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Invasive Species: Mollusks

Invasive Mollusks

Species that are not native and also have the potential to harm human health or to harm natural, agricultural or silvicultural resources can be listed as prohibited or restricted by the State of Michigan. If a species is prohibited or restricted, it is unlawful to possess, introduce, import, sell or offer that species for sale as a live organism, except under certain circumstances.

Asian Clam

(Corbicula fluminea)

The Asian clam is a small (less than an inch), yellow to light-brown clam with well defined, concentric grooves.  The shell is triangular to round in shape.  Asian clams are generally found on, or slightly buried in sediment in freshwater systems.

More information: Asian clam

Brown Garden Snail

(Cantareus aspersa)

Prohibited in Michigan

Brown garden snails have a brown body with a shell that tends to be brown, tan and yellow with swirls, bands, and flecks. Their shells can grow up to 1.25 inches in diameter. They leave behind a silvery slime trail.

More information: Brown garden snail

Carthusian Snail

(Monacha cartusiana)

Prohibited in Michigan

Carthusian snails have shells that are a pale white-yellow color and may have brown stripes. The opening of the shell is typically the darkest part of the shell in adults. The shell size is 6-10 mm high, 9-17 mm wide.

More information: Carthusian snail

Giant African Snail

(Lissachatina fulica)

Prohibited in Michigan

The giant African snail is very large - about the size of an adult's fist. Their shells can reach eight inches in length and four inches in diameter. The shell is brownish with dark brown vertical stripes on at least half of the length of the shell and coloration lightens to almost white at the tip of the shell.

More information: Giant African snail

Girdled Snail

(Hygromia cinctella)

Prohibited in Michigan

The girdled snail has a triangular or pyramid shaped shell that is about 6-7 mm high and 10-14 mm wide. The shells tend to be brown to yellow with a white band on the widest part. The shell has 5-6 whorls and the opening of the shell is oval.

More information: Girdled snail

Golden Mussel

(Limnoperna fortunei)

Prohibited in Michigan

Golden mussels have shells that are golden or yellowish, a dorsal mantle fusion, and the average length is 20 mm (maximum length is 40-60 mm). They may form colonies as large as 80,000 individuals. They are primarily a freshwater species capable of tolerating polluted and contaminated waters.

More information: Golden mussel

Heath Snail

(Xerolenta obvia)

Prohibited in Michigan

Heath snails have chalky while colored shells with dark spiral bands. They have a flattened shell shape with a relatively large umbilicus (hole on the center of the shell's underside in some species). The opening of the shell is oval.

More information: Heath snail

New Zealand Mudsnail

(Potamopyrgus antipodarum)

Watch List - Prohibited in Michigan

New Zealand mudsnails are an average of 1/8 inch long with 5-6 whorls on their shell. The shells vary from light brown to black. They can tolerate a wide variety of habitats including reservoirs, estuaries, rivers, and lakes.

More information: New Zealand mudsnail

Quagga Mussel

(Dreissena rostriformis bugensis)

Restricted in Michigan

Quagga mussels have fan-shaped shells that are more rounded than zebra mussels, and they won't sit flat on the ventral side. The shells color ranges from almost white to tan or brown and usually have darker concentric rings. Quagga mussels can reach about two inches in length.

More information: Quagga mussel

Wrinkled Dune Snail

(Candidula intersecta)

Prohibited in Michigan

Wrinkled dune snails have a shell that is pale white or yellow with brown spots or bands. Their body is often pale-yellow or blue-gray and the shell varies in size from 7-13 mm long and 5-6 mm high.

More information: Wrinkled dune snail

Zebra Mussel

(Dreissena polymorpha)

Restricted in Michigan

Zebra mussels have shells that are triangular in shape and can sit flat on the ventral side (unlike quagga mussels which have more rounded shells and cannot sit flat). Their shells rang in color from almost white to tan or brown with darker concentric rings. The average length of a zebra mussel is one inch.

More information: Zebra mussel