Marisa (gastropod)

Marisa is a genus of freshwater snails belonging to the family Ampullariidae, commonly known as apple snails. The best-known species in this genus is Marisa cornuarietis, the Colombian ramshorn snail.

Characteristics:

Marisa snails are characterized by their discoidal, planispiral shell shape, resembling a flattened coil, which is unlike the more globular shell form typical of other apple snail genera like Pomacea. The shell is typically a yellowish-brown to olive color, often with darker spiral bands. They possess an operculum, a horny plate that seals the shell opening when the snail retracts, providing protection against predators and desiccation.

Distribution and Habitat:

Marisa snails are native to South America, specifically Colombia and Venezuela. However, Marisa cornuarietis has been introduced to various parts of the world, including North America, Asia, and Africa, often as an aquarium pet or for aquatic weed control. They are found in a variety of freshwater habitats, including ponds, lakes, canals, and slow-flowing rivers.

Ecology and Behavior:

Marisa snails are primarily herbivorous, feeding on algae, aquatic plants, and decaying organic matter. Their appetite for vegetation has led to their use in controlling aquatic weeds in some regions. They are also known to consume snails of other species. They are oviparous, laying gelatinous egg masses on submerged objects. Marisa cornuarietis is an intermediate host for various parasites, including those affecting humans and livestock, which poses a health concern in some areas.

Significance:

Marisa cornuarietis has ecological and economic significance. Its herbivorous habits can be beneficial in controlling nuisance aquatic plants, but it can also damage desirable vegetation in aquaculture and agriculture. Its role as an intermediate host for parasites is a concern for public health and livestock management. The snail is also kept in aquariums as a decorative species and for algae control.