The See-Through Zoo
BBC Earth|January - February 2021
Welcome to nature’s menagerie of transparency
Ben Hoare

THAT TAKE GUTS

GLASS FROG

Tropical forests are teeming with predators for whom frogs are top of the menu, so these amphibians have understandably evolved some nifty defences. Glass frogs inhabit the humid cloud forests of South and Central America, rely on a novel form of camouflage: they bare all or almost all. As this studio photo of Hyalinobatrachium aureoguttatum shows, their see-through skin offers up an eyeful of beating heart, blood vessels, bones, and digestive tract. But why display your innards? After all, predators can still see you. A recent study revealed the secret to their curious camouflage, and it lies not so much in their body, but their legs. As the most translucent part of the animals, their legs match the brightness of the background foliage. By blending in, the disappearing phantom limbs help to hide the true outline of these freakish frogs.

THE EYES HAVE IT

PACIFIC BARRELEYE FISH

In 2004, a remotely operated vehicle (ROV) deployed at sea by researchers from Monterey Bay Aquarium Research Institute (MBARI) filmed some extraordinary video that made headlines worldwide. While exploring at a depth of 600m off California's coast, the robo-sub captured the first footage of a living Pacific barreleye or spookfish (Macropinna microstoma). Previously, the googly-eyed, deep-sea fish had only ever been found dead. Those specimens had all lost the transparent ‘hood’ that marine biologist Dr Helen Scales, author of Eye Of The Shoal, calls “a clear bubble-like an astronaut’s helmet”. Thanks to the video – a still from which appears here – scientists worked out that the barreleye’s telescopic, tubular eyes can swivel under their protective visor, enabling the fish to peer up, forwards or down. “The ocean is a near-limitless 3D environment,” says Scales, “so there’s a selective pressure for the ability to scan above and below. Plenty more fish like this are probably waiting to be discovered.”

GOING WITH THE FLOW

SEA WALNUT

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