Discovered in the deep: the crustacean with eyes for a head

Shrimp-like Cystisoma are protected from predators by being virtually invisible – thanks to unique retina and a body that casts almost no shadowThe inky depths of the ocean ’s twilight zone are home to fist-sized shrimp-like crustaceans with ridiculously big eyes. Most ofCystisoma’s head is taken up by its eyes – all the better for seeing in the dark. “The bigger you make your eye, the more likely you are to catch any photons that are out there,” says Karen Osborn, research scientist at the Smithsonian Institution in Washington DC.A big challenge for animals living in deep midwater, inCystisoma’s case between 200 and 900 metres down, is to see while not being seen by predators. “It’s basically like playing hide and seek on a football field,” says Osborn. “There’s nothing to duck behind.”Eyes are especially hard to hide because retinas always have to contain dark, photon-absorbing pigments, which predators can either make out in the dim twilight zone illumination, or in the beams of their own bioluminescent searchlights.Cystisoma disguises its huge eyes in a unique way. Instead of concentrating the pigments in a small area, Osborn says, they spread their retina into a thin sheet of tiny reddish dots that are too small for most animals to see.Cystisoma hides most of the rest of its body by being completely transparent. When scientists catch them in trawl nets and empty them into a bucket of seawater, they appear as empty, palm-sized gaps between other ...
Source: Guardian Unlimited Science - Category: Science Authors: Tags: Marine life Oceans Environment Wildlife Zoology Science Biology Source Type: news