A crab is a animal crustacean and arthropod which belongs to the order of decapods . To know its main characteristics, as you can see, it is necessary to define several terms.
A arthropod It is an invertebrate being whose body has bilateral symmetry, is formed by several segments, has appendages with articulated pieces and has a cuticle as a cover. In this group we can find the crustaceans : animals that breathe through gills and have appendages, antennae and a calcified shell. The decapods On the other hand, they are the crustaceans that have ten legs.
Crabs, therefore, are ten-legged animals with a calcified shell, antennae and appendages that develop gill breathing. Thank you to your tweezers They can fight against other animals and manipulate food.
There are about four thousand species of crabs: beyond differences, they all share the peculiarity of living in the Water or near her. Crabs, however, are not characterized by their ability to swim, but usually walk along the bottom of the body of water.
The crab is an edible animal. One of the most popular dishes is the crab soup , which can be made with the whole body or with the meat Crustacean
The hermit crabs they are very popular, thanks to the fact that they use snail shells to cover their abdomen, made up of a tissue less rigid than that of other crabs, and thus protect it. His scientific name is paguroid, and it is a superfamily (the Paguroid) of crustaceans that have ten legs.
The kind of relationship that the hermit crab maintains with the shells of others mollusks receives the name of tanatocresis and there are not many species that practice it. It is important to note that the crab does not kill to get the shell, but takes it from the carcasses. Worldwide there are approximately 500 species of paguroides and almost all of them are aquatic.
The front of the hermit crab exhibits a rigid exoskeleton, which is why you only need to increase the protection from its rear. To facilitate the task of getting into a shell, his abdomen is spirally coiled and his limbs cover the gaps to prevent other animals from sneaking.
As expected, the hermit crab must change shell more than once in its life, as a result of its natural growth. The selection process is meticulous: it does not conform to any home , but he approaches those that interest him and inspects them carefully using his tweezers until he finds the one he likes best; at that time, he proceeds to make the move as quickly as possible, since every second was in great danger.
Since not having a shell to protect your abdomen is practically surrendering to certain death, the hermit crab cannot allow another to snatch a shell if it is the only one it has found; For this reason, it is very common to in front to their contenders by force.
With regard to food, the hermit crab is mainly scavenger, although it also feeds on plants, larvae, small crustaceans, mussels, snails and worms if needed.
The concept of crab is also used in other ways. In the field of nautical , the hanger is called crab that, with a mouth semicircular at one of its ends, it fits the stick to rotate around it.
In the armors , the crab is the piece constituted with sheets to protect those sectors of the body that need to flex.