Imagine! How the World Appears to a Dragonfly
Their massive globular eyes should have been a clue. It turns out dragonflies have souped-up colour vision that's better than anything ever seen in the animal world.
We humans have what's known as tri-chromatic vision, which means we see colours as a combination of red, blue and green. This is thanks to three different types of light-sensitive proteins in our eyes, called opsins. We are not alone: di-, tri- and tetra-chromatic vision is de rigueur in the animal world, from mammals to birds and insects.
Enter the dragonfly. A study of 12 dragonfly species has found that each one has no fewer than 11, and some a whopping 30, different visual opsins.
Ryo Futahashi of the National Institute of Advanced Industrial Science and Technology in Tsukuba, Japan, also found dragonflies use different opsins at different ages. For instance, the larvae of some species that hatch in sand tend to lack blue opsins. "This is probably because blue light does not reach them easily," he says.
Do all those extra opsins mean dragonflies see the rainbow differently to us? Probably. Other studies have found that dragonflies can see ultraviolet on top of blue, green and red. And it is thought that they can recognise polarised light coming off reflective surfaces like water. "It's likely that they have better colour discrimination than humans," says Futahashi.
Journal reference: PNAS, DOI: 10.1073/pnas.1424670112 ... See MoreSee Less
3 days ago
View on FacebookHow Uber-tidy bees defend their hives from disease
For some, cleanliness is next to godliness. For honeybees, which are suffering a major decline, it's a way of saving the hive from disaster. A naturally-occurring cleaning behaviour protects colonies from harmful parasitic mites, and breeding bees to be more hygienic could protect hives from the viruses they spread.
The varroa mite sucks the blood of pupae of worker bees, reducing their immunity to disease and transmitting viruses. Mites sneak into the honeycombs, then lay their eggs and feed on the larvae in the safety of the wax-capped cells. When the cells are uncapped to release the adult bees the mites are also released – ready to parasitise other members of the hive.
Bees that have been trapped with mites are often smaller, and can show signs of infection with a disease called deformed wing virus. If present together, varroa mites and this virus can kill off a whole hive, particularly during the difficult winter months.
Saviours of the colony
But hygienic worker bees can save the day. They sniff out dead or diseased larvae, uncap their cells and dispose of the contents. Although any adult mites inside may survive this upheaval, their young offspring are killed. This cleaning behaviour, if done intensively, is highly effective at controlling mite numbers and protects the hive against deformed wing virus.
Francis Ratnieks of the University of Sussex in Brighton and colleagues studied this behaviour in 42 honeybee colonies. In each hive they placed a section of honeycomb that had been frozen to kill the pupae inside. Within a day, most colonies had uncapped and removed up to half of the dead pupae, but some particularly hygienic colonies managed to remove more than 95 per cent.
Ratnieks' team found that these super-hygienic colonies had less than half the varroa mite levels of the less hygienic colonies. Also, while around a third of less hygienic colonies had individuals with shrivelled wings – a sign of deformed wing virus – the 14 colonies that threw out at least 80 per cent of the pupae had none, suggesting that hygienic behaviour can protect hives against viruses too.
"This finding could be very useful for beekeepers as it would reduce the harmful effects of varroa in a natural way," says Ratnieks.
Heritable habit
What's more, studies have shown that the tidying behaviour is a heritable trait, suggesting that it has a genetic component. "You can breed for this behaviour by screening colonies for hygiene levels and the breeding the most hygienic," says Ratnieks.
His team has confirmed this in a separate study, which found that when queens from hygienic colonies mate with drones from another hygienic colony, cleaning levels in new colonies populated by the offspring remain high.
Varroa has been a pest of US honeybee colonies since 1987, and arrived in the UK in 1992. "Varroa is the number one health problem for the beekeeping industry worldwide," says Ernesto Guzman of the University of Guelph in Ontario, Canada. He estimates that in most countries, more than half of honeybee colonies are infested by the mite.
To control this pest, beekeepers use a range of synthetic and organic pesticides. While synthetic compounds are effective, the mites usually develop resistance to them quickly. Breeding more hygienic hives could keep varroa numbers low enough that it becomes harder for them to evolve resistance to synthetic pesticides and allow the use of organic pesticides, which are not as effective so are less attractive to beekeepers at high infection levels.
