Assassin bugs deceive spiders with coat of many corpses

The animal world is full of charlatans. Some have bodies shaped by natural selection to fade into the background or resemble other harmful species. Yet others, like chameleons and octopuses, have the rare ability to actively change their colour or shape to actively hide themselves from view.

Many species disguise themselves through their behaviour rather than their bodies; like human soldiers in camouflage gear, they don special suits to remain inconspicuous.

Decorator crabs, for example, coat their shells with a collection of sea anemones, algae, corals and sponges, held on with Velcro-like bristles while other crabs actively carry these living masks with specially modified legs. These species have the cartoonish air of a man carrying a pot plant in front of him while sneaking past on tip-toes. But some charlatans are not so amusing.

Robert Jackson and Simon Pollard from the University of Canterbury have been studying a pretender with a much more gruesome disguise – the ant-snatching assassin bug Acanthaspis petax, which covers itself with the corpses of its own prey.

Not Exactly Rocket Science’s Review of 2007

As another year finishes and it’s been a good one for me. I won a writing award, got to talk to David Attenborough and started a freelancing career. Luckily, the Christmas break has provided some much-needed relaxation so before I launched renewed into 2008, I thought I’d take a look back and pick the favourite stories which I managed to write about over the last year.

This isn’t a list of the biggest or most important breakthroughs; they are simply the stories I enjoyed writing about the most. They represent a mix of quirky results, articles I was proud of, and sheer coolness – my top ten are in green. As always for this site, all stories were written from the actual papers, rather than press releases or other news coverage.

Once again, thanks to everyone who read, commented on, or linked to this site. Hope to see you all in the new year.

Evolution

1) Living optic fibres bypass the retina’s back-to-front structure

The human retina has an ‘incompetent design’ that forces light to cross a tangle of nerves and blood vessels before reaching the light sensors at the back. The mammalian eye has solved this problem by evolving living optic fibres – Muller cells – that funnel light through the messy retina.

2) Orang-utan study suggests that upright walking may have started in the trees

A study in orang-utans suggested that our ancestors may have evolved to walk on two legs while they were still in the trees, using a bipedal stance to traverse thin branches and canopy gaps.

3) Butterflies evolve resistance to male-killing bacteria in record time

It’s always a thrill to see examples of evolution in action. This year, the beautiful blue moon butterfly of Samoa provided just such an example by evolving resistance to a bacteria that was killing off its males within just 10 generations.

4) The evolution of the past tense – how verbs change over time

Evolution’s not just about genes. In a beautifully written paper, Harvard scientists mathematically modelled the evolution of English verbs, showing that irregular verbs become standardised according to an elegantly simple mathematical model.

Animal behaviour

5) Moray eels attack ‘Alien-style’ with second pair of jaws

Even familiar animals can surprise us. Moray eels are common aquarium specimens but scientists only just discovered that they grab prey with a second set of scary Alien-style jaws that launch forwards from the back of the throat

6) Mobs of honeybees suffocate hornets to death

Cyprian honeybees are frequently attacked the formidable Oriental hornet. But the smaller, weaker bees defend themselves by working together. They mob the hornet, prevent it from expanding the breathing apparatus in its abdomen and suffocate it to death.

7) Fake cleaner fish dons multiple disguises

This year, the bluestriped fangblenny emerged as only the second animal that can change colour to mimic different species, depending on whether it wants a meal or protection. Other discoveries showed the strategic ways in which animals use defensive signals – ground squirrels heat up their tails to fool infrared-sensing rattlesnakes (but not other snakes) and cuttlefish flash up startling eye spots only in front of fish that hunt by sight.

Animal intelligence

8] Chimps trump university students at memory task

Chimps took plenty of opportunities to show how intelligent they are, not least by beating human university students at a memory test. Other studies found that chimps make their own spears to hunt bushbabies, pass on new traditions between groups, altruistically help each other out and even had their own equivalent of our Stone Age.

9) Elephants smell the difference between human ethnic groups

Elephants too have demonstrated that they are no slouches in the intelligence department. African elephants can tell the difference between human ethnic groups and react more fearfully to those that hunt elephants.

10) Clever New Caledonian crows use one tool to acquire another

Meanwhile, the astonishing New Caledonian crow showed that it can combine different tools to solve a problem, often on the first go. They are the only animals besides ourselves and the great apes that have shown this ability.

Palaeontology

11) Microraptor – the dinosaur that flew like a biplane

Flying birds evolved from land-bound dinosaurs, but like human aircraft, it seems that they may have gone through a two-wing design. A small feather dinosaur called Microraptor had wings on its legs too and used these to glide from tree to tree.

