Fishermen in Costa Rica caught (and then released) what appears to be an albino blue marlin. But experts say you have to look closer. The not-blue marlin isn’t albino, either. Instead, it’s probably leucistic. What’s the difference? Albino animals carry mutations that prevent their cells from producing pigment. Leucistic animals, in contrast, seem to have normal pigment cells, but something prevents those cells from being expressed through the skin. You can tell an albino animal from a leucistic one by the eyes — if the eyes are colored, rather than pink, the animal is leucistic.