Osmotic Regulation in Aquatic Animals

Freshwater and marine animals have problems in regulating their water. Freshwater fishes are hypertonic to the environment so they have a tendency to pick up water by osmosis. In turn, they lose salts to the environment. On the other hand, salt water fishes are hypotonic to the environment so they have a tendency to lose water to the environment.

• How does a freshwater fish regulate this uptake of water and loss of salts?
• How does a saltwater fish regulate its water and salts?
• Do you think that a starfish regulates its water and salts like a saltwater fish does? Defend your answer.
• Do you think that a crayfish regulates its water and salt like a freshwater fish does? Defend your answer.
• Some animals are called osmoconformers while other are called osmoregulators. What do these terms mean in studying osmotic regulation in animals?
• Is it possible for an animal to be an osmoconformer but an ionic regulator?

Kidneys and accessory organs play an important role in osmotic regulation.

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