Displaying an astonishing array of colours and patterns distributed among thousands of species, sea slugs are mollusks that belong to the subclass Opisthobranchia. Of these, nudibranchs, or “true” sea slugs, are often the most vibrant and are characterized by exposed gills. Lacking a shell for protection, nudibranchs have developed a powerful line of chemical defense which is believed to be “advertised” to potential predators by its striking pattern and coloration.