NudibranchNudibranchia

Nudibranchs are soft-bodied marine molluscs that lack an external shell, presenting a wide range of body forms. Often featuring bright colours and intricate patterns like spots, stripes, or blotches, many species possess external gills visible as a dorsal plume or finger-like projections called cerata. Their name, from Latin, means "naked gills," referring to these exposed respiratory structures. Sizes typically range from a few millimetres to several centimetres in length.

These animals inhabit coral reefs, rocky slopes, seagrass beds, and sandy substrates, from shallow intertidal areas down to 40 meters (130 ft). Nudibranchs are specialist feeders, preying on specific sponges, hydroids, bryozoans, soft corals, or sea anemones; some species feed on other nudibranchs. Many species sequester defensive compounds, such as toxins or nematocysts, from their prey, storing them in their cerata or skin for protection. Their bright colouration often functions as a warning to predators. On the reef, these typically slow-moving animals are often conspicuous.