Deep sea scientists find strange, transparent fish on ocean expedition

A fish biologist and her team spotted a see-through fish in Alaskan waters recently. It’s a rarely-seen blotched snailfish. 

"Been hoping to see one of these in person for a long time! Blotched snailfish (Crystallichthys cyclospilus)," tweeted Sarah Friedman, a fish biologist at the National Oceanic and Atmospheric Administration (NOAA). 

"We found four or five so far, in the couple of weeks we've been out," Friedman told Mashable. Her team encountered these fish during a routine survey that NOAA conducts every year in the Aleutian Islands off of Alaska. 

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But that doesn’t mean they're common. "They’re found around 100 to 200 meters down. So I would say your general everyday person is never going to encounter one of these fish," Friedman clarified. 

Their transparent, reddish bodies are unique, and they serve a vital purpose. It's an adaptation deep sea creatures like the blotched snailfish use to camouflage themselves, based on the wavelengths of light that pass through water. Red light has the shortest wavelength, meaning it never reaches the deep dark waters and illuminates these fish. This makes deep sea animals largely invisible to predators. 

Snailfish have yet another cool feature, too, said Friedman. They have suction cups at the bottom of their body. This helps them attach to rocks and hold tight in strong currents. The snailfish is one of few fish species that have this structure. 

Friedman also tweeted a few other interesting species she came across during the expedition, including the angler fish. These animals have a rod on their forehead, which contains millions of light-producing bacteria, that flashes light. They do this to lure prey out of the deep, dark depths.