12) Evidence that Velociraptor had feathers

This year, scientists finally proved that Velociraptor had feathers on its arms, contrary to its makeover in Jurassic Park. Until now, that had always been an educated guess based on its evolutionary relatives, but small mounds of bone – quill knobs – provided conclusive proof.

13) Sabre-toothed cats had weak bites

The fearsome sabre-toothed cat, Smilodon, was found to have a surprisingly weak bite. It’s massive canines weren’t the brute blade of a swordsman, but the precise daggers of an assassin, used to deliver a quick killing blow to prey that was already wrestled to the ground.

Health and medicine

14) Human skin cells reprogrammed into stem cells

In one of the most exciting breakthroughs of the year, two groups of scientists found a way of turning adult human cells back into the stem cells of embryos, bringing us closer towards treating a range of conditions with personalised stem cells. One such technique was used to cure mice of a genetic disease called sickle cell anaemia using stem cells reprogrammed from their own tails.

15) Brain parasite drives human culture

The thought of a microscopic creature controlling our actions isn’t a nice one, but it might be true. The brain parasite, Toxoplasma gondii, affects a huge proportion of the world’s population and could be a potent driving force of human culture.

16) Space flight turns Salmonella into super-bug

Some bad news for astronauts – a NASA study showed that bacteria react to the zero-gravity conditions of space by becoming extra-virulent super-bugs.

17) Human gut bacteria linked to obesity

Obesity may be down to food and exercise, but new research showed that the balance between two groups of bacteria in our digestive systems affects our risk of being fat.

18) Resistance to an extinct virus makes us more vulnerable to HIV

A fascinating study showed that modern infections of HIV may be the price we pay for immunity to an extinct virus. Millions of years ago, we evolved resistance to a virus called pTERV1 that plagued other primates but this adaptation makes us more vulnerable to HIV.

Environment and ecology

19) How biofuels could cut carbon emissions, produce energy and restore dead land

It’s been a big year for biofuels – hailed as a solution to climate change, they have recently been accused to worsening the problem. But amidst the debate, a small paper went unnoticed, which found that cultivating a diverse mix of woody plants, legumes and grasses could produce biofuels in a way that would curb carbon emissions, produce renewable energy, restore unusable agricultural land and improve biodiversity.

20) Is a virus responsible for the disappearing bees?

Since 2006, a mysterious condition known as Colony Collapse Disorder has been causing entire hives of bees across the US and the UK to vanish. This year, a group of scientists finally found the cause – a virus called IAPV.

21) Restoring predator numbers by culling their prey

It’s been a fascinating year for ecology, with several papers showing that changes to food webs can have very unexpected results. A Norwegian case study epitomised this concept by showing that the best way to help out a threatened predator may be to counter-intuitively cull its prey. Along similar lines, other studies found that shark-hunting harms animals at bottom of the food chain.

Genetics and molecular biology

22) An entire bacterial genome discovered inside that of a fruit fly

In one of the most remarkable examples of gene transfer, scientists discovered that a bacteria called Wolbachia has transferred its entire genome into that of a fruit fly. These extreme gene transfers have important consequences for genome-sequencing projects.

23) Molecule’s constant efforts keep our memories intact

One study this year revealed our memories to be more fragile than we thought. Rather than being permanently writ in our minds, they only remain intact thanks to the constant action of a protein called PKMzeta. Block the protein and erase the memories.

24) Discovery of ‘fat gene’ highlights stigma against obese people

Earlier this year, a gene called FTO was identified as an obesity-related gene. More pertinently, it also highlighted the massive societal stigmas faced by obese people and the incredibly poor public understanding of the how genes affect behaviour.

Psychology

25) Why music sounds right – the hidden tones in our own speech

All cultures around the world divide octaves into twelve semi-tones. Now, we know that this is because these musical intervals reflect the sounds of our own speech. They sound right because they match the frequency ratios hidden within the vowels of our languages.

26) Five-month-old babies prefer their own languages and shun foreign accents

It seems even five-month-old infants have strong prejudices – even though they can’t speak themselves, they prefer the sounds of their own languages and people who speak with native accents.

27) Subliminal flag shifts political views and voting choices

Subliminal messages can strongly affect behaviour, as a group of Israeli scientists found. They changed the attitudes of Israeli students to the Israeli-Palestine conflict, and their voting preferences, by showing them the national flag for just 16 milliseconds, not long enough to consciously register.

Neuroscience

28) Simple sponges provide clues to origin of nervous systems

This year, the possible origins of the nervous system were found in the simple sponge, an animal with no nervous system of its own. Sponges carry the genetic components of synapses, which may have been co-opted by evolution as a starting point for proper nerve cells

29) Monkeys (and their neurons) are calculating statisticians

Using a simple psychological test, scientists showed that monkeys can use simple statistical calculations to make decisions and even managed to catch individual neurons in the act of computing.

