So as I said, I will be posting wildlife pictures from my recent Australian adventure on a weekly basis. We begin with that most obvious of Australian critters – the koala. Unfortunately, we never managed to see one of these in the wild so these photos come from the Healesville Sanctuary and the Featherdale Wildlife Park, both superb collections of native species in generous enclosures.
Our amphibians are not doing well. Populations of frogs, toads, salamanders and newts the world over are falling dramatically. Their moist, permeable skins and their need for water to reproduce make them vulnerable to a multitude of threats including drought brought on by climate change, a deadly fungus, and other infectious diseases. Now, we can point an accusatory finger at another culprit – a chemical called atrazine that is second most commonly used pesticide in the United States, and perhaps the world.
Jason Rohr and colleagues from the University of Florida found that atrazine exposes the frogs to larger hordes of parasites. The pesticide encourages the growth of algae that is eaten by snails. They are host to parasitic worms called trematodes (flukes), which use snails as a transit station for their journey into the bodies of frogs. More atrazine means more algae, more snails, more parasites and sicker frogs.
Rohr discovered this tangled web by studying the northern leopard frog, a North American species that, like most of its kin, is in decline. Across 18 wetlands in Minnesota, Rohr looked at local frogs, the parasites they carried and the characteristics of their local environment. They measured everything from the numbers of other species, the soil composition, the patchiness of the habitats and the chemicals in the water, to see if anything in the local environment could consistently explain the severity of trematode infections.
Most of the planet’s ecosystems are made of a multitude of different species, rich tangles of living things all interacting, competing and cooperating in order to eke out an existence. But not always – in South Africa, within the darkness of a gold mine, there is an ecosystem that consists of a single species, a type of bacteria that is the only thing alive in the hot, oxygen-less depths. It is an ecosystem of one, living in complete isolation from the Sun’s energy.
This incredible and unique habitat was discovered by Dylan Chivian from the Lawrence Berkeley National Laboratory, leading a large team of scientists from 15 institutes. The group was interested in studying extremophiles, species of bacteria that live in the planet’s most inhospitable of conditions – in this case, the rocks of the Earth’s crust. At depths of a kilometre or more, bacteria face unique challenges that their counterparts on land or sea do not, including high 60C temperatures and a lack of sunlight, oxygen and nutrients.
The species that can beat these challenges are interesting to biologists because they provide insights into how life can persist on the edge of existence and, potentially, on other planets. To find such species, Chivian’s team of bacteria-hunters did their work in a series of mines in South Africa’s Witwatersrand basin. In one venture, they collected over 5,000 litres of water that had pooled in cracks in the rock almost 3km deep.
They used a technique called ‘metagenomics‘ to extract and analyse all the DNA from the sample. Metagenomics allows scientists to study the hidden worlds within any given habitat and to identify the multitude of bacteria and other micro-organisms that live there. Usually, the technique gives an interesting overview but would never be able to provide a complete census of the local species. But in the deep water, Chivian found a surprise. All the DNA belonged to a single species of bacteria, which they named Candidatus Desulforudis audaxviator.
We will readily describe a person’s demeanour as “warm” or “cold” but this link between temperature and personality is more than just a metaphorical one. A new study shows that warming a person’s fingertips can also bring out the warmth in their social relationships, pushing them to judge others more positively and promoting their charitable side.
Lawrence Williams at the University of Colorado and John Bargh from Yale University managed to influence the behaviour of a group of 41 volunteers without them knowing it by giving them something warm to hold. When the recruits arrived at the psychology building, a colleague (who wasn’t aware of the experiment’s goals) escorted them to the laboratory and asked them to hold a cup of coffee for her along the way. Once in the lab, they had to read a description of a stranger and rate them on 10 different personality traits.
The cups of coffee were the key element. Half were hot and half were iced, and the volunteers’ brief contact with the cups was enough to sway their later impressions. The recruits whose hands were heated by their cups rated the stranger as having a warmer personality than those who held the cold cups. On average, they gave him a score of 4.7 on a scale of 1 to 7, while the cool-handed people gave average scores of 4.3.
G’day. As of yesterday, my month-long jaunt to Australia was officially over, which means that your friendly neighbourhood science blog will continue its regular service, with new posts starting tomorrow.
The holiday was amazing – we managed to pack in some time in Sydney and Melbourne, a sailing trip round the Whitsundays, visits to Kakadu National Park, King’s Canyon and Uluru, a drive down the Great Ocean Road and even a wedding. We travelled through rainforest, coral reef, desert and wetlands and along the way, managed to avoid the many ways of being crushed or poisoned (see amusing sign on the right) including a trip on Qantas, an airline whose planes seem to have a slight engineering fault where they occasionally drop out of the sky.
We were incredibly lucky with wildlife-spotting and saw a great many cool species that I’ve never seen before, from the ubiquitous roos and cockatoos to the more elusive echidnas and thorny devils. If I’m feeling geeky enough, I may post a full list… In the meantime, I’ll be sharing photos of the species I managed to capture on film on a roughly weekly basis.
Animals often show a keen intelligence and many species, from octopuses to crows, can perform problem-solving tasks. But humans are thought to go one step further. We can reflect on our own thoughts and we have knowledge about our knowledge. We can not only solve problems, but we know in advance if we can (or are likely to).
