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Zombie Tits, Astronaut Fish and Other Weird Animals
| Title: Zombie Tits, Astronaut Fish and Other Weird Animals Author(s): Becky Crew Publisher: University of New South Wales Press Year: 2013 ISBN: 174223321X,9781742233215 |
The most powerful punch on Earth? Peacock mantis shrimp(Odontodactylus scyllarus)
At no more than 18 centimetres long, the peacock mantis shrimp is small, but it packs a punch with the acceleration of a .22 calibre bullet. There are 400 known species in the stomatopod, or ‘mantis shrimp’, group, which contains solitary-living, predatory crustaceans that are technically neither mantis nor shrimp. They are found in tropical and sub-tropical waters, with more than half of all species occurring in the IndoWest Pacific region. They spend their days holed up in burrows or crevices in shallow coral reefs and on the sandy seabed as far as 1500 metres below the surface. The peacock mantis shrimp (Odontodactylus scyllarus) is arguably the most beautiful of all the stomatopods, with velvety olive, red, and brilliant turquoise varieties, each with a dual chain of deep red legs and the strangest barely-pink eyes. They are distinguished by the spattering of orange leopard spots across the white of their anterior, or frontal, carapace, which, when the peacock mantis shrimp is face-on, give it the appearance of an exotic lily. Mantis shrimp species are grouped according to their hunting techniques. There are the ‘spearers’, with front legs that end in a barbed spike perfect for impaling fish, and the larger ‘smashers’, who thrust their club-shaped claws at speeds of up to 23 metres per second to shatter the protective shells of crabs, clams and snails. Even larger prey such as octopuses and clown fish are not safe from the peacock mantis shrimp, and you wouldn’t handle one if you were fond of having a complete set of digits. One of the world’s top mantis shrimp experts, Roy Caldwell, a professor of integrative biology at the University of California, Berkeley, tells the tale of a South African surgeon who once tried to remove a peacock mantis shrimp from its tank, only to have his finger mangled so badly it required amputation. And several aquariums have had their tanks destroyed by peacock mantis shrimp, a particular individual named Tyson famously smashing through his tank’s 0.6-centimetre-thick glass in 1998. Little Tyson was only 10 centimetres long. In 2004, Caldwell and his colleagues got hold of a US$60 000 high-speed camera, capable of shooting 100 000 frames per second, to investigate the peacock mantis shrimp’s lightning-fast punch. By slowing the action down by a factor of 883, the team discovered that the creature had an odd, saddle-shaped spring within the hinge of the club. Known as a hyperbolic paraboloid, this type of spring arrangement is often used by engineers and architects to reinforce buildings, but is rarely seen in nature. Like a crossbow, it stays locked and compressed while the mantis shrimp’s front leg is cocked, which stores elastic energy until the latch is suddenly released as the arm is extended. The spring gives the claw a peak acceleration of 10 000 times the force of gravity, and strike forces that are thousands of times the peacock mantis shrimp’s body weight. According to Sheila Patek from Harvard University, a biologist who co-authored the paper with Caldwell in Nature that year, the speed of this strike far exceeds most measured animal movements, except that of the trap-jaw ant (Odontomachus bauri) of Central and South America. Patek went on to lead a research team that measured the speed at which this ant snaps shut its mandibles, which are the pair of appendages near its mouth. Using high-speed videography, the researchers clocked the speed at 35–64 metres per second – 2300 times faster than the blink of an eye – which they claimed in a 2006 paper in Proceedings of the National Academy of Sciences is the fastest self-powered predatory strike in the animal kingdom. Patek is now investigating the movements of other mantis shrimp species, and thinks the peacock mantis shrimp could have a rival in its own family. ‘Each species has different strike features – some are faster and some are much slower,’ she says. ‘And, although we haven’t published it yet, we have found another mantis shrimp species that may be even more impressive than the peacock mantis shrimp.’ Patek and Caldwell’s team also found that the peacock mantis shrimp’s punch was particularly destructive due to a process known as cavitation. Its super-fast strike lowers the pressure in the water surrounding the point of impact, causing it to boil and produce exploding bubbles. While emitting a loud clicking noise, and sometimes even flashes of bright light, these bubbles will soften the hard shells of sea snails and clams when they explode, making it easier for the peacock mantis shrimp to break through its prey’s armoured exterior. **** Poor Peacock Mantis Shrimp. With a punch like that, he’s going to have a hard time convincing the entire ocean that he’s not a total psychopath. One night he’ll be at home, quietly ironing and watching something with Gordon Ramsay in it, when a pair of unexpected visitors will turn up on his doorstep. ‘Yes?’ Two starfish in police uniforms will invite themselves inside, drink a cup of his very expensive tea and tell him they’ve both seen this episode already and how great is Gordon Ramsay? ‘Yeah, I know. That’s why I’m watching it.’ ‘Anyway,’ they’ll say, ‘you’re the main suspect in the murder of a crab whose mashed-up remains were found in a garbage bin behind the gym tonight.’ ‘What? I don’t murder crabs, I buy my crab meat from the supermarket, like everyone else,’ Peacock Mantis Shrimp
Not only can the peacock mantis shrimp throw one hell of a punch, it also has the most sophisticated eyes of any animal in the world. Like flies, honeybees and praying mantises, the mantis shrimp has a pair of compound eyes made up of many different facets. The surface consists of two hemispheres separated by a midband, and all three sections are capable of viewing an object independently of each other. This is known as trinocular vision, and it is far superior to ZombieTitsText2Proof.indd 11 30/07/12 1:53 PM Hunters 12 the binocular vision humans have, because we need to use both of our eyes simultaneously to achieve the best result. The mantis shrimp’s midband is separated into six rows of ommatidia, which are structures that carry a cluster of light-sensitive cells called photoreceptors. The first four rows of ommatidia contain specific types of photoreceptors that respond to different wavelengths of light, allowing the mantis shrimp to see in both the infrared and ultraviolet range. Special filters allow each photoreceptor to respond to changing light conditions in the area. The fifth and six rows contain photoreceptors that can detect different planes of polarised light, according to a 2008 Current Biology study led by biologist Tsyr-Huei Chiou from the University of Maryland in the US. Non-polarised light is the kind that comes from the Sun and is visible to humans, and it is made up of electromagnetic waves that oscillate in a direction perpendicular to the way the light is travelling. If this direction is restricted, for example, if non-polarised light is made to pass through a particular type of crystal or reflected off the surface of water, the oscillations will be forced to point in the same direction that the light is travelling. This produces a particular form called linear polarised light, which appears as nothing more than a bright glare to the human eye. The mantis shrimp is the only type of animal known to detect another type of polarised light called circular polarised light (CPL), which is produced under the water where linear polarised light is scattered as it heads towards the surface. Chiou found that three species of mantis shrimp have shells ZombieTitsText2Proof.indd 12 30/07/12 1:53 PM The most powerful punch on Earth? 13 that can reflect CPL, which causes them to change colour. He suggested that the function of this could be that of a ‘secret communication channel’, allowing courting individuals to send sexual signals to each other without attracting the attention of predatory squids and octopuses that are unable to perceive the reflections. In mid-2011, researchers from Penn State University in the US described in Nature Communications how their investigation into the visual mechanisms of the peacock mantis shrimp helped them to invent two-part waveplate technology that could improve CD, DVD, Blu-ray and holographic technology. And elsewhere, researchers are working to improve the CPL filters used in both ordinary and high-tech medical photography by gaining a better understanding of just how the most incredible eyes in the world operate.
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