Snakes have necks, why do fish, which are also vertebrates, have no necks?
As vertebrates, we have obvious cervical vertebrae, which makes us have a good neck. If you look closely at land species, you will find that all land vertebrates are the same and have a neck, including snakes.
The function of the neck is to drive our head to turn quickly. Of course, the ultimate goal is to turn our mouth to the direction of food without turning the body, which allows us to get food more efficiently.
However, when we cast our eyes to the water, the same vertebrate fish does not have a neck. What is more interesting is that any species called a fish, by definition, cannot have a neck.
The moment a fish-like creature grows its neck, it is classified as another animal.
We know that it is now generally believed that life originated in the ocean, so how do these species grow necks? Why do fishes do not need necks?
Fish without neck
It can be found from anatomy that fish do not have a neck because they do not have a cervical vertebra to connect the skull to the shoulder strap. The fin is connected to the shoulder strap. It refers to the bone elements that support the forelimb, such as the clavicle and shoulder blade., Here are their fins.
In fish, the connection between the shoulder strap and the skull is not always very tight, but they are a hard bone surface, not the flexible multiple bones of the cervical spine.
Over time, some fish began to change shape. For example, some finfish, according to the fossil record, over time, they lost some of the bones that connect their shoulders and skulls.
The coelacanth belongs to the flesh-fin fish, an ancient species that is considered to be extinct until fishermen rediscovered them on the coast of South Africa in 1938.
Illustration: Talik fish, considered to be the earliest species with neck
The oldest species with neck discovered now is Tiktaalik, which also belongs to flesh-fin fish. This species lived in the Devonian period about 375 million years ago. Scientists describe it as a halfFish semi-quadrupeds.
This kind of fish has completely lost the bone that connects the skull and the shoulder strap, and replaced it with the neck or cervical spine. This neck may help it hunt in shallow freshwater environments.
After having a neck, Titalik can turn its head flexibly regardless of its body, because in shallow water or swampy areas, it is the only way to quickly turn its head to catch prey and stretch its head to breathe.
In contrast, fish without a neck must move their entire body to aim their head in a specific direction.
Then the question is, most fish also need flexible predation, why don’t they need a neck?
This is because if you live in water, a long and flexible neck may bring disadvantages. The water pressure of swimming can easily tilt your head to one side, which is not conducive to swimming.
Although having a neck may be more convenient for fish to hunt, after all, there is no need to turn the body, but if you survive underwater, it is better not to have a neck.
Is Titalik a fish or another animal
As we said before, any animal with a long neck cannot be called a fish, but why is it still called titalik fish?
Actually, Titalik fish is a transitional species. The earliest four-limbed amphibians evolved from finfish.
This kind of process has a technical term-mosaic evolution, that is, some parts of the animal evolve, but other parts still maintain the original form.
Titalik fish are in an evolutionary "gray area". They may not be considered fish, but they are very similar to fish, but whether they are called "fish" or not is just our personal will.
Just like we sometimes bring whales with "fish", they are actually mammals, species that turn from land to ocean.
But what I want to explain here is that the necks of whales are also slowly disappearing. This is an adaptive change. The cervical vertebrae of all cetaceans are very short and very stiff.
This article is uploaded and published on Baidu Know Daily from the media and authors. It only represents the author’s views. It does not mean that Baidu knows the views or positions of the Daily. It only provides an information publishing platform. For cooperation and contributions, please contact email@example.com.