It is estimated that fewer than 2,500 mature Speartooth sharks remain in the wild. Credit: Julia Constance Get the Popular Science daily newsletter💡 Breakthroughs, discoveries, and DIY tips sent six days a week. Combining lasers and sharks may sound like a bad idea, but marine ecologists are banking on it to help save some of the planet’s most threatened species. By merging optical technology and geochemistry, a group of researchers in Australia are gaining far more accurate information on the snub-nosed speartooth shark’s ( Glyphis glyphis ) age, as well as the health of its environment. Just like a tree , you can tell a lot about a shark by its rings. But instead of concentric circles in wood, biologists study similar growth patterns in a shark’s vertebrae. For years, scientists estimated a specimen’s age by examining extremely thin slices of spine using methods like transmitted light optical microscopy. The general consensus was that each circular “band” roughly amounted to a single year.…