المثانة الهوائية .. الأسماك .. كتاب في سبيل موسوعة علمية .. الدكتور أحمد ذكي

Swim bladder..fish

air bladder

And when we mention the movement of fish in the water, we mention the swim bladder, which when it exists takes the form of a long tube extending along the vertebral column, filled with a mixture of gas, including oxygen, nitrogen, and carbon dioxide, coming from the blood whose vessels are spread out, and the bladder may or may not be connected to the throat through a thin tube. It is connected to and may secrete gases, abundantly in the walls of the bladder
She may absorb it and adjust its amount. In some fish, it may be used as lung.

Its function is to raise the fish into the water to the required extent. What is strange is that the shark, which is a cartilaginous fish, not a bony fish, lacks this bladder, but it has something that replaces it: a large liver full of oil that helps lift the shark into the water.

- Fish skin and peel

The body of the fish is covered with skin, which is a living, permanent skin
Touching the water.

In the water, it secretes a sticky colloidal substance that helps the fish to slide, and it repels the fish from the action of bacteria and fungi, which are the first bulwarks of defense.

It helps fish retain its water, whether in a sweet river or in a salty sea. In sweet water, fresh water tends to enter the fish's body because it contains salt, and in salt water, fish water tends to leave it into saltier water. This is the law of solutions.

The second line of defense is the fish scale, which grows in its skin, something similar to a nail growing in human skin. It emerges from the skin, leaning against it until it is almost lying, and its free end is directed towards the fish's tail. Its crust superimposes on the next crust, covering most of its surface. The peel grows in an orderly, parallel elongated lines.

As the fish grows, the size of the scale increases, but its number does not increase.
If you look at a peel with a microscope, you will find that it is composed of rings one above the other, all of them dead, except where they approach the germ in the skin. These rings express the amount of growth each year, and therefore the age of the fish according to the students.

(This is a picture of a fish, and we have revealed its interior, and in it the internal organs appear compact, and it resembles the organs of all living creatures with vertebrates, except for modifications necessitated by the fact that the fish’s environment is water, not earth and air.)

Fish colors

He is not like the birds that are famous for the bright colors they wear.
Fish compete with them in this, but they do not have the same fame as birds, for reasons including: Fish with colorful habitats are mostly found in hot areas, and most likely where there are coral rocks, which are colored, so the fish takes on the color of its environment. One of these reasons is that fish with a bright, wonderful color die, and the color fades quickly.

The prevailing opinion is that the fish changes color in response to the environment in which it is in. If the observer looks at it, whether it is a catch or
A catch, he overlooked it, mistaking it for part of this environment.

Colored fish have a characteristic that is not found in colored birds or colored animals. There is no one among these two who can change his color. As for fish, many of their species can do this.

To explain this, we say that color is often a colored substance secreted by fish, and stored in cells resembling small bags called chromatophores, which reside in the skin. Fish can, through the action of muscle filaments, shape them into shapes, spread them out, so they become spots, or radiate them, so they become like bright stars. As envisioned by the draftsmen, or
Lines, or something else.
Some colors do not come from dyes like these
half .