Csilla Ari of the University of South Florida in Tampa observed five manta rays at the Atlantis Aquarium in the Bahamas, and discovered white markings appearing and disappearing in the space of a few minutes on their backs, fins and heads.

The changes seemed to occur in response to feeding or interaction with other manta rays, and may represent a form of communication. Two of the animals were giant manta rays (Manta birostris; one of two currently recognized species), and the other three may belong to a possible third species, which is similar but distinct from M. birostris.

Body coloration is used to identify species and individual rays, so the author says that understanding these colour changes is essential.

Biol. J. Linn. Soc. http://doi.org/txc (2014)