Nudibranchs belong to sea slugs. As all other gastropods, they are slow moving bottom dwellers. They have soft bodies and most of them lack an external protective shell. Their secondary gills are exposed outside, as reflected by their neo-latin/greek name "nudibranch" meaning "nude/naked gills". Some nudibranchs have numerous body projections (called "cerata") increasing the overall body surface and enhancing breathing. Nudibranchs carry a pair of horn-like cephalic tentacles or "rhinophores" at the front, that are used primarily as chemosensory organs (sensing chemicals). To protect themselves from predators many developed toxic or bad tasting glands in the skin, and their bright colors warn predators of their horrible taste.