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Animals excrete nitrogenous waste in many forms. In this article, we shall examine one such group called ammonotelic organisms.

What is Ammonotelism?

The process where certain organisms excrete nitrogenous waste in the form of ammonia is known as Ammonotelism.

Ammonia, which is highly water-soluble and which forms ammonium hydroxide (NH4 OH) directly injures cells by the alkaline caustic action. Therefore, the excretion of ammonia requires large amounts of water. A portion of uric acid is oxidized furthermore to form allantoic acid and allantoin. Teleost fish excrete allantoate or hydration product of allantoin. In most amphibians and fishes, allantoate is hydrolyzed into glyoxylate and urea. For few marine invertebrates, furthermore, hydrolyzation of urea to carbon dioxide and ammonia occurs. Creatine is formed in the liver from amino acids. The resultant creatinine is generated from creatine.

CategoryProduct formedSolubility in waterExamples
AmmonotelicAmmonia (highly toxic)Highly-soluble, therefore, needs plenty of water for its excretionFreshwater aquatic animals e.g. bony fish, Amoeba, etc.
UreotelicUrea                    (less toxic)Less soluble, thus needs less water for excretionMammals including man, dog etc, marine fishes and amphibians like frog and toad
UricotelicUric acid          (least toxic)Insoluble solids or semi-solid. Needs very little water just to flush out the uric acidBirds, reptiles, and insects.

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