Behold, the Rare Barreleye Fish and Its Translucent Head

It seems that the deeper one goes into the sea, the stranger underwater creatures become. For the most part, anyway. Scientists from the Monterey Bay Aquarium Research Institute (MBARI), for example, recently glimpsed a barreleye fish from the “Midnight Zone” of the ocean. And physiology does indeed get weird at 2,000 feet below the ocean’s surface.

MBARI—an organization that’s no stranger to observing brilliant and bizarre sea creatures—recently posted the above glimpse of the mysterious barreleye fish to its YouTube channel. Aquarist Tommy Knowles and his team were aboard MBARI’s research vessel Rachel Carson when they spotted the barreleye. Knowles and his colleagues were using the ship’s remotely operated submarine to collect jellies for one of the Aquarium’s upcoming exhibitions.

A barreleye fish with a translucent head, glimpsed by an MBARI remotely operated vehicle.

MBARI notes in the video’s description that the barreleye, or Macropinna microstoma,  lives in the ocean’s twilight zone; that is, at depths of somewhere between 2,000 to 2,600 feet below the sea’s surface. The fish’s eyes look upward in order to spot silhouettes of its favorite prey—small crustaceans that siphonophores have captured with their tentacles. (Siphonophores, which consist of individual zooids, are quite strange themselves.)

Even though the barreleye’s eyes seem permanently pointed toward the aquatic firmament, they’re not. MBARI notes that the fish is able to rotate its tubular eyes in its head of transparent tissue so they look forward. A necessary physiological trait as the barreleye’s mouth doesn’t point upward, but rather to the side.

A barreleye fish with a translucent head, glimpsed by an MBARI remotely operated vehicle.

Despite the fact that MBARI’s recorded more than 27,600 hours of deep-sea video, the organization’s only seen the barreleye nine times. Which, of course, makes it a seriously rare fish. Although certainly not the weirdest we’ve ever seen. That award may belong to this ethereal, almost surreal, siphonophore MBARI observed in 2020. Or maybe one of these sea-dwelling nerds.

Featured Image: MBARI

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