Do Fish Drink Water?
Do fish drink water? Obviously, humans have to, but what about fish? Fish live in water, but do they have to drink water as we do?
The reason humans have to drink water is that we need a solvent to dilute everything going on inside of us. All the chemical reactions in our bodies need a liquid to make it all happen. If you put powered Kool-Aid in a glass, nothing really happens until you add water. Same concept with the human body.
It's kinda the same situation with fish. Some fish absorb water through something called osmosis. This allows fish to take in water through their skin and gills. Freshwater fish drink through the process of osmosis. Their body fluids are saltier than the water around them, so water flows in through their gills to keep them alive.
Saltwater fish, like freshwater fish, take in water through osmosis, but not exclusively. Saltwater fish actually have to drink water as we do. Saltwater fish don't get enough water through osmosis to keep their bodily functions working so they have to purposefully drink.
Freshwater fish direct all the water that enters their mouths, out through their gills. Saltwater fish direct some of that water into their digestive tract for survival.
Both freshwater and saltwater fish have to keep a certain concentration of salt in their bodies. Both have to take in only a certain amount of water. They can't just allow water to flow through their gills constantly, if they did, saltwater fish would shrivel up and freshwater fish would explode.
So, do fish drink water? Yes, some do.
[Via: Office for Society and Science]