Excretory Systems, Nitrogen Excretion, Water and Ionic Regulation
The excretory system of all animals is responsible for maintaining a relatively constant internal environment in the face of an ever-changing external environment. It follows, therefore, that a parasite inside its host’s tissues will be inhabiting an environment that is itself rigorously controlled by the excretory and osmoregulatory systems of the host animal. Parasites disperse themselves from host to host and, during this transmission, they will be exposed to a variety of physico-chemically different environmental conditions. Many parasites have a direct life-cycle with one host and a single transmission stage. At the other end of the spectrum are parasites, e.g. the strigeid digeneans, which, during a single life-cycle, infect three different hosts and have two distinct transmission stages. We would thus expect the excretory system of parasites to be able to remove the waste products of their metabolism and carry out an osmoregulatory role when the prevailing conditions demand.
KeywordsUrea Cycle Excretory System Ornithine Transcarbamylase Contractile Vacuole Flame Cell
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