Octopus is a kind of marine organism, but they are different from most fish that also live in the ocean, and the difference in their body structure is very large. For example, octopuses do not have bones in their body structure, because octopuses are mollusks and invertebrates. Most mollusks don't have bones, but they do have shells or cartilaginous structures that protect them. However, octopuses do not belong to most mollusks, because they have neither shell nor cartilage.
Although there are no bones, nor shell and cartilage protection, octopuses can still take many effective measures to protect themselves. For example, because their bodies are very soft, they can drill through very small caves, and they can use their soft bodies to avoid enemies. Researchers have done studies, and their bodies can even drill through the very small mouth of a beverage bottle. In addition, they also have some means of protecting themselves, which are very common, such as they can change color, can also spray ink to protect themselves and so on.
a mollusk refers to a group of animals with very soft bodies, which are also invertebrates. In general, mollusks have symmetrical bodies, and because their bodies are soft, they have a wide variety of shapes. As mentioned above, octopuses belong to a group of mollusks, which have no bones. However, most mollusks have cartilage or shells to protect themselves, but octopuses do not have these structures.
