Osmoregulation in Terrestrial Environment

 Earlier you have learnt about osmoregulation in aquatic environment. In this section, we shall study how the terrestrial animals cope up with the problems of osmoregulation. Just like the aquatic animals which are submerged in an aqueous medium, animals in a terrestrial environment can be thought of as submerged in an ocean of air. Unless the humidity of the air is high, animals having a water permeable epithelium will be subjected to dehydration very much as if they were submerged in a hypertonic medium such as seawater. In order to avoid dehydration, the epithelium should be totally impermeable to water.

The evolutionary process was not found this to be a feasible solution to the problem of desiccation, since an epithelium that is impermeable to water will be dry and such a type of epithelium will have limited permeability to respiratory gases. This mechanism will not fulfil the respiratory needs of a terrestrial animal. Due to the presence of permeable respiratory epithelia, air-breathing animals lose water across it, which would result in dehydration. Various means have been evolved to minimise the water loss in to the air through the respiratory epithelium and also other parts of the body. We shall now learn about them.