Blind Octopus

Cirrothauma murrayi

Octopuses are famous for having eyes remarkably similar to those of humans but without the blind spot.

The Blind Octopus is different in that it has nothing BUT a blind spot!

Video: oceanexplorergov

Actually that's not quite true - they can at least see the difference between light and dark - but they certainly have some serious difficulties in the eyeball department.

For a start, they have no lens, which means they can't focus on anything. Second, they have a reduced retina, which is bad news if you want your eye to detect the shape of whatever it's pointing at.

Image: Michael Vecchione

Third, their eyes are completely embedded within the soft, gelatinous flesh that allows them to survive the punishing pressure at depths of up to 4,500 metres (14,800 feet).

And then, as if all that wasn't enough, it appears they like to go about with their transparent, elephant ear fins covering what little peeper-power they have left.

Perhaps they're protecting them from those freakishly spiky arms?