The Common Sea Slug (Aeolidia papillosa), also known as the Sea Mouse, is a strange-looking creature. It has a round, tapering body which is covered in small, fine cerata (tentacles) which give it a furry appearance which is compared to a mouse or other small mammal. They have larger tentacles located on their head and the colour can range from reddish to grey, purple or blue. This species grows to a maximum length of around 12cm.
Common sea slugs can be found at a range of depths from the intertidal zone to several hundred metres deep. They are most commonly found along the western coast of the British Isles, with their range extending to parts of the Atlantic and Pacific Oceans. With the limited mobility this species has they feed on creatures such as sea anenomes.