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Hypo-osmotic - Hypo-ionic Regulation

1000. e.g. Uca, Artemia. ECF osmolarity (mOsm). marine teleosts. 1000. 0. Medium osmolarity (mOsm). Hypo-osmotic - Hypo-ionic Regulation. Crustacea:. Uca - hemolymph Na = 447 mM in 175% sw (~ 800 mM). Artemia - hemolymph Na = 300 mM in as much as 4-5 M NaCl !!!. H 2 O ions.

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Hypo-osmotic - Hypo-ionic Regulation

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  1. 1000 e.g. Uca, Artemia ECF osmolarity (mOsm) marine teleosts 1000 0 Medium osmolarity (mOsm) Hypo-osmotic - Hypo-ionic Regulation

  2. Crustacea: • Uca - hemolymph Na = 447 mM in • 175% sw (~ 800 mM) • Artemia - hemolymph Na = 300 mM • in as much as 4-5 M NaCl !!!

  3. H2O ions H2O ion(s) Marine Teleost 200 mM NaCl 400 mOsm 500 mM NaCl 1000 mOsm • Solutions: • drink sea water • Problems: • osmotic water loss • diffusive salt gain • active salt extrusion • ion uptake by gut

  4. Na = 450 K = 9 Cl = 520 s.w. H2O ions Blood: Na = 200 K = 4 Cl = 190 Fluid absorption across teleost gut: NO ACTIVE TRANSPORT OF H2O! Must move ions and cause H2O to move by osmosis ant. mM post. Na = 100 K = 6 Cl = 90 Na = 20 K = 0.8 Cl = 50 >95% of salts absorbed ~75% of H2O absorbed

  5. HCO3- H+ ADP + Pi ATP ATP Na+ Cl- K+ Na+ ADP + Pi Cl- lumen of gut Cl- Na+ blood (serosa)

  6. From Evans et al. (1999) J. Exp. Zool. 283: 641-652. CC - mitochondria-rich chloride cell AC - accessory cell, PC - pavement cell

  7. Apical pit of chloride cell on surface of gill lamella From Evans et al. (1999) J. Exp. Zool. 283: 641-652.

  8. Gill epithelial cell Blood

  9. Isosmotic - Hypo-ionic Regulation mM Na Cl TMAO + ureamOsm Sea Water 450 500 0 1000 Hagfish Plasma 549 550 0 1150 Teleost Plasma 160 200 0 400 Elasmo. Plasma 290 300 350-400 1000

  10. ion(s) S.W. 500 mM NaCl 1000 mOsm 300 mM NaCl 1000 mOsm Problem: Diffusive salt gain Solution: Active salt excretion

  11. H2N C = O H2N urea CH3 H3C N = O CH3 trimethylamine oxide (TMAO) Elasmobranchs retain nitrogenous compounds as osmotic effectors:

  12. Urea and TMAO are reabsorbed from the urine. mM Na Cl TMAO + ureamOsm Sea Water 450 500 0 1000 Plasma 250 250 420 1000 Urine 250 250 110 800 Rectal gland fluid 500 500 20 1000 Salt is excreted via rectal gland and chloride cells in the gills.

  13. 1000 e.g. estuarine crustaceans ECF osmolarity (mOsm) e.g. freshwater fish & crustaceans 1000 0 Medium osmolarity (mOsm) Hyperosmotic-Hyperionic Regulation

  14. antennal gland H2O ions H2O ion(s) Freshwater crayfish, Astacus 150 mM NaCl 300 mOsm 2 mM NaCl 5 mOsm • Solutions: • produce copious urine • Problems: • osmotic water gain • diffusive salt loss • decrease permeability • active ion uptake • urinary salt loss

  15. NaCl Freshwater Fish (Teleost) Don’t drink the water Na+ Cl- Voluminous, dilute urine

  16. Water Gill Epithelium

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