The brittle star Ophiocoma wendtii inhabits coral reefs from Bermuda to Brazil. It is known for its advanced compound eyes.
Its arms are covered with calcite crystals. In addition to functioning as an armor and giving structural support, the crystals make up its unique visual systems. They minimize spherical aberration and can detect the direction of incoming light. The lenses work by filtering and focusing light on an underlying photoreceptor system. The only known animals to employ a similar visual system were the now-extinct trilobites. Phototropic chromatophores can change O. wendtiis color and regulate how much light will reach the photoreceptors.Template:Invertebrate-stub
