[Campbell Biology P.1041] Which of the following statements correctly describes the osmoregul... | Practice Question

Which of the following statements correctly describes the osmoregulatory mechanisms in marine bony fishes?

  • A: Their kidneys primarily excrete large volumes of dilute urine to eliminate excess water absorbed from the hypertonic environment.
  • B: They actively absorb monovalent ions like Na+ and Cl- from the surrounding seawater via specialized chloride cells in their gills.
  • C: Their kidneys effectively eliminate divalent ions such as Ca2+, Mg2+, and SO42- by secreting them into the proximal tubules.
  • D: They possess extensive loops of Henle and long distal tubules to concentrate urine and conserve water.

Explanation

Marine bony fishes have kidneys adapted to excrete excess divalent ions Ca2+, Mg2+, SO42- by secreting them into the proximal tubules, as they constantly drink seawater. Their kidneys produce very little urine and their nephrons often lack distal tubules and have small/absent glomeruli, reflecting their need to conserve water and excrete salt via other mechanisms, primarily chloride cells in the gills for monovalent ions.