Perhaps one of the ocean's most iconic inhabitants, starfish or "sea stars" are characterized by at least five flexible "arms" radiating from their center, each lined with hundreds of sucker-tipped "tube feet" used in locomotion. With an incredibly simple nervous system encircling the mouth and running down each arm, any large enough portion broken off from a starfish will regenerate into an entire new animal. While starfish may feed upon carrion or vegetable matter, the majority of species are strictly carnivorous, feeding on slower or sedentary animals such as corals, sponges, limpets and especially mussels. Such prey is commonly digested externally, over the course of days, when the starfish extrudes its stomach inside-out to digest its helpless victim alive.