In 2010, an article in Rolling Stone likened the investment bank Goldman Sachs to “a great vampire squid wrapped around the face of humanity, relentlessly jamming its blood funnel into anything that smells like money.”The creature it was referring to does exist – it’s not a true squid, but one of their close relatives. But despite its terrifying name and appearance, it’s not a vampire. It doesn’t suck blood. It doesn’t have a “blood funnel”.
In fact, thanks to newly published observations, we now know that the vampire squid is a garbage-eater. It extends living fishing lines from its body to snag a rain of rubbish falling from the surface, getting fat on a menu of faeces and corpses.
The Goldman Sachs metaphor still works, doesn’t it?
The vampire squid belongs to the cephalopods, the group that includes squid, octopuses and cuttlefish. But it’s an evolutionary relict that appeared well before any of these more familiar animals. Its body is gelatinous and blood-coloured, as if the internal organ of a larger animal had broken free. It swims with two wing-like flaps, sees with opal-blue eyes, and lights up the surrounding water with flashing organs found all over its body, and especially at the tips of its arms.
Two of these arms have been modified into white thin filaments, which coil up into special pockets, and can extend to 8 times the animal’s length. The other eight arms are connected by a cloak-like web that can be inverted over the vampire squid’s body to reveal a muddy charcoal interior, lined with fleshy spines. You can see where the name comes from.
The vampire squid lives all over the world, but we know very little about what it does. That’s partly because it lives at incredible depths – 600 to 900 metres below the surface, in pitch blackness. This level is known as the oxygen minimum zone (OMZ) and unlike the vampire squid, it’s well-named. While a few animals thrive here, most are choked off by the lack of oxygen.
The vampire squid copes by having an incredibly slow metabolism, blood proteins that hug oxygen molecules with an unyielding grip, and a body that so closely matches the density of water that it neither floats nor sinks. It rarely wastes energy on unnecessary movements. It simply hangs in the darkness.
But even though it lives life in the slow lane, the vampire squid needs food, and that’s in short supply in the oxygen minimum zone. What does it eat? To find out, Hendrik Hoving and Bruce Robison from the Monterey Bay Aquarium Research Institute (MBARI) analysed footage of 170 vampire squids, taken over the last decade by the institute’s submersibles.
The videos, along with feeding experiments on captive vampire squids, revealed that they use their filaments like mobile spider webs. They extend these into the surrounding water to ensnare particles of food falling from above. The filaments are covered in tiny hairs, probably for catching these particles. They also have neurons that connect to a particularly large part of the creature’s brain, presumably so it can sense what’s stuck to its fishing lines.
When the time is right, it retracts the filaments, transfers the food to its other arms, and coats them in mucus secreted from its arm tips. It then conveys these delicious balls of mucus-bound detritus into its mouth, possibly with the help of the spines within its cloak.
This strategy is very different to that of other cephalopods, most of which are active hunters that attack and kill their food. Vampire squids are definitely not that, as Hoving and Robison confirmed by checking the stomachs of captured specimens. They found eggs, algae, pellets of faeces, bits of jelly, crustacean body parts—antennae, eyes, some shells, whole copeopods—and flesh from another deep-sea squid. In both kind and quantity, these remnants don’t reflect the diet of a hunter.
Instead, Hoving and Robison think that the vampire squid is mainly a ‘detritivore’ – a rubbish-eater. With few predators in the oxygen minimum zone, it can afford to sacrifice powerful swimming muscles or a high metabolism. Instead, it leads a relatively passive lifestyle, collecting the plentiful snowing debris with its two modified arms. With these adaptations, it can greatly extend the reach of its mouth, while its body—and its life—literally hangs in the balance.
Reference: Hoving & Robsion. 2012. Vampire squid: detritivores in the oxygen minimum zone. Proc Roy Soc B http://dx.doi.org/10.1098/rspb.2012.1357
All images from Hoving and Robison
More on cephalopods
None of our machines can do what a cuttlefish or octopus can do with its skin: change its pattern, colour, and texture to perfectly blend into its surroundings, in matter of milliseconds. Take a look at this classic video of an octopus revealing itself.
But Stephen Morin from Harvard University has been trying to duplicate this natural quick-change ability with a soft-bodied, colour-changing robot. For the moment, it comes nowhere near its natural counterparts – its camouflage is far from perfect, it is permanently tethered to cumbersome wires, and its changing colours have to be controlled by an operator. But it’s certainly a cool (and squishy) step in the right direction.
