A Blog by

You’ll Find the Biggest Male Appendage in the World—at the Beach

So tell me: Of all the males on our planet—and I’m talking all, scale be damned, from the littlest insects to the biggest of whales—who’s got the most impressive appendage? Who (you should pardon the expression) is our Biggest Daddy?

And I don’t mean just sex organs, impressive as they sometimes are. I’m talking about any outstanding male appendage—whatever guys have that thrills the ladies, the obvious non-penile example being the peacock tail, which as we all know when fully displayed makes peahens dream of George Clooney.

Picture of a peacock with its feathers fanned out
Photograph by Richard I’Anson, Getty
Indian Peafowl, or Peacock, displaying tail feathers.. Photograph by Richard I'Anson

Impressive? Yes. The problem being that between trysts, a superheavy tail must be a drag to lug around. It costs energy to maintain and more energy to get up and unfurled. But the drive to reproduce is a powerful thing, and sexual selection, as Darwin taught us, just keeps pushing the limits of bigness.

Obviously, there is such a thing as too big. I imagine it gets awkward to be a walrus with tusks curling dangerously close to your chest.

Picture of a pacitic walrus with very long tusks lying on rocks
Photograph by Yva Momatiuk & John Eastcott, Minden Pictures / National Geographic
Pacific Walrus (Odobenus rosmarus) bull portrait on coastal rocks in haul-out cove, summer, Round Island, Bering Sea, Bristol Bay, Alaska. Photograph by Yva Momatiuk & John Eastcott / Minden Pictures / National Geographic

And the weight of these things? Not the absolute weight, but the proportional weight—that’s another limitation. How much can a guy carry? According to Douglas Emlen in his wonderful book Animal Weapons: The Evolution of Battle, while the rack of bone that sits atop a male caribou is hugely impressive (those antlers can weigh 20 pounds and stretch five feet across) …

Picture of a caribou with large antlers amid a lush green landscape on a misty day next to an equal sign that says ''8%''
Photograph by Bob Smith, National Geographic Creative
Close up portrait of a male caribou, Rangifer tarandus. Photograph by Bob Smith, National Geographic Creative

… as big as they are, they account for only 8 percent of the male’s total body weight. Moose and elk have even larger antlers, but even the biggest elk antlers equal only 12 percent of its body weight. So that’s doable. Once upon a time, 11,000 years ago, there was a deer (called Megaloceros giganteus, or the Irish elk) that wandered Europe and Asia, and those guys had boney tops so insanely branched, so crazily big, that our prehistoric humans painted them worshipfully onto the cave walls at Lascaux.

Picture of an Irish elk painted onto the wall at Lascaux cave next to a ''less than'' sign that says 20% next to it
Photograph by Sisse Brimberg, National Geographic Creative
Prehistoric artists painted a red deer on a cave wall. Photograph by Sisse Brimberg, National Geographic Creative

But even these antlers, 12 feet across and wildly branched, weighed less than 20 percent of the total animal.

Go Small to Get Big

You have to drop down to the insect family, to a group of horned beetles, to find a big appendage that approaches a third of the animal’s body weight. There are several beetles that have fighting, clamping horns almost the size of their bodies, and a thing like that growing out of your skull, writes Emlen, “is a little like having your leg sticking up out of your forehead.” You feel it.

Picture of a rhinocerous beetle on wood
Photograph by altrendo nature, Getty
Rhinoceros Beetle, male, Columbia, South America, Photograph by altrendo nature

But if you’re looking for the male who wears the crown, whose appendage is so big, so startling, so colorful, so attractive, so monstrous, and therefore unequaled in the animal kingdom—if you’re looking for the champ? Well …

He’s not in the African savannah. He doesn’t have a tusk. He’s not especially large. You have to look down to see him, down near your feet when you’re at the beach. This is him:

Picture of a fiddler-type crab standing on sand and waving a claw in the air
Photograph by Michael Nichols, National Geographic Creative
Loango National Park, Gabon. A fiddler-type crab with claw raised standing outside its burrow, Photograph by Michael Nichols, Getty

He’s a fiddler crab. And that appendage is his claw. And while sizes vary from crab to crab, the biggest fiddler crab claws weigh roughly half the body weight of the animal. Half! That’s nature’s biggest appendage, says Emlen. And what is it for? Not for feeding. The claw is useless at mealtime. Males eat with their other, smaller claw only. But, says Cornell biologist John Christy, the claw’s bright colors definitely attract female attention. It can also snap down and inflict real harm, so they’re potential weapons. But mostly, he discovered, males use them—I kid you not—to wave.

