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Osmoregulation in Marine Teleosts

Osmoregulation in Marine Teleosts. Cl - cells. Image credit: cornell.edu; Karnaky 1986. amazon.co.uk. Image credit: amazon.com. Osmoregulation: Regulation of osmotic pressure of internal fluids. Osmoregulation: Regulation of osmotic pressure of internal fluids Osmosis.

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Osmoregulation in Marine Teleosts

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  1. Osmoregulation in MarineTeleosts Cl- cells Image credit: cornell.edu; Karnaky 1986

  2. amazon.co.uk Image credit: amazon.com

  3. Osmoregulation: • Regulation of osmotic pressure of internal fluids

  4. Osmoregulation: • Regulation of osmotic pressure of internal fluids • Osmosis

  5. Osmoregulation: • Regulation of osmotic pressure of internal fluids • Osmosis • Excretion, ingestion, absorption

  6. Three common marine strategies: • 1. Osmoconform • Agnathan hagfish & many marine invertebrates • Conform internal [ion] to [external medium]

  7. Three common marine strategies: • 1. Osmoconform • Agnathan hagfish & many marine invertebrates • Conform internal [ion] to [external medium] • Evidence of marine origin for vertebrate life? Image credit: hawaiianatolls.org ; sagepub.com

  8. Three common marine strategies: • 2. Osmoconform and ion regulate • Sharks, coelacanth and some amphibians • Plasma concentrations > seawater • NaCl concentration ~ 1/3 seawater Image credit: templecuttingedge.files.wordpress.com; abdn.ac.uk; sagepub.com

  9. Three common marine strategies: • 2. Osmoconform and ion regulate • Sharks • Plasma concentrations > seawater • NaCl concentration ~1/3 seawater • Urea & Trimethylamine N-oxidase (TMAO) • Internal fluids ~5% saltier than seawater Image credit: templecuttingedge.files.wordpress.com; abdn.ac.uk; sagepub.com

  10. Three common marine strategies: • 2. Osmoconform and ion regulate • Sharks • Plasma concentrations > seawater • NaCl concentration ~1/3 seawater • Urea & Trimethylamine N-oxidase (TMAO) • Internal fluids ~5% saltier than seawater • Rectal gland Image credit: templecuttingedge.files.wordpress.com; abdn.ac.uk; sagepub.com

  11. Three common marine strategies: • 3. Osmoregulate • Teleosts • Regulate Na+ & Cl- ~1/3 seawater • Salt removal • Esophagus • Intestines • Gill chloride cells Image credit: wikipedia.com; sagepub.com

  12. Other regulators: • Marine birds/reptiles • Salt gland • Allows to drink saltwater and consume aquatic (salty) plants and animals Image credit: nicerweb.com; wordpress.com

  13. Other regulators: • Plants – mangroves • Roots prevent salt from entering but allow water in • Excrete salt from glands on leaves • Concentrate salt in old leaves, flowers, bark Image credit: wikimedia.org

  14. Three common marine strategies: • Units = mosmol

  15. Marine teleosts • The problem • Internal fluids hypotonic to seawater • Constant water loss • Constant ion gain Image credit: mrupp.info

  16. Marine teleosts • The problem • Internal fluids hypotonic to seawater • Constant water loss • Constant ion gain • The answer • Drink constantly • Absorb NaCl and water from ingested seawater • Keep water • Excrete NaCl Image credit: mrupp.info

  17. How do they pull this off?

  18. How do they pull this off? Image credit: mrupp.info

  19. American Physiological Society • August Krogh Distinguished Lectureship • Bodil Schmidt-Nielsen (1994) • Jared Diamond (1995) • Knut Schmidt-Nielsen (1996) • George Somero (2000) • Peter Hochachka (2001) • David Evans (2008)

  20. The characters: • August Krogh • 1874-1949 • Danish • 1920 Nobel Prize for capillary blood flow • Gas exchange • Respiration • Diffusion • Homer Smith • 1896-1962 • American • Kidney function and structure • MDIBL • Ancel Keys • 1904-2004 • American • Krogh’s post-doc in early 1930s • Influence of diet on health Image credit: nndb.com; niehs.nih.gov

