Osmoregulation in Non-Chordate Metazoans

Previously you have studied that in protozoans, particularly fresh water protozoans; contractile vacuoles play a significant role in the regulation of water content of the body. Fresh water organisms often face the problem of their body being flooded with water and have to constantly regulate the water content of their body. Marine animals, although, isotonic with the medium in which they live have to maintain an ionic composition of their body fluids that may be unique to them. Terrestrial organisms - confront the problem of water conservation and have developed adaptations that prevent the water loss from the body. Essentially osmotic relationships-of the organism have to be considered in relation to the ionic composition of body fluids. Ionic regulation could be defined as' maintenance in body fluid, of concentrations of ions differing from those that would result from a passive equilibrium from the medium. In this section we shall briefly discuss the mechanisms of osmotic and ionic regulation of metazoan organisms adapted to living in different habitats.