But to avoid reinfection, all beekeepers must be using hygienic colonies, warns Marla Spivak of the University of Minnesota in St Paul. "When some beekeepers have susceptible stock with colonies full of mites, healthy colonies with low levels of mites try to rob honey out of these weakened colonies and get re-infested," she says.
Journal reference: Journal of Apicultural Research, DOI: 10.3896/IBRA.1.53.5.10 and 10.3896/IBRA.1.53.5.07 ... See MoreSee Less
1 month ago
View on FacebookPoem in the remembrance of those little flowers who withered before blossom in the brutal terrorist attack
"There are always so many of my fingerprints to see,
On the furniture and walls from sticky, grubby me,
But if you stop and think a while,
You’ll see I’m growing fast,
Those little handprints will disappear,
You can’t bring back the past.
So here’s a small reminder,
To keep not throw away,
Of how those tiny hands once looked,
To make you really feel one day,
The barbarous act of the coward terrorists."
……. ... See MoreSee Less
2 months ago
View on FacebookSame Singing genes of Humans and Birds
It's not just great minds that think alike. Dozens of the genes involved in the vocal learning that underpins human speech are also active in some songbirds. And knowing this suggests that birds could become a standard model for investigating the genetics of speech production – and speech disorders.
Complex language is a uniquely human trait, but vocal learning – the ability to pick up new sounds by imitating others – is not. Some mammals, including whales, dolphins and elephants, share our ability to learn new vocalisations. So do three groups of birds: the songbirds, parrots and hummingbirds.
The similarities between vocal learning in humans and birds are not just superficial. We know, for instance, that songbirds have specialised vocal learning brain circuits that are similar to those that mediate human speech.
What's more, a decade ago we learned that FOXP2, a gene known to be involved in human language, is also active in "area X" of the songbird brain – one of the brain regions involved in those specialised vocal learning circuits.
Bird brains
Andreas Pfenning at the Massachusetts Institute of Technology and his colleagues have now built on these discoveries. They compared maps of genetic activity – transcriptomes – in brain tissue taken from the zebra finch, budgerigar and Anna's hummingbird, representing the three groups of vocal-learning birds.
They then compared these genetic maps with others taken from birds and primates that can't learn new vocalisations, and with maps taken from the brains of six people who donated tissue to the Allen Brain Institute in Seattle.
Their results showed that FOXP2 is just one of 55 genes that show a similar pattern of activity in the brains of humans and the vocal-learning birds. Those same genes show different patterns of activity in the brains of animals incapable of vocal learning.
"The similarities are beyond one or a handful of genes," says Pfenning. "There are just systematic molecular similarities between song-learning birds and humans."
Ideal models
The findings suggest that songbirds might make ideal animal models for studying the genetics of speech production.
"There's potential for songbirds to be used to study neurodegeneration – especially conditions like Huntington's," says Pfenning. Huntington's disease affects the ability to produce complex motor behaviour, such as singing and talking, so experiments with birds might implicate particular genes in the disease.
Constance Scharff at the Free University of Berlin in Germany, who helped identify the importance of FOXP2 for vocal learning in birds agrees that songbirds can make great models for human speech and its pathologies. "My lab's research during the past 10 years has shown that FOXP2 is as relevant for birds' song learning as it is for human speech learning," she says.
Pfenning's team's work is one of 28 studies published this week by the Avian Genome Consortium, a massive international effort to obtain genome sequences for all 48 major groups of bird – only three of which had been sequenced before the consortium got to work in 2010.
Losing teeth
The new genomes have been used to construct a definitive bird evolutionary tree, and to explore other aspects of bird evolution and behaviour – including how and when birds lost their teeth.
But even though the consortium's efforts mean we know a great deal more about bird biology than we did last week, there are still questions left to answer.
For instance, it is unclear why there is such a remarkable level of genetic similarity between vocal learning in humans and some birds, given that the last common ancestor of the two may have lived 310 million years ago – hundreds of millions of years before either birds or humans developed vocal learning. Is the genetic convergence a coincidence, or is vocal learning only possible if it involves these 55 genes?
"These genes represent really great candidates for being responsible for vocal-learning behaviour," says Pfenning. "But to test that in a rigorous way we have to manipulate them in songbirds and see whether that affects the birds' behaviour."