  21. The characters: • August Krogh • 1874-1949 • Danish • 1920 Nobel Prize for capillary blood flow • Gas exchange • Respiration • Diffusion • Homer Smith • 1896-1962 • American • Kidney function and structure • MDIBL • Ancel Keys • 1904-2004 • American • Krogh’s post-doc in early 1930s • Influence of diet on health Image credit: nndb.com; niehs.nih.gov

  22. The characters: • August Krogh • 1874-1949 • Danish • 1920 Nobel Prize for capillary blood flow • Gas exchange • Respiration • Diffusion • Homer Smith • 1896-1962 • American • Kidney function and structure • MDIBL • Ancel Keys • 1904-2004 • American • Krogh’s post-doc in early 1930s • Influence of diet on health Image credit: nndb.com; niehs.nih.gov

  23. Basis for question: • Krogh, Smith, Keys, understood that marine fish were hyposmotic to seawater • Consequences = dehydrate & gain salts • How do they regulate against this?

  24. Krogh with freshwater fish: • Salt uptake from head region • Probably gills • Guessed at Cl-/HCO3- & Na+/NH4+ exchangers

  25. Smith with marine fish: • Continual drinking • Intestines remove ions and water • Extrarenal ion elimination pathway • Excess ions excreted through gills? Image credit: Evans 2008

  26. Keys with marine eels: • Perfused heart-gill preparation Image credit: Keys 1931

  27. Keys with marine eels: • Perfused heart-gill preparation Image credit: Keys 1931

  28. Keys with marine eels: • Perfused heart-gill preparation • Gills site of active Cl- excretion • These studies formed the framework for the model of ion regulation we use today Image credit: Keys 1931

  29. Chloride Cells - gill morphology Image credit: imageshack.us; webshots.com

  30. Chloride Cells - gill morphology Image credit: Karnaky 1986; webshots.com

  31. Chloride Cells Image credit: Karnaky 1986; Degnan et al. 1977

  32. Chloride Cells - Cl- current & opercular epithelium Chloride Cells - Cl- current & opercular epithelium Ussing Chamber Apical (seawater) Opercular epithelium Basolateral (blood) Image credit: warneronline.com

  33. Chloride Cells - Cl- current & opercular epithelium Chloride Cells - Cl- current & opercular epithelium Ussing Chamber Current injection electrode Voltage recording electrode Apical (seawater) Opercular epithelium Basolateral (blood) Image credit: warneronline.com

  34. Chloride Cells - Cl- current & opercular epithelium Chloride Cells - Cl- current & opercular epithelium Ussing Chamber Current injection electrode Voltage recording electrode Apical (seawater) Opercular epithelium Basolateral (blood) Cl- Image credit: warneronline.com

  35. Chloride Cells - Cl- current & opercular epithelium Image credit: Degnan et al. 1977

  36. Chloride Cells - Cl- current & opercular epithelium Image credit: Degnan et al. 1977

  37. Chloride Cells - Cl- current & opercular epithelium Image credit: Foskett and Scheffey 1982

  38. Chloride Cells - the mechanism Image credit: Evans 2008

  39. Chloride Cells - the mechanism -70 mV -15 mV Image credit: Evans 2008

  40. Discussion Questions • Trade-offs • Energy required to kep up this process • Why no osmoconform and ion regulate as sharks do? • Euryhaline fish? • Early, simplistic experimental approaches lost?

  41. Chloride cells - Cystic Fibrosis (CF) • Caused by mutation in CFTR protein • In humans, creates • sweat • digestive juices • mucous • CF patients with CFTR failure • Cl- buildup  thicker, nutrient-rich mucous in lungs  bacterial infection • Increased Na+ & Cl- uptake  decreased water reabsorption  dehydrated  thick mucous • Lungs, pancreas, intestine • Most common fatal, inherited disease in U.S. • Life expectancy = 36 yrs

  42. Three common marine strategies: • 1. Osmoconform • Agnathan hagfish & many marine invertebrates • Conform internal [ion] to [external medium] • Blue crab example • Salinity < 28 ppt: regulate • Salinity > 28 ppt: conform Image credit: flyingfishshop.com

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