? The squid is one of the mollusks, and the characteristics of the mollusk also apply to the squid. Their bodies are relatively soft, and it is not easy to see their shells without careful observation. But squids do have shells, but they have degenerated over the course of evolution into very small pieces, and their shells are calcareous. This shell is composed of an outer part and an inner part, the outer part is a relatively hard sheath, and the inner part is composed of an inner shell and cartilage.
Specifically, their inner shell is located under the skin of their back, and there is a structure called the shell sac under their skin, in which the inner shell is located, and the shape is relatively long oval. The inner shell of squid is of great significance in their life activities. First of all, it can support their bodies and make them stronger. In addition, the inner shell can also reduce the specific gravity of their bodies to a certain extent, so that they can better maintain their body balance and swim more conveniently.
? As mentioned above, squid belong to mollusks, and their body structure basically conforms to the basic characteristics of mollusks. For example, the heart of squid has more prominent features. Cuttlefish have a heart. Their heart consists of an atrium and two auricles. The shape of their ventricles is rhombic, asymmetric, and the inner wall is relatively thick. A relatively large artery extends outward from the ventricle and a relatively large artery extends backward, both of which play a very important role. The shape of the auricle is longer and the outer wall is thinner, which is quite different from that of the ventricle.
