Snails are diverse invertebrates in the class Gastropoda, encompassing both shelled snails and shell-less slugs. While many are terrestrial, a significant number have adapted to aquatic life. This adaptability allows many snails to thrive in various water bodies around the globe.
Aquatic Snail Diversity
Aquatic snails encompass a wide array of species across different habitats. Freshwater snails are found in environments ranging from small ephemeral pools to large lakes and flowing rivers. Common examples include pond, ramshorn, mystery, Nerite, and Malaysian trumpet snails.
Saltwater snails, on the other hand, inhabit diverse marine ecosystems, from coastal shores to deep abyssal zones. This group includes species such as conchs, periwinkles, whelks, abalone, Astrea snails, and Cerith snails. Even sea slugs, like nudibranchs, are part of this aquatic gastropod diversity, though they lack a prominent external shell.
Breathing Underwater
Most aquatic species utilize specialized respiratory organs called gills. These comb-like structures are located within the snail’s mantle cavity and feature numerous feather-like filaments to maximize surface area for gas exchange. Water is drawn over these gills, allowing the snail to absorb dissolved oxygen and release carbon dioxide.
Some freshwater snails, known as pulmonate snails, have evolved a modified lung for breathing. This lung is a vascularized, sac-like modification of the mantle cavity that allows them to take in atmospheric oxygen. These snails often surface to gulp air through a small opening called a pneumostome. Some pulmonate species can also absorb oxygen directly from the water through their skin, or by filling their mantle cavity with water, which is useful in environments with low dissolved oxygen.
Land Snails and Water Exposure
Land snails require moisture for survival but cannot live submerged in water. Their skin must remain moist to facilitate oxygen absorption. These terrestrial species rely on atmospheric oxygen, taken in through a pallial lung.
The pallial lung connects to the outside through a small opening called a pneumostome, which land snails can open and close to regulate air intake and conserve moisture. If submerged for extended periods, land snails will drown because their respiratory system is adapted for air. They frequently seek out damp environments, such as beneath rocks, logs, or leaf litter, and are often seen after rain as increased humidity aids their movement.
Essential Water Conditions for Aquatic Snails
Maintaining specific water conditions is important for aquatic snails to thrive. Water quality parameters such as ammonia and nitrite levels should be zero ppm, while nitrate levels need to be managed through regular water changes. Temperature is another factor, with many freshwater snails preferring a range between 65 and 83°F (18-28°C), and saltwater snails having similar needs.
The pH level of the water is also significant, with freshwater snails generally favoring a pH between 7.0 and 8.0, though some species can tolerate levels up to 9.2. Adequate calcium content, contributing to water hardness, is beneficial for shell development and health. Snails are sensitive to copper and other metals, so their presence in the water should be avoided.