The crab, a kind of crustacean creature that walks horizontally for years in nature. In real life, we also often use crabs to mock some people, like to walk sideways. But the fact is that the crab always walks sideways for its own reasons.

I. Why do crabs need to walk sideways?

First of all, the crab's body structure determines that it can only walk horizontally when it walks, because each crab's foot has 7 small joints, only up and down, and secondly, the crab's body is flat, walking horizontally can reduce the body's energy consumption, so that they can enter their own destinations at the fastest possible speed to avoid the natural enemies of the natural world. Finally, the Earth's magnetic field has a certain effect on the crab, and the crab itself relies on the magnetic field to recognize direction, so it chooses to walk horizontally to better sense the magnetic field.

Secondly, is there a crab that walks straight?

There is really a crab called the soldier crab, this crab is walking straight, in a large number of crabs, this crab seems to be extraordinarily different, they live in the sandy tunnels, only when the tide is out of activity. It's just a relatively rare tribe, perhaps this kind of crab is not sensitive to the earth's magnetic field, and its body structure is more suitable for walking straight.

Three, the crab shell

A very interesting thing, is that the crab's shell is not with the body of the growth of the growth, they will be like a snake every time to a fixed time will need to shed their shells. And the crab will grow significantly with each molt, but if the crab itself is malnourished, it's shedding its shell instead to make the crab's overall size smaller negative growth, in addition to the crab shedding its shell can by the way the parasites attached to their own body, so that their stumps grow again. The crab walks horizontally, it walks much faster, I think this is also a result of natural evolution, if walking horizontally is much faster than walking straight, can be in the natural world a little bit more chance of survival, this is actually a kind of biological in order to survive a choice instincts.