Glass Octopus

Image: Richard E. Young

The Glass Octopus! So called because it's transparent. Not because it's made of glass. It's actually soft and gelatinous. Ice Jelly Octopus!

It's a good thing this octopus isn't made of glass because he would probably shatter in the pressure of his environment.

Also he wouldn't be able to move much unless he was constantly all hot and melted. Not even Vulcanoctopus was hot and melted so that's a tough ask!

The Glass Octopus reaches 11 cm (4.3 in) in mantle length and 45 cm (18 in) when you include the tentacles. They live in tropical and subtropical waters across the world at depths between 165 and 1,690 metres (540 and 5,550 feet). This is the Twilight Zone, where the Sun's light is reduced to a blue haze. Transparency therefore is a supreme camouflage if you can manage it.

This is a pelagic octopus, swimming through the ocean far above the sea floor. Lots of predatory fish will be looking upward from the depths, trying to discern the shadow cast by prey. For the Glass Octopus, this means orientating their body so that their decidedly opaque digestive gland stands vertical in the water column. That way, it casts the least possible shadow. Oh dear. Don't we all want our belly to cast the least possible shadow?

Image: Richard E. Young

They also have strange, rectangular eyes...

Image: Richard E. Young

on stalks.

Image: Richard E. Young
Sexy Tentacle

Like other octopuses, the male has an arm modified into a sexual organ known as the hectocotylus. Most octopuses are conservative about this sort of thing and mate on the sea floor.

Some pelagic octopuses, like the Blanket Octopus, have that crazy thing where the male just detaches his hectocotylus and gives it to the female. To the disapprobation of the other octopuses, I'm sure

It's not clear what the Glass Octopus does. They've been seen together, being about as intimate as octopuses ever are and presumably mating, but it was unclear what exactly was going on. I guess that's to be expected when they're virtually invisible. You could be shouting "get a room" at the wind.