Annelids have segmented bodies, with both a nervous and circulatory system and a one-way gut. They have mastered the art of digging and live in an incredible diversity of habitats. Tube-dwelling worms live in mud flats, stabilizing the mud. Some eat the mud while others collect food from the surface with their tentacles. Blood sucking leeches live in fresh water. Digging in the soil, earthworms both aerate and release nutrients into the soil.