Characteristics of Gastropoda (Snails, Sea Slugs and Sea Hares)

Close-up of snail on ground
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Do you know what the marine biology term "Gastropoda" means? The class Gastropoda includes snails, slugs, limpets, and sea hares. These are all animals referred to as 'gastropods.' Gastropods are mollusks, an extremely diverse group that includes over 40,000 species. Envision a seashell, and you're thinking about a gastropod although this class contains many shell-less animals as well. This article explains the many Gastropoda characteristics.

Examples of gastropods include whelks, conchs, periwinkles, abalone, limpets, and nudibranchs.

Gastropoda Characteristics

Many gastropods such as snails and limpets have one shell. Sea slugs, like nudibranchs and sea hares, do not have a shell, although they may have an internal shell made of protein. Gastropods come in a wide variety of colors, shapes, and sizes.

Here's what most of them have in common:

  • Many gastropods have one shell in which the animal can withdraw. The shell is usually coiled and maybe 'left-handed' or sinistral (spiraled counter-clockwise) or 'right-handed' or dextral (clockwise).
  • Gastropods move using a muscular foot.
  • All young (larval stage) gastropods undergo a process called torsion, in which the entire top of their body twists 180 degrees on their foot. This results in the placement of the gills and anus above the head. Gastropods have adapted in a variety of ways to avoid polluting their breathing water with their own wastes.
  • Due to torsion, adult gastropods are asymmetrical in form.

Scientific Classification of Gastropods

  • Kingdom: Animalia
  • Phylum: Mollusca
  • Class: Gastropoda

Feeding and Living

This diverse group of organisms employs a wide range of feeding mechanisms. Some are herbivores, and some are carnivores. Most feed using a radula. The whelk, a type of gastropod, use their radula to drill a hole into the shell of other organisms for food. Food is digested in the stomach. Because of the torsion process described earlier, the food enters the stomach through the posterior (back) end, and wastes leave through the anterior (front) end.


Some gastropods have both sexual organs, meaning that some are hermaphroditic. One interesting animal is the slipper shell, which may start out as a male and then change to a female. Depending on the species, gastropods may reproduce by releasing gametes into the water, or by transferring the male's sperm into the female, who uses it to fertilize her eggs.

Once the eggs hatch, the gastropod is usually planktonic larvae called a veliger, which may feed on plankton or not feed at all. Eventually, the veliger undergoes metamorphosis and forms a juvenile gastropod.

Habitat and Distribution

Gastropods live just about everywhere on Earth—in salt water, fresh water and on land. In the ocean, they live in both shallow, intertidal areas and the deep sea.

Many gastropods are used by humans for food, decoration (e.g., sea shells) and jewelry.