“Up and down, up and down, again and again,” writes Emlen, “they raise their claws high and drop them. Dozens of times each minute, thousands of times per hour, hour after hour … ” They look a little silly doing this, like a lonely fan trying to start a stadium wave. Check out this fellow:

Why are they waving? It’s a warning. “Look what I’ve got!” the male is saying to any male who would trespass into his burrow. “This thing is going to pound you if you come near, so stay away!” In effect, Emlen writes, “fiddlers are employing their claws as warnings rather than instruments of battle.” And it works. “An overwhelming majority of contests end before they ever begin, without anything even resembling a fight. A mere glance at a big claw is sufficient to deter smaller males.”

The male has built a tunnel, which leads to a nesting burrow. His claw has attracted a lady, and she’s down below raising his family. His job is to stay on top, waving till she’s done or he drops. It’s a tough life, lifting that gigantic appendage over and over, using up energy, constantly getting bothered by would-be challengers. The male can’t eat. Not while he’s guarding. His food is at the water’s edge, which is down lower on the beach. So he stands there, day after day, getting hungrier, until eventually, Emlen says, “Even the best males run out of steam and are forced to abandon their burrows to go feed and refuel. The instant they leave, others will claim their burrows.” And then they become challengers and have to start all over again.

So while it may be glamorous to top the list of Biggest Appendage Ever, what with the lifting, the waving, the straining, the not eating, the worrying about how long you’ll last, it might be better to have a medium-size claw and not have to be always worrying about the biggest bullies at the beach. Yes, the big claw does dramatically increase your chances of producing babies, which, as Darwin will tell you, is the whole point. But if I were a fiddler crab lucky enough to have the biggest appendage in the world, I think I’d get myself a nail file (claw file?), erase my genetic advantage, and spend lazy afternoons sipping pond scum by the ocean’s edge. I like a gentler life.

Douglas J. Emlen’s book, Animal Weapons: The Evolution of Battle, is a fascinating account of how animal weaponry, both offensive (claws, horns, teeth) and defensive (armor, shelter, thorns, claws again) parallel human weaponry, both offensive (arrows, lances, swords, missiles, A-bombs) and defensive (armor, castles, spying). It’s a compelling, fun, often scary analysis. And David Tuss’ drawings, especially his animals, made me jealous.

A Blog by

The Barnacle That Eats Glowing Sharks

Most barnacles sit on hard surfaces, and filter small particles of food from the surrounding water. But Anelasma squalicola is an exception. It’s a parasitic barnacle that eats sharks, by fastening itself to their flanks and draining nutrients from their flesh.

Charles Darwin, history’s greatest barnacle fanboy, described Anelasma in his 1851 magnum opus, and suggested that it was most likely a parasite. He was right, but the creature is so rare that few scientists have been able to study it in detail. That changed when Henrik Glenner discovered a large group of velvet belly lantern sharks—small fish with glowing bellies—off the western coast of Norway. The sharks were infested with the parasitic barnacles.

Glenner’s team at the University of Bergen, fronted by David John Rees, have now shown that Anelasma is a newly-minted parasite. It has only just made the evolutionary leap from filter-feeding to parasitism, and still retains many of the traits of its former life.

“The chances of finding such an organism are incredibly slim,” says Glenner. “It would have a brief evolutionary existence compared to its suspension-feeding predecessor and its parasitic successor. For evolutionary biologists, a chance to study all aspects of the biology of such a creature is a rare gift.”

Barnacles, despite their outward appearance, are crustaceans like crabs and lobsters. You can see the resemblance if you cut their shells open. Inside, you’ll find a weird creature that looks like a distorted prawn, lying on its back, with its legs sticking upwards. These legs are called cirri—they’re long and feathery, and the barnacle beats them to draw water into its shell and to sieve food from that water. There are around 1,000 species of barnacle and they’re almost all like this.

Anelasma is not. It lacks a hard shell. Its cirri are still there, but they are small and useless for feeding. It has a mouth and gut, but there’s never anything in them.