The camo-bot is an upgraded version of a soft-bodied machine that strode out of George Whitesides’ laboratory at Harvard University last year. That white, translucent machine ambled about on four legs, swapping hard motors and hydraulics for inflatable pockets of air. Now, Morin has fitted the robot’s back with a sheet of silicone containing a network of tiny tubes, each less than half a millimetre wide. By pumping coloured liquids through these “microfluidic” channels, he can change the robot’s colour in about 30 seconds.
If you grew up on a diet of 1980s cartoons, as I did, you will have seen many a giant robot shoot many a rocket-propelled fist into many a big monster. Sadly, there are no rocket punches in the real world, but I can give you the next best thing: a squid that can grabs its enemies with flashing, writhing, self-amputating arms.
The squid in question is Octopoteuthis deletron, a beautiful red animal with hook-lined arms, which grows to around five inches in length. I’ve written about it before – the males have a tendency to indiscriminately implant members of both sexes with sperm.
Imagine trying to talk to two people at the same time. I don’t mean just talking to one and then the other – I mean simultaneously saying different things to both of them. And in one of those conversations, you’re pretending to be someone of the opposite sex. That’s exactly the exchange that Culum Brown from Macquarie University has witnessed off the east coast of Australia.
The speakers were mourning cuttlefish – relatives of octopus and squid, and masters of camouflage. By rapidly expanding and contracting sacs of pigment in their skin, cuttlefish can turn their entire bodies into living video displays. Colours appear and vanish. Mesmeric waves cascade across their flanks. They can even produce different patterns on the two halves of their bodies.
Brown saw a male cuttlefish swimming between a female and a rival male, and displaying different messages to both of them. On his left half, the one the female could see, he flashed zebra-stripe courtship colours to advertise his interest. But on his right half, facing the rival male, he flashed the mottled colours of a female. As far as the competitor was concerned, he was swimming next to two females, oblivious to the act of cross-dressing/seduction going on right next to him. The cheater, meanwhile, prospers.
Many animals defend themselves by mimicking something distasteful, like a wasp or a venomous snake. But the mimic octopus can don a multitude of disguises. It becomes a sea-snake by pushing six arms down a hole and waving the other two around in a sinuous wriggle. It turns into a flatfish by folding its arms back into a leaf shape and undulating them up and down. Its repertoire of venomous animals potentially includes lionfish, sea anemones, jellyfish, and more. It is one of the most dynamic mimics in the animal kingdom.
And now, the mimic has been mimicked.
Last July, while diving in Indonesian waters, Godehard Kopp saw a black-marble jawfish hanging around a mimic octopus. The little fish perfectly matched the octopus in both colour and pattern, blending in among the brown and white stripes of its arms.
Two turtles washed up dead in Moreton Bay, Australia, with no obvious signs of injury or illness. What killed them? I tell the story in a guest-post for Last Word on Nothing, my favourite science blog network. Here’s how it starts; do go and read the full thing.
There is an old story about a scorpion and a turtle. Variants abound, but the basic tale revolves around an unusually talkative scorpion that asks a turtle for a lift across a river. The turtle refuses at first, fearing the scorpion’s sudden but inevitable betrayal. The scorpion insists, the turtle relents, and the two get halfway across before the scorpion predictably stings the turtle. As they sink to their mutual deaths, the turtle asks, “Why did you do it?” The scorpion simply replies: “It’s my nature.”
This story is similar, except an octopus plays the role of the scorpion, and no one talks.
Moreton Bay, on the eastern coast of Australia, is home to around 20,000 green turtles. Kathy Townsend found one of them on October 11, 2008, washed up on a sand bank and dead. Townsend had been studying the links between human activity and sea turtle deaths, but it was clear that this turtle was not killed by people. On the surface, it had no signs of injuries, and it seemed perfectly healthy. “By all rights, it should have still been alive,” says Townsend.
She started cutting.
There are two ways of becoming invisible: you can either be transparent so all light passes through your body, or you can blend in by taking on the colours of your surroundings. A truly incredible animal would be able to do both, switching between the two at a whim. And that’s exactly what some squids and octopuses can do.
Sarah Zylinski and Sonke Johnsen from Duke University found that two cephalopods – the octopus Japetella heathi and the squid Onychoteuthis banksii – can switch their camouflage strategy depending on how bright their environment is. When sunlight streams from above, they choose the see-through option. When their world darkens, they go for darker colours that blend in.
In the dark abyss of the ocean, animals cannot afford to be choosy. The odds of bumping into another individual are low, and appropriate willing mates are even harder to come by. To deal with this problem, the deep-sea squid Octopoteuthis deletron has become somewhat indiscriminate. The males will mate with any squid they come across, whether they’re male or female.
