1 The kidneys are used to remove excess water and ions from the blood. 2  These are then expelled as urine. 3  The kidneys perform a vital role in homeostatic regulation in mammals, removing excess water, salt, and urea from the blood.
Ectoparasites Parasites that live on the outside of the host, either on the skin or the outgrowths of the skin, are called ectoparasites. They are directly transmitted between hosts.
ectoparasite, ectozoan, ectozoon, epizoan, epizoon - any external parasitic organism (as fleas) parasitic plant - plant living on another plant and obtaining organic nutriment from it. host - an animal or plant that nourishes and supports a parasite; it does not benefit and is often harmed by the association.