Final answer:
Bony fishes primarily excrete ammonia through their gills, while ureotelic fish retain and excrete urea via the kidneys, which helps maintain osmotic balance and involves a significant amount of their energy for regulation.
Step-by-step explanation:
Excretion of Nitrogenous Waste in Bony Fishes and Ureotelic Fish The primary method of excreting nitrogenous waste in bony fishes is c. Excretion of ammonia through gills. Bony fishes are able to do this efficiently in their aquatic environment. However, some fish convert ammonia to urea for excretion through a process known as the urea cycle, mainly because b. Urea helps in maintaining a hyperosmolar blood environment, which is important for osmoregulation, particularly in marine species where water conservation is crucial.Ureotelic fish, which excrete urea as the primary waste, maintain osmotic balance in their blood primarily through c. Through a process called urea retention in the kidneys.
This process helps to maintain the necessary balance between salt and water in the body. The estimated energy cost of osmotic regulation in ureotelic fish is b. 10-15% of standard metabolism. This energy is utilized to regulate the concentration of urea and salts in their body fluids.Excess urea is ultimately excreted in ureotelic fish mainly c. Through the kidneys, where it is filtered out of the blood and then excreted. Some fish directly excrete ammonia rather than converting it to urea because b. Ammonia excretion is more energy-efficient compared to the energy-consuming process of urea formation.