Giant ramshorn snail
Marisa cornuarietis
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Photo credit: Kenneth Hayes, through the Encyclopedia of Life and the creative commons CC BY-NC 3.0 license
Marisa cornuarietis – Giant Ramshorn Snail
Description:
Habitat:
Origin and Distribution:
Impacts:
Is it found in Northern Ireland?
How could it get here?
Prevent Spread
Current legislative position (Entered into Force on 7th August 2025) This species must not intentionally be brought into the Union; kept; bred; transported to, from or within the United Kingdom, unless for the transportation to facilities in the context of eradication; placed on the market; used or exchanged; permitted to reproduce, grown or cultivated; or released into the environment.
For further queries, you can contact the Invasive Non Native Species (INNS) Team in the Northern Ireland Environment Agency on 028 9056 9558 or Email: invasivespecies@daera-ni.gov.uk
Marisa cornuarietis – Giant Ramshorn Snail
Description:
- The shell is flat and circular-shaped with defined striations
- Shell has 3-4 whorls and 3-6 spiral brown bands
- Shell colour typically ranges from dark yellow to dark brick-red tints with black spiral stripes
- Adult weight is around 500- 650 mg, while shell diameter is usually 35-50mm (sometimes larger)
Habitat:
- Inhabits still or slow-moving freshwater (ponds, rivers, lakes, irrigation systems, and swamps)
- Typically prefers depths less than 1 metre near vegetation
- Very pollution tolerant, can survive months at very low oxygen levels and higher salinity levels
- Thrives in subtropical regions and is restricted to warm-water habitats such as tectonically heated springs, lakes, streams and artificially thermal waters
- Temperatures below 8 degrees Celsius for prolonged period prove fatal
Origin and Distribution:
- Native to Central America and Brazil
- Introduced to and established in the US (found in Florida, Texas, California, and Idaho), Puerto Rico, and Cuba
- First reported in Europe in Northern Spain in August 2013
Impacts:
- A voracious herbivore, paired with its rapid population growth capabilities, allows this species to devour large numbers of aquatic macrophytes
- Considered an aquaculture pest in cultivated crops like rice, watercress, waterlilies
- Feeds on eggs of other freshwater snails and fish species at higher rate than other native or introduced snails
- Competes with native species for food resources
Is it found in Northern Ireland?
- It is not currently present in Northern Ireland
How could it get here?
- Likely pathway is from the escape or deliberate release from their use in aquaria
- Another potential spread is through the aquatic plants trade
- Snails or eggs can accidentally be distributed with host plants
- Human-mediated spread as a contaminant on boats/machinery/water sports equipment can also facilitate its dispersal
Prevent Spread
- Prevention via enforcing the IAS (Enforcement and Permitting) Order (Northern Ireland) ensuring that Marisa cornuarietis is not introduced to Northern Ireland
- Reporting any sightings so that Rapid Response can be instigated
- Following Check Clean Dry
- Properly disposing of unwanted aquarium contents
- You can help by reporting any sightings:@ the Centre for Environmental Data & Recording (CEDaR) - Or via the iRecord App.
Current legislative position (Entered into Force on 7th August 2025) This species must not intentionally be brought into the Union; kept; bred; transported to, from or within the United Kingdom, unless for the transportation to facilities in the context of eradication; placed on the market; used or exchanged; permitted to reproduce, grown or cultivated; or released into the environment.
For further queries, you can contact the Invasive Non Native Species (INNS) Team in the Northern Ireland Environment Agency on 028 9056 9558 or Email: invasivespecies@daera-ni.gov.uk