Comparative Vertebrate Physiology

Extrarenal mechanisms of osmoregulation

Lecture summary

Fish: gills

Amphibians: Integument/urinary bladder

Reptiles and birds: Salt gland/lower intestine

Mammals: Nasal exchange + kangaroo rat

Marine teleosts

Marine teleosts- chloride cells Operation

Na/K pump Na/Cl/K cotransporter Na and Cl transported into seawater

Chloride cell(note mitochondria)

Freshwater teleosts Pavement cells pump Na+ into blood

Pavement cell

Chloride cell

Amphibians Permeable integument

High rates of respiration and EWL Desert adapted frogs

Amphibians Permeable urinary bladder Recycling water-urine is more

concentrated

Reptiles Salt gland location

Supraorbital Lingual NaCl or KCl

Salt secretion droplets

Reptiles & birds-salt gland

Salt gland cells

Salt gland Function (same as chloride cell)

Na/K pump Na/Cl/K cotransporter Na and Cl transported into environment

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

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

Mammals Strategies

Keep mouth closed Nasal countercurrent exchange

Nasal countercurrent exchange

Mammals Desert adaptations

Reptile water budget

Intake: drinking 25%, food 52%, metabolic 23%

Outlet: feces/urine 36%, evaporation 58%, salt gland 6%

Bird water budget

Intake: drinking 93%, food 2%, metabolic 5%

Outlet: feces/urine 64%, evaporation 36%, salt gland ?? (data from ostrich - no salt gland)

Mammals

Intake: drinking 69%, food 4%, metabolic 26%

Outlet: feces 7%, urine 50%, evaporation 43%