Males don’t stand a chance in a warmer world, if they happen to be painted turtles. A temperature rise of around 1 °C is all it would take for the species to become 100 per cent female and earmarked for extinction.

Painted turtles (Chrysemys picta), found in lakes and streams across North America, are one of many reptile species whose sex is determined by temperature. Eggs in warm nests are likely to hatch as females, while males hatch in cooler nests, although no one is sure why.

In recent years, many researchers have raised concerns that global warming could skew the sex ratios of these reptiles. and his colleagues at Iowa State University developed a mathematical model to predict whether the painted turtles might be affected.

For over 25 years, Telemeco’s colleague, , documented the nesting times and sex ratio of painted turtle hatchlings on a small island in the Mississippi river in Carroll County, Illinois. He found that to ensure their eggs develop at temperatures that produce an even mix of males and females.

The team used this finding, along with historical records of soil and air temperatures, to create a mathematical model that predicts the sex ratio of eggs laid at different temperatures. In a preliminary test of the model, the group correctly predicted the sexes of 40 out of 46 hatchlings born in the wild.

Sex ratio

Telemeco’s team then used the same model to predict what might happen to the sex ratio of future hatchlings. Conservative climate models predict that average temperatures in the US Midwest will rise by 4 °C over the next century. The group’s model suggests that this temperature hike would result in nests of all-female hatchlings, even if the turtles nest earlier, when temperatures are cooler. In fact, average temperatures only need to rise by 1.1 °C to have this effect, the team found. “It’s ultimately extinction,” says Telemeco.

, an evolutionary biologist at the University of Sydney in Australia, who was not involved in the study, says the findings are likely to apply to many species where sex is dependent on temperature. “All crocodilians, a smattering of turtles and lizards, plus some fishes”, will be affected, he says. “Just laying your eggs a few weeks earlier won’t be enough to cancel the effects of warming,” he says.

But Shine is optimistic about the turtles’ chances of survival. The animals could adapt by laying their eggs in shadier locations, or evolving the ability to cope with warmer conditions.

Telemeco is less sure. “The problem is that climate change is happening so rapidly that an evolutionary response, especially in long-lived organisms, is not likely,” he says.

Clues to the turtles’ chances of survival may come from a better understanding of the species’ genome, . Observing how gene expression changes in response to temperature shifts might provide insight into how the turtles adapted to their current environment and also how they might respond to future changes, says Telemeco.

Journal reference: ;

When the earthquake struck the Pacific coast of Tohoku on 11 March 2011 it shifted the seafloor 7 metres vertically and 50 metres horizontally. Thirty six days after the quake, and colleagues at the Japan Agency for Marine-Earth Science and Technology from depths of up to 5.7 kilometres at four spots along the Japanese trench, near the earthquake’s epicentre.

They detected a large plume of cloudy sea water – some 500 km long, 400 km wide and 1.5 km tall – as measured from the lowest point of the trench. It was still there 98 days later, when Kawagucci returned to sample the water again.

The cloud was packed with methane at concentrations 20 times higher than before the quake. A particular carbon isotope found within the plume’s methane matched isotopes uncovered deep within the ocean floor during a previous of the Japanese trench. “The methane came from the deep sub-seafloor,” says Kawagucci.

Pluming marvellous

Genetic testing of the water samples for microbe RNA allowed the team to record the tiny critters floating in the waters. The anomalous plume triggered a rare growth of bacteria and archaea – 36 days after the quake there were seven times as many microbes at a depth of 5 km than before.

Some of these microbes always live in the deep sea and flourished among the nutrients in the plume, but other of the creatures usually live at even greater depths, or within the ocean crust itself. These were pushed into the water column by the quake.

When Kawagucci returned to the site 98 days after the quake, the number of microbes had largely returned to normal, although a few creatures known to usually live in the ocean’s crust lingered.

It’s estimated that as much as two-thirds of Earth’s total prokaryote biomass , but very little is known about them.

Journal reference: , DOI: 10.1038/srep00270

In transcranial magnetic stimulation a magnetic coil induces electric currents in the brain that can strengthen or suppress neural connections. This technique has been shown to improve symptoms in people with brain disorders such as autism and depression.

