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Osmoregulation in Marine Teleosts Cl - cells Image credit: cornell.edu; Karnaky 1986
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amazon.co.uk Image credit: amazon.com
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Osmoregulation: Regulation of osmotic pressure of internal fluids
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Osmoregulation: Regulation of osmotic pressure of internal fluids Osmosis
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Osmoregulation: Regulation of osmotic pressure of internal fluids Osmosis Excretion, ingestion, absorption
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Three common marine strategies: 1.Osmoconform Agnathan hagfish & many marine invertebrates Conform internal [ion] to [external medium]
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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
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Image credit: templecuttingedge.files.wordpress.com; abdn.ac.uk; sagepub.com Three common marine strategies: 2.Osmoconform and ion regulate Sharks, coelacanth and some amphibians Plasma concentrations > seawater NaCl concentration ~ 1/3 seawater
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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
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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
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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
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Other regulators: Marine birds/reptiles Salt gland Allows to drink saltwater and consume aquatic (salty) plants and animals Image credit: nicerweb.com; wordpress.com
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Other regulators: Plants – mangroves 1.Roots prevent salt from entering but allow water in 2.Excrete salt from glands on leaves 3.Concentrate salt in old leaves, flowers, bark Image credit: wikimedia.org
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Three common marine strategies: Units = mosmol SolutesSeawater1) Invertebrates & hagfish 2) Sharks3) Teleosts Na+470500350180 Cl-570500350180 Urea002300 TMAO001700 Total104010001100360
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Marine teleosts The problem Internal fluids hypotonic to seawater Constant water loss Constant ion gain Image credit: mrupp.info
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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
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How do they pull this off?
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Image credit: mrupp.info How do they pull this off?
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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)
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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
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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
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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
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Basis for question: Krogh, Smith, Keys, understood that marine fish were hyposmotic to seawater Consequences = dehydrate & gain salts How do they regulate against this?
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Krogh with freshwater fish: Salt uptake from head region Probably gills Guessed at Cl - /HCO 3 - & Na + /NH 4 + exchangers
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Smith with marine fish: Continual drinking Intestines remove ions and water Extrarenal ion elimination pathway Excess ions excreted through gills? Image credit: Evans 2008
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Keys with marine eels: Perfused heart-gill preparation Image credit: Keys 1931
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Keys with marine eels: Perfused heart-gill preparation Image credit: Keys 1931
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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
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Chloride Cells - gill morphology Image credit: imageshack.us; webshots.com
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Image credit: Karnaky 1986; webshots.com Chloride Cells - gill morphology
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Chloride Cells Image credit: Karnaky 1986; Degnan et al. 1977
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Chloride Cells - Cl - current & opercular epithelium Ussing Chamber Image credit: warneronline.com Apical (seawater) Basolateral (blood) Opercular epithelium
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Chloride Cells - Cl - current & opercular epithelium Ussing Chamber Image credit: warneronline.com Apical (seawater) Basolateral (blood) Current injection electrode Voltage recording electrode Opercular epithelium
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Chloride Cells - Cl - current & opercular epithelium Ussing Chamber Image credit: warneronline.com Apical (seawater) Basolateral (blood) Current injection electrode Voltage recording electrode Cl - Opercular epithelium
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Chloride Cells - Cl - current & opercular epithelium Image credit: Degnan et al. 1977
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Chloride Cells - Cl - current & opercular epithelium Image credit: Degnan et al. 1977
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Chloride Cells - Cl - current & opercular epithelium Image credit: Foskett and Scheffey 1982
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Chloride Cells - the mechanism Image credit: Evans 2008
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Chloride Cells - the mechanism Image credit: Evans 2008 -70 mV -15 mV
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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?
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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
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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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