Journal reference: Science, DOI: 10.1126/science.1256846 ... See MoreSee Less
3 months ago
View on FacebookGeoengineering the planet Earth
Proposals for the first trials to cool the planet include cloud brightening and spraying aerosols into the ozone layer. They might start in just two years
IF WE can't reduce emissions enough, what else can cool the planet? We need to find out if geoengineering works, and soon, say a group of atmospheric scientists.
Engineering the planet's weather and climate is a highly controversial idea. That's why we need experiments, the group say, and they want the first to start in two years' time. The frontrunners are schemes to alter the atmosphere to reflect more of the sun's rays back into space, or to change clouds so that they let more of Earth's heat out instead of trapping it.
Last week, the group published a "road map" of proposals for how real-world experiments might be carried out (Philosophical Transactions of the Royal Society A, doi.org/xb9).
One would explore the effects of injecting aerosols of sea salt into marine clouds. The aim is to increase the water droplet content of the clouds, making them reflect more sunlight – so called marine cloud brightening.
The second, and most detailed, devised by John Dykema of Harvard University, would explore the effects of injecting sulphur-containing substances at an altitude of 20 kilometres – the lower reaches of the boundary with outer space (Philosophical Transactions of the Royal Society A, doi.org/xb8).
The aim of the so-called stratospheric controlled perturbation experiment, or SCoPEx, is to see if sulphate ions would undermine measures to rebuild the ozone layer. The fear is that such substances might set off chemical reactions that deplete the ozone.
The third experiment would explore the potential for making cirrus clouds in the upper atmosphere more porous to radiation bouncing back into space from Earth. Water vapour in the clouds behaves like a greenhouse gas, trapping heat almost as efficiently as carbon dioxide. By seeding them with substances like bismuth tri-iodide, which cause water to form into ice particles, the hope is to reduce the water vapour and allow more radiation to escape.
Geoengineering to cool the planet by deliberately altering Earth's atmosphere is highly controversial, with sceptics fearing it will fail and mess up the climate even more. Altering cloud cover, for example, could change rainfall patterns and increase droughts and floods unpredictably. Opponents also fear that if we rely on geoengineering solutions, people will no longer strive towards the main goal of dramatically reducing our reliance on the fossil fuels that are inexorably heating up the planet.
Nevertheless, some ideas deserve further exploration, say proponents. The road map, conceived at a Harvard workshop in March, is "a big move forward", says lead author David Keith, who is also at Harvard.
So far, all geoengineering work has been in the lab or based on computer models. "Modelling and lab experiments are critical," says Dykema. "But to understand the intricate chemistry people are concerned about, the only way to find out is in the atmosphere, where you have the right flux of solar radiation, the right mix of chemical species and the real dynamics of aerosol particle interactions in gas, liquid and solid phases."
"The proposed experiments are quite small scale, and the environmental consequences are likely to be negligible compared with a lot of human activity we already take for granted," says co-author Doug MacMartin of the California Institute of Technology in Pasadena.
Dykema's experiment, for example, involves releasing just a kilogram of sulphur, the same amount as emitted in just 1 minute by a standard commercial jet.
However, a major UK project to investigate geoengineering, called the Integrated Assessment of Geoengineering Proposals, is more cautious and pessimistic about solar radiation management.
Scaling up
For example, researchers using computer simulations have found that attempts to reduce solar radiation in the Arctic to stop sea ice from retreating are infeasible. "We found that the scale of deployment in both time and space would have to be huge before current observing systems could detect any effect," says principal investigator Piers Forster of the University of Leeds.
And he is sceptical of small-scale tests. "We've emitted 500 billion tonnes of carbon dioxide and we only recently have any certainty this is affecting our climate, so limited field tests would tell you next to nothing about the climate effects of solar geoengineering."
The would-be experimenters argue that, if anything, reliance on modelling increases their case to pursue more real-world data, to make the models more accurate. Models are potentially compromised by having too little real-world data to work with, they say.
"There are many aspects of climate interactions, especially those that affect clouds, that are poorly understood because the range of scales, from nanometres to kilometres, can't be accurately included in global models," says Lynn Russell of the Scripps Institution of Oceanography in San Diego, California, a member of the experimentation group.
Trials would provide invaluable insights for mainstream climate research, she says, even if geoengineering ultimately proves to be impractical. Observations from such experiments would also allow us to understand cloud processes better and lead to improvement in climate models more generally, she says. ... See MoreSee Less
3 months ago
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