Swordfish’s Sword Doesn’t Break

SwordfishBillfish like marlin and swordfish are known for their characteristic protruding upper jawbone (also called a rostral bone), which they use to help stun and catch their prey.

For the bone to remain strong, it needs to not only withstand a large amount of force, but also be repaired when it is damaged. In mammals, this requires two different types of bone cells: one to break down and absorb damaged bone and another to add new, healthy cells. This process, known as remodeling, leaves telltale marks within the bone that biologists can detect.

Swordfish, however, don’t have either of these cell types in their bone. If the swordfish can’t repair its sword, wondered Ron Shahar, a biologist at the Hebrew University in Jerusalem, how does it remain strong enough to help the fish catch its dinner?

To study billfish bone, Shahar needed samples—no easy task considering that many species of billfish are protected. Maria Laura Habegger, a Ph.D. student at the University of South Florida, in Tampa, routinely attended fishing competitions to obtain any castoffs for study. Shahar convinced her to collaborate, so she traveled from Florida to Spain and on to Israel, all while lugging a suitcase full of billfish bones through some of the world’s strictest airport security.

“No one said a thing, but it was probably a very long 12 hours of travel,” Shahar said.

source : http://newswatch.nationalgeographic.com/2014/10/20/why-a-swordfishs-sword-doesnt-break/





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