10 Types of Gastropods

Introduction to Marine Gastropods

Gastropods are a diverse group of mollusks that comprises over 40,000 species of snails, slugs and their relatives. Some gastropods are responsible for some of the most beautiful sea shells you could find, while some gastropods don't have shells at all. Marine animals in the gastropod class include whelks, cowries, abalone, conchs, limpets, sea hares and nudibranchs.

Despite their differences, all gastropods do have a couple things in common. All move using a muscular foot. Have you ever watched a snail crawl around? That fleshy thing that it moves about on is the foot.

In addition to their means of locomotion, all young gastropods have a larval stage, and in this larval stage they go through something called torsion. During this process, the top of the gastropod's body twists 180 degrees on its foot. Therefore, the gills and anus are above the animal's head, and all gastropods are asymmetrical in form. 

Many gastropods with shells have an operculum, which is a horny cover that, like a trap door, fits to the shell opening and can be closed to retain moisture or protect the snail from predators.  

There are so many species of gastropods, it would be impossible to include them all here. But, in this slideshow you can learn about some of the different types of gastropods, and see some beautiful images of these interesting sea creatures. 

Conchs

Want to feel close to the ocean? Pick up a conch shell.

Conchs have beautiful shells that are often sold in souvenier shops. Pick up an empty shell and hold it to your ear and you can "hear the ocean." The term conch is used to describe over 60 species. Conchs live in tropical waters and have been overharvested for their meat and shells in some areas. In the U.S., queen conch are found in Florida but harvesting is no longer allowed.  

Murex

Murex are snails that have elaborate shells with spines and spires. They are found in warmer waters (in the U.S., in the southeast Atlantic), and are carnivores who prey upon bivalves. 

Whelks

Whelks have beautiful spiraled shells that may grow to over two feet long in some species. These animals are carnivores that feed on crustaceans, mollusks, worms and even other whelks.

Whelks drill holes into the shell of their prey using their radula, and then suck out the meat of their prey using their proboscis.

Moon Snails

Moon snails have a beautiful shell, but unlike some of their relatives, the shell is smooth and round. You might wander along a beach where there are moon snails nearby without ever seeing one, as these animals like to use their huge foot to burrow into the sand.

Moon snails feed on bivalves such as clams. Like whelks, they can drill a hole into the shell of their prey using their radula and then suck out the meat inside.  In the U.S., various species of moon snails are found from New England to Florida, in the Gulf of Mexico and from Alaska to California.

Limpets

Unlike some of their other relatives, limpets have a distinctive, round or oval shell which covers the body of the animal within.  These animals are found on rocks, and some may even scrape out enough rock so that they can create a "home spot" that they return to after foraging.  Limpets are grazers - they feed on algae that they scrape off the rocks with their radula.

Cowries

Adult cowries have a smooth, thick, glossy shell. The shell in some cowries may be covered by the snail's mantle.

Cowries live in warmer waters. The tiger cowries shown in this image are found throughout the tropical Pacific Ocean. In some areas, they were traded as currency, and they are prized by collectors for their beautiful shells.                                   

Periwinkles and Nerites

Periwinkles and nerites are herbivorous snails that you might find in the intertidal zone.These snails move through the rocks, sand and seaweed, grazing on algae and leaving a trail of mucus. 

Abalone

Abalone are valued for their meat - their main predators are humans and sea otters. In addition, the inside of the shell of many abalones is iridescent, and provides mother-of-pearl for jewelry and decorative items.

Abalone are found in many coastal areas around the world. In the U.S., they are found in the Pacific Ocean from Alaska to California.Species found in the U.S. include the  white, black, green, pink, pinto, red, threaded, and flat abalone. White and black abalone are listed as endangered. In many areas, abalone have been overharvested. Many of the abalone sold commercially are from aquaculture farms. To aid recovery efforts, there are also programs that grow young abalone and then transplant them to the wild. 

Sea Hares

Look closely at a sea hare and you may see a resemblance to a hare or a rabbit...maybe.

This group of gastropods includes a number of species of slug-like animals that can range from less than an inch in size to over two feet in length. Like sea slugs, sea hares don't have an obvious shell. The shell of a sea hare may be a thin calcium plate inside their body. 

Sea Slugs

Sea slugs refer to a number of species of gastropod that don't have a shell. Nudibranchs, are an example of a sea slug. They are colorful, amazing-looking gastropods. I'll confess that often in the middle of writing articles like these, I get caught up in looking at nudibranch images and am always astounded at the wide array of body shapes, colors and sizes.

Unlike many of their gastropod relatives, many sea slugs don't have a shell as adults, but they may have a shell during their larval stage. Then again, there are some animals classified as sea slugs, like ​bubble shells, that do have shells. 

The nudibranch shown in this image, Dirona pellucida, is found in the Pacific Ocean, but nudibranchs are found in oceans around the world, and may even be in your local tide pool. 

Now that you know more about gastropods, head to the ocean and see what types you can find!

Sources and Further Reading

• Coulombe, D. A. 1984. The Seaside Naturalist. Simon & Schuster. 246pp.
• Meinkoth, N.A. 1981. National Audubon Society Field Guide to North American Seashore Creatures. Alfred A. Knopf, Inc. 813pp.
• NOAA Fisheries. 2015. The era of abalone-rich waters, retired fishermen recalls collecting daily limit with one dive. Accessed April 30, 2015.
• NOAA Fisheries. 2015. Partnerships and innovation contributing to recovery of West Coast abalone populations
• . Accessed April 30, 2015.
• NOAA Fisheries. Abalone. Accessed April 30, 2015.
• Rudman, W.B., 1998. What Are Sea Hares?. Sea Slug Forum. Australian Museum, Sydney.
• Smithsonian National Museum of Natural History. Morphological Variation in the Tiger Cowrie Shell, Cypraea tigris Linnaeus, 1758. Accessed April 29, 2015.