Instead, it feeds with a unique organ called a peduncle, which looks like a yellow onion with tree roots sprouting out of it. It’s not connected to the animal’s gut. Instead, the peduncle may be a modified version of the stalk that allows other barnacles to anchor themselves onto rocks; Anelasma uses it to anchor itself in flesh. Once there, it absorbs nutrients through the root-like filaments.

Two barnacles in cross-section: Analesma (left) and Lepas (right).
Two barnacles in cross-section: Analesma (left) and Lepas (right). Ci = cirri; m = mouth; pd = peduncle; r = rootlets; ma = mantle. Credit: Rees et al, 2014, Current Biology.

There are other parasitic barnacles. The rhizocephalans (from the Greek for “head root”) target their own kin—crabs and other crustaceans. As adults, they consist of little more than an external sac, and a root-like digestive system that threads its way through the body of their victims. They also castrate their hosts and addle their minds, so that the crabs care for their parasitic bulge as if it were a clutch of their own eggs. Even the males do this.

Rhizocephalans are completely unrecognisable as barnacles. That’s typical of many parasites, which have so thoroughly adapted to their exploitative lifestyles that they look nothing like their closest relatives. Anelasma bucks the trend. It’s very clearly still a barnacle. It has evolved a completely new feeding system, but it still has traces of the old one (the cirri). “This is a highly unusual situation,” says Glenner. “The selection pressure for both getting rid of the old redundant feeding system, and for improving the novel one, would change the [shape] of such an organism very fast.” That it exists in its current form is an unexpected delight.

Anelasma’s DNA yielded even more surprises. It’s reasonable to think that it evolved from whale barnacles, which attach themselves to whales without parasitising them. After all, this family is already adapted to riding on free-swimming animals, and often bury deeply into their hosts’ skin. But Anelasma’s closest relative is actually Capitulum mitella, a traditional filter-feeding barnacle that lives on rocky Indo-Pacific shorelines. Not a whale barnacle. Also: really quite a long way from Norway!

This suggests that Anelasma might be the last survivor of a much broader group of barnacles. Indeed, C.mitella might be Anelasma’s closest relative, but the two diverged from each other during the Cretaceous period, 120 million years ago. Since that time, perhaps Anelasma’s dynasty spread throughout the world, only to mostly go extinct.

A velvet-belly lantern shark with two (?) Analesma barnacles attached to it. Credit:  Irvin Kilde
A velvet-belly lantern shark with two (?) Analesma barnacles attached to it. Credit: Irvin Kilde

Perhaps the weirdest thing about Anelasma is that it’s the only barnacle to parasitise a back-boned host. It’s not the others lack for opportunities. Many barnacles attach to whales, turtles, sea snakes and manatees. As Rees writes, there’s a “virtually endless food resource (tissue and blood) available just a few millimetres below the attachment site”. So why have so few of them evolved to tap into this nutritious seam?

No one knows. Glenner suspects that it’s just very hard for a barnacle to evolve the peduncle that Anelasma uses. It probably required a “rare combination of rare events” and his team are now trying to find out what those events were.

They also want to solve a few other mysteries about Anelasma. For example, how does it circumvent its host’s immune system? There’s never any inflammation around the buried peduncle, so the shark apparently treats the parasite as part of itself.

And why is it almost always found in pairs, sitting side by side on a lantern shark’s skin? It certainly doesn’t arrive in pairs. As larvae, Analesma is streamlined and can swim surprisingly fast in pursuit of sharks. But it settles independently, which is why some pairs contain a large individual (the longer resident) and a small one (the newer arrival). Perhaps, they eventually settle in pairs so they can always find a mate. Or perhaps these creatures have even more surprises left to discover.

Reference: Rees, Noever, Hoeg, Ommundsen & Glenner. 2014. On the Origin of a Novel Parasitic-Feeding Mode within Suspension-Feeding Barnacles. Current Biology. http://dx.doi.org/10.1016/j.cub.2014.05.030

More on barnacles: Poorly-endowed barnacles overthrow 150-year-old belief

A Blog by

Of 70,000 Crustacean Species, Here’s The First Venomous One

If you wanted to find a venomous animal, you could do far worse than picking up a random arthropod—the group of animals that includes spiders, scorpions, centipedes, ants, bees and wasps. The group includes hundreds of thousands of venomous members, who inject their debilitating chemical weapons via fangs and stings.

