Why is this animal unusual?
Its eyes are tubes that work like binoculars, and they can rotate inside the head. Pointing up, they spot the shadows of prey overhead. Then they swivel forward so the fish can see what it’s about to eat.
Why does it look like that?
The two dots above its mouth that look like eyes are actually its nostrils. The real eyes are the green domes inside the head. The clear shield around them may protect them from the stinging cells of the jellies it steals food from.
Strangest biological feature
The transparent dome. It’s so fragile that it was destroyed every time a barreleye was pulled up in a net – so for decades nobody knew it existed.
Why is it strange?
The barreleye was described in 1939, but scientists drew it wrong for 70 years. Only in 2009, after watching live fish with a deep-sea robot, did researchers work out that the eyes sit inside a clear dome and can turn.
Interesting behavioral facts
It hangs almost motionless in the water, using its large flat fins for tiny, precise adjustments, with its eyes aimed at the faint light above.
