pomfret
Do you want to know how fish swim?
What can a fish do to be stationary in the water and swim away in an instant?
Wondering why flounder's eyes are on one side? Do flounder juveniles look the same as adults?
If you want to know why, listen to me.
Fish have a spine made up of vertebrae inside their bodies and are vertebrates.
The spine of the fish
The body of the fish is divided into three parts: head, trunk and tail. It is usually flattened left and right, mostly streamlined. This body shape helps to reduce the resistance that fish encounter when moving in the water.
Schematic diagram of the fish structure
< h1 class= "pgc-h-arrow-right" > the movement of the fish</h1>
First, the fish swim in the water, and the power comes from the movement of the muscles of the whole body. It uses the alternating movement contraction of the trunk and tail muscles to twist the body left and right to hit the water flow, and the fish push the body forward with the help of the reaction force generated by the water. This is the most common and important way fish move.
Not only that, but the fins of fish are unique motility organs. Guess what, fish have five kinds of pectoral fins, ventral fins, dorsal fins, fins, and caudal fins, which fin has a greater effect on movement?
The caudal fin has a greater effect on the movement of the fish. Not only can it combine the activity of the muscles to keep the body balanced, but it can also control the swimming direction of the fish like a rudder. At the same time, it can also cooperate with the movement of the muscles of the whole body, which is one of the driving forces to promote the progress of the fish body.
The dorsal and fins maintain balance in the body.
The pectoral fins can change direction.
The ventral fins are less effective and assist the dorsal and fins to maintain balance in the body.
There are exceptions to everything, and in nature, there are very few fish that move entirely on their fins, such as seahorses, which do so entirely on the swing of their dorsal fins as they move forward.
Finally, the movement of the fish, there is another factor due to the gill hole drainage. You read that right. The gill holes drain the water, using the flow of water that sprays from the gill holes during breathing.
For example, one of the reasons why a fish keeps moving its pectoral fins at rest is that it can counteract the propulsion caused by the drainage of the gill holes, which ensures that the fish can stay in a certain position.
The phenomenon of gill hole drainage assisting fish movement is generally more obvious when the fish body is advancing rapidly, or when it is converted from a static state to a moving state.
< h1 class= "pgc-h-arrow-right" > the lateral line of the fish</h1>
When we make fish to eat, experienced mothers in order to avoid the heavy smell of fish, they must pick out a thin white line-like thing from each side of the fish body, which is the side line we want to say.
The lateral line is a special sensory organ of the fish, which can be seen from the outside of the fish body.
Fish side line structure pattern diagram
The lateral lines in the opening appearance of the body surface are many small holes. These small holes are called lateral line tube holes and grow on some scales. The small holes are connected to each other on the side close to the body, forming a long tube, which is a side line pipe.
When the water flow stimulation passes through the lateral line tube hole on the scale and is transmitted to the sensory cells in the side line tube, the sensory cells generate excitement; and pass it to the fish's brain, the water flow feeling can be generated.
Fish sense the direction of water flow, the size of water pressure, the speed of water flow, the position of objects in the water and various changes through the side line, which is not very magical.
< h1 class= "pgc-h-arrow-right" > the breath of a fish</h1>
The respiratory organ of the fish is the gills.
Gill structure diagram
One on each side of the gills. It is the respiratory organ of a fish.
The outside is called a gill cover.
The cavity inside the gill lid is called the gill cavity.
Inside the gill lid, there are four gills on each side of the fish's throat, each of which is divided into two rows of gills, each of which consists of a number of gill filaments arranged.
On the sides of each gill filament, many tiny gill flakes are produced.
When the fish is in the water, each gill piece, gill filament, gill piece is fully open, at this time the gills and water contact area is the largest, increasing the chance of the fish ingesting dissolved oxygen in the water. The microvessels in the epidermis of the gill slices are very thin, and when the water flows through here, the gas exchange is completed.
The process of gas exchange is manifested in the entry of dissolved oxygen in water through the microvascular vessels, and the waste carbon dioxide produced by the body passes through the microvascular vessels.
At this time, the mouth and gill lid of the fish are alternately opened and closed. The mouth and gill caps are not open and closed at the same time.
The breathing of the fish is complete.
< h1 class = "pgc-h-arrow-right" > the eyes of a flounder</h1>
Structure diagram of adult flounder
We usually see flounder, and the eyes of the adult fish are located on the left or right side of the head. As for whether it grows on the left or right side of the fish's head, there is no fixed determinant.
In fact, the distinctive appearance of flounder eyes on the same side is acquired and is not innate. The newly hatched flounder juveniles, their eyes are also like ordinary fish, born on the left and right sides.
When they grow to about 3 centimeters, the eyes begin to move. Probably like adolescent boys and girls, the body begins to stir.
As a result of the agitation, one eye begins to move in the direction of the skull, eventually bypassing the skull and moving close to the eye position on the other side.
This is why when we buy them in the fish market, sometimes we see that the eyes of the fish are off the line, one eye position is normal, and the other eye grows to the skull. I think it's a deformed fish. Fish that are not considered normal are not flounders at all. In fact, the flounder you see at this time has not yet grown into an adult fish.
Because of the special physiological structure of flounders, it determines that their living habits are particularly interesting.
When they swim in the water, they do not have their backs up, but the side with their eyes up. Swim sideways. Sometimes in the swimming pool, we see naughty children, diving obliquely sideways, imitating the swimming posture of flounders.
They are more different from "regular fish" when they prey. Usually, lying flat on the bottom of the sea, the body is covered with a layer of sand, only a pair of eyes are exposed, quietly waiting for the prey to approach. When the prey is close enough, kill instantly. Their endurance, our good human snipers, is no more than that.
And because they are covered with a layer of sand, they can better avoid being eaten. At this time, the advantage of two eyes on one side can be most prominent.
Think about it, beneath a layer of sand, the eyes of two calm fish remain motionless, allowing predators to swim around their heads: I just don't move, I don't move. Heck, you just can't see me. This scene is not funny enough. Bold enough and cunning enough!
Flounder is not very smart! This is also a good interpretation of the survival of the fittest in nature.
Agen tells stories