30) ‘Brainbow’ paints individual neurons with different colours

Monkeys weren’t the only ones to have their neurons watched. One group of scientists developed a technique that paints the neurons of mice with over 90 colours using a palette of fluorescent proteins. This ‘Brainbow’ provides an unprecedented view of the connections in our brains.

Geology

31) Megaflood in English Channel separated Britain from France

Just in time for the major summer floods in England, a group of scientists found that a megaflood broke through a land bridge that connected England to France, created the English Channel and separated Britain from the rest of Europe.

32) How India became the fastest continent

Continents may move slowly but among them, India is the champion sprinter. When it broke off from the supercontinent Gondwana, a plume of molten rock melted away India’s large rocky roots, turning it into a free-floating raft among strongly anchored peers.

Whales evolved from small aquatic hoofed ancestors

Travel back in time to about 50 million years ago and you might catch a glimpse of a small, unassuming animal walking on slender legs tipped with hooves, by the rivers of southern Asia. It feeds on land but when it picks up signs of danger, it readily takes to the water and wades to safety.

The animal is called Indohyus (literally “India’s pig”) and though it may not look like it, it is the earliest known relative of today’s whales and dolphins. Known mostly through a few fossil teeth, a more complete skeleton was described for the first time last week by Hans Thewissen and colleagues from the Northeastern Ohio Universities. It shows what the missing link between whales and their deer-like ancestors might have looked like and how it probably behaved.Whales look so unlike other mammals that it’s hard to imagine the type of creature that they evolved from. Once they took to the water, their evolutionary journey is fairly clear. A series of incredible fossils have documented their transformation into the masterful swimmers of today’s oceans from early four-legged forms like Pakicetus and Ambulocetus (also discovered by Thewissen). But what did their ancestors look like when they still lived on land?

Cuttlefish tailor their defences to their predators

The best communicators know to cater to their audiences, and cuttlefish are no different. A new study shows that these intelligent invertebrates can target their defensive signals to the hunting styles of different predators.

Cuttlefish and their relatives, the octopuses and squid, are expert communicators whose incredible skins can produce a massive range of colours and patterns. Cuttlefish mostly use these abilities to blend into the background but they can also startle and intimidate predators by rapidly changing the display on their dynamic skins.

Keri Langridge and colleagues from the University of Sussex, watched young cuttlefish as they were threatened by three very different predators – juvenile seabass, dogfish (a type of shark) and crabs. A glass partition protected the cuttlefish from any actual harm but gave them full view of the incoming threats.

She found that the cuttlefish only ever used startling visual displays when they were faced by seabass, which hunt by sight. As the fish approached, the young cuttlefish suddenly flattened their bodies to make themselves look bigger and flashed two dark eye-spots on their backs to startle the predator. This pattern is called a ‘deimatic display’ and it was used in 92% of encounters with seabass.

There’s a video of the deimatic display after the jump…

Short lives, short size – why are pygmies small?

For decades, anthropologists have debated over why pygmies have evolved to be short. Amid theories about their jungle homes and lack of food, new research suggests that we have been looking at the problem from the wrong angle. The diminutive stature of pygmies is not a direct adaptation to their environment, but the side-effect of an evolutionary push to start having children earlier.

Andrea Migliano at the University of Cambridge suggests that pygmies have opted for a ‘live fast, die short’ strategy. Their short lives gives them very limited time as potential parents, and they have adapted by becoming sexually mature at a young age. That puts a brake on their pubescent growth spurts, leaving them with shorter adult heights.

Encephalon #38

UPDATED – Following a tiny admin issue, I now have the full selection of entries. This, then, is the Director’s Cut of Encephalon #38, now fortified with extra bloggy goodness.

Once again, thanks to Mo from Neurophilosophy, who kindly asked me to host this fortnight’s edition of the neuroscience carnival Encephalon. This site, Not Exactly Rocket Science, is dedicated to provide posts on new discoveries that are interesting and understandable to everyone, even people with no scientific background. With this in mind, posts are ordered (very, very roughly) in order of complexity of language, so that earlier posts can be enjoyed by pretty much anyone, while those later on demand a bit more technical knowledge.

Prehistoric meat-eating fungus snared microscopic worms

Cowboys have been lassoing cattle for several centuries, but it turns out that fungi developed the same trick 100 million years ago when dinosaurs still walked the Earth.

Alexander Schmidt and colleagues from the Humboldt University of Berlin found evidence of this ancient Wild West scene in a beautiful chunk of French amber.

