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