https://phys.org/news/2018-06-sleuthing-peculiar-ocean-fish.html

"The more we looked, the more differences we could pull out," said Karen Underkoffler, lead author of a recently published paper in the peer-reviewed journal Zootaxa that describes the anatomical characteristics of the different species of opah, including one marked by its big eyes and a purple tongue.

In all, the team of scientists with NOAA Fisheries identified five distinct species of opah, revealing that there isn't a single global species. Three are newly identified, one was already named and researchers better identified another that had been previously described.