First, the difference between families and genera
1, Squid: Squid belongs to mollusks of the animal kingdom, mollusca, Cephalopoda, Neooctopus, Squid, Squid suborder, sepiidae and Squid.
2. Octopus: Octopus is a mollusk of the animal kingdom, mollusca, Cephalopoda, Octopus, Octopus, Octopus.
Second, the difference between wrist and foot
1, squid: the squid foot has been specialized into a wrist and a funnel, with wrist 10 strips symmetrically arranged left and right, with the first pair in the center of the back and 2-5 pairs to the ventral side in turn, among which the fourth pair of wrists is particularly long, with a tongue-shaped terminal, a spherical front end and a mouth at the top.
2. Octopus: The body of octopus is short oval, saccate and flipless, and the boundary between head and body is not obvious. There are big compound eyes and eight retractable wrists on the head, and each wrist has two rows of fleshy suckers. Usually, it crawls with the wrist, sometimes it swims by stretching the interosseous membrane, which can effectively hold other things and use the funnel at the lower part of the head to spray water for rapid retreat.
Physiological structure of squid
The body wall of squid is composed of upper skin, muscle and so on, with endoskeleton. Epithelium is a monolayer cell with many pigment cells under it. Pigment cells are flat, with elastic membrane and radial muscle fibers around them. Due to the contraction of muscle fibers, the pigment cells expand into a star shape, the muscle fibers relax, and the pigment cells return to their original state, which can change the depth of skin color.
There is also an iridescent cell under the epidermis to make the body surface shiny. The endoskeleton of squid consists of an inner shell and cartilage. The inner shell is located in the shell capsule under the skin on the dorsal side of the body, which is very developed, with a long oval front end and a pointed protrusion at the end. The shell is calcareous, hard on the back, loose on the ventral side, with many gaps.
The inner shell can not only increase the firmness of the body, but also reduce the specific gravity of the body, which is beneficial to swimming and helps to maintain balance. Cartilage is developed, and its structure is similar to that of vertebrates, but the cells have long branches. The main cartilage is cephalic cartilage, which surrounds the central nervous system and the balance capsule, and has holes on it, from which the nerves can extend. There are also cervical cartilage, wrist cartilage and so on. Endoskeleton develops from ectoderm.