Fish that live in salt water. Fauna of the seas and oceans. Starfish, hedgehogs, lilies

Yesterday, I completed the experiment and nevertheless tested the dendrobene for survivability in the salt water of the Mediterranean Sea, and at the same time tested the dung beetle. A video about the passage of the experiment is presented to your attention, and you will find the conclusions in this article.

Background of the experiment

Not so long ago I got a Dendroben worm, and the main reason for choosing this bait was the information that this worm is able to live for several hours, both in salt water and fresh water. Various Internet resources claim that she is able to live in salt water for several hours, some sites write that this time even reaches 6. But is it really so?

On the Internet, I found only one sensible video in which an experiment is conducted with dendrobene in the salt water of the Black Sea, as a result of which it turned out that this worm on a hook is able to keep signs of life in it for about an hour. Here it is.

But the problem is that the salinity of the Black Sea water is 18 ppm, and the Mediterranean is 38, which is almost 2 times more. For this reason, I decided to conduct my own test and check for survivability in this water of two types of worm, dung and dendrobene, which has been living with me for about 2 months.

My video is about how long a dendrobena and a dung worm can live in the salty water of the Mediterranean Sea.

Results:

• The active phase of life of both worms in salt water was approximately 5-6 minutes.
• The total time of manifestation of the activity of the dung beetle is 8 minutes.
• The total time of manifestation of dendrobene activity is 15 minutes.

But, despite the fact that the dendrobena remained alive much longer than the dung worm, about 9 minutes out of 15, she practically did not move, but only shook her head, which, in my opinion, will not greatly affect her performance as a bait, I don’t think that these sluggish movements are able to attract fish. I'll try to test it out soon.

For the first 5-6 minutes, both worms look more than worthy. Of course, this behavior is certainly not what it could be on the hook, but still.

But already hooked. Lifetime results are quite different.

conclusions. The probability of a bite increases for the first time 5-6 minutes after casting and falls catastrophically after this time. It remains only to test all this in practice, in the Mediterranean Sea. So the series of experiments has just begun.

P.S. There is still a chance that there are other varieties of dendrobene that are able to live in salt water for a longer time. However, I think that this probability is negligible, the salinity of the waters of the Mediterranean Sea is too high.

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What are your thoughts on this? Leave your comments with criticism and suggestions, as well as ideas for the next experiments.

Shark - sea, carp - pond

Surely many of the visitors to the site wondered - why can some fish live only in fresh water, while others - only in salty sea water? What is the difference between these aquatic animals? It turns out that there is a difference, and for many fish it is so significant that if you place them in an alien environment (the sea or, conversely, a river), they will die.
It is curious that the origins of the causes lie in physics textbooks. The work of all metabolic and excretory processes in the body of fish depends and is adjusted by the so-called osmotic pressure.
What is it?

Osmotic regulation in sharks

Osmosis- the desire of any solution to lower the concentration of substances dissolved in it upon contact with the solvent (the basis of this solution) through a partition permeable to the solvent. The solvent begins to penetrate into the solution through this very partition, reducing its concentration. This creates a certain pressure, called osmotic pressure.
In relation to aquatic animals, for example, fish, osmotic pressure occurs when the internal environment of the fish body (blood, lymph) interacts with the external environment (water) through the skin. Depending on which of these media contains more minerals and salts, it can act either as a solvent (giving water to the solution) or a solution (sucking water out of the solvent).

Perhaps the explanation is a bit confusing, so let's try to simplify it.
The internal environment of the fish (blood, lymph) is in contact with the external environment (water) through the skin of its body, which passes water through itself in one direction or another in order to equalize the concentration of dissolved substances in both environments. The process proceeds in one direction and is called osmosis. The pressure of water moving out of the body of the fish (or vice versa - from the external environment into the body) is called osmotic pressure.

Now things are starting to become clear.
In the case of freshwater fish, their internal environment (blood and lymph) contains more salts and minerals than the external environment - river or lake water, i.e. in this case, the solvent is the external environment, the solution is the internal one. Through the skin of freshwater fish, water is constantly absorbed into the body in order to equalize the concentration of salts outside and inside, in accordance with the aforementioned laws of physics.
Freshwater fish have to protect the body from excessive watering, leaching of salts and minerals, so nature has provided a protective mechanism for them - effectively working kidneys. They filter the internal environment, carefully separating salts and minerals useful for the body from it, and excess water is removed with urea and other waste products.

