Vertebrate Osmoregulation

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Vertebrate Osmoregulation

• Comparative Animal Physiology

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Today
I. Water balance in elasmobranchs II. Salt glands
in reptiles and birds III. Gills as
osmoregulatory organs IV. Comparison of transport
cells function V. Overview of osmoregulation in
verts VI. Animal of the Day
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Shark/ray rectal salt gland
1. Excretes NaCl enriched urine but isoosmotic to
blood with urea/TMAO. 2. Water follows passively
but not urea/TMAO. 3. Save urea, dilute
urine (save or excrete H2O?)
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Epithelial functions
Mammal ascending loop
Shark/ray rectal gland
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Birds employ counter-current salt gland

• Drink seawater
• Increase NaCl in ECF decrease ECF vol. as H2O
  into gut
• Further inc. NaCl in ECF, then H2O follows
• I.f.f. high NaCl hypothal. high ECF vol. -gt
  then, salt gland activation
• 2-3 X plasma NaCl
• Why not in mammals?

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Birds employ counter-current salt gland
low Na
low Na
high Na
high Na
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Epithelial functions
Reptile/bird salt gland
Frog skin
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Epithelial functions
Teleost in salt water
Teleost in fresh water
prolactin
Transition to SW
Cortisol G.H.
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Overview of water balance
1. Na/K ATPase is located on basal surface of
epithelium. (signif. age of metabolism!) 2.
Apical membrance xporters are passive. 3. Vert
kidneys are usu. glomerular (if not?). FW
teleosts use kidneys to excrete H2O SW teleosts
use to excrete divalent ions 4. Only birds
mammals have loop of Henle. 5. Fish use gills
reptiles use salt glands too.
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THE ANIMAL OF THE DAY (PhChordata,
GeOnchorhynchus)
Salmon are anadromous (stenohaline euryhaline)