Now, from the University of Western Australia in Crawley and colleagues have found that stimulating the brain at intensities lower than would make a neuron fire can remove unwanted neural connections in mice.

As children, our brains produce too many connections between cells. As we develop, some connections are pruned away while others are strengthened. Inept pruning has been implicated in schizophrenia.

Rodger’s team used genetically modified mice with abnormal connections in an area of the brain called the superior colliculus (SC), which is involved in motion detection. In these mice, 90 per cent of the axons in the SC had extended into the wrong areas. These bad connections make it difficult for the rodents to follow moving objects in their line of sight.

Rodger used low-intensity, pulsed magnetic field stimulation (PMF) on the rodents’ SC for 10 minutes a day over two weeks. It is thought that PMF is too weak to make healthy neurons fire. But after treatment, tissue analysis showed that only 45 per cent of the abnormal axons were still there. “The axons that weren’t in the right place were wiped out,” says Rodger. After treatment the mice were also better at tracking objects.

“Pulsed magnetic field stimulation awakens unwanted connections, so the brain can remove them”

“PMF is awakening unwanted connections, so the brain can detect and remove them,” says Rodger.

Unwanted neurons generally express high levels of a specific NMDA glutamate receptor. According to Rodger, this makes them sensitive to changes in electrical activity and so even low-intensity pulses can activate these neurons.

NMDA receptors send out signals that trigger the recruitment of two chemicals called nitric oxide and brain-derived neurotrophic factor (BDNF), which help remove abnormal circuitry in healthy brains. Indeed, modified mice given PMF expressed higher levels of both chemicals, while only minor changes were found in healthy mice or those given a sham procedure (The FASEB Journal, ).

“I think it is a very promising avenue for treatment of nervous system disorders that involve abnormally abundant and inaccurate connections,” says Rodger.

at the University of New South Wales in Sydney, Australia, says it is “very exciting” and also surprising that low-power magnetic pulses can reverse a developmental disorder. But you can’t be sure normal circuits are not affected, he adds. “One cannot assume that these effects will always be positive.”

Species: Brookesia micra, Brookesia tristis, Brookesia desperata, Brookesia confidens
Habitat: Northern Madagascar, within the leaf litter on the floor of rainforest and dry deciduous forest

They’ve got independently rotating eyes, a curiously curly tail, and strangely depressing names. Meet the world’s tiniest – and cutest – chameleons.

Brookesia leaf chameleons are renowned for being small. Some of them – Brookesia minima, for example – are downright miniscule. From head to tail they are all between 22 and 48 millimetres. Four new species of these miniature reptiles have now been uncovered in northern Madagascar.

Like any good miniature, Brookesia chameleons function much like the full-size versions. Their eyes move independently of each other to zero in on a tasty meal, they can also rapidly change their colours when stressed, have long projectile tongues and prehensile tails that can grasp objects.

Added features

Then there are the added features. Unlike other chameleons, Brookesia use their tails as an extra leg. The tiny reach of their arms makes it difficult to safely grasp branches. Instead, the tip of their tail curls down and provides extra stability.

In 2010, at the Museum of Natural History in Paris, France, imaged the tails of two species of Brookesia chameleon with three-dimensional synchrotron X-ray imaging.

That revealed an unusual internal architecture. The tails had 20 vertebrae instead of the usual 50 found in larger chameleons. The ventral tendons were also particularly well developed, presumably to allow the downward curl. What the tails lacked were developed dorsal tendons. These, said Boistel, would have allowed them to push back on a branch, propelling them forward. In essence, the fancy tail is a peg-leg.

Peering into the inner ear of Brookesia with the imaging system, Boistel also found that Brookesia have unusually shaped semicircular canals that resemble turtles’ ears more than those of other chameleons. He suspects these aural cavities adapted to help with stability too.

Small matter of size

Scouring the forests of northern Madagascar for over eight years, Frank Glaw of the in Germany and his colleagues found 35 lizards belonging to the four new species.

