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.
Ectoparasites are those which live on skin or attach to hair follicles. The following listed external parasites are those that can most often affect rats. Lice (phylum: Arthropoda, class: Insecta ) are of two orders, the mallophaga which are of a species that bite or chew, and the order of Anoplura (family Pediculidae) which are a species that suckle blood.