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Osmoregulation
Freshwater Osmoregulation
The physiological work required for a freshwater fish - constantly expelling incoming water while actively absorbing scarce ions.
System: Excretory Level: Intermediate Discipline: Physiology
📖 Overview
A freshwater fish is a bag of salty fluid in a bath of nearly-pure water. Osmosis pushes water inward and diffusion pulls salts outward - constantly. Freshwater fish survive by producing enormous volumes of dilute urine (up to 20% body weight per day) while active gill ion pumps reabsorb sodium and chloride from the surrounding water.
🔑 Key Concepts
Water influx, ion loss, active uptake at gills, dilute urine.
✨ Fun Fact
A freshwater fish drinks almost no water - it does not need to. Its problem is expelling water that keeps flooding in, not seeking hydration.