Deep under the sea…

“Up on the shore they work all day/Out in the sun they slave away/While we devotin’/Full time to floatin’/Under the sea”. Wise words from Sebastian the crab, courtesy of Disney’s ‘The Little Mermaid’, which have stuck with me far longer than most useful information, but perfectly demonstrate our very human fascination with the sea.

Most people enjoy, at very least, a brief paddle in the sunlight shallow waters that lap beaches and rock pools, some may venture a bit further out, diving deeper for a brief glimpse of the creatures beneath the waves, but what happens further offshore, down in the deep, dark depths…?


Well, the best answer is that we still don’t really know, the deep sea is classified as ‘depths below 1,800m’ within the bathypelagic zone (1,000-4,000m) and includes the more ominous sounding, abysso- (4,000>6,000m) and hado-pelagic (6,000>11,000m). It is a long touted cliché in marine biology that we know more about the surface of the Moon and Mars that the deep sea and that humans have explored <5% of the world’s oceans to date. Well in answer to this, recent mapping of the seafloor around the world has been conducted at 5km accuracy which enables identification of all major features, ocean ridges, volcanoes, trenches etc. However, to put this in context, NASA has been able to map 98% of Venus to a resolution of 100m and >60% of Mars to 20m. It’s the watery bit that gets in the way of such detailed exploration here on Earth.

But is it worth looking at? As a marine biologist I am really interested in what life can survive at such depths, without sunlight, at pressures that would easily crush a person…

94% of the ocean is below the photic zone, perpetually dark and relatively uniformly cold, around 40C. This world may seem very alien to us, but like most extreme environments, it is still home to an incredible diversity of creatures, with many new species still to be discovered!

Here are three of the most interesting new species found over the last few years…


This little lady was discovered in 2011, during surveys following the Deepwater Horizon oil spill. A member of the anglerfish family, this snaggletoothed species is named Lasiognathus dinema. Interestingly, all specimens found so far have been female, however the lack of males may be similar to other anglerfish species, which have parasitic dwarf males that latch onto the female and then are slowly absorbed into her tissues, leaving only their testes, so they can be hard to find… (I assume the female puts this down to a bad dating experience and moves on?)


This creature looks more like a clothes horse made up of giant earbuds than a living animal, but it is in fact a carnivorous deepsea sponge called Chondrocladia lyra, first found in 2012. This species can reach up to 37cm long, where they are firmly anchored to the seafloor by a rootlike rhizoid. The fronds are made up by Velcro-like hooks, to ensnare copepods and small crustaceans, which are then coated with digestive membranes and absorbed through external pores. Yum!

deep 3

Last, but by no means least, is this cute little octopus, just to prove that not all deep sea critters are the toothy, snaring, engulfing monsters produced by excessive late night cheese-eating. This species, with huge eyes and large swimming appendages on its head was discovered only this year off Puerto Rico and has yet to be named. (Or is this cuddly exterior hiding still further terrors!?)

The deep sea is one of earth’s final frontiers, rich with amazing (and occasionally horrifying) species and I for one, cannot wait to see what swims up from the depths!


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