In the inky depths of the ocean’s twilight zone live fist-sized, shrimp-like crustaceans with ridiculously large eyes. Most of Cystisoma’s head is taken up by its eyes. “The bigger the eye, the more likely it is to capture all the photons that are there,” said Karen Osborne, a research scientist at the Smithsonian Institution in Washington.
The big challenge for animals living in deep water, in the case of Cystisoma between 200 and 900 meters deep, is to see and at the same time not be noticed by predators. “It’s basically like playing hide-and-seek on a football field,” says Osborne. “There’s nothing to hide behind.”
Cystisoma conceals its huge eyes in a unique way. Instead of concentrating the pigments in a small area, Osborne says, she spreads her retina into a thin line of tiny reddish dots that are too small to be seen by most animals, The Guardian reports.
Cystisoma is completely transparent. When scientists catch them in nets and empty them into a bucket of seawater, they appear empty – with palm-sized gaps between the other animals. “You can’t really see these animals until you get them out of the water,” says Osborne.
Viewed under an electron microscope, parts of Cystisoma’s exoskeleton are covered in tiny bumps that Osborne likens to a carpet of downy hairs. Other parts are covered in a single layer of spherical shapes that the scientists believe could be colonies of an unknown form of bacteria.
The nanoscopic carpet and spheres make it 100 times more likely that light will pass straight through the Cystisoma instead of reflecting into the eye of a passing predator. “It works in exactly the same way as the anti-reflective coating on camera lenses,” says Osborne. “These guys are absolute masters of transparent camouflage in deep water.”
These crustaceans need mating to reproduce. The key to how mates find each other is in the male Cystisoma’s large antennae, covered in structures that detect chemicals in the surrounding water. “They actually feel each other,” Osborne says.