Comparative Vertebrate Kidneys
Jan 29, 2016
Comparative Vertebrate Kidneys
Vertebrate Kidneys: Fish
• Highest development in FW fish; degeneration in those species that migrated to SW (why?)
• No loop of Henle in FW teleosts–produce most monovalent-ion free urine in vertebrates
• Aglomerular forms (e.g., toadfish)---proximal tubule subs for glomerus (highly
vascularized) Antarctic fish that produce anti-freeze proteins
also aglomerular (care to speculate why?)
Vertebrate Kidneys: Amphbians
• All parts of nephron except loops• Can produce isosmotic or hyposmotic urine• Amt of glomerular filtrate voided (14-90%)
much higher than mammals (1%)• ADH plays important role depending upon
hydration state
Ask about Rana cancrivora
Vertebrate Kidneys: Reptiles
• Similar to amphibians, but lack bladder
• Reabsorb water from cloaca; remaining urine converted to uric acid pellets
• GFR and reabsorption values much greater than for amphibians, but less than humans
• Marine species – rely more on extra-renal pathways
Vertebrate Kidneys: Birds• Kidney divided into 3 (non-functional) lobes• Like mammals, can produce a hypertonic urine
• Nephron more like reptiles than mammals; a few with long loops• No bladder (exc. Ostrich)---ureters open directly into cloaca• Salt glands (esp. marine species) important