Hendrik Hoving from the Montery Bay Aquarium Research Institute found evidence of these same-sex matings with a robot submarine. Controlled from a surface ship, these vehicles can explore depths that humans cannot. The subs have captured videos of O.deletron since 1992 (videos here), but the team have only just revealed the nature of the squid’s sex life by studying the archival footage.
Ammonites – the ancient relatives of squid and octopuses – left behind some of the most common and beautiful fossils. But look closely at their elegant, spiral shells and you might be able to spot a sinister secret. Some of them are dotted with small pits along their inner walls. Kenneth de Baets from the University of Zurich thinks that the remains of parasitic worms that infested the ammonites and were eventually trapped and killed.
The pits were first described by Michael House in 1960 and they’re known as “Housean pits” in his honour. They’re also called “pearls” since House suggested that these precious stones once resided in the pits. We associate pearls with oysters but any shelled mollusc can produce them, from ammonites to clams. If parasites or irritating particles get inside the shell, the animal protects itself by sealing off the intruder in a mineral sphere. Pearls may be pretty but they’re also a defensive prison.
Now, de Baets, together with Christian Klug and Dieter Korn, has confirmed House’s ideas by studying a large sample of ammonite shells, which he uncovered in Morocco. He thinks that the pits were indeed once filled by pearls. These precious prisons were created to trap parasitic worms.
The critical piece of evidence was a series of thin tubes within each of the pits, which led to the shell’s outer surface. De Baets discovered these tubes by looking carefully at cross-sections of ammonite shells, and he thinks that they’re tunnels created by parasites.
Certainly, they’re not normal parts of the ammonite’s shell – you can’t find them in all specimens and they’re seldom arranged symmetrically. And they’re not the result of objects penetrating or boring through the shell from outside, because no such marks have been found. Instead, their shape and size suggest that they were created by a living thing. De Baets thinks that they’re a close match to the tubes created by modern flukes or trematodes – a group that commonly infects snails, cephalopods and other molluscs.
The trematodes could have swum through the gap between the shell and the ammonite’s body. Alternatively, they could have wormed their way towards the shell from an internal organ, after being swallowed. Once inside, they would have fed upon the host’s tissues until they were sealed in by the overgrowing shell and trapped within a pearl.
If de Baets is right, these parasites have been infecting their cephalopod hosts for around 400 million years. To understand their evolution, he compared the different types of pits and built a family tree that revealed their evolutionary relationships. The tree shows that over time, the parasites went from creating a few big pits to several, smaller ones. The tree provides a tantalising glimpse into the battles between parasite and host, with some trematodes giving up soon after infecting ammonites, others jumping from host to host and yet others co-evolving with the same partner for around 15 million years.
Studying prehistoric parasites isn’t easy. They’re usually small, they tend to live inside their hosts, and their typically soft bodies don’t fossilise well. Often, the only clues to their presence at the traces of the damage they caused. Like the Housean pits of ammonite shells, many of these signs are obscure to the untrained eye, including cysts on the surface of shells and holes created by driller-killers.
I’ve written about two of the most compelling examples, discovered in recent years. David Hughes from Harvard University claimed that small scars on the veins of fossil leaves were left behind by ants that were infected by a lethal fungus. In their deaths, the ants gripped the leaves in their jaws while the fungus fatally erupted from their heads. And Ewan Wolff from the University of Wisconsin thinks that small pits in the jaws of Tyrannosaurus rex were caused by a parasite whose relatives cause trichomonosis in modern birds. This “plague of tyrants” would have created ulcers throughout the dinosaur’s jaw and eroded its bone.
In the most exciting examples, parasites are preserved together with their hosts in mutual death throes. Witness, for example, a mite that was trapped while sucking the blood from a spider. George Poinar Jr, the scientist who popularised the Jurassic Park idea of extracting DNA from insects trapped in amber, has found several such cases. In pieces of amber, he has discovered: a sand fly whose body is riddled with a parasite similar to those that cause sleeping sickness; several parasitic worms actually bursting out of their hosts; a parasite feeding on another parasite, growing on the world’s oldest mushroom; and many more.
Reference: Klug, C. (2010). Devonian pearls and ammonoid-endoparasite co-evolution Acta Palaeontologica Polonica DOI: 10.4202/app.2010.0044
More on parasites:
In a flash, schools of male longfin squid can turn from peaceful gatherings to violent mobs. One minute, individuals are swimming together in peace; the next, they’re attacking one another. The males give chase, ramming each other in the sides and grappling with their tentacles.
These sudden bouts of violence are the doing of the female squid. Males are attracted to the sight of eggs, and females lace the eggs with a chemical that transforms the males into aggressive brutes. Yesterday, I wrote about scientists who could instigate aggression in mice with pulses of light. The longfin squid do the same thing with a rage-inducing chemical