The smallest of the new crew, the aptly named Brookesia micra, was found on the archipelago. Just 29 millimetres long from the tip of its nose to the end of its tail, this little fellow is among the smallest reptiles in the world, in the same league as the dwarf gecko, Sphaerodactylus ariasae.

S. ariasae is about 30 millimetres long from head to tail, but biologists often exclude the tail in such measurements. By the head-and-body metric, S. ariasae is a full 2 millimetres shorter than B. micra.

, an evolutionary biologist at University of Sydney in Australia, says warm-blooded animals cannot function if they are too small, because they lose too much heat through their body surface. Cold-blooded animals, like reptiles, take up heat from outside their bodies rather than generating it within themselves.

Name game

Glaw is concerned about protecting the environment of these lizards. Each species was found in its own tiny pocket of northern Madagascar. If that home is destroyed, an entire species could be wiped out. Glaw named the finds accordingly.

B. tristis, with faint brown bars radiating from its eyes was collected only at the Montagne des Français in northern Madagascar. The Latin “tristis” means “sad”, and Glaw says he chose this epithet because the Montagne des Français suffers from severe deforestation and habitat destruction, despite recently being declared a nature reserve.

With three enlarged nodules on its head, B. desperata lives in the Forềt d’Ambre special reserve, which is also subject to habitat destruction. That leaves B. confidens, which Glaw feels can be more confident of its future: it was found in Madagascar’s well protected Ankarana National Park.

Comparing the DNA of the newbies with a database of other chameleon DNA revealed large differences between the species, which may have begun diverging about 20 million years ago.

Journal reference: PLoS One, DOI: 10.1371/journal.pone.0031314

Read previous Zoologger columns: Don’t bite – how the zebra got its stripes, The only males with more brain than females , How a blurry-eyed spider pounces on target, Gecko’s amputated tail has life of its own, Unique life form is half plant, half animal, Transgender fish perform reverse sex flip, My brain’s so big it spills into my legs, Dozy hamsters reverse the ageing process, To kill a mockingbird? No, parasitise it, Chill out with the world’s coldest insect, ‘Werewolf birds’ hook up by the full moon, Cannibal shrimp shows its romantic side, The only cross-dressing bird of prey, The biggest spider web in the world.

Species: Equus burchelli, E. grevyi, E. zebra

Habitat: Open grassland areas and woodlands

Zebras are quite the communists. They graze together, groom each other and stay in packs to protect themselves from predators. And while some herds reportedly contain harems, .

But it’s not their egalitarian habits that define them, it’s their distinctive black and white stripes, which for centuries have puzzled biologists. Now Adam Egri at Eötvös University in Budapest, Hungary, and colleagues have an answer: they believe zebras evolved stripes to protect themselves from blood-sucking insects.

The zebra is completely black as an early embryo, and white stripes only appear in a later embryonic stage, when the production of dark pigmentation is blocked. Each zebra has subtly different stripes, acting like nature’s own barcode.

Charles Darwin wondered what purpose they served. A popular theory, both in the 19th century and today, is that zebras evolved striped coats as camouflage in tall grass. But, , the “stripes cannot afford any protection in the open plains of South Africa”.

Social stripes

More recently, biologists have observed that zebras don’t attempt to conceal themselves by freezing in response to predators. Zoologist Desmond Morris wrote in his that “compared to many hoofed animals on the plains of Africa, they are remarkably mobile and noisy and never attempt to hide in cover”.

Darwin suggested that zebras developed their unique stripes to recognise each other, which could be particularly important for male and female courtship. “A female zebra would not admit the addresses of a male ass until he was painted so as to resemble a zebra,” Darwin wrote.

at the University of Queensland, Australia, agrees that the stripes have an obvious social function. “But it’s possible they appeared for another reason and the social benefits came later.”

How says he has unpublished evidence suggesting that the stripes evolved to confuse predators, giving zebras crucial time to escape. He analysed videos of zebras with a motion detection program that mimics how movement is encoded in the animal brain. Their stripe pattern generated a range of optical illusions which would baffle a predator, he says. This effect was particularly strong when the animals moved together as a herd.

