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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 MarineTeleosts 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
Osmoregulation: • Regulation of osmotic pressure of internal fluids • Osmosis • Excretion, ingestion, absorption
Three common marine strategies: • 1. Osmoconform • Agnathan hagfish & many marine invertebrates • Conform internal [ion] to [external medium]
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
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
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
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
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
Other regulators: • Marine birds/reptiles • Salt gland • Allows to drink saltwater and consume aquatic (salty) plants and animals Image credit: nicerweb.com; wordpress.com
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
Three common marine strategies: • Units = mosmol
Marine teleosts • The problem • Internal fluids hypotonic to seawater • Constant water loss • Constant ion gain Image credit: mrupp.info
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
How do they pull this off? Image credit: mrupp.info
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)
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
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
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
Basis for question: • Krogh, Smith, Keys, understood that marine fish were hyposmotic to seawater • Consequences = dehydrate & gain salts • How do they regulate against this?
Krogh with freshwater fish: • Salt uptake from head region • Probably gills • Guessed at Cl-/HCO3- & Na+/NH4+ exchangers
Smith with marine fish: • Continual drinking • Intestines remove ions and water • Extrarenal ion elimination pathway • Excess ions excreted through gills? Image credit: Evans 2008
Keys with marine eels: • Perfused heart-gill preparation Image credit: Keys 1931
Keys with marine eels: • Perfused heart-gill preparation Image credit: Keys 1931
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
Chloride Cells - gill morphology Image credit: imageshack.us; webshots.com
Chloride Cells - gill morphology Image credit: Karnaky 1986; webshots.com
Chloride Cells Image credit: Karnaky 1986; Degnan et al. 1977
Chloride Cells - Cl- current & opercular epithelium Chloride Cells - Cl- current & opercular epithelium Ussing Chamber Apical (seawater) Opercular epithelium Basolateral (blood) Image credit: warneronline.com
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
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
Chloride Cells - Cl- current & opercular epithelium Image credit: Degnan et al. 1977
Chloride Cells - Cl- current & opercular epithelium Image credit: Degnan et al. 1977
Chloride Cells - Cl- current & opercular epithelium Image credit: Foskett and Scheffey 1982
Chloride Cells - the mechanism Image credit: Evans 2008
Chloride Cells - the mechanism -70 mV -15 mV Image credit: Evans 2008
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?
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
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