Passage I

Double the Manta Rays

There are thousands of new animal species identified each year, the vast majority are small or geographically isolated. So as graduate student Andrea Marshall studied manta rays, which are neither small nor isolated, she didn't expect to identify a new species. Mantas, which are plankton-eating relatives of stingrays that look like pairs of enormous black wings—up to twenty-five feet wide—flying slowly through the water. Encompassing wide swaths of both temperate and tropical oceans, the manta's range abuts every continent but Antarctica.

During Marshall's research off the coast of Mozambique, she observed intriguing physical variations, in the mantas she swam amongst. Her beachside lodgings in Mozambique now house the Marine Megafauna Research Center. She began to suspect that the one recognized species of manta might in fact be two species.

[1] To investigate, Marshall began collecting data. [2] Other data required a closer look. [3] The skin of all mantas, for example, is embedded with tiny, toothlike "denticles." [4] Marshall found that denticles on some mantas were randomly spaced and occasionally overlapped, whereas denticles on other mantas were evenly spaced and never overlapped. [5] Another discovery was: that some mantas bad egg-shaped masses at the base of their tail fins. [6] Each mass contained a bony spine about an inch long一the vestige of a stinging barb from the manta's ancestors. (8)

In 2009, Marshall announced, with two other scientists, that indeed there is two manta species. The reef manta, Manta alfredi, is the smaller and more common of the two. Thriving in shallow water, it kind of sticks around one area. In contrast, the giant manta, Manta birostris, favors deep water and migrates thousands of miles a year.

The fact that such large animals went undifferentiated highlights how little scientists know for so long about these gentle giants. At the moment, manta ray populations face an array of threats worldwide.