Osmoregulation = keeping water and salt
balanced in the body
• Question 1: why is this important
– Come up with three reasons
• Question 2: What water and salt problems do
the following organisms face?
– Freshwater fish
– Marine fish
– Marine birds
– Marine mammals
• Question 3: How might each group solve
those problems?
Definitions
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Solute
Solvent
Osmosis
Osmotic Pressure
Osmolarity
Hyperosmotic
Hypoosmotic
Osmoconformer
Osmoregulator
Solutes are dissolved particles in
solution (any type)
Water always moves from an area of low osmotic
pressure to an area of high osmotic pressure
osmotic pressure:
Osmosis:
Freshwater teleosts: Osmoregulators
Hyperosmotic to environment
Problems?
Solutions?
Active transport of salts via skin:
3 Na+
ClCl-
Cl-
2 K+
ATP
• Active transport of Na+ into animal
• Cl- follows passively (electric gradient)
Marine Strategies
Cl-
Na+
Cartilaginous fish
Marine teleosts: Osmoregulators
(hyposmotic to environment)
Problems?
Solutions?
Marine reptiles and birds…
How do
they get
rid of huge
salt load?
seawater
Salt glands!
Nasal fluid
urine
Salt glands
Na+ mOsm
seawater
470
sea snake
620
sea turtle
690
Marine Iguana
1000-1400
gull
600-900
cormorant
500-600
petrel
900-1100
• salt is excreted from the gland to outside the body
• more concentrated than sea water!
• mechanism is same in marine reptiles
-but salt gland is in different places
How do mammals make
concentrated urine?
Each nephron has a
loop of Henle:
nephron
loop
of
Henle
mammalian nephron:
Loop of Henle
mOsm
Cortex
Na+
Na+
Na+
Na+
Na+
Na+
Outer
Medulla
Inner
Medulla
Marine Mammals
Several Adaptations:
1. Long loop of henle in the kidney
--concentrated urine
--less water lost with waste
2. Diet
--carnivores, eating mostly
vertebrates
--vertebrates have lower osmolarity
3. Absence of sweat glands
Nitrogenous Wastes affect Water
Balance
Proteins
Nucleic acids
Nitrogenous waste products
AMMONIA
UREA
URIC ACID
Excretion
Tortoises and Turtles:
% of urinary nitrogen
Species
Habitat
Red-eared slider
Freshwater
Forest hinge-back
tortoise
Moist Terrestrial
Mediterranean spurthighed tortoise
Dry terrestrial
Texas tortoise
Desert
Ammonia
Urea
Uric Acid
• ammonia
Teleost fish
Amphibians
reptiles
• urea
chondrichthyes
Teleost fish
Amphibians
• uric acid
Amphibians
Birds and reptiles
reptiles
mammals
Terrestrial summary
• Water in:
– Food and drink
– Metabolic water
• Water out:
– excretion
– Evaporative water loss
• Adaptations in the desert?
– Extended loop of henle
– Reduced evaporative water loss
• (gain in camel nose)
– High dehydration tolerance