Banded mystery snail (Callinina georgiana)

Synonyms: Vivipara georgiana, Paludina georgiana, Viviparus georgianus

Common Names: banded mystery snail, mystery snail, Georgia mystery snail

Description:

The banded mystery snail (Callinina georgiana) is a freshwater snail native to the southeastern United States that people have spread far beyond its home range since the 1800s, mostly through the aquarium trade [1]. It now lives in lakes, ponds, and slow rivers across the Northeast and Midwest, where it can build up into very dense populations [1]. MISIN tracks it because it invades largemouth bass nests and kills bass eggs, and because large die-offs can foul shorelines with dead snails [4][1].

Identification:

The banded mystery snail has a rounded, coiled shell that grows up to about 1.75 inches tall ? roughly the size of a large grape [1]. The shell is olive to yellow-green or light brown, smooth, and wrapped by four reddish-brown bands that follow the spiral; on some snails the bands are faint or hard to see [1][2]. Like other "mystery" snails, it has a hard plate called an operculum ? a trapdoor that seals the shell opening when the snail pulls inside [2]. Look for it in summer in shallow, calm water over silt, mud, or sand, where it grazes along the bottom. After a die-off, empty banded shells often pile up along the shoreline in late summer [1].

At-a-glance cues:

1. Rounded shell up to about 1.75 inches tall, olive to yellow-green or light brown [1]
2. Four reddish-brown bands spiraling around the shell, sometimes faint [1][2]
3. A hard "trapdoor" (operculum) seals the shell opening when the snail withdraws [2]
4. Found on silt, mud, or sand in calm, shallow water; dead shells wash up after summer die-offs [1]

Habitat:

The banded mystery snail is native to the southeastern and midwestern United States, from Florida north to Illinois [1][3]. People have moved it well beyond that range, and it is now established across the Northeast and the Great Lakes region [1]. It lives in lakes, ponds, and slow-moving rivers and streams, usually in calm water over soft silt, mud, or sand [1].

The snail grazes and filter-feeds on dead plant and animal matter on the bottom [2]. It handles a wide range of conditions but does poorly in salty water, which limits where it can survive [1].

Reproduction:

Most banded mystery snails reach new waters by hitchhiking with people. Young snails, some as small as a grain of rice, cling to boats, trailers, anchors, ropes, and fishing or diving gear [2]. Many populations also start when someone empties an aquarium into or near a lake ? this snail has been a popular aquarium pet for over a century [1]. Its trapdoor shell lets it survive out of water for several days, so it travels overland easily [2].

The snail has separate males and females, and females give birth to live young instead of laying eggs in the water [1]. A female carries her young inside her body for 9 to 10 months and releases them fully formed, with shells already in place [1]. Each female produces a modest number of young ? usually around a dozen, but up to about 80 a year ? yet populations can still climb to hundreds of snails per square yard [1][5]. Females live about 2 to 4 years and males a bit less [1].

Because the snails breed in place and the young are tiny, the best way to keep them out is to stop moving water and gear between lakes [2].

Impact and Damage:

For waterfront property owners, the most noticeable problem is die-offs. Some populations die in large numbers after breeding, leaving piles of dead snails and sharp shells that foul beaches and shorelines [1][2]. The snails are not directly harmful to people, but they carry parasites ? tiny worms called trematodes ? that can sicken wildlife. In one Wisconsin lake in 2007, more than 3,000 ducks and coots died after eating infected snails [1].

In natural areas, the snail's biggest known impact is on fish. Banded mystery snails invade the nests that male largemouth bass guard and feed on the eggs, lowering the number that survive ? an effect shown in both laboratory and pond studies [4][1]. The snails also compete with native snails for food and space, and they often become the most abundant bottom-dwelling animal in a lake, reaching densities of hundreds per square yard [5][1].

Hard dollar costs have not been well measured, but the threat to bass and to native snails is the main concern for fisheries and lake managers [1].

Similar species:

Chinese mystery snail is the look-alike most often confused with the banded mystery snail, because it is also a large, round snail with a trapdoor shell. You can tell them apart by size and color: the Chinese mystery snail grows larger, up to about 2.5 inches tall, and its olive to brownish shell usually lacks the distinct reddish bands [2].

Japanese mystery snail is another introduced snail with the same trapdoor shell. It tends to be taller and more pointed than the banded mystery snail and does not have the banded pattern. It is often grouped together with the Chinese mystery snail because the two are so similar.

Pointed campeloma (Campeloma decisum) is a native snail of similar size that also carries a trapdoor. Its shell is plain and more elongated, without the reddish bands, which sets it apart from the banded mystery snail.

Faucet snail is a smaller invasive snail found in the same waters. It is easy to separate by size ? usually under half an inch ? and by its plain, unbanded shell, but it is worth knowing because it is another aquatic invader to watch for [2].

Monitoring and rapid response:

Signs to watch for:

1. Clusters of round, banded snails grazing in shallow, calm water over silt or mud
2. Piles of dead snails and empty banded shells along the shoreline, especially in late summer
3. Snails or tiny, rice-sized young clinging to boats, anchors, ropes, or gear

What you can do:

1. Clean, Drain, and Dry every boat, trailer, and piece of gear between waters. The young are tiny and the trapdoor lets adults live out of water for days, so dry equipment thoroughly ? several weeks is safest ? or rinse it with hot water.
2. Never release aquarium snails or pour aquarium water into or near a lake, pond, or stream. Mystery snails are a common pet, and many infestations start this way.
3. In a small, contained spot such as a private swimming area or dock, you can hand-pick snails and bag them for the trash. Clearing them from open water is rarely possible, so focus on stopping the spread.
4. Natural-area crews can walk shorelines to find new populations early, map and prioritize small or isolated outbreaks, and remove snails by hand across a site before they build up.

When to call a professional:

1. Large, well-established populations or whole-lake situations
2. Repeated die-offs fouling public beaches, or any situation that needs in-water treatment ? contact a lake manager or an aquatic invasive species program
3. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. U.S. Geological Survey, Nonindigenous Aquatic Species Database. Callinina georgiana (banded mysterysnail) Species Profile. nas.er.usgs.gov
2. Minnesota Department of Natural Resources. Banded Mystery Snail (Callinina georgiana). dnr.state.mn.us
3. U.S. Fish & Wildlife Service. Banded Mysterysnail (Callinina georgiana). fws.gov
4. Eckblad JW, Shealy MH Jr (1972). "Predation on largemouth bass embryos by the pond snail Callinina georgiana." Transactions of the American Fisheries Society 101(4):734?738. semanticscholar.org
5. Browne RA (1978). "Growth, mortality, fecundity, biomass and productivity of four lake populations of the prosobranch snail Callinina georgiana." Ecology 59(4):742?750. semanticscholar.org

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