The ghost catfish, a small aquarium fish native to rivers in Thailand, is known for its transparent skin that allows us to see its internal organs. However, when the light hits it just right, its body displays a shimmering iridescent glow that flickers with rainbow colors.
Other creatures also exhibit iridescence, displaying a luminous rainbow effect as the viewer moves. However, these creatures typically possess shiny exteriors that reflect light, such as the feathers of a hummingbird or the wings of a butterfly. Unlike other species, the Glass Catfish does not have scales.
A recent study published in the Proceedings of the National Academy of Sciences has discovered that the fish's glow comes from within. As light passes through its skin, it hits tiny structures in the muscle that turn the light into a colorful spectrum, producing a glinting range of colors as the ghost catfish swims. Unlike other iridescent creatures that have shiny outer surfaces that reflect light, the ghost catfish has tightly packed structures in its muscles that bend light into rainbow hues.
Its transparent skin is essential for us to see the colors since it lets in around 90% of outside light. While some species use their iridescence to attract mates or give off warning signals, it's not yet clear whether the ghost catfish's colors serve a purpose.