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Archive for April, 2010
Aphids got their colours by stealing genes from fungi
Aphids, those sap-sucking foes of gardeners, come in a variety of colours. We usually think of them as green, but pea aphids sometimes wear a fetching red ensemble. That may not strike you as anything special; after all, lots of animals are red. But the aphid’s colour is unique in a couple of extraordinary ways.
The colour comes from pigments called carotenoids. Animals use them for all sorts of purposes; they act as antioxidants, and they contribute to red, orange and yellow colours. But the pea aphid is one of only a few known species (all aphids) that manufacture their own carotenoids; everyone else gets theirs from their food. But it’s the source of the pea aphid’s ability that’s truly remarkable – it stole the skill from fungi. By integrating fungal genes into its own genomes, it gained a superpower that almost all other animals lack.
These sorts of “horizontal gene transfers” go on all the time in bacteria, but they’re supposedly a rarity among more complex creatures like animals and plants. And yet, scientists have recently documented several examples of such transfers. Rotifers smuggle genes from fungi, bacteria and plants. “Space Invader” genes have jumped across animals as diverse as lizards and bushbabies. One bacterium, Wolbachia, has even inserted its entire genome into that of a fruit fly. And parasites can transfer their genes to humans.
In most of these cases, it’s unclear whether the imported genes are actually doing anything useful. But the story of the pea aphid, told by Nancy Moran and Tyler Jarvik, is very different. The colour of a pea aphid determines the predators that target it. Ladybirds (one of their major enemies) prefer to attack red aphids on green plants but parasitic wasps are more likely to lay their eggs in green aphids, to fatal effect. Colour clearly matters to an aphid, so here is a clear example of a transferred gene shaping an obvious trait in its new host and in doing so, shaping its evolution.
A single genetic fault makes one hand mirror the other's movements
Clench your left hand into a fist. What happened to your right hand when you did it?
If you’re like most people, the answer is nothing. But, surprisingly, not everyone can do this. Some people make “mirror movements”, where moving one side of the body, particularly the hands, causes the other to move unintentionally. Clench the left fist, and the right one closes too. Doing things like playing the piano or typing are very difficult. In 2002, a Chinese man with the disorder failed to get into the military because he couldn’t use the monkey bars.
Young children sometimes make mirror movements but they almost always grow out of it by the age of 10. The only exceptions tend to be people with rare genetic disorders of the nervous system, like Klippel-Feil and Kallmann syndromes. Now, Myriam Srour from the University of Montreal has found that a single faulty gene can cause the condition.
Dramatic restructuring of dinosaur feathers revealed by two youngsters of same species
At the Chinese Academy of Sciences, Xing Xu is looking at two beautiful dinosaur fossils, both with clear feathers on their arms and tails. In the smaller specimen, the feathers are like thin ribbons at their base and quills at their tips (with vanes coming off a central shaft). The larger specimen is different – its arm and tail feathers are like quills across their entire length.
With such different feather structures, you might assume that these animals belonged to different species, but you’d be wrong. They’re actually different life stages of the same animal – Similicaudipteryx. Both are youngsters, but the one with the quill-like feathers is an older version of the one with the ribbons. Together, they demonstrate that the feather of some dinosaurs changed dramatically as they grew older, in a way that we don’t see in any modern bird.
By now, readers of this blog should be familiar with the idea of feathered dinosaurs (and, indeed, Xing Xu has discovered many of them). A spectacular series of fossils have revealed a wide range of plumes in a wide range of species, and we even know something about their colour. But we still know very little about how these feathers developed as the animals matured, because fossils of young feathered dinosaurs are few and far between. So for Xu to find two, and two of the same species no less, is a real treat.
Both hailed from Liaoning province of China (where else?), and based on their skulls, spines and hips, Xu has confidently classified them both as Similicaudipteryx, a small predator from the oviraptosaur group. Both animals are clearly youngsters. Although one is larger than the other, they’re both smaller than adult specimens of the same dinosaurs, and some of their bones haven’t fused completely yet.
The younger animal (a-c below) has downy feathers over much of its back and hips. Elsewhere, it has larger pennaceous feathers (with a shaft and vanes) – 10 on each arm, and 11 much larger ones on its tail. All of these are ribbon-like at the base and quill-like at the tips. The more senior juvenile (d-f below) also had downy feathers on its head, back and hips but its pennaceous feathers are very different to its younger peer. Each arm has 10 primary feathers and 12 secondary ones, and the tail had at least 12 pairs. All of them are quill-like from base to tip and the arm feathers are just as long as the tail ones.
Power breed hypocrisy – powerful people judge others more harshly but cheat more themselves
Last year, the UK press was abuzz with the so-called “expenses scandal”. In a time when the county was gripped by recession, we were told that Members of Parliament (MPs) were claiming for all sorts of ridiculous luxuries, all at the taxpayer’s expense. The revelations dominated the news, but the idea that people in positions of power often behave hypocritically isn’t new. It is said, after all, that power corrupts. Now, Joris Lammers from Tilburg University has found solid evidence for this.
