Crab is a crustacean, but also an invertebrate.Almost all animals in the world have blood, because only through blood can the animal body need some oxygen and nutrients, in the body structure is indispensable.Crabs also have blood.However, not all animal blood is red, can not be mistaken for all animals like people have red blood.Blood appears red because it contains hemoglobin, which is very efficient at transporting oxygen and nutrients.But the blood of ordinary lower animals does not have this kind of advanced hemoglobin, so it is not red.
The same is true of crabs, which, as mentioned above, belong to invertebrates and are therefore a relatively low animal.Although they have blood, there is no hemoglobin in it, so their blood is not red, but light blue or light blue, which contains some hemocyanin.Many people mistakenly believe that crabs have no blood because of the color of their blood.
As mentioned above, crabs have blood, but just because they have blood does not mean they have blood vessels.Human beings and some more advanced animals have blood vessels in their bodies, and the channels through which blood flows are blood vessels.However, crabs do not have this structure, because their blood circulation pattern belongs to the open circulation.
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