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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.

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Common name: giant ramshorn

Synonyms and Other Names: giant rams-horn, striped ram's horn snail, Goldenhorned Marissa, Colombian ramshorn applesnail

Taxonomy: available through www.itis.gov

Identification: Marisa cornuarietis is a relatively large snail with a flat, circular-shaped shell. The shell is smooth with defined striations and about 3-4 whorls and 3-6 spiral brown bands (OGATT 2018). Their coloring varies greatly from dark yellow to dark brick-red tints with black spiral stripes. There are color variates with no stripes and a completely yellow shell. The body color can be white with a pattern of yellowish, gray, and black, with pigment spots (Texas Invasive Species Institute 2014).

This snail is sexually dimorphic, with males having a round-shaped aperture (opening) and a thicker shell, and females having a more oval-shaped aperture and thinner shells (OGATT 2018).

Size: Shell diameter is usually 35-50 mm (Rawlings et al. 2007, OGATT 2018).

Native Range: Marisa cornuarietis is native to northern South America and several of the southern islands of the Caribbean (Robins 1971) including Bolivia, Brazil, Colombia, Costa Rica, Cuba, French Guiana, Guyana, Panama, Suriname, Trinidad and Tobago and Venezuela (OGATT 2018).

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Ecology: This species is found in freshwater habitats with a preference for still or slow-moving water with live aquatic vegetation (Robins 1971, OGATT 2018). Hunt (1961) demonstrated that Marisa cornuarietis tolerates salinities of up to 25 percent seawater. This snail is limited to warm water and spring-fed systems with high calcium concentrations for shell-building (OGATT 2018). Robins (1971) showed that exposure to low temperatures for any significant time (8 °C for 8 hours) is fatal. This species is in the Ampullariidae family of snails and has both gills and a lung (Demian 1965). Marisa cornuarietis is omnivorous and feeds on live or decaying plants, fish, eggs, and juvenile snails (Robins 1971, OGATT 2018).

The life cycle of the snail is dependent on the availability of food and the water temperature. At high temperatures and high abundance of food, the life cycle is short (less than three months) and reproduction occurs throughout the year (OGATT 2018). In less than conducive conditions, the life span can be around two years, and reproduction will only occur in the spring and early summer (Robins 1971, OGATT 2018).

Marisa cornuarietis reproduce sexually, with females being able to store sperm for months (OGATT 2018). Eggs are laid in large, clear gelatinous masses-containing 20-80 eggs that are 2-3 mm in size. The eggs are laid on the surface of objects under the water (Robins 1971, OGATT 2018). The eggs swell up to 4 mm after ten days and become transparent enough to see the snail moving. After hatching, the emergent snail resembles an adult snail, and will continue to grow in size with time and calcium availability in the water (OGATT 2018).

Means of Introduction: The first introductions into the U.S. were probably as a result of releases by aquarium hobbyists (Neck 1984, Horne et al. 1992). Marisa cornuarietis has been in the aquarium trade as early as the 1930s but fell out of favor in the 1950s (Hunt 1958). Currently, the Marisa cornuarietis is available for purchase at numerous pet stores and online.

Marisa cornuarietis are also used in ecotoxicological studies, suggesting specimens could have escaped or been released from a laboratory. Florida and Puerto Rico have stocked this snail for biocontrol of weeds and pulmonate snails (Radke et al. 1961, Demian and Lufty 1965). Secondary dispersal has occurred downstream on floating macrophytes (Robins 1971).

Status: It is established in southern Florida, Texas, Puerto Rico and warm springs of Idaho

Impact of Introduction:

Summary of species impacts derived from literature review. Click on an icon to find out more...

Ecological	Economic

Herbivory
Marisa cornuarietis is known as a voracious herbivore and may devour large numbers of aquatic macrophytes (Pointer and David 2004), potentially altering plant communities (Neck 1984, Horne et al. 1992). The snail could also be an aquaculture pest in cultivated rice, water-cress, water lilies, or dasheen (Seaman and Porterfield, 1964). The herbivory impact can also extend to federal and state-listed plant species. Neck (1984) suggested that the introductions in the San Marcos River, TX could have an impact on the endemic wild rice (Zizania texana) populations. Laboratory studies have shown a feeding preference for other Texas natives like Ludwigia repens and American eelgrass (Vallisneria Americana; Grantham et al. 1993).

This snail has been tested as a biocontrol agent for several important aquatic weeds and has been shown to control nuisance weeds in both Puerto Rico and South Florida canals as early as the 1960’s and as recently as the early 2000’s (Pointer and David 2004, Seaman and Porterfield 1964; some of the targeted weeds include Illinois pondweed (Potamogeton illinoensis), southern naiad (Najas guadalupensis), coontail (Ceratophyllum demersum) salvinia (Salvinia rotundifolia), waterhyacinth (Eichhornia crassipes), and waterlettuce (Pistia stratiotes), alligatorweed (Alternanthera philoxeroides).

Competition/ Predation
Marisa cornuarietis are known as a competitive feeder and an incidental predator on egg masses and newly hatched pulmonate snails (Demian and Lufty 1965). This snail’s competitive ability has been utilized in biocontrol in Puerto Rico and Guadeloupe for Biomphalaria glabrata, an intermediate snail host for the trematode Schistosoma mansoni (Oliver-Gonzalez et al. 1956, Radke et al. 1961, Ruiz-Tiben et al. 1969, Pointer and David 2004). This trematode is one of the main schistosomes that infect humans. Marisa cornuarietis is also known to prey or compete with numerous African intermediate snail hosts for schistosomes: Biomphalaria alexandrina (Demian and Lutfy 1965), Biomphalaria pfeifferi, Lymnaea natalensis, and Bulinus tropicus (Nguma et al. 1982).

