The HMS ‘Challenger’ Expedition and Creatures of the Deep
Karran Danks describes some of the mysterious deep sea creatures brought back by the HMS Challenger expedition of 1872-76.
Karran Danks: Hello, I’m Karran Danks and I work as a Gallery Assistant at the National Maritime Museum. At the Museum, the gallery assistants are encouraged to give talks for visitors about objects in the museums collections that intrigue them. This recording is part of a series of talks about the curious stories, facts and histories behind some of the objects in our collections. During my talk, I discuss the HMS Challenger and look at some of the mysterious deep sea creatures that were brought back.
As human beings living today in the 21st century, we think we know all that there is around us; we’ve been everywhere, explored, mapped and charted all there is to know. But there’s places we haven’t been too: the oceans. They cover over 71 % of the Earth, but we’ve explored less than 5% of it! This is due to three things.
Firstly, the water pressure which increases rapidly the deeper we go. If you were to take your little fingernail and squeeze it as hard as you could, this would be similar to the pressure at 10 m, and not just on your fingernail! Most nuclear submarines would implode before they reach 1 km down. The deepest-diving whales and their prey, the giant and colossal squid, go no farther than 3 km down.
Close your eyes and squint through your eyelashes: this is close to the light conditions at 10 m off the coast of Britain and it gets worse the deeper you descend. Finally there is the temperature, which drops rapidly the deeper you go. At the very bottom, more than 6 miles down, is the Mariana Trench. Twelve humans have walked on the moon. No one has set foot in the Deeps, and only two have seen it with their own eyes.
The deepest part of the trench is the Challenger Deep at nearly 7 miles. Just to give you an idea: if you were to take Mount Everest, place it in the Deep and then stood on the top of the mountain, you‘ll still be 4,000 ft from the surface!
It seems a very desolate place at the bottom of the ocean; it’s cold, dark, with little food. However, it’s remarkably stable. The temperature remains 2-4?C, salinity is constant, and although the deep pressures would destroy us, marine creatures have amazing adaptations that us humans are only just starting to scratch the surface of.
Forty years before the Challenger expedition of 1872-76, Charles Darwin set out in the Beagle and came back with his theories on natural selection and evolution. Amongst those ideas, was the idea that the ocean deeps were as teeming with life as the jungles of Africa. This divided the top scientists of the day: there was those who simply refused to believe that life could exist below 180 ft; if people couldn’t go that far, how could anything else! And there were those who thought from their own studies that he may be right. For years this debate had raged, until it was decided to settle it once and for all with the Challenger voyage.
The Challenger set out on her four-year voyage of discovery in 1872. During that time she covered 69,000 nautical miles, and stopped at over 600 set places known as sounding stations, where she carried out experiments on water temperature, the depth, the weather conditions, what the seabed consisted of; and of course surveyed for marine life. The Challenger brought back over 13,000 specimens, some 4,000 of which were completely new to science. Some of these were uniquely adapted to life at great depths. Like the deep sea angler fish. If you’ve seen Finding Nemo, these are the same guys as the one that lives at the bottom of the ocean, and waves a little light above his head to attract prey to him to eat. One variant is known as monkfish and served in restaurants.
When it is mature, the male’s digestive system degenerates, making him incapable of feeding independently, which means he needs to quickly find a female angler fish to prevent his death. When he finds a female, he bites into her skin, releasing hormones from her body, which draws his head end into her body. For the rest of his life he is carried on her body, and provides her with sperm as and when needed.
Among other specimens were octopuses. Now octopuses are pretty clever creatures! One octopus I knew, learnt how to undo the bolts on his tank lid to go for a walk, into another tank to help himself to a crab! The octopus also has a pretty nasty way of feeding: its mouthpart is made up of a parrot-like beak and a toothed tongue called a radula, which is used to drill holes into the shells of crabs and clams and stuff. It then injects paralysing saliva into the hole where they can then prise the shell apart.
They also brought back varieties of spider crabs, and the cool thing about spider crabs is that they can moult much like a snake does. Also, strangely, it’s not uncommon for a spider crab to be half-male and half-female and carry eggs only on one half of their bodies! A spider crab is the largest crab to be found in British waters, and the Japanese spider crab is the largest known arthropod; fully grown it can reach a leg span of almost 13ft, a body size of up to 15 in. and a weight of up to 44 lb.
Now corals are actually little marine animals called polyps that look a bit like upside-down sea anemones or jellyfish. They can live in all seas, including our coastline, and down to 1000 m. The polyps secrete a little limestone cup using calcium carbonate dissolved in seawater, to provide a hard surface to protect their tiny soft bodies. They can take a year to grow to 150 mm. And because of this slow growth, corals are massively under threat. It’s thought that 60% of all reefs are under threat and 27% have already been destroyed. This is mainly due to such actions as pollution, over-fishing, and even souvenirs and building materials.
Corals are massively important; not only do they support over 25% of all marine fish species, a square kilometre can provide 15 tonnes of food, enough for 1000 people a year, and act as natural coastal defences, protecting shores from rampaging waves. It’s estimated that it’d cost $1000 per square metre to replace the protection given by reefs. So next time you’re on holiday and are tempted by the piece of coral on sale in the shop, think twice before you bring it home as a holiday reminder!
To find out more about the Gallery Favourite talks that are on this month in the Museum, please visit our website: nmm.ac.uk/gallery-favourites. Thank you for listening.