33. Aquatic animals generally are ammonotelic in nature where as terrestrial forms are not. Comment.
The process of excreting ammonia is called ammonotelism. many bony fishes, aquatic amphibians and aquatic insects are ammonotelic in nature. Ammonia, as its readily soluble, in water is excreted by diffusion across body surface or through gill surfaces (in fishes) as ammonium ions.
It is highly soluble in water and requires large amounts of water to be lost from the body. Such a mode of excretion is thus suitable for aquatic organisms which have a constant access to water.
Terrestrial adaptation requires the production of lesser toxic nitrogenous wastes like urea, as urea is less toxic and less soluble in water. This is important adaptation for water conservation in animals body. Mammals, many terrestrial amphibians and marine fishes mainly excrete urea and are called ureotelic animals.
In most insects land snails, reptiles etc., uric acid is excreted, hence they are called uricotelic animals. Conversion of ammonia to uric acid and its elimination requires less water, thus it is very essential for terrestrial forms that do not have constant water supply.