The amber piece lacked the transparent clear beauty of a jeweller’s piece and the debris and dirt inside it suggests that it came from tree sap that had fossilised after it had fallen to the ground. There, it perfectly preserved the species living in the leaf litter, including a species of predatory fungi and the small worms – nematodes – that Schmidt thinks it hunted.

The fungus’s weapons were single cells coiled into rings just 10 micrometres in diameter. A thousand of these tiny loops could fit in a centimetre, but they were more than large enough to accommodate a blundering nematode. Once a worm swam through, the fungi constricted its snare, trapping the animal.

Time doesn’t actually slow down in a crisis

In The Matrix, when an agent first shoots at Neo, his perception of time slows down, allowing him to see and avoid oncoming bullets. In the real world, almost all of us have experienced moments of crisis when time seems to slow to a crawl, be it a crashing car, an incoming fist, or a falling valuable.

Now, a trio of scientists has shown that this effect is an illusion. When danger looms, we don’t actually experience events in slow motion. Instead, our brains just remember time moving more slowly after the event has passed.

Chess Stetson, Matthew Fiesta and David Eagleman demonstrated the illusion by putting a group of volunteers through 150 terrifying feet of free-fall. They wanted to see if the fearful plummet allowed them to successfully complete a task that was only possible if time actually moved more slowly to their eyes.

Mud time capsules show evolutionary arms race between host and parasite

Evolution can sometimes be seen as a futile contest. Throughout the natural world, pairs of species are locked in an evolutionary arms race where both competitors must continuously evolve new adaptations just to avoid ceding ground. Any advantage is temporary as every adaptive move from a predator or parasite is quickly neutralised by a counter-move from its prey or host. Coerced onward by the indifferent force of natural selection, neither side can withdraw from the stalemate.

These patterns of evolution are known as Red Queen dynamics, after the character in Lewis Carroll’s Through the Looking Glass who said to Alice, “It takes all the running you can do, to keep in the same place.”

These arms races are predicted by evolutionary theory, not least as an explanation for sex. By shuffling genes from a mother and father, sex acts as a crucible for genetic diversity, providing a species with the raw material for adapting to its parasites and keep up with the arms race.

Watching the race

We can see the results of Red Queen dynamics in the bodies, genes and behaviours of the species around us but actually watching them at work is another matter altogether. You’d need to study interacting species over several generations and most biologists have neither the patience nor lifespan to do so.

But sometimes, players from generations past leave behind records of the moves they made. Ellen Decaestecker and colleagues from Leuven University found just such an archive in the mud of a Belgian lake.

Sickle cell mice cured by stem cells reprogrammed from their own tails

Stem cells have long been hyped as the shiny future of medicine. Their ability to produce to every type of cell in the body provided hope for treating diseases from Alzheimer’s, to Parkinson’s to stroke, by providing a ready supply of replacement cells. Despite years of slow progress, we are now tantalisingly close to turning this hype into reality and a new study suggests that the dawn of promised stem cell treatments is getting closer.

For the first time, scientists have cured mice of a genetic disorder called sickle cell anaemia using personalised stem cells reprogrammed from cells in their tails. The study is a powerful ‘proof-of-principle’ that reprogrammed stem cells could one day fulfil their potential in fighting human disease.

The personal touch is of the utmost importance. It’s no good just giving someone any old stem cells. Genetic differences between the donor and recipient could cause problems in the long-term and trigger attack and rejection from the hosts’ immune system in the short-term. The trick is to convert a patient’s own cells into personalised stem cells for their own private use.

Last year, a group of Japanese scientists found a way to do this in mice and produced “induced pluripotent stem cells” (iPSCs) that were very similar to embryonic stem cells. And just last month, I blogged about two breakthrough papers which showed that human cells could also be reprogrammed into iPSCs.

Now, Jacob Hanna and colleagues from the Whitehead Institute for Biomedical Research, the University of Alabama and MIT, have used these reprogrammed cells to cure a genetic disease – sickle cell anaemia.

Subliminal flag shifts political views and voting choices

For all the millions that are poured into electoral campaigns, a voter’s choice can be influenced by the subtlest of signals. Israeli scientists have found that even subliminal exposure to national flags can shift a person’s political views and even who they vote for. They managed to affect the attitudes of volunteers to the Israeli-Palestine conflict by showing them the Israeli flag for just 16 thousandths of a second, barely long enough for the image to consciously register.

These results are stunning – even for people right in the middle of the one of the modern age’s most deep-rooted conflicts, the subconscious sight of a flag drew their sympathies towards the political centre.

Carnivals

Several new carnivals are up. For a whirlwind tour of recent science writing, have a look at:

Encephalon 37 (on neuroscience) over at A Blog Around the Clock

Carnival of the Blue 7 (on marine life) over at Natural Patriot

Tangled Bank 94 (on all things science) over at Life Before Death