Vertebrates have developed various mechanisms of osmoregulation to maintain homeostasis as their environments present different challenges of varying salt and water concentrations. Marine animals face hypotonic environments and must conserve water while excreting excess salts, using gills or kidneys. Freshwater animals face hypertonic environments and must conserve salts while excreting excess water, also using gills or kidneys. Terrestrial animals face water loss and must minimize evaporation while maximizing water retention and concentrated urine production through specialized organs like the kidney.

1. OSMOREGULATION IN
VERTEBRATES
M.ANGEL HELEN

2. CONTENTS
•DEFINITION
•MECHANISM OF OSMOREGULATION
•OSMOSIS AND OSMOLALITY
•OSMOCONFORMERS
•OSMOREGULATORS
•OSMOREGULATORY ORGANS IN VERTEBRATES
•IN MARINE VERTEBRATES
•IN FRESH WATER VERTEBRATES
•IN TERRESTRIAL VERTEBRATES

3. HOMEOSTASIS
It is a maintaining of steady state equilibrium in the
internal environment of an organism.
TWO PROCESS THAT MAINTAIN HOMEOSTASIS
• OSMOREGULATION – Regulate solute concentration and balances the
gain and loss of water.
• EXCRETION - It is the process of removal of metabolic wastes from
the body.

4. definition
• The process by which the movement of water takes place.
• Animals as well as plants contain a large amount of water.
• In an animal’s body water may enter the result of drinking.
• The more or less steady state of water contents - maintained - between the
amount of water.
• The term osmoregulation was coined by HOBER in 1902.

5. • Different organisms have different limits of tolerance both for water.
• Animals whose body fluids and blood have the same concentration as
that of surrounding medium is known as isotonic.
• Animals which live in a medium of a lower salt concentration is known
as hypotonic.
• Animals which live in a medium of high salt concentration is known as
hypertonic.

6. OSMOSIS AND OSMOLALITY
• A process by which molecules of solvent tend to pass through semi permeable
membrane from a less concentrated solution into a more concentrated
one.(hypo-osmotic to hyper-osmotic).
• OSMOTIC CONCENTRATION- Number of osmoles(units) of solutes per litre
of solution. i.e., total concentration of all solutes in the organism.
• OSMOLALITY- Movement of water across a selectively permeable membrane.
If two solutions are iso-osmotic, the movement of water is equal in both
directions.
• If two solutions differ in osmolality, the net flow of water is from the hypo-
osmotic to the hyper osmotic solution.

7. OSMOCONFORMERS
• Osmoconformers are those animals which are osmotically dependent.
• Those animals are having a high tissue tolerance and can survive such
changes as long as their metabolic functions can proceed effectively.
• Osmotic regulation is practically absent but ionic regulation is essential.
• Eg; HAG FISH.

8. OSMOREGULATORS
• Osmoregulators are those animals which are osmotically stable
(independent) and are able to maintain their internal osmotic
concentration.
• In general osmoconformers can tolerate greater variations in their internal
environment than osnoregulators.
• Osmoregulators can tolerate greater variation in their external
environments than osmoconformres.
• So animals change in volume ( due to alternations of water content ) as
the external osmotic concentration changes.

9. MECHANISM OF OSMOREGULATION
• To maintain the internal osmotic concentration to an optimum or at a constant
level animals have developed various types of adaptations.
• One of these is a reduction in the area of permeability.
• Another is the reduction in the permeability of the exposed area.
• Loss of salts and water may be compensated by their absorption through some
part of the excretory system.

10. OSMOREGULATORY ORGAN IN
VERTEBRATES
MAIN ORGAN – Kidney through urine production.
OTHER ORGANS- Skin, lungs, gills and digestive system.

11. 3 MAJOR ENVIRONMENT
• Marine environment
• Freshwater environment
• Terrestrial environment
1. The nature of osmoregulatory problem is quite different in
these environment.
2. Vertebrates live successfully in a wide range of habitats-
freshwater, the ocean, tidal regions and on land including desserts.
3. Animals inhibiting their exhibit variety of osmoregulatory
adaptations.

12. OSMOREGULATION IN MARINE
ANIMALS
• Marine animals such as hag fishes, bony fishes, elasmobranch fishes, sea birds,
marine reptiles and marine mammals are hypoosmotic to their surrounding
environment.
• In bony fishes the body fluids are hypotonic in relation to the surrounding
environment.
• This is solved by a special gland cells called CHLORIDE SECRETARY
CELLS in the gills that excrete excess salt.
• The water molecules are diffused into the gut.

13. • The marine cartilaginous fishes have solved this problem in a different
way. They have same amount of salts in their body fluids.
• Finally they excrete large amounts of dilute or isotonic urine.
• Excess salt is also excreted by kidneys.
• High concentration of urea makes the body fluids slightly hypertonic to
sea water.

