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You probably never thought that an animal could live without a head, heart, or bones. In fact, this species existed 500 million years ago and exists to this day, in addition they are considered “cousins” of the ancestors of many species of vertebrates today. The vertebrate family of today is extremely prosperous, with more than 60,000 members, all of them with different looks, habits and temperament, but this “cousin” has only one child. Only alive, they are called Amphioxus – Van Xuong fish, this species is also considered living fossils.
Although Van Xuong fish is called fish and at first glance it is very similar to fish, it is not actually fish. On our planet today, most animals that exist are vertebrates, such as horses, cattle, sheep, chickens, ducks, dogs, cats, tigers, ba … Of course, there are us as well. What makes this particular “fish” so exotic and unlike any fish is that they are vertebrates, have no vertebrates but are still grouped with vertebrates, cord animals and form the Chordate branch.
Biologists believe that the Van Xuong fish is an animal in the evolutionary transition from invertebrates to vertebrates, today they are considered to be the ancestors of fish, but they are completely not fish.
The skin of Van Xuong fish has 2 main layers, the outer epidermis and the dermis on the inside. Unlike most vertebrates, their epidermis has only 1 cell layer, while the epidermis is underdeveloped, mainly composed of colloidal or elastic connective tissue.
There are more than 66,000 species of animals in the order Phylum Chordata. The most remarkable thing is that vertebrates make up the largest proportion, with more than 66,000 species, the main caudal subsector is the sea level, and there are currently about 3,000 known species; and head vertebrates, only two families of fish Van Xuong and fish Asymmetron – there are 30 species.
In fact, the skeleton of this fish is the wire that runs along the body and back from the tail to the head. The gill region, the skeleton, is a network of horizontal and vertical interconnected 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 film.
Although the Van Xuong fish looks like a fish, the biggest difference between it and its vertebrates is that it does not have a real head, sensory organs such as smell, sight and hearing, even a skull. The teeth are also something too fictional for them. This animal has only a bunch of elastic “legs” on the head to play the role of supporting the body. The most amazing thing is that it doesn’t even have a heart, instead it relies on the beat of part of the blood vessel to carry blood.
Their musculoskeletal system is less differentiated and typical dissociated. Therefore, muscles can only ensure simple bending movements, consistent with the lifestyle of being buried in the sand. The muscular system consists of many muscles (myomera), arranged from the front end to the posterior end of the body. The muscle segments are intersected by septum by connective tissue (myosepta). The muscle segments on the sides of the body are arranged alternately with combs together. As a result, when swimming, the Pangasius swim, its body bends along the horizontal plane.
Amphioxus is widely distributed in the shallow waters of the ocean, and Qingdao and Xiamen in China are their primary habitats. In addition, there are coasts of Southeast Asia and coasts of California and Florida, Norway, the Mediterranean and Africa. Due to its rich nutrition and delicious taste, Van Xuong fish is considered a delicious traditional dish in Southeast Asia.
Van Xuong fish is 3 to 5cm long, and its morphology is very strange. The long and flattened body looks almost like a burden. The whole body color is pink, semi-transparent, the parallel longitudinal muscle fibers can be seen. They have no scales, no fins, no vertebrae, and their internal organs are just a rhythmic, rhythmic, complex. No senses like eyes, nose, or ears. There is no differentiation to the digestive tract. Apart from the mouth and throat, just a piece of intestine that leads straight to the anus. Van Xuong fish often follows tidal water to swim in estuaries where the seabed is shallow, almost unable to defend themselves but capable of penetrating into 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 the plankton from the river.
Their muscles are less differentiated, so they can only move in water by simple bending movements. When not moving they often bury themselves in the sand. The way of respiration of Van Xuong fish is similar to that of fish. They vibrate to inject capillaries (mouth tassels) to carry the stream of water from the gill slits. The wall of the gill slot has many blood vessels, where gas exchange occurs.
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