Now consider this process in the body of marine fish, for example, sharks.
Her blood and lymph contain less salts than sea water, so a reverse osmotic process takes place here - water is intensively drawn from the internal environment through the skin to the outside. Since water is a vital element for metabolic processes, here nature had to provide other protective mechanisms to prevent dehydration of the sharks.
The way out was very simple - sharks constantly "drink" sea water, from which the fresh component is absorbed through the walls of the stomach into the blood and lymph. The excretory system of sharks is set up to intensively remove excess salts and minerals through the intestines, gills and with the help of the rectal gland. And water is carefully stored in the body.
It is for this reason that sharks produce very little urine - it contains valuable fresh water.

The osmotic pressure of each species of fish is a relatively constant value and is tuned to the ratio of the concentration of substances in the internal environment of their body with the preferred habitat.
At the slightest change in this ratio, the excretory system begins to fail. Therefore, if freshwater fish is placed in sea water, its body will quickly lose water, dehydration will occur with all the ensuing consequences. Freshwater fish do not have mechanisms to remove excess salts from the body, and their concentration in the blood and lymph will exceed the norms acceptable for life.
If a shark is placed in fresh water, the effect will be the opposite - its internal environment will quickly lose salts and minerals, since the shark does not have protective mechanisms that prevent the loss of these substances from the internal environment and they will be washed out of the blood and lymph into the external environment (fresh water ).

As you can see, the reason that freshwater fish live in fresh water, and marine fish live in salt water, is related to the work of their excretory organs. Some provide for the removal of excess water from the body, while others - excess salts.

Reading this article, the smartest are already wondering - what about migratory, semi-migratory fish? And how, after all, the famous blunt shark able to live wherever he wants?

It turns out that some fish are "armed" with a universal system of excretory organs. They can automatically rebuild their body to function in different environments, with different osmotic pressure in the direction. In the event of contact with sea water, their gills and intestines take on the main function of the excretory system, and when they enter rivers and freshwater reservoirs, the intensive work of the kidneys is activated, and the process of removing excess water from the internal environment of the body begins.
Of course, this scheme is somewhat simplified, but the basic principle is as follows.

I hope now you understand why river and lake fish will feel discomfort in the sea, and may even die, and sharks (with the exception of some species) "turn up their noses" from fresh and even brackish water.

About 35 grams of salt are dissolved in one liter of sea water, mostly table salt. However, in the blood and tissue fluid of most marine fish, the concentration of salts is three times lower.

This creates a strong osmotic pressure (that is, the pressure that occurs between solutions of different concentrations when they come into contact). It "sucks" the water out of the body of the fish. And although its covers prevent the outflow of fluid, a certain amount of water is still lost through gills, mucus, excrement, etc. Compensating for this loss, fish drink sea water and “desalinate” it inside the body, removing excess salts - partly through the intestines, but mostly through the gills.

And even more...

The so-called Case-Wilmer cells are responsible for this, in the membranes of which there are special proteins that carry salt ions into the external environment. Since this transfer is carried out towards sea water (where the concentration of salts is higher), it requires energy. In freshwater fish, the same proteins act in the opposite direction, capturing ions from outside. In anadromous fish that migrate from seas to rivers for spawning or vice versa, these proteins switch from one mode to another.

Osmotic pressure is the force acting on a semipermeable membrane separating two solutions with different concentrations of solutes and directed from a more concentrated to a more dilute solution. Osmotic pressure can be very significant. In a tree, for example, under the action of osmotic pressure, plant sap rises from the roots to the very top. But in a tree, the movement of a concentrated solution, which is vegetable juice, is not limited in any way. If such a solution is in a closed space, for example, in a blood cell, then the osmotic pressure can lead to a rupture of the cell wall. It is for this reason that drugs intended for administration into the blood are dissolved in an isotonic solution containing as much sodium chloride (table salt) as necessary to balance the osmotic pressure created by the cellular fluid. If infused drugs were made with water, osmotic pressure would force water into the blood cells and cause them to rupture. If a too concentrated solution of sodium chloride is introduced into the blood, then the water from the cells will come out, and they will shrink.

The value of the osmotic pressure created by the solution depends on the amount, and not on the chemical nature of the substances dissolved in it (or ions, if the molecules of the substance dissociate). The greater the concentration of the solution, the greater the osmotic pressure created by it. This rule, called the law of osmotic pressure, is expressed by a simple formula, very similar to the ideal gas law.

The law of osmotic pressure can be used to calculate the molecular weight of a given substance.