Within this toxic dynasty, one of the major arthropod groups—the crustaceans—sticks out. There’s no such thing as a venomous crab or lobster, prawn or shrimp. There are some 70,000 species of crustaceans and, until recently, it seemed that all of them were venom-free.

The only exceptions live in coastal caves, which are connected to the ocean by underground tunnels. The dark, salty worlds are home to blind, white, sinuous creatures called remipedes. Although they look a lot like white centipedes, that’s just a coincidence. They’re actually crustaceans, and possibly close relatives of the insects.

The remipedes were first discovered in the 1980s, and named after the Latin for “oar-footed” because of their many pairs of swimming legs. Observant scientists soon noticed that on either side of their head, behind their jaws, they had a pair of fangs —sharp, hollow-tipped and connected to glands. Others noticed them eating other crustaceans in the wild. Connecting the dots, it looked as if these creatures were venomous.

Now, Bjorn von Reumont from the Natural History Museum in London has proved as much. His team has thoroughly described the fangs of the remipede Speleonectes tulumensis, and characterised the cocktail of toxins in its venom. These creatures are undoubtedly venomous crustaceans, and perhaps the only ones on the planet.

Von Reumont showed that the remipede’s venom system is very sophisticated. One set of muscles contracts the creature’s glands, pumping venom into its fangs. A second set of muscles stabs the fangs forwards, while squeezing a duct to prevent the venom from flowing backwards.

Remipede venom consists of big enzymes like peptidases, which destroy other proteins, and chitinases, which break down the chitin in the external skeletons of arthropods. Together, these substances combine to soften the hard shells of the remipede’s prey, and to digest their innards.

But before a remipede can liquefy its meal, it must first capture it. It probably does that with another chemical—a single unique neurotoxin that’s similar to others found in spider venom. The team thinks that the toxin causes the victim’s motor neurons to fire continuously, paralysing it through its own spasms. “We had to do some work to confirm this, but that was the coolest finding,” says study leader Ronald Jenner. “It makes sense for a blind, aquatic, cave-dwelling predator to have a paralysing toxin so that prey can be instantly overwhelmed.” In a dark, largely empty cave, second chances don’t come often.

Still, the remipede’s venom is weird. Other arthropods, like scorpions or spiders, mainly rely on small proteins that poison nerve cells. The remipede has just the one neurotoxin and relies instead on beefy digestive enzymes. If anything, its venom is more similar to that of vipers and rattlesnakes—a clear case of convergent evolution, where different life-forms independently turn up to the party with the same outfits.

Why? “I don’t know,” says Jenner. It may be that they live in water, while other venomous arthropods are land-lubbers.  What works on land may not work in water. There’s also the fact that creatures like centipedes and scorpions have powerful mouthparts for chewing up their prey. Remipedes seem to feed more like spiders—they liquefy they prey and suck the juices through the shell.

And why are they the only crustaceans to have evolved venom? Again, it’s not clear. Jenner notes that most crustaceans scavenge off debris or feed on small particles in the water. There aren’t many of them that specialise in killing larger prey. “If you want to do that, you either need power or a trick,” says Jenner. The pugilistic mantis shrimps went for power. Remipedes use venom as their trick.

“There might be a few more instances of venomous crustaceans, for which current evidence is anecdotal,” says Jenner. The branchiurans, for example, are a group of fish lice that stab through the skin of their hosts with a sharp spine. That causes heavy bleeding, which “can wreak havoc on the fish and be a real burden on aquaculture operations,” says Jenner. “It would be cool to have a closer look at those.”

Reference: Von Reumont, Blanke, Richter, Alvarez, Bleidorn & Jenner. 2013. The first venomous crustacean revealed by transcriptomics and functional morphology: remipede venom glands express a unique toxin cocktail dominated by enzymes and a neurotoxin. Mol Biol Evol http://dx.doi.org/10.1093/molbev/mst199

Fossil Crabs, Reefs Hint at the Future of Earth’s Seas

Paleontology is often viewed as a science of the dead. The goal of the fossil expert is to find, restore, and understand life that no longer exists, filling out the long backstory of the modern world. But paleobiologists with an ecological bent are challenging this scientific stereotype. The past is not merely a graveyard of strange species, but a record of how life responds to environmental changes that our species is now having an ever-greater role in spurring. Given how greatly past climate change has altered the pattern of life, especially, researchers are scouring the past for hints about how catastrophes triggered by human activity might unfold. Ancient crustaceans, and the reefs they lived upon, may hold such clues.

