Sea snails are fascinating molluscs that we usually recognize by their spiral shells, like those found along the shoreline. They belong to the class Gastropoda, a huge group of invertebrates with over 62,000 described living species, although some experts believe the actual number may exceed 100,000. Not all gastropods are marine, but those that live in the ocean form a very important and diverse part of this group.
In terms of classification, sea snails are distributed among several groups of varying size:
- Subclass Caenogastropoda: includes most present-day sea snails. Here we find families such as Muricidae (murex or rock snails), Conidae (cone snails), and Turbinidae (turban snails). They are the most abundant and diverse group.
- Subclass Vetigastropoda: includes more primitive species, such as Haliotidae (abalones) and Trochidae (top shells). They often have highly ornamented shells and a more ancient gill system in evolutionary terms.
- Subclass Neritimorpha: small snails such as the family Neritidae, with smooth, shiny shells, common in intertidal zones and estuaries.
Morphologically, sea snails have a muscular foot for movement, a head with tentacles and eyes, and a special tongue called a radula, covered with tiny chitinous teeth that allow them to scrape, bore, or cut food. Their shell, generally spiral-shaped, is made of calcium carbonate and grows throughout the animal’s life, protecting it from predators and harsh conditions.
Their geographical distribution spans all seas and oceans, from warm tropical waters to polar regions, and from coastal areas to the deep abyss. They inhabit reefs, seagrass beds, sandy bottoms, and rocky shores exposed to waves.
In terms of diet, some are herbivores feeding on algae and seagrasses others are detritivores, consuming decaying organic matter, while carnivorous predators hunt worms, bivalves, other molluscs, and even small fish. Some, like the Conidae, have developed potent venoms delivered through a modified, harpoon-like tooth.
Most species reproduce through internal fertilization, producing egg capsules that are attached to the substrate or algae. The larvae, called veligers, are part of the plankton before metamorphosing into juvenile snails. Some species have separate sexes, while others can be hermaphroditic, changing sex during their lifetime.
In summary, sea snails display a remarkable diversity of forms, strategies, and adaptations, reflected in their scientific classification. They are key components of marine ecosystems and a perfect example of how evolution has shaped life in the ocean.
