? Invertebrates are the result of animal classification. They are classified according to whether animals have a spine or not. Those with a spine are vertebrates, while those without a spine are invertebrates. Compared with vertebrates, invertebrates are relatively low-level animals, their body structure is far less complex than that of vertebrates, and they basically do not have too advanced structures and organs. In fact, there are many kinds of invertebrates, accounting for about 95% of all species. There are many specific species in invertebrates, including protozoa, echinoderm, mollusk, coelenterate and annelid.
Squid is one of the more common animals in daily life, which is an animal in the class Cephalopoda of the phylum Mollusca. That is to say, squid belongs to mollusks, and mollusks belong to invertebrates, so squid also belongs to invertebrates. The squid also conforms to the basic characteristics of invertebrates. They do not have a spine in their body, which is a relatively low-level creature.
? As mentioned above, squid belong to invertebrates, and there is no spine in their body structure. Although the squid's body is relatively soft and does not look like a bone, it also has a structure similar to a bone. The cuttlefish has a bone-like inner shell, which has a special name of "cuttlebone". Of course, the bony inner shell of squid is different from the bones of humans and many animals, and it is not the bones that people usually understand. Nevertheless, the bony inner shell of squid can also play an important role, such as protection and support.
