The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

Marisa cornuarietis
Marisa cornuarietis
(giant ramshorn)
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Marisa cornuarietis (Linnaeus, 1758)

Common name: giant ramshorn

Taxonomy: available through www.itis.govITIS logo

Identification: It is an easily recognizable species, brick red in color with a flat coiled shell. Color may be darker or more vivid.

Size: Shell diameter is usually 35-50 mm (2 in.) or larger.

Native Range: The giant rams-horn snail is native to northern South America and several of the southern islands of the Caribbean.

US auto-generated map Legend USGS Logo
Alaska auto-generated map
Hawaii auto-generated map
Caribbean auto-generated map
Puerto Rico &
Virgin Islands
Guam auto-generated map
Guam Saipan
Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Nonindigenous Occurrences:

Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Marisa cornuarietis are found here.

StateYear of earliest observationYear of last observationTotal HUCs with observations†HUCs with observations†
Florida195720194Big Cypress Swamp; Caloosahatchee; Everglades; Florida Southeast Coast
Idaho199120161Upper Snake-Rock
Puerto Rico200720073Cibuco-Guajataca; Eastern Puerto Rico; Southern Puerto Rico
Texas198320183Middle Guadalupe; San Marcos; Upper San Antonio

Table last updated 8/29/2019

† Populations may not be currently present.

Ecology: Still or slow-moving fresh water, depending on vegetation. Easily adaptable to captivity, it may invade and damage aquarium vegetation. It is practically omnivorous and feeds on animal and vegetal detritus. Acts as a useful aquarium scavenger when not extensively numerous. It has gills as well as a lung, to ensure an efficient underwater respiration. A hermaphrodite, it lays eggs in characteristic disk-shape clutches adhering to various substrates.

Means of Introduction: Probably as a result of releases by aquarium hobbyists. This species has been in the aquarium trade in Florida as early as the 1930s but fell out of favor in the 1950s (Hunt 1958).

Status: It is established in Broward, Dade, Monroe, and Palm Beach counties.

Impact of Introduction: Studies revealed that this species retards the growth of water hyacinths by feeding on the roots of the plants. It has been suggested that the snail be used as weed-control agent in the canals of south Florida. The snail has been released in some areas to control hydrilla. It has also been released to control snail populations that carry schistosomiasis. A study looking at the feeding rate of snails on the eggs of the endangered fountain darter (Etheostoma fonticola) found that Marisa cornuarietis not only fed on the eggs, but a greater portion of the eggs than other nonnative and native snails (Philips et al. 2010).

References: (click for full references)

Hunt, B.P. 1958. Introduction of Marisa into Florida. Nautilus 72(2):53-55.

Phillips, C.T., M.L. Alexander, and R. Howard. 2010. Consumption of eggs of the endangered fountain darter (Etheostoma fonticola) by native and nonnative snails. Southwestern Naturalist 55(1):115-117. http://www.bioone.org/doi/abs/10.1894/JS-26.1.

Author: Benson, A.J. and Daniel, W.M.

Revision Date: 8/30/2019

Citation Information:
Benson, A.J. and Daniel, W.M., 2019, Marisa cornuarietis (Linnaeus, 1758): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=981, Revision Date: 8/30/2019, Access Date: 9/16/2019

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.


The data represented on this site vary in accuracy, scale, completeness, extent of coverage and origin. It is the user's responsibility to use these data consistent with their intended purpose and within stated limitations. We highly recommend reviewing metadata files prior to interpreting these data.

Citation information: U.S. Geological Survey. [2019]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [9/16/2019].

Contact us if you are using data from this site for a publication to make sure the data are being used appropriately and for potential co-authorship if warranted. For queries involving fish, please contact Matthew Neilson. For queries involving invertebrates, contact Amy Benson.