Osmoregulation in freshwater and marine fish:
Mechanism of osmoregulation in fish enables them to maintain a stable internal environment despite the changing osmotic conditions of their surrounding water.
Osmoregulation in Freshwater Fish:
Osmoregulation in freshwater fish involves processes that allow them to regulate water and ion balance in an environment where the surrounding water has a lower salt concentration than their bodily fluids.
| Aspect |
Description |
Examples of Freshwater Fish |
| Environment
|
· Freshwater has hypotonic surroundings having lower salt concentration compared to fish’s body fluids. |
Goldfish
· Exert copious amounts of dilute urine. They have well-developed gill chloride cells.
· Obtain water and ions from their food.
Catfish
· Catfish actively excrete excess ions.
· Catfish can adjust their ion-transporting cells.
Trout
· They also excrete dilute urine to manage their water balance.
· Trout absorb ions from their diet.
Carp
Carp have efficient ion-transporting cells in their gills
Produce dilute urine and taking in water through osmosis. |
| Specialized gill chloride cells
|
· Freshwater fish have specialized cells in their gills known as chloride cells.
· To maintain a proper ion balance and prevent the loss of essential electrolytes, these cells actively transport ions, including sodium (Na+) and chloride (Cl–), out of the fish’s body into the surrounding water. |
| Water Uptake |
· Freshwater fish absorb water through gills and skin by osmosis. |
| Production of Dilute Urine |
· Freshwater fish excrete large volumes of dilute urine to eliminate excess water. |
| Limited Drinking |
· Freshwater fish do not drink water actively but may ingest small amounts of it. |
| Ion Reabsorption |
· Freshwater fish actively absorb ions (Na+, Cl–) from their food to maintain proper ion balance. |
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|
Osmoregulation in Marine Fish:
Osmoregulation in marine fish involves processes that enable them to regulate water and ion balance in an environment where the surrounding water has a higher salt concentration than their bodily fluids.
| Aspect |
Description |
Examples of Marine Fish |
| Environment |
· Seawater has hypertonic surrounding having higher salt concentration as compared to fish’s body fluids. |
Salmon
· Salmon actively absorb ions, like sodium and chloride, from the seawater.
· Salmon get water and ions from their diet.
Clownfish
· Clownfish drink small amounts of water.
Flounder
· Flounder have an impermeable skin for preventing excessive water loss through the skin.
Sharks
· Sharks have specialized salt glands located near their rectal glands.
· These glands actively excrete excess salts from their bodies.
Tuna
· Tuna produce concentrated urine to save water.
· They also obtain additional water and ions through their diet.
Clownfish
· Clownfish can adjust their osmoregulation mechanisms. |
| Specialized gill chloride cells |
· Specialized cells actively transport ions (Na+ and Cl–) from the surrounding water into the fish’s body through gills. |
| Impermeable skin |
· Skin is impermeable to water to prevent excessive water loss. |
| Drinking Small Amounts of Water |
· Marine fish drink small amounts of water. |
| Salt Gland |
· Some marine fish have specialized salt glands to actively excrete excess salts from their bodies. |
| Production of concentrated urine |
· Marine fish produce small amount of concentrated urine to minimize water loss. |
| Taking ions through Diet
|
· Marine fish obtain water and ions from their food to help maintain hydration and ion balance.
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