The Transparent Crystal Dome
The barreleye fish possesses one of the most astonishing cranial structures in the animal kingdom. Its entire forehead is enclosed in a delicate, transparent shield filled with clear liquid.
Two small indentations on the front of its face, which look like eyes, are actually olfactory organs called nares. Its real eyes are two large, emerald-green tubular barrels mounted entirely inside its skull.
Rotating Green Optical Scanners
Equipped with bright green pigments that filter out downwelling sunlight, the barreleye’s eyes can spot the faint bioluminescent silhouettes of siphonophores and jellies drifting overhead.
When prey is detected above, the fish rotates its tubular eyes 90 degrees forward, tracking the food as it points its tiny mouth upward to strike with surgical precision.
The Siphonophore Food Pirate
The barreleye frequently steals food directly from the stinging tentacles of large colonial siphonophores.
Its transparent head shield acts as protective armor, shielding its delicate eye tissues from venomous nematocyst stings while it picks off captured copepods and larval fish trapped within the jelly’s web.
