Which process facilitates osmoregulation if a saltwater fish migrates from the ocean into a freshwater river?

💡 Explanation

When a saltwater fish enters freshwater, the external environment becomes hypotonic; water diffuses *into* the fish's body while salts are lost to the environment via osmosis. Kidney tubule salt reabsorption decreases minimizing salt loss leading to increased dilute urine production to excrete excess water. Therefore lessened salt retention results, rather than altered gill excretion or more water intake behaviors required by saltwater or blocking all water by the scales.

• Which outcome results when countercurrent exchange fails during antifreeze glycoprotein (AFGP) synthesis in Antarctic fish?
• Which mechanism dictates nocturnal moths navigating by starlight?
• Which outcome occurs when a basking sea lion experiences overheating during rest?
• Which mechanism explains the generation of lift in a soaring albatross with slotted primary feathers?
• Which outcome is directly optimized by the countercurrent exchange mechanism in fish gills submerged in cold water?
• Which metabolic consequence ensures survival when groundhog heart rate slows exceedingly during hibernation?