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Difficulty: HardMorphological and Physiological Adaptations to Environments

Freshwater teleost fishes maintain osmotic balance in their environment by continuously drinking surrounding water and excreting small amounts of highly concentrated urine.

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Answer

The statement is False. Freshwater teleost fishes live in a hypotonic environment relative to their body fluids, causing water to enter their bodies passively via osmosis across the gills. To maintain osmoregulation, they avoid drinking water, produce large volumes of dilute urine, and actively absorb essential ions across their gills.
The statement is false because freshwater teleost fishes are hyperosmotic to their hypotonic environment. Water continuously enters their body by osmosis across the gills, so drinking water is unnecessary and harmful. They excrete large volumes of dilute urine to eliminate excess water while actively pumping salts into their blood using specialized chloride cells in their gills.

Step-by-Step Solution

1
Analyze the osmotic gradient between freshwater teleosts and their environment.
Freshwater teleost body fluids have a higher solute concentration (hyperosmotic) than the surrounding fresh water (hypotonic).
Understanding relative osmolarity determines the direction of passive water movement via osmosis.
2
Determine the direction of passive water movement and ion flux.
Water passively diffuses into the fish across permeable membranes (gills), while salts tend to diffuse outward into the water.
Water moves from lower solute concentration (environment) to higher solute concentration (fish body fluids).
3
Evaluate the physiological adaptations required to counter this osmotic stress.
The fish must expel excess incoming water by producing large volumes of dilute urine and avoiding water ingestion, while actively absorbing salts via gill chloride cells.
Drinking water or producing concentrated urine would aggravate osmotic overload and solute loss.
4
Compare the required physiological mechanisms with the given statement.
The statement claims freshwater fishes drink large quantities of water and produce concentrated urine, which accurately describes marine teleosts, not freshwater teleosts.
The statement incorrectly applies marine teleost osmoregulatory adaptations to freshwater teleosts.

Key Concept

Osmoregulation in Freshwater Teleost Fishes
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Topics

Morphological and Physiological Adaptations to Environments

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