Gastropods fact sheet | Field of Mars EEC

What are gastropods?

Gastropods are soft-bodied invertebrates in the mollusc group. Snails, slugs, limpets, abalones, whelks, periwinkles, sea slugs and sea hares are all gastropods.

Most gastropods have a head, tentacles, a mantle and a strong muscular foot. Many snails have a single coiled shell that helps protect their soft body. Slugs and sea slugs have either a very small shell, an internal shell or no visible shell.

Gastropods live in many different places. They can be found in oceans, rock pools, estuaries, freshwater, wetlands, gardens, forests, leaf litter, soil and under logs. Around Field of Mars Reserve, land snails and slugs are most likely to be found in cool, damp places after rain.

Snails are gastropods with a soft body, muscular foot, tentacles and usually a coiled shell.

The Mount Kaputar pink slug is a bright pink land slug found in the cool, moist habitats of Mount Kaputar National Park.

How do you know it is a gastropod?

Gastropods usually have a soft, moist body and move on a broad muscular foot. Snails have a single shell, while slugs have no obvious external shell.

Many land snails and introduced slugs have two pairs of tentacles. The longer upper pair has eyespots and helps them sense light and movement. The shorter lower pair helps them smell and feel their surroundings. Some native Australian slugs, such as the red triangle slug, have only one pair of tentacles.

Gastropods feed using a rough, tongue-like structure called a radula. It works like a tiny file and helps scrape algae, fungi, lichens or plant material from surfaces.

Snails and slugs use a radula to scrape food from surfaces, leaving tiny feeding marks.

Gastropod groups

Land snails and slugs

Land snails and slugs live in damp places such as leaf litter, soil, gardens, forests and under logs. Many are most active at night, after rain or during cool, wet weather.

Some land gastropods feed on fungi, algae, lichens and decaying plant material. Others feed on living plants. Not all snails and slugs are pests. Many native species help recycle nutrients and are part of healthy bushland food webs.

Red triangle slugs are native land gastropods found in eastern Australia.

Freshwater gastropods

Freshwater gastropods live in creeks, ponds, wetlands, dams and slow-moving water. They may graze on algae, feed on decaying material or move across aquatic plants and rocks.

Freshwater snails can be part of aquatic food webs. They are eaten by fish, birds, turtles, insects and other animals. Changes in freshwater snail diversity can also help show changes in water quality and habitat condition.

Freshwater snails are aquatic gastropods that move across plants, rocks and other surfaces in ponds, creeks and wetlands.

Marine gastropods

Marine gastropods live in the ocean, from the intertidal zone to deeper water. They include turban snails, periwinkles, limpets, abalones, cowries, whelks and many other sea snails.

Some marine gastropods graze on algae. Others are predators or scavengers. Limpets cling tightly to rocks, while many sea snails use shells for protection.

The Australian trumpet snail is a marine gastropod with a tall spiral shell.

Sea slugs and sea hares

Sea slugs and sea hares are marine gastropods with reduced or hidden shells. Many have bright colours, unusual body shapes and special defences.

Sea hares live in rock pools, shallow marine habitats and seagrass areas. They glide over rocks and algae using their muscular foot. Some can release a purple dye when threatened, which helps confuse predators.

Sea slugs are shell-less or nearly shell-less marine gastropods.

What is the life cycle of gastropods?

Most gastropods hatch from eggs. Land snails often lay small round eggs in damp, sheltered places such as soil, leaf litter or under logs. Some freshwater and marine gastropods lay eggs in clusters, capsules, ribbons or jelly-like masses.

Young gastropods look like small versions of adults in many land species. As snails grow, they add new shell material around the shell opening. Slugs also grow larger, but they do not build a large external shell. Gastropods need moisture to help their eggs and young survive because their soft bodies can dry out quickly.

Many land snails lay eggs in damp, protected places such as soil or leaf litter.

What adaptations do gastropods have to help them survive?

Gastropods have many adaptations that help protect their soft bodies. A shell can protect a snail from predators, drying out and rough surfaces. Some snails can pull their head and foot back inside the shell when disturbed.

Mucus helps gastropods move across rough surfaces and reduces water loss. Many land snails and slugs are active at night or after rain when conditions are cooler and damper.

Tentacles help gastropods sense their surroundings. A radula helps them scrape food from bark, rocks, leaves, algae, fungi or other surfaces. Some gastropods use camouflage, warning colours, strong shells, bad tastes or chemical defences to avoid being eaten.

The Mount Kaputar pink slug is adapted to cool, moist mountain habitats.

Why are gastropods important?

Gastropods are important in many ecosystems. Some feed on algae and help keep surfaces clear. Others break down fungi, lichens, decaying leaves and dead organic material, returning nutrients to the soil.

Gastropods are also food for many animals, including birds, reptiles, frogs, fish, beetles, flatworms and other predators. In bushland, leaf litter, bark, logs and damp soil can support native snails, slugs and many other small invertebrates.

Freshwater and land snails can also help scientists learn about habitat health. Some species need very specific habitats, so changes in their numbers may show that an environment is changing.

Gastropods are food for many bushland animals, including eastern blue-tongue lizards.

How can you help gastropods?

You can help native gastropods by protecting damp habitat. Leave leaf litter, bark, logs, rocks and fallen branches in place where it is safe to do so. These places provide shelter, food and moisture for snails, slugs and other invertebrates.

Plant local native plants to create shade, leaf litter and habitat. Avoid removing every fallen leaf from garden beds, as bare soil can become too hot and dry for many small animals.

Avoid unnecessary pesticide and snail bait use. Some chemicals can harm native snails, slugs, beetles, reptiles, frogs and other animals. If introduced garden snails are a problem, use safer control methods and avoid spreading soil, pot plants or garden waste into bushland.

Protecting bushland, leaf litter and natural habitats provides shelter, food and moisture for gastropods.

Explore more

Use the fact sheet links on this page to learn more about invertebrates found in bushland, gardens, wetlands and school grounds.

You can also compare molluscs with other invertebrate groups such as insects, crustaceans, arachnids, worms, myriapods and springtails.

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