How Fishes Use Osmosis Process

A Fin-astic Idea

As we discuss osmosis and how it channels water in and out of the cell going towards the higher areas of solutes, we find ourselves in a predicament. A question arises that makes us really wonder. Why don’t freshwater fish explode, and saltwater fish shrivel up? It’s a very good question to ask because if osmosis was doing its job correctly that would be happening, wouldn’t it? Through careful research, we find that Fish do in fact use osmosis and osmoregulation.

We know that in osmosis water moves from lower areas to higher areas of solutes and water always will have a net movement toward the solution of higher osmotic pressure until it reaches its equilibrium. But we also know that Fish may not always be in isotonic environments so they are in need of osmoregulation.

This brings us to the most important information. Osmoregulation does what it says in the name it regulates osmosis, by controlling the balance of water/salt concentrations for fish to adapt to their environments. In freshwater, fish are hypertonic to their water environment and therefore they have a gill membrane that diffuses water into their blood. Freshwater fish require energy to regulate the ion loss and fluid uptake to keep water moving. When water moves toward the higher osmotic pressure of the blood, sodium, and chloride will diffuse out of the fish. This will move their concentration gradients to the external environment.

To counteract the effects of osmosis freshwater fish’s kidneys will continually produce large amounts of urine. So fish use the bathroom a lot. The kidneys will also all some salts to be lost in the urine. If the kidneys are damaged by a freshwater fish, it will surely lead to death. The reason being is that they have lost the ability of osmoregulation.

Pretty much the same thing happens to saltwater fish. They will excrete excess salts to keep the balance in their hypertonic environment. Marine fish produce gill which is made up of Na+/K+ ATPase. This is an enzyme that helps them get rid of their excess salt. The salt builds up when they drink seawater. Like the freshwater fish, they require energy. For them, it’s to pump all the excess sodium out of their gills. Also, like the freshwater fish, their kidneys are used for the purpose of selecting filter out divalent ions to excrete.

Thankfully fish have been able to adapt and mutate to better fit their environment or we would not be able to enjoy delicious sushi. Without osmoregulation, the world would be down a lot of meat, but luckily the ability to do this is given to the fish to help them live in their watery home.