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.
2. parasitic fetus. accidental parasite one that parasitizes an organism other than the usual host. facultative parasite one that may be parasitic upon another organism but can exist independently. incidental parasite accidental parasite.malarial parasite Plasmodium. obligate parasite (obligatory parasite) one that is entirely dependent upon a host for its survival.arasite. a plant or animal that lives upon or within another living organism at whose expense it obtains some advantage. See also symbiosis. Among the many parasites in nature, some feed upon animal hosts, causing diseases ranging from the mildly annoying to the severe and often fatal.