May 18

Headless, heartless, boneless, Van Xuong fish can survive for 500 million years until today


You probably never thought that an animal could live without a head, heart and bones. In fact, this species existed 500 million years ago and still exists today.

You probably never thought that an animal could live without a head, heart and bones. In fact, this species existed 500 million years ago and exists until today, in addition, they are also considered “cousins” of the ancestors of many vertebrates today. The family of vertebrates today is extremely prosperous, with more than 60,000 members, all of whom have different looks, habits and temperaments, but this “cousin” only has one child left. The only living fossils, they are named Amphioxus – Van Xuong fish, this species is also considered a living fossil.

Although Van Xuong fish is called a fish and at first glance, it is very similar to a fish, but it is not actually a fish. On our planet today, most of the animals that exist are vertebrates, such as horses, cattle, sheep, chickens, ducks, dogs, cats, tigers, tortoises.. Of course, there are us humans as well. What makes this particular “fish” so strange and unlike any other is that they are cephalopods, without a backbone, but still grouped with vertebrates, Chordates live and form the phylum Chordate.

Biologists think that Van Xuong fish is an animal in the transitional evolutionary stage from invertebrates to vertebrates, today they are considered to be ancestors of fish, but they are completely different. not fish.
The skin of Van Xuong fish consists of two main layers: the epidermis (epidermis) on the outside and the dermis (dermis) on the inside. Unlike most vertebrates, their epidermis has only one layer of cells, while the dermis is underdeveloped, mainly composed of glue or elastic connective tissue.

There are more than 66,000 animals in the order Phylum Chordata. The most special thing is that vertebrates account for the largest proportion, with more than 66,000 species, the main subphylum is the sea squid, and there are currently about 3,000 known species; and cephalopods, there are only two families of Van Xuong and Asymmetron fish – there are 30 species.

In fact, the skeleton of this fish is the rope that runs along the body and back from the tail to the head. In the gill slit region, the skeleton is a network of many horizontal and vertical connecting rods. The fins and tentacles are also supported by the connecting rod. Their central nervous system is a neural tube running along the body, located above the spinal cord but not reaching the end of the spinal cord, wrapped in a protective glue membrane.

Although Van Xuong fish looks like a fish, the biggest difference between it and vertebrates is that it does not have a real head, sense organs such as smell, sight and hearing, not even a skull or a skull. teeth are also something too fictitious for them. This animal has only a tuft of elastic “legs” on its head that serves as support for the body. The most amazing thing is that it doesn’t even have a heart, instead it relies on the beating of a portion of blood vessels to transport blood.

Their musculature is less differentiated and typically segmented. Therefore, the muscles can only guarantee simple bending movements, suitable for the lifestyle buried in the sand. The muscular system consists of many muscle segments (myomera), arranged from the anterior end to the posterior end of the body. The muscle segments are separated by septa of connective tissue (myosepta). The muscle segments on both sides of the body are arranged alternately with comb teeth. As a result, when swimming, the body bends in a horizontal plane.

Amphioxus is widely distributed in the shallow waters of the ocean, Qingdao and Xiamen in China are their main habitats. In addition, there are the coasts of Southeast Asia and the coasts of California and Florida, Norway, the Mediterranean and Africa. Due to its rich nutrition and delicious taste, Van Xuong fish is considered a traditional delicacy in Southeast Asia.

Van Xuong fish is 3 to 5cm long, very strange shape. The long, flattened body looks almost like a pole. The whole body is pinkish-pink, semi-transparent, the muscle fibers are clearly visible. They have no scales, no fins, no spine, their internal organs are just a rhythmically pulsating complex tube. There are no senses like eyes, nose, ears. There is no decomposition for the gastrointestinal tract. Apart from the mouth and pharynx, all that remains is a segment of intestine that leads directly to the anus. Van Xuong fish often follow the tide to swim into the estuary where the seabed is shallow, almost defenseless but capable of penetrating the ground. Their lifespan is about 3-4 years, they often bury half of themselves in the sand, while the other half is exposed to receive plankton from the river.
Their musculature is less differentiated, so they can only move in the water by simple bending movements. When not moving, they often bury themselves in the sand. The respiration of Van Xuong fish is also similar to other fishes. They vibrate the cilia (the tentacles in the mouth) to bring water from them to the gill slit. The wall of the gill slit has many blood vessels, where gas exchange occurs.


Van Xuong fish

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