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Osmoregulation
Saltwater Osmoregulation
The reversed problem for marine bony fish - constant water loss and salt gain requires drinking seawater and excreting excess salt via specialised gill cells.
System: Excretory Level: Intermediate Discipline: Physiology
📖 Overview
A marine teleost is a bag of relatively dilute blood in a saltier ocean. Water diffuses out; salt diffuses in. Marine fish drink seawater constantly, absorb the water in the gut, and excrete concentrated salt via specialised chloride cells (ionocytes) in the gills. Urine volume is minimal but urine is highly concentrated.
🔑 Key Concepts
Constant drinking, chloride cells, hypertonic urine, active Na/Cl excretion.
✨ Fun Fact
Marine bony fish drink 3-4% of their body weight in seawater per day - the equivalent of a human drinking 3 litres of ocean water daily.