The Macropinna microstoma has tubular eyes and a see-through head.
Image: © 2004 MBARI
The common name for the fish is "barreleyes." Monterey Bay Aquarium Research Institute investigators recently figured out why this species has such an unusual head. Its eyes can actually rotate within its "skull," so the transparency allows the wary swimmer to keep a literal eye on happenings above it, as well as to the sides and directly in front.
Using video cameras, MBARI researchers Bruce Robison and Kim Reisenbichler revealed the fish's eye movements. When remotely operated vehicles approached the fish, its eyes glowed a vivid green shade in the bright lights of the ROVs. Usually the fish were just hanging out motionless under the deep waters offshore California's central coast.
Here's a "face-on" view showing the green glow.
A siphonophore jelly
Image: © 2001 MBARI
Such a potentially painful dinner requires incredible stealth, so it's now thought that barreleyes carefully maneuvers its body near such stinging organisms, keeping its "eyes on the prize," as the researchers said, throughout the entire hunt. Its tiny mouth then picks at the victim while a transparent shield protects the fish's eyes.