Tuna has scales, but their scales are not very obvious. Because tuna has evolved and improved for a long time, their scales have degenerated. Nowadays, tuna scales are relatively small and densely arranged, and individual scales are also relatively thick. If you don't look carefully, you can't find the scales of tuna. The scales evolved to speed tuna up and make them swim faster in the water. In addition, scales can also play a protective role, which can isolate most bacteria in tuna and prevent them from getting sick. In addition, scales can also reflect light, which can help them camouflage well.

Tuna has fishbone. They are common fish, which are not only edible, but also have high nutritional value. Many people don't find a bone when they eat tuna, so most people think tuna doesn't have a bone. Actually, tuna has fishbones, and their fishbones are equivalent to their own skeletons. Fish bones can support their bodies and protect their internal organs. However, tuna rarely has small spines, which are much less than freshwater fish. Because they live in seawater and need to resist great pressure and pressure, fish bones will be thicker.