Does the fish drink water?

Perhaps this question may risk the mind of each and every one of us. We may be particularly puzzled by the fish that lives in seas and oceans, in salt water that is not suitable for drinking humans or wild animals. Does the sea fish drink this salt water? If the answer is yes, what mechanism would make him "drink" from this water? In fact, the fish are already drunk. But it does not necessarily drink by mouth. Water enters the body of the fish through the gills that extract oxygen from the water and release carbon dioxide. The exchange of water and gases controls a property called osmotic pressure. (Some of us may hear this term being repeated for water purifiers and its filtration with reverse osmosis.)

The osmotic pressure seeks to reach a state of equilibrium between the concentration of salts dissolved in the water inside the body's cells and the surrounding water. This means that freshwater fish have a problem to overcome, because the concentration of soluble salts in the water in their gills is higher than in the fresh water in which they swim. For this reason, the osmotic pressure will make this fresh water enter a large amount of cells and explode.

In order not to get this thing, these fish get rid of a large amount of water through the urine, which is very light and contains little salt and waste. In addition, these fish never drink by mouth, and the cells of their nostrils regulate the entry and exit of mineral salts so as not to leave these salts into fresh water endanger their lives.

The situation in salt water is the opposite of what it is in fresh water. The concentration of salts within the gills and the body in general may be less than its concentration in salty sea water. Here, the osmotic pressure seeks to make the concentration equal in and out of cells. By removing water from the cells or absorbing them for additional salts.

In order to avoid this, the fish developed two or two methods, depending on the type of fish. Cartilaginous fish, such as sharks and marine invertebrates, have a high concentration of mineral salts such as sulphates or sodium salts, which makes their concentration in and out of cells - in sea water, so no exchange of water or salts between gills. Also, these fish never drink water through the mouth.

As for bone fish - and most fish are present in the seas, the concentration of salts in the cells of the body less than its concentration in sea water, which offers them to enter the sea salts into their cells or the exit of water. In order to avoid this phenomenon, these fish drink water continuously through the mouth. And get rid of excess water through the kidneys, and also by special glands in the gills. Also, there are specialized cells in their nostrils controlling the entry and exit of salts of mineral salts to maintain their proper concentration within the body.