Tardigrades have eight legs.
Arachnids are a class ( Arachnida ) of joint-legged invertebrate animals ( arthropods ) , in the subphylum Chelicerata . All arachnids have eight legs , although the front pair of legs in some species has converted to a sensory function , while in other species , different appendages can grow large enough to take on the appearance of extra pairs of legs . Tardigrades ( [ ˈtɑrdᵻˌgreɪd ] also known as water bears , space bears , or moss piglets ) are water-dwelling , eight-legged , segmented micro-animals . They are short and plump with four pairs of legs , each with four to eight claws also known as `` disks '' .