Ophiocoma wendtii, a cousin of the starfish, doesn’t have eyes; however, the creature can see. The starfish inhabits the coral reefs of the Caribbean and Gulf of Mexico. Experts have studied the brittle red star, discovering that it is the second creature having extraocular vision joining a single species of sea urchin.
The Ophiocoma wendtii can see without eyes due to its light-sensing cells (photoreceptors), coating its body and pigment cells (chromatophores), that shift during the day and provokes the creature’s color to switch from stripy beige at nighttime to deep reddish-brown in the daytime.
The brittle red star has long, thin arms emanating from a small, disk-shaped body and are about the size of an outstretched human hand. The sea animal lives in bright and complex habitats. It hides from reef fish predators during the daytime and feeds on detritus during nighttime.
The animal’s chromatophores surround its photoreceptors during the daytime. The process helps to narrow the field of the light being detected. Photoreceptors are similar to pixels that form an image when put together. However, this process is not visible during nighttime, when the chromatophores contract.
Ophiocoma Wendtii Is The Second Known Creature That Can See Without Eyes
“If our conclusions about the chromatophores are correct, this is a beautiful example of innovation in evolution,” said Lauren Sumner-Rooney, a research fellow at Oxford University Museum of Natural History who led the study.
Researchers have experimented with these brittle stars and discovered that they have an original vision. From the experiment, the brittle star moved its position toward walls that were white with a black bar, in a circular arena, showing its instinct to hide during the daytime.
Another experiment showed they were not merely detecting brightness versus darkness. The starfish were put in an arena with gray walls; they still drifted toward the black stripe, which was centered on a white line to display the same mass of light as the gray.
“It’s such an alien concept for us, as very visually driven animals, to conceive of how an animal might see its habitat without eyes, but now we know of two examples,” Sumner-Rooney added.