Crabs are amazing creatures with an unusual body structure. But why do crabs move that way and not go straight to the goal? At first, it may seem that the crustacean acts illogical and complicates the process of movement, but it's not as simple as it seems.
History of the origin of crabs
Scientists believe that the first species of crabs appeared during the Jurassic period (201-145 million years ago). It is rather difficult to make a reliable description of individuals living at that time. However, zoologists were able to study in detail the unique species found in Canada and the United States. Presumably these individuals lived 90 million years ago. They were small in size, swam perfectly thanks to lobate claws and had large round eyes.
Around the same period, bone fish began to evolve, which began to use the distant ancestors of crabs as food. In order to protect them, crustaceans gradually gained a robust carapace that protects them from the teeth of most aquatic predators.
Since then, crabs began to grow their population, gradually new families with unique characteristics appeared. At the moment, zoologists distinguish 6,780 different species. Among them there are both small crustaceans, the size of which is a couple of centimeters, and huge creatures with a leg span of several meters. Now crabs are present in most bodies of water, feeling great in both marine and fresh waters.Most of them live in the shallow waters of the Pacific Ocean, but there are also species that live in the Antarctic.
Why do crabs go sideways?
In fact, the answer to this question is extremely simple: because their body is structured in this way. Since crabs live under rocks and in crevices, in the process of evolution their body has become flattened. This made it easy to climb into narrow aisles.
However, in the process of narrowing the body, their legs began to extend not down, but to the sides. Because of this, the opportunity to step forward has disappeared. With a great desire, the crab can move straight, but it will do it slowly and awkwardly.
Interesting fact: when moving sideways, the crab sees where it is heading. Their eyes have circular vision and record everything that happens around.
Crabs move sideways, because in the process of evolution their limbs began to look not down, but away from the hull. This made moving forward as uncomfortable and almost impossible.
