Snails (gastropoda) are found in all the world’s seas, in freshwater, and on land. Most snails are most at home on hard bottoms and on the plants and algae they feed upon.
The rough perrywinkle (Littorina saxatilis) is likely the most common snail in Northern Iceland, as it is found in great abundance everywhere there is a hard surface. Other snails found at the bottom of the beach and into deeper water are: northern lacuna (Lacuna vincta), flat perrywinkle (Littorina obtusata), pointed cingula (Onoba aculeus), and dog whelk (Nucella lapillus).
In the deeper waters of the fjords, away from shore but within diving range, there are larger snails such as the common whelk (Buccinium undatum) and the neptune whelk (Neptunea despecta). The Neptune whelk is likely the more common of these two large snails in Northern Iceland. The common whelk is edible and harvested in some parts of Iceland. However, the Neptune whelk is toxic to humans and should not be eaten. Both of these snails are scavengers that eat dead animals they find on the seafloor.
Other gastropods do not look much like the well-known snails. For instance, the tortoise limpet (Testudinalia testudinalis) and white tortoise shell limpet (Tectura virginea) have a shell shaped like a flattened cone and they use their foot to anchor themselves tightly to a hard surface, usually rock. These limpets are both common on the northern coas, where they graze on the thin layer of algae that grows on rocks.
Two other groups of gastropods are found in the fjords. Sea slugs (Nudibranchia) and sea butterflies (Clionidae) are both unlike the animals most people picture when they think of a snail. Like terrestrial slugs, sea slugs don’t have a shell. Instead, they rely on other methods of defense such as toxins and the stinging cells from anemones that they feed on. They crawl on the bottom feeding on sessile animals such as hydrozoans. On the other hand, sea butterflies are pelagic snails that spend their life in the surface layers of the ocean. The foot of these snails has evolved to allow the animal to swim by moving the foot in a similar motion as birds’ wings.