In high spirits: meet Charles Darwin's favourite octopus

Behind the scenes at the Museum's Darwin Centre, the Spirit Collection houses 27 kilometres of shelves filled with animal specimens.

Amongst them are several specimens collected by English naturalist Charles Darwin.

This common octopus, which would rest comfortably in the palm of your hand, is a small but distinguished member of the approximately 22 million wet specimens which make up the Museum's spirit collection.

It was the subject of great interest to the young Darwin who as a recent Cambridge graduate gained his first experience of tropical climates as a naturalist aboard HMS Beagle.

Darwin's delight

Leaving home in 1831 at just 22, Darwin's first stop on the Beagle voyage was Cape Verde, off the west coast of Africa.

In his diaries, the ship's captain, Robert FitzRoy, recorded Darwin's sense of scientific wonder while experiencing a tropical environment for the first time. 'A child with a new toy could not have been more delighted,' he wrote.

'We know from Darwin's diaries and the diaries of Beagle captain Robert FitzRoy that this octopus is one of the first things that Darwin collected,' Jon says.

'Darwin was enthralled by the octopus's ability to emit clouds of dark ink, squeeze into crevices, squirt water at him and change colour.'

Full of excitement about what he was discovering every day, Darwin wrote to his friend the Reverend Professor John Stevens Henslow about an octopus that could change colour. He believed he had discovered a new species. 'This fact appears to be new, as far as I can find out,' the young Darwin wrote.

Jon says, 'Darwin thought it was a new discovery though actually it had been known for a long time, but it's just lovely to see the passion that someone who knows a lot about natural history has when you see something you think may be new in nature.' 

A glowing evaluation

Darwin's letters contain poetic descriptions of his observations of octopuses and other cephalopods that he encountered in the region.

'While looking for marine animals, with my head about two feet above the rocky shore, I was more than once saluted by a jet of water accompanied by a slight grating noise,' he wrote.

'From the difficulty which these animals have in carrying their heads, they cannot crawl with ease when placed on the ground. I observed that one which I kept in the cabin was slightly phosphorescent in the dark.'

According to Jon, the specimen in this last sentence is the very same octopus now in the Museum's collections. It was originally labelled Octopus rugosus but later re-classified as Octopus vulgaris, also called the common octopus.

Darwin took the animal live on board the Beagle - where it would have died shortly after - before he preserved it in alcohol.

'He observed that at night it seemed to fluoresce in the dark,' Jon says. 'Many deep-sea creatures do show bioluminescence, but common octopuses like this one don't glow in the dark.'

'I think what is very likely is that Darwin collected some seawater to keep the octopus in, and that there was possibly some phosphorescent algae or some other organism in the water that glowed as the octopus moved around the container and disturbed it.'

'So I guess the fact is that Darwin didn't get it right every time - but 99% of the time, he did.'

Darwin's common octopus is not one of the many type specimens he left to the Museum. Type specimens - marked in the fish collections by yellow paint on the jars - are the specimens used in science to first describe and name a species.

Preserving in spirit

'It's great being able to show the public,' says Jon. 'The fact you can get it out and it's still flexible shows just how good the preservation process is.

'Personally, I love the link to history and the fact that you can look at and examine a specimen that Charles Darwin himself examined and dissected.

'In the recent past someone has actually dissected the beak out of Darwin's octopus to look at the structure of it, which is a reminder that these collections are here and exist to be used.

'It really sums up the whole reason that these collections are here - so that as scientists, we can check and check again.'

A very wet library

When many people think about Museum collections, they think of dust and boxes - but these are only part of the story.

Spirit collections, or wet collections, are animals preserved in liquid, usually in alcohol (the 'spirit'), which allows scientists to preserve far more of an organism for study than other methods. 

Preserving in alcohol spirit is not a new method. The Museum's earliest wet collections date from the early 1700s and the technique hasn't changed much since the beginning.

'Collections are like a library,' says Jon. 'Each specimen that we have here is like a book, and that book contains information that needs to be available to scientists to take off the shelf to sample and study.

'Sometimes people forget that the Museum isn't just a tourist attraction - it's also a world-leading research centre. One of my main roles is to provide access to the Museum collections to scientists from all around the world, to use.'

See Darwin's specimens

See Darwin's favourite octopus, along with a number of type specimens that he collected, as part of a behind-the-scenes spirit collection tour.