Lamnid sharks maintain an elevated temperature in the red muscle concentrated in their mid-region near the backbone. This specialized anatomy allows the predators to swim fast and continuously, which in turn, allows heat to be retained in the core of the fish leading to local warm-bloodedness. In most other fish, the red muscle is located close to the skin, yielding a fully cold-blooded body and only short bursts of rapid, powerful swimming.

Credit: Zina Deretsky, National Science Foundation