1. Comparative Vertebrate Physiology Osmoregulation in non-mammalian vertebrates

2. Osmoregulation Strategies Osmoconformers (plasma > 290 mOsm) Osmoregulators (plasma ~ 290 mOsm)

3. Osmoregulation

4. Aquatic environment Euryhaline Estuarine, salt marshes Stenohaline Most other species

5. Aquatic environment Freshwater problems High amount of water intake Loss of body salts Problem Solution

6. Aquatic environment Saltwater problems Prone to losing water Build up of body salts Problem Solution

7. Terrestrial environment Problem is dehydration Solutions in lectures to come Nasal countercurrent exchange Water from food Metabolic water Salt glands Concentrate urine

8. Kidney/nephron structure

9. Renal processes Filtration What is filtered? Water and solutes What isn’t filtered? Protein Blood cells Basis for filtration Size and charge

10. Renal processes Reabsorption 99% of water & solutes Passive and active Proximal tubule (60-80%)

11. Renal processes Secretion Water and solutes (1%)

12. Vertebrates Functional unit is the nephron Components Glomerulus Proximal tubule Loop of Henle (birds, mammals) Distal tubule Collecting duct

13. Teleosts Freshwater Large glomeruli Dilute, copious ultrafiltrate Ions reabsorbed Dilute, copious urine

14. Teleosts Saltwater Small glomeruli “Concentrated”, little ultrafiltrate Ions secreted Isotonic, little urine

15. Amphibians Function resembles that of a FW teleost Nephron structure Dilute, copious ultrafiltrate 25 - 100 ml/Kg/hr Ions reabsorbed (99%) Copious, dilute urine 10 - 25 ml/Kg/hr

16. Amphibians Most solutes are reabsorbed distally

17. Reptiles Only have 1 kidney that is bi-lobed Kidney Caudal junction Vertebrae

18. Reptiles Nephron structure Lower GFR than amphibians 0.5 - 20 ml/Kg/hr Ion reabsorption (99%) Isotonic, little urine

19. Birds Tri-lobed kidneys Comprised of lobules Has cortex and medulla Cortex Medulla

20. Birds Nephron structure Bird Mammalian - Type

21. Birds Little ultrafiltrate (1 - 4 ml/Kg/hr) Ion and water reabsorption (99%) Slightly hyperosmotic urine

22. Urine to plasma osmolarity