Since dried filters from the mouths of filter-feeding rays hit apothecary shop menus in  Asia – the thought being that eating ground-up filters will cleanse one’s liver – there’s been no way to know which of these gentle-natured rays was being slaughtered. Unlike predatory rays that attack and crush prey with their mouths, the filter-feeder rays eat plankton particles, larvae and fish eggs that they sieve from seawater. Most lack barbs other rays are notorious for, and the filter-feeders are generally considered harmless, although one group is provocatively named devil rays – they have horn like fins on their heads – and the other group includes the monstrous-sized manta, measuring up to 23 feet (7 meters) across and weighing 2½ tons.

Now, scientists with the University of Washington’s Friday Harbor Laboratories have discovered enough differences in the filters to be able to identify the giant manta and eight of the devil rays using the part from inside their mouth that has been dried and is being sold.  Read more in UW Today.