In a new Geology study, Kent State University paleontologist Adiël Klompmaker and coauthors tracked the history of lobsters, shrimp, true crabs, and squat lobsters in the 252 to 66 million year window of time called the Mesozoic. This was the timespan when these major groups, still present today, evolved and spread. And as Klompmaker and colleagues found when they looked at the habitats the fossil crustaceans were found in and fluctuations in prehistoric sea level, the fate of crabs and their kin has been closely tied to reefs.

The evolutionary story of crustacean lineages is one of ups and downs. Outlined in the new study, the rough version of the story goes something like this.

During the 252 to 201 million year old stretch of Triassic time, when weird crocodile cousins ruled the terrestrial realm, shrimp and lobsters were the dominant forms of crustaceans in the seas. True crabs didn’t start to become a prominent presence in the seas until about 175 million years ago, but their diversity quickly ramped up and outpaced that of the lobsters and shrimp. Crustaceans in general took a major hit during the mass extinction that closed the Jurassic, about 145 million years ago, but lobsters, shrimp, true crabs, and squat lobsters picked up where they left off in the Cretaceous, with true crabs and squat lobsters remaining dominant. As far as crustaceans go, the seas just prior to 66 million years ago may have looked familiar – Klompmaker and coauthors estimate that about 65% of decapod species were crabs and squat lobsters, similar to the count today.

Modern crabs are descendants of crustaceans that proliferated during the Mesozoic. Image by Hans Hillewaert, distributed under a Creative Commons Attribution-Share Alike 3.0 Unported license.
Modern crabs are descendants of crustaceans that proliferated during the Mesozoic. Image by Hans Hillewaert, distributed under a Creative Commons Attribution-Share Alike 3.0 Unported license.

Changes in reefs appear to explain the explosive diversification and recovery of true crabs and squat lobsters through time. The spread of these particular crustacean groups happened during the Late Jurassic, when reefs were expanding, and many of the fossils of these decapods from this time studied by Klompmaker and coauthors were found in sediments associated with reefs. The pattern also shows that decapod genera which lived on reefs had many more species than those that did not, making ancient reefs prehistoric biodiversity hotspots where new species spun off from their parents more often than those scuttling about elsewhere.

The fossil record of crustaceans is far from perfect. The invertebrates don’t fossilize as readily as other organisms, and compared to about 15,000 decapod species known today, a comparatively slim 3,300 species are known from 542 to 1 million years ago. All the same, from the partial record that exists, Klompmaker and colleagues make the case that reefs were critical to the evolutionary pattern of these hard-shelled marine creatures.

While not as well-known as other mass extinctions, the global disaster at the end of the Jurassic had a major influence on evolutionary history. The causes of the catastrophe remain unclear, but fossils leave a stark trail of victims and survivors. In the seas, reefs died back and took many crab and squat lobster species with them. Today, Klompmaker and colleagues point out, extant crabs, squat lobsters, and shrimp are similarly tied to modern coral reefs that are under threat from ocean acidification driven by human input into the atmosphere, climate change, disease, and other  forms of destruction. As the reefs go, so will their decapods in an echo of Jurassic tragedy.

But the fossil record also offers hope. Reefs have taken various forms through time – incorporating organisms such as bivalves, algae, now-extinct lineages of coral – and decapods diversified among the various reef types for over 150 million years. Even if the reefs we know are totally annihilated, decapods surviving elsewhere in the seas may colonize and eventually proliferate among whatever reefs may form over evolutionary time. Life will survive the self-destructive compulsions of our species, but in forms woven from the ecological tatters we leave behind. From concentrated studies of modern ecology and the big picture view of the fossil record, we know how critical reefs are to life on Earth and how our species is acting as an instrument of ecological devastation. The questions is what we’re willing to do to prevent our fossil legacy from being a scar of the world’s sixth mass extinction.


