You must have heard the saying "Even if you die of thirst at the sea, you cannot drink sea water." Since sea water cannot drink , how do marine animals drink fresh water?
Sea fish school
Why can’t sea water be drunk directly?
Some people say that the sea water is very salty, and people will become more thirsty as they drink.
is indeed a reason for saltiness. Do you know why it is so salty?
This starts with the origin and development of the ocean. At the beginning, various water sources on land were gathered in the ocean, and under the changes in the geological environment, the ocean gradually formed.
One of the formation process of the ocean
While river and sea water resources also carry various substances , , is mainly salt substances .
Since seawater cannot be exchanged with other water bodies, these substances accumulate in seawater. During this period, the water in it continues to evaporate and participates in the water circulation. Even if fresh water is constantly diluted, it still cannot catch up with the speed of saltification of Shanghai water, and the saltiness of seawater becomes higher and higher.
water cycle process
In fact, you can simply regard the sea as a huge "static lake" , only entering and not leaving, and the reason why the water inside is so salty is easy to understand.
Nowadays, the various substances in seawater seriously exceed the acceptable standards that organisms can use, so seawater should not be consumed directly.
In addition, the human body itself has a certain amount of salt, and the salt content of seawater is more than three times that of the human body. When the human body intakes seawater, the salt of seawater will force the body's salt, causing the concentration to rise rapidly.
The result is that the fresh water in cells loses . Drinking seawater while hungry is tantamount to suicide. The same is true for organisms in the ocean.
In order to survive, organisms in the ocean have evolved unique purification organ .
magical purification organ
As the largest and most complex species in the ocean, fish, they use the sea water filtered by chlorine-secreting cells in fish gills.
chlorine-secreting cells are like an microprocessor in the gills of fish. On the one hand, they decompose the salt in the water body, and on the other hand, they retain qualified water sources.
chlorine-secreting cells
Everyone knows that fish gills are the respiratory organs of fish. When obtaining water oxygen , they will inevitably intake a small amount of sea water.
If this continues, the salt of these seawater accumulates in the fish body. Wouldn’t it be marinated and tasted? In this case, how did fish solve it?
The internal structure of some fish is "rectal" type, and unpurified water can be directly discharged from through the anus.
Other fish will perform secondary purification in their bodies, use their own cells, liver and other parts to regulate to reduce the remaining salt in the body.
Internal organs can purify less sea water, which mainly plays an auxiliary role.
However, there is a creature in the ocean that dares to fight against the sea, that is whale .
whales are not fish, but marine mammals, which are closer to terrestrial organisms. When obtaining fresh water, they swallow large areas of sea water and then purify the water source through their powerful kidney .
The visceral structure of whales
Of course, whales cannot purify all sea water, and some of the unpurified sea water will be discharged as the whales move.
At this time, you may have questions. If a whale drinks the sea water in one gulp, aren’t you afraid of the reverse effect of sea water on the cells?
whales are of course not afraid, because their intestines and stomach have a very thick layer of special mucosa . On the one hand, it is to prevent whales from scratching their intestines when they eat sharp things when they "swallow them in one bite".
For example, sperm whale likes to feed in the deep sea king squid . skull of squid is very hard, sharp, and not easy to digest. Only when the stomach and intestines are strong enough can you avoid being scratched by the skull of the skull.
It is worth mentioning that after the skull of the king squid was excreted from the body by the sperm whale, after decades of fermentation, it formed " ambergris ", which is more expensive than gold.
On the other hand, the special mucosa of the stomach can also effectively prevent harmful substance from being absorbed by whales.
The location of the whale's stomach is shown in the figure
Before a whale absorbs food and water, it needs to undergo three layers of digestion. Each layer must undergo strict screening. Any unqualified ones will be discharged from the body as waste.
Therefore, even whales of such a large size can live happily in the ocean.
"crying" fresh water
Next, this creature has a heavyweight ability to purify seawater. It is sea turtle , relying on crying to filter out salt.
Previously, in order to verify the authenticity of turtles crying to purify sea water, scientists specially poured 3 liters of sea water on a turtle.
Sea Turtle Experiment
Shortly after, scientists discovered that a sticky liquid flowed out of the corners of the turtle's eyes. The scientists hurriedly collected it and performed the test.
The salt content of is surprisingly high. Later, scientists extracted the blood of sea turtles, and the salt content in it did not increase significantly.
This experiment strongly confirms the statement that sea turtles rely on tear glands to purify sea water.
The principle is that after sea water enters the turtle's body, the salt in it is taken away by the cells, but it is not absorbed. Instead, it accumulates near the tear glands , dissolves together with the tears and is discharged.
Sea Turtle: I cried. Water knows
The purification ability of sea turtles has forced humans to sigh at the wonders of natural species.
If the example of a turtle can be called magical, then the next person is a weird one, it is a shark.
Freshwater with "flavor"
You may have heard that although shark fin is a food that the rich have sought after, shark meat has a urine smell , so many illegal hunters throw the shark into the sea after cutting off the fins.
Shark internal structure
In fact, the smell of shark meat comes from their purification process of sea water.
When sharks excrete, they do not excrete urine from their bodies, but accumulate under the body's cortex.
When the shark grabs sea water through the body surface, the osmotic pressure difference formed between the urea in the cortex and the sea water , resulting in the salt not entering the shark's body.
Shark osmotic pressure regulation diagram
The composition of the cortex and urea is like a natural water purification barrier, allowing sharks to replenish moisture anytime and anywhere.
Of course, urea accumulates in shark's cell tissue for a long time, which also makes the shark meat smell a pungent and taste extremely poor.
"dry rice" replenishment
This way of replenishing is mostly found in marine carnivores, and they replenish their needs for fresh water by eating in organisms.
Terrestrial organisms also have this habit of replenishing. Lions living in Africa rely on preying on medium-sized herbivores to obtain water, so they do not need to rehydrate frequently during drought seasons.
The King of the Grassland Big Lion
This is particularly obvious in Marine Life .
For example, the blood of fish, eyeballs, the spinal cord and water in the cells of marine vertebrates are important sources of supply for predators.
For whales, due to their huge size and high demand for water, it is impossible for them to rely on their internal organs to purify them at all times.
You should know that the size of blue whales is 19 times that of humans. Humans need 8 cups of water every day. Blue whales also need to consume at least 150 cups of water.
Adult Blue Whale
Where does so much fresh water come from? At this time, the fish and shrimp swallowed into the belly will replenish fresh water sources to the whales, thereby reducing the purification pressure of internal organs.
It is worth mentioning that this method is the same auxiliary means , and more fresh water sources must be solved by their own purification capabilities.
Magical Bird
Although seabirds do not belong to marine life, they often live on the ocean and are used to drinking sea water.
The seabirds purify seawater in the same way as turtles, but seabirds discharge substances containing salt crystals through nostrils .
Albatross
Therefore, seabirds have stronger purification capabilities than turtles and maintain their long flights at sea.
The species in nature are wonderful and diverse, and there is no reason why we don't protect them.
