Question

Some sharks live in freshwater. How should the kidneys of marine and freshwater sharks function?

Answer 1

Usually all sharks live in marine water. only few sharks live in boyh marine water and fresh water. Ex: bull sharks

The difference is the salinity of water. So their organs have shift some of their functions to maintain salinity by osmoregulation. in the sharks, kidneys control the process of dsmoregulation.

Osmoregulation is the ability of an organism to maintain a constant concentration of water in its body. Freshwater and saltwater fish both osmoregulate

The kidneys of bull sharks are gradually adjusted to suit the salinity of the water where they live in.

When they want to move from marine water, they can migrate gradually into freshwater and their kidneys remove less salt and more urea from the bloodstream through urination, essentially reversing the normal marine osmoregulation. This adaptation allows bull sharks to live entirely in estuaries or freshwater.

In sharks, the normal mechanism of Osmoregulation in a marine environment is the high concentration of urea and other biological solvents in their blood and the removal of excess salt from their bloodstream through urination.The higher concentration of urea and other solvents allows them to absorb water from their marine surroundings.. This is regulated primarily by the kidneys in marine sharks.