Gastropoda Facts

Close-up of snail on ground
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The class Gastropoda includes snails, slugs, limpets, and sea hares; the common name for all of these animals is as 'gastropods.' Gastropods are a subset of 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.

Fast Facts: Gastropods

  • Scientific Name: Gastropoda
  • Common Name(s): Snails, slugs, limpets, and sea hares
  • Basic Animal Group: Invertebrate
  • Size: From .04–8 inches
  • Lifespan: 20–50 years
  • Diet: Carnivore or Herbivore.
  • Population: Unknown
  • Habitat: Oceans, waterways and terrestrial environments of all sorts worldwide
  • Conservation Status: Most are Least Concern, at least 250 are extinct and many others Near Threatened or Endangered.
Pleuroploca trapezium half in the flat water
 

Description

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

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. Due to torsion, adult gastropods are asymmetrical in form.

The class of gastropods belongs to the Animalia kingdom and the Mollusca phylum.

Habitat and Distribution

Gastropods live just about everywhere on Earth—in salt water, fresh water and on land. In the oceans, they live in both shallow, intertidal areas and the deep sea. On land, they are in wet marshy environments to deserts, from shorelines and beaches to the mountaintops.

The complexity of a given habitat, whether on sea or shore or mountaintop, positively affects the density and richness of the gastropods found within it.

Snail Eating Food On Rock
 Annika Bornheim / EyeEm / Getty Images

Diet and Behavior

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.

Reproduction

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.

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.

Threats

Most gastropods on earth are listed by the International Union for Conservation of Nature (IUCN) as "Least Concerned." There are many exceptions, such as the Xerocrassa montserratensis, a terrestrial gastropod that lives in shrublands and mountain peaks in Spain and is listed as endangered by fires and fire suppression and recreational activities. Well over 200 species are listed as extinct by the IUCN; many others, particularly freshwater and terrestrial species, are listed as endangered.

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