Klompmaker, A., Schweitzer, C., Feldmann, R., Kowalewski, M. 2013. The influence of reefs on the rise of Mesozoic marine crustaceans. Geology. doi: 10.1130/G34768.1


Why are stabby mantis shrimps much slower than punchy ones?

Credit: Professor Roy Caldwell at UC Berkeley.

If you want to find an ocean animal that kills with speed, don’t look to sharks, swordfishes, or barracuda. Instead, try to find a mantis shrimp. These pugilistic relatives of crabs and lobsters attack other animals by rapidly unfurling a pair of arms held under their heads. One group of them—the smashers—have arms that end in heavily reinforced clubs, which can lash out with a top speed of 23 metres per second (50 miles per hour), and hit like a rifle bullet. These powerful hammers can shatter aquarium glass and crab shells alike.

Most research on mantis shrimps focuses on smashers, but these pugilists are in the minority. The majority are “spearers”, whose arms end in a row of fiendish spikes, rather than hard clubs. While the smashers actively search for prey to beat into submission, the spearers are ambush-hunters. They hide in burrows and wait to impale passing victims. They’re Loki to the smashers’ Thor.

Given their differing lifestyles, you might expect the spearers to be faster than the smashers. They rely on quick strikes to kill their prey, and they target fast victims like fish and shrimp rather than the tank-like, slow-moving crabs favoured by smashers. But surprisingly, Maya DeVries from the University of California, Berkeley, found that the fastest spearer strikes at just a quarter of the speed of the fastest smasher.



How mantis shrimps deliver armour-shattering punches without breaking their fists

For engineers looking to create the next generation of armour, the ocean is the place to look. Animals from snails to crabs protect themselves with hard shells whose microscopic structures imbue them with exceptional durability, surpassing even those of most man-made materials. They are extreme defences.

The mantis shrimp smashes them apart with its fists.

That’s the animal that David Kisailus from the University of California, Riverside is studying. “People have been studying molluscs for decades because they’re thought to be very impact-resistant,” he says. “The mantis shrimp eats these guys for dinner.”


A Blog by

Flying plankton take to the air to flee from fish

Even the topmost layer of the ocean, just millimetres below the air above, is full of life. This zone, where two worlds meet, is home to small creatures like animal larvae, algae, bacteria, and other plankton. Among the most abundant residents of this zone are copepods – tiny relatives of crabs and shrimp. And some of them have the ability to leave this world altogether, and take to the air.

When threatened by fish, some copepods can jump straight out of the water and shoot over many times their own body lengths. From the fish’s point of view, its prey suddenly disappears.  Flying fish use the same tactic to escape from predators. Now, we know that one of the most common groups of ocean animals shares their strategy.


A Blog by

Yeti crab farms bacteria on its arms

I’ve got a new piece in Nature about a newly discovered species of “yeti crab” that farms bacteria on its arms, then eats them. It lives in the deep ocean, near seeps that belch out methane. The bacteria living on its bristly arms (hence the name “yeti crab”) feed off the seeping gases, and the crab encourage the bacteria to grow by rhythmically waving their arms.

Go to Nature to read the full piece. Meanwhile, I loved this quote from lead author Andrew Thurber, which gets across how much there is left to discover about the oceans: “It was a big surprise. There’s a tonne of them, they’re not small, and they’re six hours off a major port in Costa Rica.”

(Photos by Andrew Thurber)

A Blog by

Fossil eyes show wraparound three-dimensional vision, half a billion years ago

Each of our eyes sees a slightly different view of the world, and our brain combines these signals into a single three-dimensional image. But this only works in one direction, because our eyes face straight ahead and their respective fields of vision only overlap in a narrow zone. But there was once a creature that had binocular vision in a massive arc around its body, not just in front but to the sides as well. It’s called Henningsmoenicaris scutula and it lived around half a billion years ago.

H.scutula lived in the Cambrian period, the part of Earth’s history when most of today’s major animal groups exploded into existence. It was a crustacean, one of the earliest members of the group that includes crabs, prawns and lobsters. It was just a millimetre long and almost totally encased within a bowl-shaped shield. From beneath the shield, weird spike-tipped legs propelled it along, while two stalked eyes, each just half a millimetre across, peered out at the Cambrian oceans.

