8.3.1 Osmoconformers and Osmoregulators

Animals may be either osmoregulators or osmo-conformers with respect to their external environment. Osmoconformers change the osmotic concentrations of their body fluids according to the surrounding medium, while osmoregulators maintain internal osmotic concentrations different from the surrounding medium.

Definition

Osmoconformers: Those animals that change the osmotic concentrations of the body fluids according to that of surrounding medium are called osmo-conformers. These are isotonic to their external environment.

Osmoregulators: Those animals that can maintain internal osmotic concentrations different from the surrounding medium are called osmoregulators. Such animals are hypotonic or hypertonic to their environment.

Main Idea

• Animals may be osmoregulators or osmo-conformers.
• Osmoconformers change osmotic concentrations with the environment.
• Osmoconformers are isotonic to their environment.
• Osmoregulators maintain internal osmotic concentrations different from the environment.
• Osmoregulators are hypotonic or hypertonic to their environment.

Core Concept

• Osmoconformers = change osmotic concentrations with environment
• Osmoconformers = isotonic to environment
• Osmoregulators = maintain internal osmotic concentrations different from environment
• Osmoregulators = hypotonic or hypertonic to environment
• Examples of osmoconformers = marine invertebrates, some freshwater invertebrates, Myxine, elasmobranchs
• Examples of osmoregulators = almost all freshwater animals, most marine vertebrates
• Osmolytes = organic substances that increase osmotic concentration
• Urea and TMAO = osmolytes in marine vertebrates

Detailed Explanation

Osmoconformers

• Those animals that change the osmotic concentrations of the body fluids according to that of surrounding medium are called osmo-conformers.
• These are isotonic to their external environment.
• These include:
• All marine invertebrates
• Some freshwater invertebrates
• Some marine vertebrates like Myxine (hag fishes) and elasmobranchs (sharks and rays)

Osmoregulators

• Those animals that can maintain internal osmotic concentrations different from the surrounding medium are called osmoregulators.
• Such animals are hypotonic or hypertonic to their environment.
• Almost all of the freshwater animals and most of the marine vertebrates are osmoregulators.

Science Titbits

• The unusual higher osmotic concentration than other vertebrates of marine habitat is maintained by high levels of urea and trimethylamine oxide (TMAO) in the blood.
• These organic substances are called osmolytes because they increase the osmotic (solutes) concentration.
• In most vertebrates, the level of urea to this high concentration would damage the proteins because it is chaotropic (denaturing) agent that disrupts non-covalent and ionic bonds between amino acids residues, but the presence of TMAO helps to stabilize these protein molecules against the adverse effects of urea.

Summary Table of Osmoconformers and Osmoregulators

Summary of Osmolytes

Intermediate Level

Osmoconformers and Osmoregulators

Osmolytes

Examples of Osmoconformers and Osmoregulators

Formula / Mathematical Form

Not applicable to this topic.

Solved Example

Not applicable to this topic (descriptive topic).

Important Points

• 1. Osmoconformers change osmotic concentrations with environment.
• 2. Osmoconformers are isotonic to environment.
• 3. Osmoregulators maintain internal osmotic concentrations different from environment.
• 4. Osmoregulators are hypotonic or hypertonic to environment.
• 5. Examples of osmoconformers: marine invertebrates, some freshwater invertebrates, Myxine, elasmobranchs.
• 6. Examples of osmoregulators: almost all freshwater animals, most marine vertebrates.
• 7. Osmolytes are organic substances that increase osmotic concentration.
• 8. Urea and TMAO are osmolytes.
• 9. Urea is a chaotropic agent.
• 10. TMAO stabilizes proteins against urea.
• 11. Osmoregulation is essential for survival.
• 12. It keeps cells working.
• 13. It maintains water balance.
• 14. It maintains solute balance.
• 15. It is a part of homeostasis.

Remember

• - Osmoconformers = change osmotic concentrations with environment
• - Osmoconformers = isotonic to environment
• - Osmoregulators = maintain internal osmotic concentrations different from environment
• - Osmoregulators = hypotonic or hypertonic to environment
• - Examples of osmoconformers = marine invertebrates, some freshwater invertebrates, Myxine, elasmobranchs
• - Examples of osmoregulators = almost all freshwater animals, most marine vertebrates
• - Osmolytes = organic substances that increase osmotic concentration
• - Urea and TMAO = osmolytes in marine vertebrates

Common Mistakes

• 1. Confusing osmoconformers and osmoregulators — Osmoconformers = change with environment; osmoregulators = maintain different concentrations.
• 2. Mixing up the tonicity — Osmoconformers = isotonic; osmoregulators = hypotonic or hypertonic.
• 3. Forgetting the examples — Marine invertebrates = osmoconformers; freshwater animals = osmoregulators.
• 4. Mixing up the role of osmolytes — Increase osmotic concentration.
• 5. Forgetting the role of urea — Chaotropic agent.
• 6. Forgetting the role of TMAO — Stabilizes proteins.
• 7. Believing osmoregulation is not important — It is essential for survival.
• 8. Mixing up the types of animals — Freshwater animals are osmoregulators.
• 9. Confusing osmoregulation and thermoregulation — Osmoregulation = water balance; thermoregulation = temperature balance.
• 10. Thinking all marine animals are osmoconformers — Most marine vertebrates are osmoregulators.

Quick Revision

Animals may be either osmoregulators or osmo-conformers with respect to their external environment. Those animals that change the osmotic concentrations of the body fluids according to that of surrounding medium are called osmo-conformers. These are isotonic to their external environment. These include all marine invertebrates, some freshwater invertebrates and some marine vertebrates like Myxine (hag fishes) and elasmobranchs (sharks and rays). Those animals that can maintain internal osmotic concentrations different from the surrounding medium are called osmoregulators. Such animals are hypotonic or hypertonic to their environment. Almost all of the freshwater animals and most of the marine vertebrates are osmoregulators. The unusual higher osmotic concentration than other vertebrates of marine habitat is maintained by high levels of urea and trimethylamine oxide (TMAO) in the blood. These organic substances are called osmolytes because they increase the osmotic (solutes) concentration. In most vertebrates, the level of urea to this high concentration would damage the proteins because it is chaotropic (denaturing) agent that disrupts non-covalent and ionic bonds between amino acids residues, but the presence of TMAO helps to stabilize these protein molecules against the adverse effects of urea.

60-Second Revision

• Osmoconformers = change osmotic concentrations with environment
• Osmoconformers = isotonic to environment
• Osmoregulators = maintain internal osmotic concentrations different from environment
• Osmoregulators = hypotonic or hypertonic to environment
• Examples of osmoconformers = marine invertebrates, some freshwater invertebrates, Myxine, elasmobranchs
• Examples of osmoregulators = almost all freshwater animals, most marine vertebrates
• Osmolytes = organic substances that increase osmotic concentration
• Urea and TMAO = osmolytes in marine vertebrates
• Warning: Osmoconformers are isotonic to their environment; osmoregulators are hypotonic or hypertonic

NEXT TOPIC

• Chapter:
• 8. Thermoregulation and Homeostasis

• Topic:
• 8.3.2 PROBLEMS FACED BY OSMOREGULATORS

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