Dark horse

Another suggestion is that the stripes create a visual illusion, which makes the zebra look bigger that it is. Or perhaps the stripes assist with thermoregulation. But there is little evidence to support these claims, so the evolutionary explanation for the zebras’ stripes has remained murky.

Egri’s team picked up on a theory first proposed in 1930 and backed up in 1981, when it was demonstrated that , when compared to black or white models.

Now Egri has taken the research one step further, by showing that horseflies () also avoid the stripes. Biting insects transmit several equine diseases, such as equine infectious anaemia, as well as leaving painful bites.

Heading to a fly-infested farm in Budapest the team painted trays with different black and white patterns, and filled them with salad oil to trap the horseflies. Trays coated with thick horizontal stripes attracted less flies than diagonal lines, or criss-crosses. Thin black stripes mimicking those of the zebra attracted fewer flies than thick lines.

Insect defence

“The stripes are messing with their heads,” says , a sensory neurobiologist, also at the University of Queensland. “It confuses them and provides an unattractive surface to land on.”

According to experiments carried out by Egri’s team, the stripes could also disrupt polarised light, making zebras less appealing to the pests. Horseflies are attracted to horizontally polarised light because they detect water through horizontal polarisation. At the watering hole, flies drink, mate and lay eggs.

, an evolutionary biologist at the University of New South Wales, Australia, calls this “a delightfully innovative explanation for something that’s long puzzled mammalogists.”

“Having been bitten myself many times by tabanids, which really hurt, this new explanation makes a great deal of sense to me,” he says.

Journal Reference:

Read previous Zoologger columns: The only males with more brain than females , How a blurry-eyed spider pounces on target, Gecko’s amputated tail has life of its own, Unique life form is half plant, half animal, Transgender fish perform reverse sex flip, My brain’s so big it spills into my legs, Dozy hamsters reverse the ageing process, To kill a mockingbird? No, parasitise it, Chill out with the world’s coldest insect, ‘Werewolf birds’ hook up by the full moon, Cannibal shrimp shows its romantic side, The only cross-dressing bird of prey, The biggest spider web in the world.

It’s green and very, very old. A swathe of seagrass in the Mediterranean could be the oldest known living thing on Earth.

Carlos Duarte of the University of Western Australia in Perth sequenced the DNA of Posidonia oceanica at 40 sites spanning 3500 kilometres of seafloor, from Spain to Cyprus. One patch off the island of Formentera was identical over 15 kilometres of coastline.

Like all seagrasses, Posidonia oceanica reproduces by cloning, so meadows spanning many kilometres are genetically identical and considered one organism.

Given the plant’s annual growth rate the team calculated that the Formentera meadow must be between 80,000 and 200,000 years old, making it the oldest living organism on Earth. It trumps a Tasmanian shrub, Lomatia tasmanica, believed to be 43,600 years old.

Despite its historical robustness, Duarte says the patch of ąĘ.Ěý´ÇłŚąđ˛š˛ÔžąłŚ˛š is now threatened by climate change. The Mediterranean is warming three times faster than the world average, and each year ąĘ.Ěý´ÇłŚąđ˛š˛ÔžąłŚ˛š meadows decline by around 5 per cent. “They have never experienced the speed of climate that the Mediterranean is currently experiencing,” he says.

Journal reference:

Correction (8 February 2012): A previous version of this story incorrectly identified Lomatia tasmanica as a seagrass – it is a shrub.

Ah ref! Now you have an excuse for thinking your team always performs best. Your brain perceives the actions of people in your own team differently to those of a rival team.

at the University of Queensland in Brisbane, Australia, divided 24 volunteers into two teams and had them judge the speed of hand actions performed by two people, one from each team.

As expected, most of the volunteers were biased towards their own team, judging their players as faster, even when the two actions were performed at identical speeds.

Surprisingly, brain scans taken during the task showed that this bias arises from differences in brain activity during perception of the hand action and not during the decision-making process. The work will appear in Human Brain Mapping.

, a psychologist at Monash University in Melbourne, Australia, says the research is an important step to unravelling the mechanisms of how people develop perceptions of “in-groups” and “out-groups”. This can inform our understanding of racism and discrimination, she adds.

