In freshwater the release of aldosterone and neurohypophysea

In freshwater, the release of aldosterone and neurohypophyseal hormones into the blood results in increased hydration of body fluids. Why? As water salinity levels increase, what negative impact would the release of aldosterone and neurohypophyseal hormones have on an amphibian?

Solution

10.As salinity continues to increase, aquatic amphibians will begin to lose water rapidly across the skin via osmosis. Water movement via osmosis is bidirectional; water molecules passively fl ow down their concentration gradient. As water leaves the frog, the osmolality of its blood begins to increase. This stimulates the release of hormones such as aldosterone and neurohypophyseal hormones, which work in concert to increase active Na+ transport across the skin into the body and increases the reabsorption of Na+ within the proximal convoluted tubules. In dilute freshwater, these  hormones would actually help the amphibian remain hydrated, but work against the animal as salinity levels increase.

11.Increasing water salinity levels trigger the kidneys to slow the loss of body water by decreasing the rate of glomerular fi ltration, thus reducing the volume of urine produced. The nephrons of amphibians are unable to produce hyperosmotic urine so a decrease in urine production is likely their best option. However, as the rate of glomerular filtration slows and the production of urine decreases, ammonia is not removed as quickly as it should be from the blood. If these renal system adjustments are only needed for a very short period of time the animal can survive, but long-term environmental changes can overwhelm the capabilities of the renal system.