Why Some Tropical Fish Are Gettin’ Squiggly With It

When American painter Bob Ross said, “There are no mistakes, only happy accidents,” he was ostensibly referring to paint on a canvas.

But Mr. Ross’s mantra is just as true for fish from coral reefs, where the eggs of one species of fish and the sperm from another can sometimes combine to produce hybrid offspring with colors even more startling than that of their parents. Think of them as the happy little shrubs of speciation.

Take, for example, the multibarred angelfish (Paracentropyge multifasciata), which boasts black-and-white stripes like window blind slats, and the purple masked angelfish (Paracentropyge venusta), which resembles a lemon drop with a brilliant purplish-blue backside. When the two fish breed, they produce a blue-and-yellow hybrid swirled with white, almost like a slice of babka.

When Yi-Kai Tea, a graduate student at the University of Sydney and the Australian Museum Research Institute first saw this squiggly angelfish, he suspected it was a hybrid. Although coral reefs may appear to be a panoply of bright hues, many coral reef fish have colorful patterns as distinct as stamps. So when a hybrid happens, it’s easy to spot.