Tuna has fishbone. They are edible fish and have high nutritional content. But when many people eat tuna, they don't find fishbone, so they think tuna has no fishbone. In fact, tuna has spines, but their spines are relatively thick and rarely have small spines. Because they all live in the ocean, and tuna is larger and needs to resist greater pressure, their spines are relatively thick. Tuna spines can not only support their bodies, but also protect their hearts.

Tuna is scaly, but their surface looks scaleless. Because they have been degraded for a long time, the scales on their body surface have become very small round scales, which are difficult to find without careful observation. This kind of fish scale is not only small, but also dense, and each fish scale is thick. Such scales can make them swim faster, and can isolate most bacteria outside the body, which can protect their own safety. In addition, these fish scales also reflect light and can be used as a natural camouflage means. Although their scales are relatively small, they need to be scraped off before eating.