1. The amount of water that marine fish absorb depends on the degree of salinity. The saltier the water, the more the fish will drink.
2. The gills of fish that live in salt water absorb some salt.
3. Under the influence of osmosis, fish can pass a large amount of water through the gills.
4. Excess salt is excreted in the urine.
5. Water swallowed by saltwater fish is absorbed by the intestines.

Freshwater fish excrete salt and absorb water through their skin, so they don't need to drink water. The level of salt in the body of freshwater fish is replenished with food and ions (salt) deposited in the gills.

1. Driven by the force of osmosis, water enters the body of the fish through the gills.
2. Part of the salt is lost by the gills as a result of osmosis.
3. Freshwater fish have excess water, which they excrete in the form of very dilute urine.

If the fish are swapped

In their habitual home, marine fish maintain a normal water-salt balance by drinking large amounts of water and excreting excess salt. In fresh water, marine fish absorb water, diluting it with the liquid medium of their body. Unable to retain salt or get rid of excess water, the fish dies. Normally, freshwater fish regulate the level of salt in their body tissues by absorbing salt and excreting water. In salt water, fish lose water they cannot replace; the salt content in her body rises to lethal levels.

Fickle natures

Several species of fish are diadromous, meaning they can live in both salt and fresh water, adjusting their body fluids to suit environmental conditions. They drink water - or abstain from it - depending on the concentration of salt in their habitat. In addition, their gills and kidneys are able to quickly change from processing salt water to fresh water, and vice versa. Salmon that live in the ocean but spawn in rivers, as well as sturgeons, shads and lampreys that live in estuaries, are also among the easily adaptable fish. Some species of diadromous fish are shown in the illustration above.

sources

The marine animal world is the kingdom of many millions of living beings. Those who at least once had to descend into the depths of the sea were amazed by the charming beauty and bizarre forms of the underwater world.

Amazing fish, fabulous algae, creatures that are sometimes difficult to distinguish from plants. For example, sponges. For a long time, scientists argued where to attribute them to animals or plants. After all, there is no bark, no stomach, no brain, no nerves, no eyes - nothing that makes it possible to immediately say that this is an animal.

photo: Jim McLean

Sponge

Sponges are primitive multicellular animals that mainly live in the seas and oceans, from the very coast to great depths, clinging to the bottom or to underwater rocks. There are more than 5000 species of these animals. Most of them are heat-loving animals, but some have adapted to the harsh conditions of the Arctic and Antarctic.

Sponges have a variety of shapes: some look like a ball, others look like tubes, and others look like glasses. They come in not only different shapes, but also have different colors: yellow, orange, red, green, blue, black and others.

The body of the sponge is very uneven, easily torn, crumbled, and everything is permeated with numerous holes, pores through which water penetrates and brings oxygen and food to the sponges - small planktonic organisms.

photo: Katalin Szomolanyi

Despite the fact that the sponge does not move and cannot even move, it is very tenacious. Sponges don't have many enemies. Their skeleton consists of a large number of needles, and they protect sponges. In addition, if a sponge is divided into many particles, even into cells, it will still connect and live.

During the experiment, two sponges were divided into parts and joined into two former sponges, and each part of the sponge was connected to its own. Sponges have different life spans. Short in freshwater - a few months, others - up to 2 years, and some of them long-livers - up to 50 years.

corals

Corals, or rather coral polyps, are called primitive marine invertebrates that belong to the type of intestinal. The coral polyp itself is a small animal, shaped like a grain of rice, covered with tentacles. Each small polyp has its own well-known skeleton - corallites. When the polyp dies, the joined corallites form a reef, on which the polyps settle again, changing generation after generation. This is how reefs grow.

photo: Charlene

Colonies of corals amaze with their beauty, sometimes they form real underwater gardens, reefs. There are three types: 1) stony or limestone, living in colonies and forming coral reefs 2) soft corals 3) horn corals - gorgonians, which are distributed from the polar regions to the equator.

Most corals can be found in the waters of tropical seas, where the water is never colder than + 20 degrees. Therefore, there are no coral reefs in the Black Sea.

Now science knows more than 500 species of coral polyps that form reefs. Most corals live in shallow water and only 16 percent go down to depths of 1000m.

Photo: LASZLO ILYES

While corals make strong reefs, the polyps themselves are very delicate, vulnerable creatures. Corals lie on the bottom or grow in the form of separate bushes and trees. They come in yellow, red, purple and other colors and reach a height of 2m and a width of 1.5m. They need clean salt water. Therefore, near the mouths of large rivers, which carry a lot of fresh muddy water into the ocean, corals do not live.

Sunlight plays an important role in the life of corals. This is due to the fact that microscopic algae live in the tissues of polyps, which provide respiration to coral polyps.

