These voracious animals, like the threadfin dragonfish, cast searchlights through nearby waters. To counter the transparent tactic, many predators have turned to bioluminescence. An Evolutionary Arms RaceĪ crystal-clear body isn’t exactly a checkmate on open ocean predators. That clears space in the rest of the body to become transparent. To become see-through, some crustaceans “smush all their organs into one area,” Bagge says, like their head. Crustaceans, for instance, have complex body plans involving diverse organs and tissues. Though not all animals have the luxury of becoming a homogenous lump. “If you stretch anything thin enough - even metal - it will become transparent,” Bagge says. Of this type, small animals can become transparent more easily. Animals with simple body plans like jellyfish can make themselves as homogenous as possible others flatten themselves so light doesn’t have to travel far through their bodies. “That’s really difficult to achieve,” says Lydia Mathger, a sensory biologist at the Marine Biological Laboratory.īut some creatures have optical tricks up their sleeves. įor animals to become see-through, their greatest challenge is to minimize these changes in density within their bodies. Scattering is why gummy bears glow under bright light, why milk is opaque and why yeasty beer is hazy.
This latter pinball effect, which scientists call scattering, occurs when light passes through materials of different densities - say, between muscle and blood. When light hits something, there are four potential outcomes: The light may bounce backwards, pass through unobstructed, be absorbed or deflect in different directions within the object. Read More: The Ocean Twilight Zone’s Mysterious ‘False Bottom’
īut in the ocean’s twilight zone, transparency has really taken off. “I think you can find transparent representatives from every single animal phyla in the midwater,” says Laura Bagge, a visual ecologist at Torch Technologies who works as a contractor for the U.S. Take the anemone shrimp, which lives in waters shallower than 20 meters deep and is so transparent you could read a book through its body. It’s helpful to be transparent in shallower waters too, of course. Predators in this region tend to have eyes that face upward, like the hatchetfish and cockeyed squid this is better for scanning the water above for silhouettes of potential prey.īut to veil their silhouettes, many of the twilight zone’s animals have evolved to become transparent. The last glimmer of sunlight disappears in the ocean’s twilight zone, a region that spans 200 to 1,000 meters in depth and has light levels similar to a starry night.
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