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Osmoregulation in fishes
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Osmosis The phenomenon of water flow through a semi-permeable membrane that blocks the transport of salts or other solutes through it van't Hoff formula for osmotic pressure: p = cRT –c is the molar solute concentration –R is the gas constant –T is the absolute temperature
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Osmoregulation Osmoconformer only Hagfish (Myxini) Osmoregulators Lampreys, elasmobranchs and teleosts Stenohaline Euryhaline
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Accumulation of organic osmolytes (metabolic by-products): –Urea –TMAO (Trimethylamine n-oxide) Protein stabilization properties Achieve a slightly higher osmotic pressure than seawater FW sharks and rays do not accumulate urea/TMAO Elasmobranch osmoregulation in SW
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Osmotic gradients in teleosts High salinityLow salinity
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FW SW
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Teleost osmoregulation in SW
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Chloride Cell Saltawater teleost Location: Gill & Operculum epithelia
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Chloride Cell Saltawater teleost
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Teleost osmoregulation in FW
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“Chloride” Cell Freshwater teleost
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Fundulidae Mummichog Fundulus heteroclitus Keep cholride cells at all times, even when in freshwater
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Salmonidae Atlantic salmon Salmo salar Develop more chloride and accesory cells when migrate to SW (parr-smolt) Degenereration of chloride- accessory cell complexes when returning to FW (adults)
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