Bizarre deep-sea dweller has see-through head
What has bulging green eyes, a transparent head, and lives in the dark? It's Macropinna microstoma, a fish that lives in the dark depths of the ocean.
Marine biologists discovered the funky-looking fish in 1939. But until recently, they had not been able to view the fish up close while it was still alive.
Researchers have been trying for 50 years to figure out why Macropinna's head has such a bizarre construction. So the Monterey Bay Aquarium Research Institute (MBARI) decided to probe the fish-head mystery by observing Macropinna in its natural habitat.
MBARI sent remotely operated vehicles (ROVs) into the waters off the coast of central California to find the intriguing species. The ROVs found Macropinna more than 2,000 feet below the surface of the Pacific Ocean. The vehicles took hours of video of the fish maneuvering in its deep-sea home.
Marine biologists Bruce Robison and Kim Reisenbichler studied the videos of the bizarre fish to see what new things they could learn.
The videos show the fish hanging very still in the water most of the time. Macropinna has large flat fins that help it stay motionless.
Robison and Reisenbichler also got a better look at the fish's eyes. They are shaped like tubes, and very good at collecting light from the ocean's surface. That's a good trait to have when you live in one of the darkest parts of the sea!
Researchers had thought that the fish could see only what was directly above its head because its eyes were fixed in place. But Robison and Reisenbichler determined that Macropinna's field of vision is not that limited. Its eyes actually rotate within a transparent bubble that covers its head.
The fish's windshield-like head is made of a clear membrane that is very delicate. Marine biologists were not able to identify this fascinating feature in previous studies because they had never actually seen it. When specimens of the transparent-headed fish were brought up in nets, the membrane would pop before it could be examined.
Adapting to the Deep
Robison and Reisenbichler discovered Macropinna's bright green eyes are key to its hunt for food.
While floating very still, the fish looks up and scans the waters for potential prey swimming above it. When the fish spots something appetizing, its tubular eyes rotate to focus forward. Then Macropinna can turn and swim upward to capture the tasty morsel.
The rotating eyes of Macropinna are evidence of how the fish has physically adapted to survive in its habitat. Robison and Reisenbichler hope to use their discoveries about Macropinna to learn more about how other fish with tubular eyes have adapted to their environments.
Observe Macropinna microstoma for yourself with this video narrated by marine biologist Bruce Robison.
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