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
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
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
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 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
Three common marine strategies: Units = mosmol SolutesSeawater1) Invertebrates & hagfish 2) Sharks3) Teleosts Na Cl Urea TMAO Total
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 How do they pull this off?
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 Danish 1920 Nobel Prize for capillary blood flow Gas exchange Respiration Diffusion Homer Smith American Kidney function and structure MDIBL Ancel Keys American Krogh’s post- doc in early 1930s Influence of diet on health Image credit: nndb.com; niehs.nih.gov
The characters: August Krogh Danish 1920 Nobel Prize for capillary blood flow Gas exchange Respiration Diffusion Homer Smith American Kidney function and structure MDIBL Ancel Keys American Krogh’s post- doc in early 1930s Influence of diet on health Image credit: nndb.com; niehs.nih.gov
The characters: August Krogh Danish 1920 Nobel Prize for capillary blood flow Gas exchange Respiration Diffusion Homer Smith American Kidney function and structure MDIBL Ancel Keys 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 - /HCO 3 - & Na + /NH 4 + 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
Image credit: Karnaky 1986; webshots.com Chloride Cells - gill morphology
Chloride Cells Image credit: Karnaky 1986; Degnan et al. 1977
Chloride Cells - Cl - current & opercular epithelium Ussing Chamber Image credit: warneronline.com Apical (seawater) Basolateral (blood) Opercular epithelium
Chloride Cells - Cl - current & opercular epithelium Ussing Chamber Image credit: warneronline.com Apical (seawater) Basolateral (blood) Current injection electrode Voltage recording electrode Opercular epithelium
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
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 Image credit: Evans mV -15 mV
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