In technical terms, this ability is known as ‘metacognition’. It’s what students do when they predict how well they will do in an exam when they see the questions. It’s what builders do when they work out how long a job will take them to finish. But can animals do the same? Finding out is obviously difficult. No animal is going to tell us what it is thinking. To work that out, we need clever experiments.
Allison Foote and Jonathon Crystal searched for metacognition in rats by giving them a test that they could decline. If they passed, they received a big reward and if they failed, they got nothing. But the cunning part of their study lay in giving the rats a small reward if they declined the test. If they knew they were unlikely to succeed, they’d be better off bowing out. In this experiment, a measured attitude beats a gung-ho one.
Evolution mostly involves small, gradual changes, and for good reason – we might expect that large changes to an animal’s genetic code, and therefore to its body plan, simply wouldn’t work. It would be like shoving an extra cog into a finely-tuned machine and expecting it to fit in – the more likely outcome is a malfunctioning mess.
But that’s not always the case, at least not for the evolution of the human eye. New research shows that the eye and its connections to the brain are surprisingly flexible, and can incorporate major evolutionary changes with ease.
In our retinas, cone cells are responsible for giving us colour vision. Most mammals have just two types, one that is sensitive to short violet-ish wavelengths of light (S cones), and another that responds strongly to medium greenish-blue wavelengths (M cones).
But somewhere in our history, humans and many other primates picked up a third cone sensitive to longer wavelengths (L cones), that allows us to see colours near the red end of the spectrum.
You might expect that adding another type of cone cell into the eye would be a very large step, requiring substantial (and gradual) changes in the wiring of both the retina and the brain. But Gerald Jacobs from the University of California has shown that it’s as easy as installing new software into your computer. Together with Jeremy Nathans from Johns Hopkins Medical School, Jacobs genetically engineered a strain of mice that had human L cones in addition to their medium- and short-wavelength ones.
The plague, or the Black Death, is caused by a microbe called Yersinia pestis. In the 14th century, this microscopic enemy killed off a third of Europe’s population. While many people consign the plague to centuries past, this attitude is a complacent one. Outbreaks have happened in Asia and Africa over the last decade and the plague is now recognised as a re-emerging disease. In 1996, two drug-resistant strains of plague were isolated from Madagascar. One of these, was completely resistant to all the drugs that are used to control outbreaks.
Anyone interested in bacteria can attest to their ability to evolve resistance to drugs. In the case of drug-resistant plague, the secret to its powers is a plasmid – a small free-floating ring of DNA, that carries drug resistance genes. Bacteria can trade plasmids across individuals, transferring genes between each other in ways that humans can only achieve with technology. The worry is that common and less harmful bacteria could transfer drug-resistance plasmids over to Yersinia, resulting in new resistant strains.
Humans are a funny lot. While we seem to be relentless voyeurs, we generally frown on eavesdropping as an invasion of privacy. But in the animal world, eavesdropping can be a matter of life or death. Animals rarely communicate in isolation. Often it pays for one species to monitor the dialogues of others, particularly when predator warnings are involved.
Small animals in particular do well to pay attention to the alarms of other species, as they are often preyed upon by the same larger hunters. Even very unrelated species can listen in and understand each other’s signals. Vervet monkeys respond to the alarm calls of superb starlings, while mongooses are well-versed in hornbill calls.
Alarm calls aren’t just a simple matter of shouting “Look out!”, and many species have different calls for different predators. But one of the most sophisticated alarm systems so far discovered is used by a small, unassuming bird called the black-capped chickadee.
The chickadee acts as an inadvertent sentry for a multitude of bird species. Its name comes from its distinctive “chick-a-dee” alarm call, made in response to a perched bird of prey or a land predator. When this call sounds out, anywhere between 24 and 50 species of bird marshall together and mob the predator, robbing it of the element of surprise and harassing it from the area.
Fighting malaria with mosquitoes seems like an bizarrely ironic strategy but it’s exactly what many scientists are trying to do. Malaria kills one to three million people every year, most of whom are children. Many strategies for controlling it naturally focus on ways of killing the mosquitoes that spread it, stopping them from biting humans, or getting rid of their breeding grounds.
But the mosquitoes themselves are not the real problem. They are merely carriers for the true cause of malaria – a parasite called Plasmodium. It suits neither mosquitoes nor humans to be infected with Plasmodium, and by helping them resist it, we may inadvertently help ourselves. With the power of modern genetics and molecular biology, scientists have produced strains of genetically engineered mosquitoes that cannot transmit the malarial parasite.
These ‘GM-mosquitoes’ carry a modified gene – a transgene – that produces chemicals which interfere with Plasmodium‘s development. Rather than being suitable carriers, the bodies of the modified mosquitoes spell death for any invading Plasmodium.
But scientists can’t very well change the genes of every mosquito in the tropics. To actually reduce the burden of malaria, the genetic changes that induce malaria resistance need to be spread throughout the mosquito population. The easiest way to do this is, of course, to let the insects do it themselves. And Mauro Marrelli and colleagues from the Johns Hopkins University have found that they are more than up to the task.