CATDOLL : CATDOLL: What is the function of fish skin?

What is the function of fish skin?

The skin of fish is actually the same as the skin of other vertebrates, with two layers: the outer thin layer is called the epidermis, and the inner thicker layer is called the dermis. In addition, the skin of fish has a special gland that can secrete a large amount of mucus, making the skin slimy.

The amount and composition of mucus vary with the type of fish: for example, if you put a hagfish in a bucket, the water will quickly turn into a milky white gel, but other fish do not have this phenomenon. The skin of fish is surrounded by different scales, which are formed by the gradual deposition of calcium in the body tissue into the dermis.

Fish scales protect the skin. Generally speaking, fish scales can be divided into four types: shield scales, round scales, comb scales and hard scales. Shield scales: are bony baseplates buried in the skin, and the exposed parts are enamel spines. Sharks and fish among cartilaginous fish are covered with shield scales.

Shark skin with shield scales is not only very strong but also very tough. It can be used to make leather or various decorations. Round scales: The common carp has round scales. It is very similar to human nails. The front end of the scales extends into the dermis, and the back end is completely exposed. They are arranged in layers in a regular manner, much like tiles on a roof.

Ctenoid scales: The main feature of this type of scales is that the rear edge of the scales is serrated. There are many fish species with ctenoid scales, such as yellow croaker, rock bass, red sea bream, etc. Interestingly, among flatfish, the yellow cap flounder has two types of scales: the colored side of its body is ctenoid scales, while the colorless side is round scales. There is also a grouper with tender meat, which also has two types of scales on its body: the scales above the lateral glands are ctenoid scales, while the scales below the lateral glands are round scales.

Fish has a rejuvenating and beautifying effect on the skin

First: Eat fish to fight depression

Second: Eat fish to prevent asthma

Third: Eating fish reduces dementia

Fourth: Eating fish can prevent stroke

Fifth: Eat fish to prevent aging

Why do sharks show their fins?

I think that's because "showing fins" can directly arouse people's imagination of sharks, which makes it easier to show ocean crises in movies or comics. Therefore, many authors or directors are happy to use the "showing fins" plot, so that everyone thinks that sharks like to "show their fins".

Personally, I think sharks generally don't show their fins easily, because the dorsal fin can't serve as a directional wing once it leaves the water.

First introduce the relevant knowledge:

External appearance

Section 1 External divisions of the fish body

◆ The fish body can be divided into the head, trunk and tail.

* The division between the head and the trunk is the last pair of gill slits in cyclostomes and elasmobranchs without gill covers, and the last pair of gill slits in bony fish with gill covers.

etc. is the posterior edge of the operculum.

* The division between the trunk and tail is usually the posterior edge of the anus or urogenital opening.

Section 2 Body shape of fish

◆The body shape of fish is generally bilaterally symmetrical.

Fish

Body axis

It can be divided into the following three types:

* The head-tail axis (spindle) is an axis running through the center of the fish body from the head to the tail;

* Dorsoventral axis (sagittal axis) - an axis that runs from the highest part of the fish body through the head and tail axis and runs through the dorsoventral part;

*Left-right axis (horizontal axis) - an axis that runs through the center of the fish body and is perpendicular to the head-tail axis and the dorsal-ventral axis.

◆Representative body shape

* The most common type is the spindle-shaped body, which is enlarged in the middle and slightly tapered at the head and tail. From the perspective of the body axis, the head-tail axis is the longest, the dorsal-ventral axis is shorter, and the left-right axis is

The shortest. Most fast-moving fish have this body type. For example: tuna, mackerel, herring, grass carp. This body type

It can reduce water resistance to a minimum, consume minimal energy to achieve a higher swimming speed, and is beneficial for finding food.

Now as for the fins, I personally think that they are exposed unintentionally when they are hunting, not voluntarily.

Related information:

The skin of fish is actually the same as the skin of other vertebrates, with two layers: the outer thin layer is called the epidermis, and the inner thicker layer is called the dermis. In addition, the skin of fish has a special gland that can secrete a large amount of mucus, making the skin slippery. The amount and composition of mucus vary with the type of fish: for example, if you put a hagfish in a bucket, the water will quickly turn into a milky white gelatinous liquid, but other fish will not have this phenomenon.

The skin of fish is surrounded by different scales, which are formed by the gradual deposition of calcium in the body tissue into the dermis. Fish scales play a role in protecting the skin.

Generally speaking, fish scales can be divided into four types: shield scales, round scales, ctenoid scales and hard scales.

Shield scales: These are bony baseplates buried in the skin, with enamel spines exposed outside. Sharks and fishes such as cartilaginous fishes are covered with shield scales. The shark skin with shield scales is not only very strong but also very tough, and can be used to make leather or various ornaments.

