Question

Study the following statements regarding osmoregulatory adaptations in marine and freshwater fish and identify the correct statements: 
Statements 
I. Marine fishes actively excrete excess salt through their gills. 
II. Freshwater fishes have glomerular kidneys. 
III. Marine fishes face the problem of exosmosis. 
IV. Freshwater fishes have salt-excreting chloride cells. 
 

• A. I, II, and III
• B. I and II
• C. II and III
• D. Marine Fish: - Salt excretion via gills. - Drink seawater to combat dehydration.

Hint:

{Key Concepts:} (1) Marine Fish: - Salt excretion via gills. - Drink seawater to combat dehydration. (2) Freshwater Fish: - Absorb salt via gills. - Produce dilute urine (large glomeruli).

Answer 1

The Correct Option is A

Analysis of Statements:
- I. Correct: Marine fish use chloride cells in gills to actively excrete excess salt (NaCl).
- II. Incorrect: All fish have glomerular kidneys, but this is not unique to freshwater species.
- III. Correct: Marine fish face exosmosis (water loss) due to hypertonic seawater; they drink water and excrete salt.
- IV. Correct: Freshwater fish absorb salt via chloride cells (opposite of marine fish) to counter hypotonicity.

Conclusion: Statements I, III, and IV are correct.