Flabellinopsis iodinea (Spanish shawl) is a species of aeolid nudibranch, a very colorful sea slug. This is a marine gastropod mollusk in the family Flabellinidae.
This nudibranch displays a stunning set of colors: the body is purple, the cerata are orange and the rhinophores are secret. The neon orange appendages on the back of Flabellinopsis iodinea are the cerata which extract oxygen from the sea water they are surrounded by and live in. The cerata are also extensions of the digestive system, and are used to store the stinging cells of the anemones and fan-like hydroids they eat. The red rhinophores are sensory structures used for detecting the presence of possible mates and prey. The purple, red, and orange colors are derived from a single carotenoid pigment, astaxanthin. The pigment appears in three modified states, leading to the three distinct colors.
Scientists think the reason why the Spanish Shawl’s gills are orange is so they can camouflage with their prey while they are eating. The orange gills on their backs are also a warning to potential predators. The color tells their predators that they are either poisonous or distasteful.