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Introduction

Marisa cornuarietis is a large freshwater snail native to tropical regions of South America and nearby islands. Its flattened, spiralled shell, often marked with brown and cream bands, resembles that of a ramshorn snail, although its adult size is considerably larger. In aquaria, this species is known for its constant activity, air-breathing ability and strong appetite for algae, tender plants and organic matter. It is best suited to aquariums with sturdy plants or dedicated invertebrate setups, because it may damage delicate vegetation.

General species description

Marisa cornuarietis is a freshwater gastropod belonging to the family Ampullariidae. Despite its ramshorn-like appearance, it is not a member of Planorbidae. Its body combines gill respiration with aerial respiration through a pulmonary cavity, allowing it to use water that may be relatively low in oxygen. The species is active during both daylight and nighttime, moving across glass, décor and substrate while searching for food. It is generally peaceful toward adult invertebrates, but its appetite for plants must be taken seriously. Eggs are deposited in gelatinous clusters above or close to the waterline, often on a damp surface. Care is straightforward in stable, mineral-rich water kept free of copper.

Geographical origin and biotope

Countries of reference: Venezuela, Colombia, Brazil, Bolivia and Trinidad are associated with its natural South American and Caribbean range. Marisa cornuarietis inhabits still or slow-moving environments, including ditches, marshes, ponds, floodplains and marginal areas of waterways. These habitats commonly have warm water, limited depth and substantial accumulations of plant debris. Aquatic and emergent vegetation provides grazing surfaces and spawning sites. In aquaria, water at 24 to 28 °C, moderately hard and well oxygenated generally reflects its broad requirements better than very soft, acidic water. The species tolerates some variation, but sudden changes can affect its condition.

Precise location and local name

Within its natural range, Marisa cornuarietis is associated with the tropical floodplains and wetlands of northern South America and with Trinidad. No single local name is used throughout this wide distribution. In the aquarium trade, it is commonly called the Colombian ramshorn snail or giant ramshorn snail; French names include grand planorbe de Colombie and escargot planorbe géant. These popular names refer to its shape or commercial origin and should not be confused with true ramshorn snails of the family Planorbidae. Aquarium movement has also contributed to introductions in several warm environments, where the species may become undesirable.

Appearance and physical characteristics

The shell of Marisa cornuarietis is discoid, laterally flattened and formed by clearly visible whorls. It can reach about 5 cm in shell diameter, with colours ranging from golden brown to dark brown and often showing bands or irregular markings. The foot is broad and muscular, while the tentacles are thin and elongated. A respiratory opening allows it to renew the air in its pulmonary cavity at the surface. The shell is vulnerable to acidic conditions and calcium deficiency, so adequately mineralized water supports healthy growth and maintenance. Individuals may vary in colour, and juveniles often display more contrasting markings. Its flattened shape and adult size readily separate this species from small aquarium ramshorn snails.

General diet

Marisa cornuarietis is an omnivore with a strong plant-based diet. It grazes on algae and biofilm growing on glass, rocks and wood, but also consumes dead leaves, uneaten food, weakened organisms and some tender aquatic plants. In a planted aquarium, algae alone should not be considered a complete food source. Invertebrate wafers, blanched vegetables and fibre-rich foods can supplement its diet. Zucchini, cucumber and leafy greens are generally suitable, provided leftovers are removed before they decay. Calcium supports shell development, while copper should be avoided. Excessive feeding, however, increases pollution and can encourage overpopulation.

Essential data

• Original river name: floodplain waterways and tropical wetlands within its natural range
• Local name used: giant ramshorn snail; Colombian ramshorn snail
• Origin of the scientific name: a taxonomic combination based on the species originally described as Planorbis cornuarietis
• Etymology of the full name: Marisa is the genus name; cornuarietis comes from the Latin cornu arietis, meaning “ram’s horn,” referring to the spiralled shell
• Common/vernacular names: giant ramshorn snail, Colombian ramshorn snail, grand planorbe, escargot planorbe géant
• Family: Ampullariidae
• Subfamily: Ampullariinae
• Name pronunciation: ma-REE-sa - kor-noo-are-ee-ET-is
• Discovery: Carl von Linné, 1758
• Maximum adult size: about 5 cm shell diameter
• Water temperature and pH: 24 to 28 °C; approximately pH 7.0 to 8.2
• Waterway appearance and surrounding vegetation: still waters, marshes, ditches and vegetated floodplain margins with abundant aquatic and emergent plants
• Typical tank companions: Poecilia reticulata, Xiphophorus hellerii, Hoplisoma paleatus, Paracheirodon innesi, Trichopodus leerii
• Temperament and behaviour: peaceful, active and grazing-oriented, with air breathing at the surface; may consume tender plants
• Water depth: shallow areas and vegetated margins
• Sexual dimorphism: separate sexes; external identification is difficult, although adult females may be bulkier
• Bottom structure and flow: mud, silt, plant debris and soft substrates; still to slow current

In your aquarium

Success with Marisa cornuarietis depends on stable, adequately mineralized water kept free of copper. Use a cover because the species may leave the water, and monitor egg clusters placed near the surface. Provide supplemental plant-based food without allowing leftovers to pollute the aquarium. Avoid fish that nip at or consume snails, as well as very delicate plants. Regular maintenance, population control and sufficient calcium will help maintain a strong shell and normal long-term behaviour.