risso

Risso is a genus of marine gastropod molluscs, commonly known as rissoid snails. These small snails are found in oceans worldwide and are characterized by their generally elongated, conical shells. The shells are typically thin and translucent, with a pointed apex. The aperture is usually oval and lacks an operculum, or the operculum is small and horny. Their sculpture varies, but often includes spiral ribs or cords.

Rissoids inhabit a variety of marine environments, from intertidal zones to deep-sea habitats. They are often found on rocky substrates, among algae, or in association with seagrass beds. Many species are detritivores or grazers, feeding on algae and organic matter. Their small size and widespread distribution make them an important component of many marine ecosystems, serving as a food source for larger invertebrates and fish.

The taxonomy of rissoids is complex and has undergone revisions. Traditionally, the family Rissoidae encompassed a broad range of small marine snails. However, current classifications often divide this group into several smaller families based on detailed morphological and genetic studies. Despite these taxonomic changes, the common name "rissoid" is still widely used to refer to snails within this general grouping. Identification of individual species can be challenging due to their small size and subtle shell variations.