Barreleye Fish

A deep-sea fish with a transparent head and upward-pointing tubular eyes/Deep Sea & Ocean Life

The barreleye fish (Macropinna microstoma) has one of the most unusual heads in the animal kingdom: its skull is completely transparent, filled with clear fluid, with two bright green tubular eyes visible inside looking upward. This allows it to detect the silhouettes of prey above while protecting its sensitive eyes with the transparent shield. The fish can rotate its eyes to face forward when it moves upward to feed. Discovered in 1939, the transparent dome was only confirmed in 2004 when researchers first observed a live specimen at depths around 600 to 800 meters in the North Pacific.