman snail Helix pomatia).

Movie: Underside of a Creeping Snail (Cornu aspersum). MOV file, approx. 2 MB.

When crawling, snails leave behind a proverbial trail of mucus, which is created because a large gland at the head end of the sole of the foot produces mucus, which reduces the friction between the sole of the foot and the ground, one of the reasons why land snails are capable of such amazing performances as unharmed over one Crawling knife blade.

The speeds that snails can reach with this type of locomotion are different. The Roman snail (Helix pomatia) reaches about 7 cm / min. Water snails are usually faster - the mud snailLymnaea stagnalis reaches 12 cm / min., the whelk (Buccinum undatum) reaches 16 cm / min while searching for food. The speed of the bladder snails (Physidae) is astonishing. These small water snails sometimes move at around 20 cm / min. away. According to unconfirmed information, the fastest species is the moss bubble snail (Aplexa hypnorum) be.

Many land snails, including the Roman snails, use their feet not only to actually move about, but also to dig in the ground. Some predatory snails, such as the backpack snails (Testacellidae) and the Daudebardia (Daudebardiinae), live almost exclusively underground and hunt earthworms.

Beautiful land snail (Pomatias elegans), with shell
lid (operculum). Image: Michael Stemmer.
A mud snail (Lymnaea stagnalis) creeps on the
Water surface. Image: Robert Nordsieck.

Land snails represent a special case among land snails, such as the beautiful land snail (Pomatias elegans). These developed from other ancestors than the land snail (Stylommatophora), to which the Roman snail belongs. Therefore, their locomotion looks a little different, although it is based on the same basic principle. The land snail moves forward by moving the two halves of its foot forward separately, it crawls "bipedal", so to speak.

But it is by no means just land snails that crawl on their feet. Also a limpet (Patella vulgata), which spends its resting phases clinging to rocks, crawls around in search of food, and so does a whelk (Buccinum undatum) looking for prey, only the latter is much faster. Some predatory sea slugs also use their feet to hold the shell halves of a clam apart while they eat the resident.

Creeping on the surface of the water

Based on the example of land snails, it is of course assumed that snails mainly crawl around on the ground. While this also applies to land snails, freshwater snails, such as the mud snails (Lymnaeidae) in particular, can also crawl along the underside of the water surface. The air-filled mantle cavity (mud snails are lung snails that breathe oxygen from the air) gives them buoyancy and together with the slime track, the surface tension of the water is enough to carry the snail so that it can graze on algae, for example.

Jumping snails

In this cub from Conomurex luhuanus can be seen well
the tip of the foot (top left) recognize the saber-shaped lid.
Image: Richard Ling (source).

However, some bottom-living marine snails do not only move by crawling. The winged or fenced snail (Strombidae) also use their crescent-shaped bowl lid, the operculum, for this purpose. Pushed into the ocean floor, they use it to catapult themselves forward and thus jump over the ocean floor. They are not called winged snails because of this, but because their shell is wing-like. They owe their name to fencing snails to a misappropriation of their shell lid: with the sharp-edged operculum they can deal sensitive blows when they have to defend themselves.

Ulrich Wieneke, Han Stoutjesdijk and Philippe Simonet: Gastropoda - Stromboidea: Extensive homepage about wing snails and their relatives.

In the following film from BBC Earth you can see how the tulip snail (Fasciolaria tulipa), by the way itself a carnivorous snail, tries to jump the giant one Pleuroploca gigantea to escape.

"Bouncing" Cornu aspersum (see text).
Image: Robert Nordsieck.

Giant Horse Conch and Burglar Hermit Crabs! Source: BBC Earth on YouTube.

Unfortunately the tulip snail is Pleuroploca gigantea Incidentally, the largest snail species in the western hemisphere; however, although called "horse conch" in English, it is not a winged snail (Power bus), but a relative of the European whelk (Buccinum undatum).

On the other hand, when you say that a land snail hops, you mean another method of locomotion: many land snails, such as the spotted garden snail (Cornu aspersum), which have to fear the loss of water through evaporation, especially in dry weather, only touch parts of the soles of their feet when crawling and thus leave a "dashed" trail of slime. But of course they don't really bounce.

Swimming snails

Many marine snails have developed a different method of locomotion: While many species crawl around the ocean floor, protected by a heavy armored shell, these species have given up the protection of a shell in favor of greater mobility.

The parapodies of this sea hare (Aplysia punctata) are in
At rest, folded over the back.
Image: Erling Svensen.

The sea hare (Aplysia depilans) is, for example, a sea snail, which owes its name to its antennae that are widened like a rabbit's ear, but whose hemline is also widened like wings. The snail can form the fin-shaped appendages (parapodia) into a funnel and press the water through it, allowing it to swim around in the vegetation of the ocean floor, for example in seagrass beds. A sea hare has a shell, but it is very light, thin-walled and protected by the coat.

Left: Sea Angel (Clione limacina). Right: sea butterfly (Limacina helicina).
Images: Russ Hopcroft (Arctic Ocean Diversity).

Other sea snails have developed this swimming way of life to perfection and do without any protection by a shell. So did the sea butterfly Limacina helicina, developed two large parapodies from her foot, with the help of which she receives enough buoyancy to float through the water. Sea butterflies live on plankton, small crustaceans and snail larvae, which they catch from the water with a slime net.

The large collections of sea butterflies often fall victim to another species of swimming sea snail, the sea angel, Clione limacina. This sea nudibranch, which owes its name to the large, wing-like parapodia, also eats jellyfish, the stinging cells of which are ineffective against the snail's slime.

The violet snail (Janthina janthina): She swims with the help of a self-made raft made of air-filled mucus bubbles. She cannot swim herself, but by means of her raft she is floating on the surface of the sea and can do just like that ClioneTo hunt jellyfish.