Barreleye Fish

With a head like a fighter-plane cockpit, a Pacific barreleye fish shows off its highly sensitive, barrel-like eyes—topped by green, orblike structures—in a picture released today but taken in 2004.

The fish, discovered alive in the deep water off California's central coast by the Monterey Bay Aquarium Research Institute (MBARI), is the first specimen of its kind to be found with its soft transparent dome intact.

The 6-inch (15-centimeter) barreleye (Macropinna microstoma) had been known since 1939—but only from mangled specimens dragged to the surface by nets.


The beady bits on the front of the Pacific barreleye fish in this picture released February 23, 2009, aren't eyes but smell organs.

The grayish, barrel-like eyes are beneath the green domes, which may filter light. In this picture the eyes are pointing upward—the better to see prey above in the darkness of the barreleye's deep-sea home.

Since the eyes are upright tubes, "it just looked like [they only] looked straight up," MBARI marine technician Kim Reisenbichler said. But by watching live fish from a remotely operated vehicle (ROV) and by bringing a barrelfish to an aquarium for study, the scientists discovered that the eyes can pivot, like a birdwatcher pointing binoculars.


The barreleye lives more than 2,000 feet (600 meters) beneath the ocean's surface, where the water is almost inky.

The transparent-headed fish spends much of its time motionless, eyes upward, MBARI scientists discovered while watching the barreleye fish from a remotely operated vehicle.

The green cap atop each of the fish's eyes filters out what little sunlight makes it down from the surface, allowing the fish to focus on the bioluminescence of small jellies or other prey passing overhead.

Then the eyes rotate forward to follow the prey, allowing the fish to home in on its meal.

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I have stayed away from deep sea inhabitants on the blog, because for me they are something that defies any type of explanation. I have studied and read about them for years, and tend to just say, "OK, if you say so," to any explanation offered by learned folks studying them, because in my mind there is no debate, and "OK, if you say so," works for everything down there and makes sense.