Giant African Snails

Giant African Snails (GAS)

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This picture is from the website of Annette Goodman.

One of the defining anatomical characteristics of snails (and mollusks in general) is the presence of a foot (Nordsieck 2007). It is a heavily muscled appendage that is used primarily for locomotion. This muscular foot can also be used for digging and (in many aquatic species) swimming (Nordsieck 2007). Below is a picture of the bottom of a snail's foot. You can make out the bands that make up this powerful muscle.

Also from Annette Goodman.

Snails also have a semi-permeable skin, allowing water and oxygen to enter, and water and carbon dioxide to leave freely (Nordsieck 2007). A large concern for snails is to avoid high concentrations of salts; dehydration can occur rapidly through the skin being in contact with salts. Most snails have another method of extracting oxygen from their environment; in aquatic snails we find gills, and in terrestrial snails there is what is called a snail lung, a rudimentary lung that is comprised of a tight band of capillaries through which gas exchange can occur (Nordsieck 2007). Oxygen enters the snail lung through the same process as a human uses its diaphragm (Nordsieck 2007).

From the snail website of Robert Nordsieck.

Snails are different from most other animals in that their body is asymmetrical; they only have one breathing duct through one side of their bodies, and their reproductive organs are also set to one side (Nordsieck 2007). This asymmetry is due in part to the torsional qualities of their bodies (Nordsieck 2007). During embryonic development, snails have their internal organs twisted up onto their bodies in an 180º angle; this places their stomachs at the back of the shell and their anus laying just above their shell opening (Nordsieck 2007). Below is an illustration of the torsional process that occurs in snails. Snails also have a distinct head separated from the rest of their body (encephalization) that holds a mouth, eyespots, and a central "brain" region (ganglion).

Also from Robert Nordsieck's website.

Snails have evolved to cover every nutritional niche found on the planet Earth; from predators to scavengers, filter feeding and grazing; the only defining characteristic common in all of these is a tongue-like toothed apparatus called a radula (Nordsieck 2007). Below is a close-up illustration of a snail's radula; it looks a lot like a digging assembly line.

Picture from the Enzyklopädie der Natur website.

Please contact me if you have any questions regarding sources, illustrations, or general questions.