Fossil Presence of Limb Bone Marrow Discovered in Fin of 370-Million-Year-Old Fish

Spongy and flexible-like that portion of the hip and the thigh bones, we can thank French and Swedish researchers for this new discovery. According to recent findings, they've come across the earliest fossil presence of limb bone marrow in the fin of a 370-million-year-old fish.

Long bones, which are typically found in the limb of tetrapods, are not only important for movement and support of body weight, but also home to a host of bone marrow-which plays a significant role in haematopoiesis.

But bone marrow is responsible for even more magic, particularly in humans. It also has an important role in the immune system. For instance, blood cells found in bone marrow start off as these young, immature cells, otherwise referred to as stem cells. The bone marrow, in turn, creates all three types of blood cells-red blood cells, white blood cells and platelets--to keep us healthy.

For the study, researchers from Uppsala University in Sweden and the European Synchrotron Radiation Facility (ESRF) in France examined the origin of bone marrow within vertebrates by using synchrotron microtomography to investigate the interior structure of fossil long bones without damaging them. They also discovered that Eustenopteron, a Denovian (370 million year old) lobe-finned fish from Miguasha in Canada is very closely related to the first tetrapods.

Using the beam power of the ESRF, researchers were able to reach submicron resolutions and accurately reconstruct a 3D arrangement of the long-bone microanatomy from the close relatives of tetrapods.

"We have discovered that the bone marrow certainly played a major role in the elongation of fin bone through complex interactions with the trabecular bone" said Sophie Sanchez, a researcher from Uppsala University and the ESRF, via a press release. "This intimate relationship, which has been demonstrated by molecular experiments in extant mammals, is actually primitive for tetrapods".

Researchers found this discovery to be particularly important in understanding the evolutionary steps that make up the distinctive architecture of tetrapod limb bones and their location.

"Without the 3D information provided by the synchrotron, we could never have understood the internal organization of the marrow space" said Per Ahlberg from Uppsala University, via the release. "If you cut a slice through a bone like this, which would damage it irreparably, you would only see an uninformative pattern of holes in the cut surface. With the synchrotron we can image the whole internal structure and understand how the marrow processes are organized, without doing any damage to the bone at all."

What do you think?

More information regarding the study can be found via the journal Proceedings of the Royal Society B.