Biology
Osmoregulation and Water Balance in Marine Versus Freshwater Teleosts
Quick fact
A marine teleost drinks up to 10% of its body weight in seawater daily to counteract water loss, while a freshwater teleost almost never drinks and instead pumps out up to a third of its body weight in dilute urine each day.
Why this is interesting
A fish in the ocean is constantly losing water to the sea, while a fish in a lake is constantly gaining it. How do they both survive?