I’ve been asked about the origin of my tentacled orange avatar. So a quick explanation. It’s a screen grabbed and cropped still from The Deep episode of the BBC’s excellent Blue Planet series. I was given the DVD set for my birthday once. I have long had a fascination with cephalopods (octopus, squid and nautilus) ever since as a kid in Dunedin I saw a common octopus up close in the university’s Marin Aquarium. I found young ones in the local rock pools and in summer large dead ones washed up on the shores of Anderson’s Bay Inlet and stank in the sun. I now know they are probably females who have expired after protecting their eggs until they hatched. The females don’t eat and die of starvation.
In The Deep episode we meet Grimpoteuthis the Dumbo octopus. So named because it appears to have ears like Dumbo, Disney’s elephant which it uses to ‘fly’ through the water. What fascinated me was how it moved, like a fish’s fin or a bird’s wing: flat on the downstroke and rotated edge on on the upstroke. It will have evolved from the long fin which fringes the mantle of squid. Ripples in it help cuttlefish and the like to manoeuvre slowly and carefully. Grimpoteuthis has taken this basic design, reduced it and obviously added greater muscular and nervous control. It’s roughly equivalent to the evolution of fish fins from those of sharks and rays. A shark cannot swim with it’s pectoral fins (the ones at the front that stick out the side like stubby wings), it can only incline them like wing flaps on a plane. Rays can undulate their long fringing fins like a cuttlefish. Bony fish (teleosts) have pectoral fins that can be rotated and moved and used for propulsion. Some fish can swim backwards using them, useful for backing out of crevices that might contain food. Those fish fins became our legs and hands.
Dumbo octopus have made a similar evolutionary change. Taking a simple structure and elaborating it for further function.
But a picture is worth a thousand words so here are some videos of Grimpoteuthis in action.
You won’t find Grimpoteuthis in a rock pool though, they are creatures of the very deep, the deepest Octopus known, some living as far down as 7,000metres. About as far down as Everest is high. They hover over the seabed or in the water column eating polychaete worms and small arthropods.