Corals feed on small marine plankton, which stick to the tentacles of animals and then pull the prey into the mouth, which is located under the tentacles.

Sometimes the ocean floor rises (for example, after an earthquake), then the coral reef comes to the surface and forms an island. Gradually it is populated by plants and animals. These islands are also inhabited by people. For example, the islands of the oceans.

Starfish, hedgehogs, lilies

All these animals belong to the type of echinoderms. They are very different from other types of animals.

Echinoderms live in salt water, so they inhabit only the seas and oceans.

Starfish have 5, 6, 7, 8 and even 50 "rays". At the end of each is a tiny eye that can perceive light. Sea stars come in bright colors: yellow, orange, red, purple, less often green, blue, gray. Sometimes starfish reach a size of 1m across, small ones - a few millimeters.

photo: Roy Ellis

Sea stars swallow small mollusks whole. When a large mollusk comes across, she hugs him with her "rays" and begins to pull the sash after the sash from the mollusk. But this is not always possible. The star is able to digest food from the outside, so a gap of 0.2 mm is enough for the star to push its stomach in there! They are able to throw a stomach even on live fish. For some time, the fish swims with the star, gradually digesting it while still alive!

sea ​​urchins Omnivorous, they devour dead fish, small starfish, snails, mollusks, their own relatives, and algae. Sometimes hedgehogs settle in granite and basalt rocks, making a small mink for themselves with their incredibly strong jaw.

photo: Ron Wolf

sea ​​lilies- creatures that really look like a flower. They are at the bottom of the ocean and in adulthood lead a motionless lifestyle. There are more than 600 species of them, most of which are stemless.

Jellyfish- unique marine animals that inhabit all the seas and oceans on Earth.

The bodies of most jellyfish are transparent, as they are 97 percent water.

Adult animals are not like young jellyfish. First, the jellyfish lays eggs, from which larvae appear, and already from them a polyp sprouts, which resembles an amazing bush. After some time, small jellyfish break away from it, which grow into an adult jellyfish.

photo: Mukul Kumar

Jellyfish come in a variety of colors and shapes. Their sizes range from a few millimeters to two and a half meters, and the tentacles sometimes reach 30m in length. They can be found both on the surface of the sea and at great depths, which sometimes reach 2000m. Most jellyfish are very beautiful, they seem to be creatures that are not able to offend. However, jellyfish are active predators. On the tentacles and in the mouth of the jellyfish there are special capsules that paralyze prey. In the middle of the capsule is a coiled long "thread", armed with spikes and poisonous liquid, which is thrown out when the victim approaches. For example, if a crustacean touches a jellyfish, it will immediately stick to the tentacle and poisonous stinging threads will be stuck into it, paralyzing the crustacean.

photo: Miron Podgorean

Jellyfish venom does not affect humans in the same way. Some jellyfish are quite safe, others are dangerous. The latter include the cross jellyfish, the size of which does not exceed the usual five-kopeck coin. On her transparent yellow-green umbrella, you can see a dark cross-shaped pattern. Hence the name of this very poisonous jellyfish. Touching the cross, a person receives a severe burn, then loses consciousness and begins to suffocate. If you do not provide timely assistance, then a person may die. Jellyfish move due to the reduction of the domed umbrella. In one minute, they carry out up to 140 such movements, so they can move quickly. Jellyfish spend most of their time at the surface of the water. In 2002 a huge jellyfish was discovered in the central part of the Sea of ​​​​Japan. The size of her umbrella reached a diameter of more than 3 m, and a weight of 150 kg. Until now, such a giant has not been registered.

Interestingly, jellyfish of this species, measuring 1m in diameter, began to meet in the thousands. Scientists cannot explain the reasons for their sudden increase. But it is believed that this is due to an increase in water temperature.

photo: Amir Stern

Just as many m mammals inhabit the oceans, seas and fresh water. Some of them, like dolphins, spend their whole lives in the water. Others go there mainly to search for food, as otters do. All aquatic animals swim perfectly, and some even dive to great depths. The size of land animals is limited by the strength of the limbs that can support the weight. Near water, the body weight is less than on land, so many species of whales have reached enormous sizes in the process of evolution.

photo: Alaska Region U.S. Fish & Wildlife Service

Four groups of mammals live in the seas and oceans. These are cetaceans (whales and dolphins), pinnipeds (real seals, eared seals and walruses), sirens (manatees and dugongs) and sea otters. Pinnipeds and sea otters come to land to rest and breed, while cetaceans and sirens spend their entire lives in the water.

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