Glass octopus in the Atlantic Ocean off Cabo Verde

© Solvin Zankl/Minden Picture

See-through cephalopod. World Octopus Day

Rarely seen and little understood, this glass octopus lives in the depths of the ocean where sunlight can't reach, about 3,000ft (914m) down. They're a great example of the diversity of the order Octopoda, which we're celebrating today on World Octopus Day.

Among the most intelligent creatures in the sea, octopuses can remember and recognise individual humans and are among the very few animals known to use tools. Some, like the giant Pacific octopus, are enormous, while others are tiny. You’ll find them in a variety of habitats, from tidal p…..