These eyes are compound ones, made up of several units or ‘ommatidia’. They’ve also withstood the test of time. Their organic tissues have since been converted into the mineral apatite, and the resulting fossils perfectly retain the shape and angle of each ommatidium. The eyes are so well-preserved that Brigitte Schoenemann from the University of Bonn could use them to reconstruct how H.scotula saw the world to a “quite impressive degree”.


A Blog by

Crayfish females lure males with urine, but then play hard to get

Fighting_crayfishReleasing a steady stream of urine to attract a mate and then fighting off anyone who still dares to approach you doesn’t seem like a great idea for getting sex. But this bizarre strategy is all part of the mating ritual of the signal crayfish. A female’s urine, strange as it sounds, is a powerful aphrodisiac to a male.

Fiona Berry and Thomas Breithaupt studied these courtship chemicals by organising blind speed-dates between male and female crayfish, whose eyes had been covered with tape. They also injected a fluorescent dye into the animals’ bodies, which accumulated in their bladders. Every time they urinated, a plume of green dispersed through the water.

If the duo blocked the female’s nephropores (her urine-producing glands), the males never showed her any interest. If they met, they did so aggressively. But when the duo injected female urine into the water, things took a more lustful turn, and the males quickly seized the females in an amorous grip. Female urine is clearly a turn-on for males.

But the female doesn’t want just any male – she’s after the best, and she makes her suitors prove their mettle by besting her in a test of strength. As he draws near, she responds aggressively, even though it was her who attracted him in the first place. No quarter is given in these fights. The female only stops resisting if the male can flip her over so that he can deposit his sperm on her underside.


A Blog by

Mantis shrimp eyes outclass DVD players, inspire new technology

The most incredible eyes in the animal world can be found under the sea, on the head of the mantis shrimps. Each eye can move independently and can focus on object with three different areas, giving the mantis shrimp “trinocular vision”. While we see in three colours, they see in twelve, and they can tune individual light-sensitive cells depending on local light levels. They can even see a special type of light – ‘circularly polarised light’ – that no other animal can.

But Nicholas Roberts from the University of Bristol has found a new twist to the mantis shrimp’s eye. It contains a technology that’s very similar to that found in CD and DVD players, but it completely outclasses our man-made efforts. If this biological design can be synthesised, it could form the basis of tomorrow’s multimedia players and hard drives.

Previous studies have found that mantis shrimps can detect polarised light – light that vibrates in a single plane as it travels. Think of attaching a piece of string to a wall and shaking it up and down, and you’ll get the idea. Last year, scientists discovered that they can also see circularly polarised light, which travels in the shape of a helix. To date, they are still the only animal that can see these spiralling beams of light.

Its secret lies at a microscopic level. Each eye is packed with light-sensitive cells called rhabdoms that are arranged in groups of eight. Seven sit in a cylinder and each has a tiny slit that polarised light can pass through if it’s vibrating in the right plane. The eighth cell sits on top and its slit is angled at 45 degrees to the seven below it. It’s this cell that converts circularly polarised light into its linear version.

In technical terms, the eighth cell is a “quarter-wave plate”, because it rotates the plane in which light vibrates. Similar devices are also found in camera filters, CD players and DVD players but these man-made versions are far inferior to the mantis shrimp’s biological tech.

Synthetic wave plates only work well for one colour of light. If you change the wavelength slightly, they become ineffective, so designing a wave plate that works for many colours is exceptionally difficult. But the mantis shrimp has already done it. Its eyes work across the entire visible spectrum, from ultraviolet to infrared, achieving a level of performance that our technology can’t compete with.

What’s more, the same eighth cell not only manipulates circularly polarised light, but it can sense ultraviolet light too. It’s a detector and a converter – a two-for-one deal that nothing man-made shares.

Why the mantis shrimp needs such a sophisticated eye is unclear. It could help them to see their prey more clearly in water, which is rife with circularly polarised reflections. It needs good eyesight to be able to hit its prey accurately. Like a crustacean Thor, mantis shrimps shatter their victims with devastating hammer blows inflicted by the fastest arms on the planet. Their forearms, which end in clubs or spears, can travel through water at 10,000 times the acceleration of gravity and hit with the force of a rifle bullet.

Another option is that their super-eyes allow them to send and receive secret messages. A mantis shrimp’s shell reflects circularly polarised light, and males and females produce these reflections from different body parts. Their ability to see this type of light could give them a hidden channel of communication that only they can see, for use in courtship or combat.