14. MARINE CARTILAGENOUS FISH- SHARK

16. FRESH WATER VERTEBRATES
• All fresh water animals are hypotonic to the surrounding water.
• Animals tend to loose water osmotically.
• They also take in salt.
MECHANISM EVOLVED TO MAINTAIN HOMEOSTASIS IN
TELEOSTS
• To compensate the water lose animals drink large quantity of water.
• Intestinal membrane also absorb water and salts and most of them are passed out with faeces.
• Some salts are excreted by kidneys.
• Some absorbed salts such as Nacl, K, Cl are eliminated by active transport through the gill
membranes .
• Chloride secreting cells are present at the base gills and very little urine are excreted by kidneys.

17. FRESHWATER FISHES

18. TELEOSTS

19. • In general it has been suggested that the renal system of fresh water -
remove sugar, salts and other useful materials.
• They possess semipermeable areas for respiratory and digestive purposes.

20. MAIN PROBLEM –Salt concentration of body fluids is higher than environment. So hypertonic to their medium.
ADAPTATIONS IN FRESH WATER FISHES
• Body covered by scales and mucous secretion retard the passage of water into the body.
• Drink little or no water.
• Some water leaves the body through gills.
• Kidneys are adapted to excrete large amount of dilute urine.
• In Amphibians like Rana and Xenopus they are hypotonic to the watery medium.
• Rana carnivora – crab eating frog can tolerate sea water.
• Bufo and Viridis tolerate environmental salinities.
• Any extra water gained through food can be removed by kidneys.
• They produce dilute urine so excess water can be eliminated.

21. • Trionyx spinifer (turtle) conserves sodium by active reabsorption.
• Fresh water birds and mammals – hypertonic.
ADAPTATION
• Integument less permeable to both water and salts.
• Does not drink water.
• Active reabsorption of salts in kidneys, tubules and dilute urine is
produced.
• F.W birds - Goose, swamp, Flamingos
• F.W – Hippopotamus, Otters, River Dolphins.

22. OSMORECULATION IN FROG

23. TERRESTRIAL ANIMALS
• The terrestrial habitat lacks both water and salts in the surrounding
medium so they often loss water and salt.
• Therefore the terrestrial animals usually drink large amount of water.
• In terrestrial animals such as reptiles, birds, mammals and some
crustaceans and annelids - physiological adaptations to meet the osmotic
problem.

24. AMPHIBIANS - Inhabit moist environment.
ADAPTATIONS
• Reduction of permeability of the skin.
• Seek habitat of high humidity whenever air is dry.
• High tolerance of dessication.
• Rapid absorption of water whenever available.
• Excrete urine and absorb water from urinary bladder.
EXAMPLE
• Urinary bladder acts as a water reservoir in DESERT FROG – Chiroleptes.
• Urinary bladder volume is large in Bufo congnotus.

25. TERRESTRIAL REPTILES
• Water loss from skin is minimised due to heavy keratinisation - impermeable
to water.
• Poikilothermic so characterised by low respiratory and metabolic wastes-
evaporation of water through respiration is reduced.
• Trachysarus(desert lizard) has glomerular surface - reduced so eventually urine
formation is reduced.
• Urinary bladder absent, ureters opens into cloaca and cloacal regions absorbs
water from faecal content.
• Excrete uric acid which requires very little water.

26. TERRESTRIAL BIRDS AND MAMMALS
• Maintain constant body temperature and have a high rate of metabolism.
• Unique capacity to produce urine and have hyperosmotic to blood.
ADAPTATION OF TERRESTRIAL BIRDS
• Conserve water- uric acid.
• By efficiently reabsorbing water.
• Has unique capacity of producing hyper osmotic urine.
ADAPTATION TO TERRESTRIAL MAMMALS
• Excrete urea.
• Produce concentrated urine.
• Water need is satisfied by drinking it.
• Utilise metabolic water.

27. TERRESTRIAL BIRDS AND MAMMALS

28. DESERT MAMMALS
• These animals which inhabit in hot dry region.
• They have adapted to a lack of drinking water as they obtain water
entirely from the metabolic reaction.
• EX: Dipodomys spectabitis.(kangroo rat)

29. KANGROO RAT
• It is found in some of the hottest and driest regions of South western United
States.
• It eats only dry seeds and never drinks water. It has no sweat glands.
• It produces very dry faeces and excretes a very concentrated urine.
CAMELS
• It can go for a long periods without water in hot, dry deserts.
• It can lose as much as 40 % of the water in its body fluids and still survive.
• A dehydrated camel appears very thin as if from starvation - drinks water - body
fluids- restored- normal volume.

30. • DESERT MAMMAL CONTENT
• Food materials vary in their metabolic water potentials. Depend on
metabolic water totally.
• 1g of CHO produces 0.6g of water.
• 1g of protein produces 0.4g of water.
• 1g of fat produces 1.07g of water.
• Fats give maximum output - so desert animals feed on fat rich dry
seeds.

32. VAMPIRE BAT FROM MEXICO
Feeds on blood so large quantities of water
incorporated in body.
In other animals the osmoregulation is
performed by sweat glands, mouth, tongue, lungs, kidney.

33. REFERENCE:
Animal physiology by Verma and Agarwal.