These transparent fish turn rainbow with white light. Now, we know why

Light gets diffracted by repeated structures in the ghost catfish’s muscles

A close up photo of several ghost catfish swimming on a black background while a light is shining on some of their scales which appear iridescent.

The ghost catfish (several shown) becomes iridescent when white light passes through its mostly transparent body.

Nan Shi, Xiujun Fan and Genbao Wu

The ghost catfish transforms from glassy to glam when white light passes through its mostly transparent body.