Fish is not an invertebrate. Fishes belong to the subphylum Vertebrata of the phylum Chordata, so they have a backbone. This animal is characterized by breathing with gills, while swimming by the swing of the trunk and tail, feeding mainly on its upper and lower jaws. Most of them are cold-blooded animals, only a few are warm-blooded animals.
1. Spindle shape: The most common body shape of fish is the spindle shape. Whether freshwater fish or marine fish, most of them are of this shape. The body is spindle-shaped, but slightly flat. This body shape is suitable for swimming in the water and encounters little resistance when moving forward. Usually, fish with this shape inhabit the middle and upper layers of water and can migrate long distances.
2. Club-shaped: Club-shaped fish are more like snakes, generally longer, but much smaller in height and width, such as eel, eel and so on. Interestingly, the fins of these fish are often incomplete, but their swimming ability is second only to the spindle shape, which is suitable for living in the bottom of the water and has the ability to burrow.
3, side flat type: side flat type of fish from the side looks very wide, but if you look down, you will find that they are particularly narrow, such as pomfret, swallow fish and so on are this kind. They live in the middle and lower layers of water, rarely migrate long distances, and their swimming ability is relatively poor.
4. Flat type: The flat type and the side flat type are similar, but the difference is that they are flat up and down, move slowly, and live mostly underwater. There are common rays, rays and catfish.
