Maintaining a proper internal fluid environment is essential for any organism. Marine invertebrates whose body fluids are isotonic to sea water can face several problems when exposed to brackish water of estuaries or fresh water of lakes and rivers. Variation of internal osmotic concentration with external osmotic concentration in three marine invertebrates is shown in the graph.
Choose the correct statement.
(A) Nereis shows a better osmoregulatory capacity than shore crab.
(B) Spider crab shows the most effective regulation of osmotic concentration of body fluids among the three invetebrates.
(C) When in low salt conditions, body fluid of shore crab is hypertonic compared to surrounding medium.
(D) In order to survive in low salt conditions, spider crab has to take in salts from surrounding water.