Round scales: The common carp has round scales. They are very similar to human fingernails, with the front end of the scales extending into the dermis and the back end completely exposed. They are arranged in regular layers, much like tiles on a roof.

Ctenoid scales: The main feature of this type of scales is that the rear edge of the scales is serrated. There are many fish species with ctenoid scales, such as yellow croaker, rock bass, red sea bream, etc. Interestingly, among flatfish, the yellow cap flounder has two types of scales: the colored side of the body is ctenoid scales, while the colorless side is round scales. There is also a grouper with tender meat, which also has two types of scales on its body: the scales above the lateral glands are ctenoid scales, while the scales below the lateral glands are round scales. However, it should be mentioned here that there are exceptions in some cases: for example, the rear end of the round scales can also be wavy; the rear end of the ctenoid scales can also be soft and round.

Hard scales: This type of scale is in the shape of a rhombus and is composed of three layers of tissue. The top layer is a layer of shiny enamel-like substance called hard scales, which is where the name hard scales come from; the bottom layer is a thicker bone layer, and there is also a whole layer of microvessels in the middle. However, this special structure of hard scales makes the fish body easy to bend. The main representative of hard scales is bowfin fish, which no one has seen because it has long been extinct. However, its descendant is sturgeon, and now you can still see a row of medium hard scales on the upper edge of its tail fin. From fish fossils, we know that this hard armor was gradually developed and complete at first, and then gradually degenerated.

The above are some common scales of fish. Some species of fish have some specialized scales. For example, the horse mackerel has a row of shield-shaped ridge scales on its side glands, and this scale has sharp knife-like spines at the tail. There is also a glass armor fish, which is surrounded by a transparent soft bone plate. Its abdomen is like a sharp blade. Someone accidentally cut his finger with it.

In the past, the rubber fish that was often sold in our vegetable market was called the green-finned horse-faced fish (Yutun). It was covered with a layer of rough scales, and there were very tiny spines on the scales, so we had to peel off the hard skin on the rubber fish before eating it. The scales of the box (Yutun), a close relative of the scale (Yutun), are even more peculiar. Each of its scales is a hexagonal plate, and each plate is healed very neatly, naturally forming a hard bone box; the shape of the bone box is also different, some are triangular, some are quadrilateral or pentagonal, and sometimes there are hard spines on one or several sides of its body. The three-sided box (Yutun) living in the West Indies has two long spines on its forehead, like the two horns of a cow. There is also a kind of thorn (Yutun) fish that looks even more strange. It has densely packed hard spines all over its body, and the base of each spine is connected to each other to form a continuous plate. These hard spines like cones can usually move.

Some bony fish have a particularly large knife-shaped scale at the base of their pectoral fins and the outer corners of their pelvic fins. Ichthyologists call this scale an axillary scale. Some axillary scales are large and hard, while others are soft and elastic.

The size of fish scales also varies with the type of fish. For example, a single scale of a tarpon is 6 cm long, and a fish called yuba, which lives in Indian rivers, has even larger scales, 7 cm long. On the contrary, the scales of mackerel and tuna are very small, and the scales of eels are even smaller, and can only be seen under a microscope.

Some fish have no scales, but they have other ways to protect their skin. For example, under the hard and rough skin of the sunfish, there is a 8-9 cm thick cartilage layer that makes the skin harder.

Scientists have discovered that fish scales not only protect the fish body, but also play an important role in fish classification. At the same time, because there are different widths of the scales, people can determine the age of the fish through the scales.

Scales sometimes fall off due to mechanical damage or some other reasons, but the fish will grow new scales to replace them. These newly grown scales are called replacement scales. They do not have concentric circles, so they are of little value in studying the life history of fish.

This is because the shark's dorsal fin is tall, and when it swims to the surface or shallow water, the dorsal fin is inevitably exposed to the water. The shark's dorsal fin is upright, which is very helpful for maintaining stability in the water.

TV and movies are just to create a thrilling atmosphere.

When a real shark attacks a target on the sea, it is too late to disguise.

How could anyone be so stupid as to expose himself?

Of course, if it is near the coast, it is different.

The water level is relatively low, so sharks are forced to expose their fins.

But the biggest danger it faces is running aground.

The fish body can be divided into head, trunk and tail.

* The division between the head and the trunk is the last pair of gill slits in cyclostomes and elasmobranchs without gill covers, and the last pair of gill slits in bony fish with gill covers.

etc. is the posterior edge of the operculum.

* The division between the trunk and tail is usually the posterior edge of the anus or urogenital opening.