Meet the Sea Mouse: A Rainbow Worm Covered in Optical Fibers

So-called “sea mice” are not actually mice at all. While they sometimes can resemble furry mice, they are actually marine worms whose spines can reflect a rainbow array of light.

And despite the fact that they have no eyes and spend their time with their heads burrowed in the sand searching for food, their bristles have natural photonic crystals that perform more efficiently than man-made optical fibers.

Their bristles or spines are called “setae,” and give the worms their hirsute appearance. They are also a defense mechanism. When light filters into the spines, they give off a deep red sheen that warns off predators; and when light comes in at a perpendicular angle, it creates a spectacular blue or green hue.

Each tiny spine is made up of many hexagonal cylinders, and when they’re stacked, they form photonic crystals that refract light with nearly perfect efficiency. These natural structures have become the blueprint for synthetic optical communication fibers.

Sea mice, or Aphrodita aculeata, are not always as beautiful as their scientific name and their rainbow-making ability suggest. In direct light, they are very plain looking, a fuzzy greyish brown.

But when the light hits just right, they shimmer with color.

Aphrodita aculeata. Photo by MichaelMaggsOwn work, CC BY-SA 3.0, Link

Scientists assume this natural optic ability is the product of habitat. Sea mice have been found at more than 2,000 meters deep, where so little light reaches the ocean floor that the creatures developed the means to maximize even the most minimal bits of light.

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