Origin
Marisa cornuarietis is native to northern South America and multiple islands in the Caribbean. Giant Ramshorn were likely introduced to the United States as intentional releases by aquarium hobbyists.

Life Cycle
M. cornuarietis are large snails at 1.4-2 in. (35-50 mm) in diameter. Shells are flat and circular in shape with smooth, well-defined striations, 3-4 whorls, and 3-6 spiral brown bands. The coloration varies from dark yellow to dark red with black spiral stripes. M. cornuarietis are sexually dimorphic with males having a round opening and a thicker shell while females have oval openings and thinner shells. Giant Ramshorn snails are competitive herbivorous feeders found in still or slow-moving freshwater habitats. Life cycle of M. cornuarietis is temperature and food availability dependent with shortened cycles (less than 3 months) during hotter temperatures and as long as 2 years during colder temperatures.

Distribution
M. cornuarietis is established in Florida, Idaho, Texas, and Puerto Rico.

Control Efforts
M. cornuarietis has the potential to alter plant communities and has been tested for use as a biocontrol agent for nuisance weeds.

https://nas.er.usgs.gov/queries/factsheet.aspx?speciesid=981
 

Selected Images

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Maps

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Invasive Listing Sources

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• Everglades Cooperative Invasive Species Management Area
• Florida Invasive Species Partnership
• Idaho Invasive Species Act