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Question #46316
The Question
Euryhaline teleosts can tolerate wide fluctuations in environmental salinity. When migrating from an estuary to a highly hypersaline marine environment, these fish actively excrete excess monovalent ions via gill ionocytes to maintain internal osmolarity. However, if the environmental osmotic gradient exceeds their regulatory capacity, a secondary systemic failure occurs. Based on the functional trade-off in gill ionocytes, which of the following best describes this failure?
Options
- A.
Metabolic alkalosis, due to the over-activation of the Cl⁻/HCO₃⁻ exchanger for salt excretion depleting internal bicarbonate reserves.
- B.
Metabolic acidosis, due to the excessive retention of H⁺ ions as the Na⁺/H⁺ exchanger reverses its direction to excrete sodium.
- C.
Respiratory alkalosis, due to hyperventilation required to meet the high ATP demand of the Na⁺/K⁺ ATPase pumps in chloride cells.
- D.
Respiratory acidosis, due to the thickening of the gill epithelium to prevent water loss, which severely impairs CO₂ diffusion.
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
Chloride_Shift|Osmoregulation_in_Aquatic_Adaptations|Renal_Threshold_Concept
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: The integration of osmoregulation and acid-base homeostasis.
Students typically view gills only as respiratory organs or simple salt-excreting pumps (NCERT base).
The advanced application requires recognizing the shared transport mechanisms (like the Cl⁻/HCO₃⁻ exchanger) that force a physiological trade-off.
When salinity stress is extreme, osmoregulation takes precedence, causing a secondary failure in acid-base balance.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Breathing and Exchange of Gases - Class 11 |
| Concept | Chloride Shift (Hamburger Phenomenon) |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |