1. Comparative Vertebrate Physiology
Extrarenal mechanisms of osmoregulation

2. Lecture summary Fish: gills Amphibians: Integument/urinary bladder
Reptiles and birds: Salt gland/lower intestine
Mammals: Nasal exchange + kangaroo rat

3. Marine teleosts

4. Marine teleosts- chloride cells
Operation
Na/K pump
Na/Cl/K cotransporter
Na and Cl transported into seawater
Chloride cell (note mitochondria)

5. Freshwater teleosts Pavement cells pump Na+ into blood Pavement cell
Chloride cell

6. Amphibians Permeable integument High rates of respiration and EWL
Desert adapted frogs

7. Amphibians Permeable urinary bladder
Recycling water-urine is more concentrated

8. Reptiles Salt gland location Supraorbital Lingual NaCl or KCl
Salt secretion droplets

9. Reptiles & birds-salt gland
Salt gland cells

10. Salt gland Function (same as chloride cell) Na/K pump
Na/Cl/K cotransporter
Na and Cl transported into environment

11. Reptiles: Lower Intestine
Cloaca
Urinary bladder in reptiles only
Purpose: Na+, K+, Cl-, water absorption

12. Birds: Lower intestine
Cloaca (temporary storage organ)
No urinary bladder
Purpose: Na+, K+, Cl-, water absorption

13. Mammals
Strategies
Keep mouth closed
Nasal countercurrent exchange

14. Nasal countercurrent exchange

15. Mammals
Desert adaptations

16. Reptile water budget Intake: drinking 25%, food 52%, metabolic 23%
Outlet: feces/urine 36%, evaporation 58%, salt gland 6%

17. Bird water budget Intake: drinking 93%, food 2%, metabolic 5%
Outlet: feces/urine 64%, evaporation 36%, salt gland ?? (data from ostrich - no salt gland)

18. Mammals Intake: drinking 69%, food 4%, metabolic 26%
Outlet: feces 7%, urine 50%, evaporation 43%