Whatever the reason for it, Roberts thinks that the eye’s structure is “beautifully simple”. It’s all in the shapes of the cells, their size, and the amount of fat in their membranes. For all its outstanding performance, the eye’s abilities were probably easy to evolve, requiring only small tweaks to the basic blueprint of the light-detecting cells.

Now that we know about the microscopic structures behind the mantis shrimp’s amazing eye, Roberts is hopeful that engineers can mimic it using liquid crystals. “The cool thing is I think it’s actually something you could make and it would improve the workings of current technologies such as Blu-Ray, which uses multiple wavelengths of light, and of future data storage devices,” he said. It wouldn’t be the first time that crustaceans have inspired technology. A new type of X-ray telescope, for example, was based on the eye of the lobster.

Reference: Nature Photonics DOI: 10.1038/NPHOTON.2009.189

A Blog by

The mantis shrimp has the world’s fastest punch


Blogging on Peer-Reviewed ResearchIn April 1998, an aggressive creature named Tyson smashed through the quarter-inch-thick glass wall of his cell. He was soon subdued by nervous attendants and moved to a more secure facility in Great Yarmouth. Unlike his heavyweight namesake, Tyson was only four inches long. But scientists have recently found that Tyson, like all his kin, can throw one of the fastest and most powerful punches in nature. He was a mantis shrimp.

Mantisshrim.jpgMantis shrimps are aggressive relatives of crabs and lobsters and prey upon other animals by crippling them with devastating jabs. Their secret weapons are a pair of hinged arms folded away under their head, which they can unfurl at incredible speeds.

The ‘spearer’ species have arms ending in a fiendish barbed spike that they use to impale soft-bodied prey like fish. But the larger ‘smasher’ species have arms ending in heavy clubs, and use them to deliver blows with the same force as a rifle bullet.


A Blog by

Mantis shrimps have a unique way of seeing

Blogging on Peer-Reviewed ResearchEagles may be famous for their vision, but the most incredible eyes of any animal belong to the mantis shrimp. Neither mantises nor shrimps, these small, pugilistic invertebrates are already renowned for their amazingly complex vision. Now, a group of scientists have found that they use a visual system that’s never been seen before in another animal, and it allows them to exchange secret messages.

Odontodactylus_scyllarus1.jpgMantis shrimps are no stranger to world records. They are famous for their powerful forearms, which can throw the fastest punch on the planet. The arm can accelerate through water at up to 10,000 times the force of gravity, creating a pressure wave that boils the water in front of it, and eventually hits its prey with the force of a rifle bullet. Both crab shells and aquarium glass shatter easily.

Amazing eyes

As impressive as their arms are, the eyes of a mantis shrimp are even more incredible. They are mounted on mobile stalks and can move independently of each other. Mantis shrimps can see objects with three different parts of the same eye, giving them ‘trinocular vision’ so unlike humans who perceive depth best with two eyes, these animals can do it perfectly well with either one of theirs.

Mantis_shrimp_eye.jpgTheir colour vision far exceeds our too. The middle section of each eye, the midband, consists of six parallel strips. The first four are loaded with eight different types of light-sensitive cells (photoreceptors), containing pigments that respond to different wavelengths of light. With these, the mantis shrimp’s visible spectrum extends into the infrared and the ultraviolet. They can even use filters to tune each individual photoreceptor according to local light conditions.

The fifth and six rows of the midband contain photoreceptors that are specialised for detecting polarised light. Normally, light behaves like a wave that vibrates in every possible direction as it moves along. In comparison, polarised light vibrates in just one direction – think of attaching a piece of string to a wall and shaking it up and down. While we are normally oblivious to it, it’s present in the glare that reflects off water and glass and we use polarising filters in sunglasses and cameras to screen it out.

Light can also travel in a the shape of a helix, moving as a spiralling beam that spins either clockwise (right-handed) or anti-clockwise (left-handed). This phenomenon is called ‘circular polarisation’. Tsyr-Huei  Chiou from the University of Maryland found that the mantis shrimp’s eye contains the only known cells in the animal kingdom that can detect it. Our technology can do the same, but the mantis shrimps beat us to it by as much as 400 million years.