Scientifically known as Platyhelminths, flatworms are soft bodied, unsegmented invertebrates that are usually flattened in form. The flattened body is to allow efficient absorption of oxygen and nutrients as they do not have circulatory or respiratory systems. They have cilia on the underside of their body to move along surfaces. Most flatworms are hermaphroditic, meaning they have both female and male reproductive organs. Nearly all flatworms are free living but around 20% of the species are parasitic, this includes the flukes and tapeworms. They feed on bacteria, protozoa (single celled organisms) and smaller invertebrates either alive or dead. Some species consume algae and plant material. Flatworms can occur in most moist environments and are found in both fresh and salt water with a life span of around 4 months. They are widespread across the UK.