Osmoregulation in fishes. Osmosis The phenomenon of water flow through a semi-permeable membrane...
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Transcript of Osmoregulation in fishes. Osmosis The phenomenon of water flow through a semi-permeable membrane...
Osmoregulation in fishes
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
Osmoregulation
• Osmoconformer•only Hagfish (Myxini)
• Osmoregulators•Lampreys, elasmobranchs and
teleosts
• Stenohaline• Euryhaline
• 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
Elasmobranch osmoregulation in SW
Osmotic gradients in teleosts
High salinity Low salinity
FW SW
Teleost osmoregulation in SW
Chloride CellSaltawater teleost
Location:Gill & Operculum epithelia
Chloride CellSaltawater teleost
Teleost osmoregulation in FW
“Chloride” CellFreshwater teleost
FundulidaeMummichogFundulus heteroclitus
•Keep cholride cells at all times, even when in freshwater
SalmonidaeAtlantic salmonSalmo salar
•Develop more chloride and accesory cells when migrate to SW (parr-smolt)
•Degenereration of chloride- accessory cell complexes when returning to FW (adults)