BIOL 22000 Lecture Notes - Lecture 5: Osteichthyes, Osmoregulation, Malpighian Tubule System
8 Jun 2018
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Lecture 5
• Water and Ion Balance
o
o Extracellular fluid compartment interacts with the external environment the most
o Intercellular fluid compartment is in balance with extracellular fluid compartment
o For Isosmotic Line, Body Fluid Osmotic concentration is equal to environment
osmotic concentration
o Osmoregulatory – an animal that maintains a stable BFOC despite osmotic stress
(example: mammals)
▪ Not on the isosmotic line
o Osmoconformer – an animal whose BFOC tracks environmental osmotic
concentration
▪ An organism that lives on the isosmotic line
o Euryhaline – an animal that can survive over a wide range of environmental
osmotic concentrations
o Stenohaline – an animal that can tolerate only a limited range of environmental
osmotic concentrations
o
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o
▪ Hagfish has basically the same osmolarity as its environment (seawater)
• This distribution of solutes in hagfish is almost the same as its
environment, so we call this type of animal ionoconformer (and
osmoconformer)
▪ Marine bivalve has the same osmolarity as it environment, but the solute
is different, so we call this type of animal osmoconformer for having the
same osmolarity and ionoregulator for having different solutes
▪ Bony fish has a different osmolarity and solute then their environment, so
it is both osmoregulator and ionoregulator
▪ Advantage of osmoconformer:
• Saves energy
• Better water balance (water can only move by passive flow of
osmosis) (they don’t have to worry about water coming in and out)
▪ Advantage of being both osmoconformer and ionoregulator:
• To maintain environment for cells to do what they need to do, such
as cell signaling
• Maintain the asymmetrical compartments
• Osmoregulators
o In most cases, vertebrates are osmoregulators with a BFOC of around 300 mOsm
o
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