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 more significant portion of the eggs than other nonnative and native snails (Phillips et al. 2010). Neck (1984) suggested that the San Marcos River introduction of Marisa cornuarietis may compete with Balcones elimia, (Elimia comalensis) populations.

Remarks: Marisa cornuarietis are often used in ecotoxicological studies (Schulte-Oehlmann et al. 1995).

References: (click for full references)

California Department of Fish and Game. 2003. List of the Californian macroinvertebrate taxa and standard taxonomic effort. California Department of Fish and Game, Rancho Cordova. 45 pp.

Demian, E.S. 1965. The respiratory system and the mechanism of respiration in Marisa cornuarietis (L.). - Arkiv För Zoologi 17: 539-560.

Demian, E.S., and R.G. Lutfy. 1965. Predatory activity of Marisa cornuarietis against Biomphalaria alexandrina under laboratory conditions. Annals of Tropical Medicine and Parasitology 59(3):337-339

Grantham, O.K., Moorhead, D.L., and M.R. Willig. 1993. Feeding preference of an aquatic gastropod, Marisa cornuarietis: effects of pre-exposure. Journal of North American Benthological Society 12(4):431-437.

Horne, F.R., Arsuffi, T.L., and R.W. Neck. 1992. Recent introduction and potential botanical impact of the giant rams-horn snail, Marisa cornuarietis (pilidae), in the Comal Springs ecosystem of central Texas. The Southwestern Naturalist 37(2):194-214.

Howells, R.G., L.F. Burlakova, A.Y. Karatayev, R.K. Marfurt, and R.L. Burks. 2006. Native and introduced Ampullariidae in North America. Pages Pages 73-112 in Joshi, R.C. and L.S. Sebastian, eds. Global advances in the ecology and management of golden applesnails. Philippine Rice Research Institute. Munoz, Ecija.

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

Hunt, B.P. 1961. Tolerance of a freshwater snail Marisa cornuarietis (L.) to sea water. - Quart. J. Florida Acad. Sci. 23: 278-284

Jobin, W.R. 1970. Population dynamics of aquatic snails inthree farm ponds of Puerto Rico. American Journal of Tropical Medicine and Hygiene 119: 1038–1048.

Neck, R.W. 1984. Occurrence of the striped ram's horn snail, Marisa cornuarietis, in central Texas (Ampullariidae). The Nautilus 98(3):119-120.

Nguma, J.F., McCullough, F.S., and E. Masha. 1982. Elimination of Biomphalaria pfeifferi, Bulinus tropicus and Lymnaea natalensis by the ampullarid snail, Marisa cornuarietis, in a man-made dam in northern Tanzania. Acta Tropica 39(1):85-90.

Oliver-Gonzalez, J., Bauman, P.M., and A.S. Benenson. 1956. Effect of the snail Marisa cornuarietis on Australorbis glabratus in natural bodies of water in Puerto Rico. American Journal of Tropical Medicine and Hygiene 5(2):290-296.

Online Guide to the Animals of Trinidad & Tobago (OGATT). 2018. Marisa cornuartietis (giant ramshorn snail). https://sta.uwi.edu/fst/lifesciences/animals-trinidad-tobago. Created on 07/06/2018. Accessed on 09/06/2019.

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.

Pointer, J.P. and P. David. 2004. Biological control of Biomphalaria glabrata, the intermediate host of schistosomes, by Marisa cornuarietis in ponds of Guadeloupe: long-term impact on the local snail fauna and aquatic flora. Biological Control 29:81-89.

Radke, M.G., Ritchie, L.S., and F.F. Ferguson. 1961. Demonstrated control of Australorbis glabatus by Marisa cornuarietis under field conditions in Puerto Rico. American Journal of Tropical Medicine and Hygiene 10: 370–373.

Rawlings, T.A., Hayes, K.A., Cowie, R.H. and T.M. Collins. 2007. The identity, distribution, and impacts of non-native apple snails in the continental United States. BMC Evolutionary Biology 7:97.

Robins, C.H. 1971. Ecology of the introduced snail, Marisa cornuarietis (Ampullariidae) in Dade County, Florida. Biologist 53:136-152. 

Ruiz-Tiben, E., Palmer, J. R., and F. Ferguson. 1969. Biological control of Biomphalaria glabrata by Marisa cornuarietis in irrigation ponds in Puerto Rico. Bulletin of the World Health Organization 41(2):329.

Schulte-Oehlmann, U., Bettin, C., Fioroni, P., Oehlmann, J., and E. Stroben. 1995. Marisa cornuarietis (Gastropoda, Prosobranchia): a potential TBT bioindicator for freshwater environments. Ecotoxicology 4(6): 372-384.

Seaman, D.E. and W.A. Porterfield. 1964. Control of aquatic weeds by the snail Marisa cornuarietis. Weeds 12(2):87-92.

Other Resources:
US Fish and Wildlife Service Ecological Risk Screening Summary for Marisa cornuarietis

Author: Benson, A.J., Daniel, W.M., and Morningstar, C.R.

Peer Review Date: 9/27/2019

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.