How this little see-through fish gets its rainbow shimmer

NEW YORK — You can see right through this little aquarium fish from Thailand: Its skin is almost completely transparent. Usually, they have shiny outer surfaces that reflect the light — like a hummingbird’s feathers or a butterfly’s wings, explained Arizona State University biologist Ron Rutowski, who was not involved with the research. But the ghost catfish has no scales, said senior author Qibin Zhao, a physicist at China’s Shanghai Jiao Tong University, who became fascinated by the fish after seeing it in an aquarium store. And the very see-through skin, which lets in around 90% of outside light, is essential: “We wouldn’t be able to see the colors if the skin of the fish is not so transparent,” Zhao said in an email. Some species use their iridescence to attract mates or give off warning signals, but it’s not clear whether the ghost catfish’s colors serve a purpose, Rutowski said.