The two green spheres in the video are the lenses of its tubular eyes.
The eyes are enclosed within the transparent shield… sort of like the glass canopy of a jet fighter.
Above the mouth, the two dark capsules that appear to be eyes, actually contain the fish’s olfactory organs, or the equivalent of nostrils.
When it spots food, it can rotate its eyes to look forward to include its mouth in the field of view.
Scientists speculate that the barreleye steals food from siphonophores-- elongated jellies with tentacles that capture prey that swims into them. They believe the barreleye swims into the tentacles and steals the food from the siphonophore.
The shield over its eyes protects them from the stinging cells of the siphonophore’s tentacles.
The barreleye can also rotate its eyes to avoid predators, or avoid being captured by scientists.
The fish, discovered alive by the Monterey Bay Aquarium Research Institute, is the first specimen of its kind to be found with its soft transparent dome intact.
It had been known since 1939—but only from mangled specimens dragged to the surface by nets.