Nudibranchs are a widespread group of marine Gastropod mollusks. The name means ‘naked gills’. They are mostly very small on average 20-30mm (0.7874-1.1811 inches) in length. They don’t have shells and uncoiled Gastropods, famous for their brilliant colors. There are more than 3000 known species. Nudibranchs are one of the groups which are informally known as sea slugs.