With a head like a fighter-plane cockpit, a Pacific barreleye fish
shows off its highly sensitive, barrel-like eyes--topped by green,
orblike lenses--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 barreleye to an aquarium for study, the scientists
discovered that the eyes can pivot, like a birdwatcher pointing
binoculars.
The transparent-headed Pacific barreleyes may steal fish from
siphonophores (such as this one photographed in 2001)—jellies that can
grow to more than 33 feet (10 meters) long, according to researchers
who released new barreleye findings and pictures on February 23, 2009.
The barreleye's flat, horizontal fins may allow it to swim very
precisely among the siphonophore's stinging tentacles—and if the fish
fumbles, the clear, helmet-like shield may protect its eyes, according
to MBARI scientists.
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 lens 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.
