Living organisms release metabolic wastes produced by the body through excretion. The process of nitrogenous excretion of certain living organisms in the form of ammonia is called Ammonotelism. These organisms are broadly classified as ammonotelics.
Process of Ammonotelic Excretion
Ammonia is a compound formed by Nitrogen and Hydrogen and is highly water soluble. This mode of excretion requires the least energy expenditure.
The high-water solubility of Ammonia makes it highly toxic. It reacts with water to form Ammonium Hydroxide which can damage living cells directly by caustic alkaline reaction. Due to this property the excretion of Ammonia requires a large amount of water. 1gm of ammonia excretion requires almost 300 to 500 ml of water. This requirement thus entails all ammonotelic organisms to be aquatic organisms such as bony fishes, amoeba, amphibian larvae, etc.
In the process of conversion of proteins to carbohydrates, uric acid is formed by the deamination of amino acids. This uric acid is oxidized to allantoin and allantoic acid for excretion. Allantoin undergoes hydrolysis to allantoate which is further hydrolysed to urea and glyoxylate. In ammonotelic organisms, the urea is further broken down into ammonia and carbon dioxide. Then the ammonia is excreted out with usage of a large amount of water.
Anatomical aspects of Ammonotelic Excretion
Ammonia has a small molecular size and is highly water soluble. Hence, it can easily cross the cellular membrane. The diffusion of ammonia in aquatic organisms can take place through the skin, gills or kidneys.
Organisms like certain aquatic invertebrates, protozoans, echinoderms, Platyhelminthes, crustaceans, poriferans, cnidarians and aquatic animals are ammonotelic. Based on their anatomical structure the process of ammonia formation & diffusion for excretion is different.
Protozoans being single-celled majorly excrete via the contractile vacuole that maintains the fluid levels through osmosis. Echinoderms, Platyhelminthes, cnidarians excrete directly by simple diffusion through the skin as they do not possess any specific excretory organs. Most molluscs possess a renal gland that is a wide tube present in their body structure that helps in the filtration of blood. They majorly excrete out ammonia but Octopuses excrete out ammonium chloride. Aquatic crustaceans excrete via the coxal glands while aquatic fishes majorly excrete through the gills while a certain amount of ammonia is released in the urine via kidneys for osmotic regulation.
Conclusion
- The process of excretion of ammonia is called ammonotelism. The organisms that excrete ammonia are classified as ammonotelic.
- Ammonia due to high-water solubility is toxic and requires a large quantity of water for excretion. Hence, the organisms that excrete ammonia are majorly aquatic.
- Excretion of ammonia is least energy intensive and takes place by the simple process of diffusion.