Through five compelling experiments, Lammers has shown that powerful people are more likely to behave immorally but paradoxically less likely to tolerate immorality in other people. Even thinking about the feeling of power can trigger these double standards.
To begin with, Lammers asked 61 students to remember a time when they either felt powerful or powerless. Those that reminded themselves of power were more likely to frown on cheating; compared to the powerless group, they thought that overclaiming on travel expenses was less acceptable. However, they were also more likely to cheat. Lammers gave the recruits the chance to decide how many lottery tickets they would receive by privately rolling two dice. Those who were primed with power were more likely to lie about their scores to wangle extra tickets.
To explore this hypocrisy further, Lammers did three further experiments where he manipulated a volunteer’s feelings of power and then gave them a common moral dilemma. All of these involved acts that are technically illegal but that many people take part in, such as speeding or tax-dodging. Their job was to say either whether they would be okay with doing it themselves, or whether they would think it acceptable if someone else did it.
How chimpanzees deal with death and dying
On the 7th of December, 2008, in the heart of Scotland, a chimpanzee called Pansy died peacefully. She was over 50 years old and lived on an island in Blair Drummond Safari Park with three other chimps – her daughter Rosie, another adult female called Blossom, and Blossom’s son Chippie.
Their reaction to her passing was recorded by the park’s cameras (see video above) and many of their actions seem remarkably human. The others seemed to care for Pansy in her final minutes, examine her body for signs of life, and avoid the place where she died. Rosie even conducted the equivalent of an all-night vigil.
This footage provides a rare glimpse into how one of our closest relatives deal with death, and it’s one of two such examples that have been published today. The second took place several thousand miles away in the forests of Bossou, Guinea. In 2003, a respiratory epidemic killed five of the local chimps, including two babies called Jimato and Veve.
Their mothers, Jire and Vuavua, carried their babies’ lifeless bodies around for 68 and 19 days respectively. They groomed the dead youngsters and chased away the flies that circled them (see image and video below). Even after both babies had completely mummified into dry, leathery husk, the mothers still carried them, and other groups members investigated them.
Photo safari – Orangutans Part 4
A few more shots from Perth Zoo’s orangutan exhibit. I’ll be back with some proper posts tomorrow, also with a great ape theme…
Photo safari – Orangutans Part 3
More shots from Perth Zoo’s wonderful orangutan exhibit. These apes are incredibly intelligent and it would be terrible to let them sit in an enclosure with nothing to stimulate them. So the zoo runs a “behavioural enrichment” programme, which essentially means that they leave plenty of toys, items and challenges to keep the orangutans mentally engaged. Here’s a sequence of a female making use of one such opportunity, and demonstrating the orangutan’s prowess with tools.
She grabs a sturdy stick from the grounds…
Photo safari – Orangutans Part 2
More shots from Perth Zoo’s wonderful orangutan exhibit. Orangutans are all too capable of walking on two legs from time to time, and this penchant for bipedalism allows them to negotiate tricky parts of the canopy. One of the females in Perth Zoo is particualrly fond of ambling around on two legs. These photos of her doing so look for all the world like a human in an orangutan costume…
Photo safari – Orangutans Part 1
One of the bright sides of being stranded at Perth by a giant ash cloud was a visit to Perth Zoo and, particualrly, visiting their orangutan exhibit. I’ve been to quite a number of zoos in my time and that had to rank with the best enclosures I have ever seen. The zoo is part of an international conservation programme and its six or so orangutans have a sizeable area to roam around, complete with tall towers, ropes, ladders and more. The next couple of posts will showcase some of the photos I took of these animals, and will help to fill some bloggy time as I wind my weary way back to the UK.
We start with the baby, who was undoubtedly the highlight of the day. Just try and look at these photos without grinning.
Good teachers help students to realise their genetic potential at reading
Genetic studies suggest that genes have a big influence on a child’s reading ability. Twins, for example, tend to share similar reading skills regardless of whether they share the same teacher. On the other hand, other studies have found that the quality of teaching that a child receives also has a big impact on their fluency with the written word. How can we make sense of these apparently conflicting results? Which is more important for a child’s ability to read: the genes they inherit from their parents, or the quality of the teaching they receive?
According to a new study, the answer, perhaps unsurprisingly, is both. Genes do have a strong effect on a child’s reading ability, but good teaching is vital for helping them to realise that potential. In classes with poor teachers, all the kids suffer regardless of the innate abilities bestowed by their genes. In classes with excellent teachers, the true variation between the children becomes clearer and their genetic differences come to the fore. Only with good teaching do children with the greatest natural abilities reach their true potential.
This study demonstrates yet again how tired the “nature versus nurture” debate is. As I wrote about recently in New Scientist, nature and nurture are not conflicting forces, but partners that work together to influence our behaviour.
This latest choreography of genes and environment was decoded by Jeanette Taylor from Florida State University. She studied over 800 pairs of Florida twins in the first and second grades. Of the pairs, 280 are identical twins who share 100% of their DNA, and 526 are non-identical twins who share just 50% of their DNA. These twin studies are commonly used to understand the genetic influences of behaviour. If a trait is strongly affected by genes, then the variation in that trait should be less pronounced in the identical twins than the non-identical ones.
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