Question

Metabolic processes create toxic by-products; many of which contain nitrogen. Most freshwater fish will excrete the nitrogenous waste across their gills as ammonia. Since this will decrease the osmolarity of the freshwater fish, which of the following must the freshwater fish perform to maintain homeostasis?

• A. Production of uric acid to condense the ammonia waste and prevent water loss.
• B. Increasing temperature since ectothermic fish are dependent on heat for excretory systems to properly function.
• C. Uptake of sodium from the water through the gills to restore fluids to isotonic levels.
• D. Increase synthesis of proteins and nucleic acids, since nitrogenous waste products, such as ammonia, are produced through dehydration synthesis of these macromolecules.

Answer 1

The correct option is A Production of uric acid to condense the ammonia waste and prevent water loss.

Freshwater fishes have to regulate the osmolarity of the body fluids and they do so by converting ammonia into the uric acid and urea. They are also provided with efficient kidneys that remove the water quickly and reabsorb the essential solutes.

Hence, the correct answer is 'Production of uric acid to condense the ammonia waste and prevent water loss'