The bones of prehistoric fish "acted as skeletal batteries" that supplied minerals to power the animals as they swam long distances, according to new research described in National Geographic. Berlin Museum of Nature paleontologist Yara Haridi and her colleagues analyzed fossilized bones of fish that lived 400 million years ago. The fish, called osteostracans, grew a bone shell on the outside of the body. From National Geographic:
A method developed for materials science and other engineering applications allowed Haridy and colleagues to reveal bone structures that scientists have not previously been able to study. "I saw one of my colleagues' posters in the hallway with amazing images of pores in batteries, and they looked like cells," Hariday recalls[…]
While [using the scanning method on osteostracan fish fossils], Haridy and her team noticed that the bone tissue around the cell cavities was eaten away. These little divots were not the sign of a disease or injury, however. The bone cells had dissolved some of the tissue so that the calcium, phosphorous, and other minerals inside could be sent into the ancient fish's bloodstream.
The cells turned bone tissue into a kind of battery, releasing stored minerals needed for bodily processes such as nourishing the muscles needed to swim. In turn, the need for additional minerals helped drive the evolution of cellular bones, a change that influenced the trajectory of vertebrates.