DNA sequencing has identified difficult-to-diagnose diseases in humans – the first time the technology has been used in a clinic.

The technique, which decodes thousands of genes simultaneously, has been used in laboratories to uncover genes related to diseases .

Now it has successfully moved to the clinic, where patients do not know what is wrong with them and may not know their family history of disease, and clinicians have few clues about which genes might be causing the problem.

Mitochondrial diseases, which affect the way the body produces energy, are notoriously difficult to diagnose. Found in at least one in every 5000 people, the diseases often involve many genes, and symptoms vary across organs. For example, common manifestations can include blindness, seizures, slow digestion and muscle pain.

Currently, diagnosing such disorders can take months or even years, and involves an invasive muscle biopsy. DNA sequencing technology may help to speed things up.

Diagnostic data

and colleagues from the Murdoch Childrens Research Institute in Sydney, Australia, along with from Harvard Medical School, sequenced the genomes of 42 children who had traits that suggested they carry a mitochondrial disorder. To work out exactly which disorder each child carries, the team looked both at the DNA in their mitochondria and at the 100 or so genes within their nuclear DNA that have already been linked to mitochondrial diseases. They also looked at a further 1000 nuclear genes that play a part in mitochondrial biology.

To distinguish between harmless genetic variations and those that might cause a disease, the team compared the patients’ genomes with databases of genetic variation recorded in the general population.

Ten of the children had mutations in genes previously linked to mitochondrial diseases, and so could be given a precise diagnosis. Mutations not previously associated with any disease were found in another 13 children. Tucker says that these patients can expect a full diagnosis once studies confirm the function of these genes.

“We are quite excited,” says Tucker. “Most of these diagnoses were in children whose [illnesses] could not easily be diagnosed using traditional methods.”

Needle in a haystack

, a biochemist at La Trobe University in Melbourne, Australia, who was not involved in the work, says the diagnosis rate “will improve” within the next couple of years as the list of genes known to be linked to mitochondrial diseases grows, and it becomes clearer how mutations combine to cause diseases.

“It’s a fantastic study,” says at Monash University in Melbourne. Finding genetic mutations in mitochondrial patients is “like searching for a needle in a haystack”, he says. “I think it was a very good result to transfer to a clinical setting.”

Journal reference: , DOI: 10.1126/scitranslmed.3003310

at the University of Oxford and colleagues looked at 43 genomic studies of the menopause, covering more than 50,000 women. By comparing the age that menopause began, Perry’s team identified 13 regions with possible links to menopause timing. Three of the regions were housed within genes associated with the immune system. Other regions occurred within genes that control gene repair, regulate hormones and trigger inflammation.

It’s not yet clear whether the immune system is the main driver of the menopause or merely a backseat player to biological forces such as hormonal fluctuations. “This will become clearer when we have identified more of the genetic basis of menopause onset,” says Perry. However, a genetic test to predict when menopause will begin is still a distant prospect.

The link between ovulation and the immune system isn’t unexpected: some women with primary ovarian insufficiency, who undergo an unusually early menopause, have an autoimmune disease of the ovaries.

Journal reference: Nature Genetics, DOI: 10.1038/ng.1051

Carbon dioxide in the ocean acts like alcohol on fish, leaving them less able to judge risks and prone to losing their senses. The intoxication adds to the threats that global warming and ocean acidification pose to marine ecosystems.

Around of human-caused CO₂ emissions dissolve into the world’s oceans every year, turning the water more acidic.

and colleagues at James Cook University in Townsville, Queensland, Australia, have previously found that if you put reef fish into water with more CO₂ than normal in it – similar to the levels expected in oceans by the end of the century – they become bolder and attracted to odours they would normally avoid, including those of predators and unfavourable habitats.

Munday and his colleague at the University of Oslo, Norway, have now discovered that CO₂ leads to riskier behaviour by interfering with a neurotransmitter receptor called GABA-A.

The pair reared clownfish () larvae in seawater with normal (450 microatmospheres) and elevated (900 microatmospheres) CO₂ levels. When they reached adulthood, the fish were given a choice between a water stream containing the odour of common predators such as the rock cod () or a stream lacking predatory odours. Those reared in high levels of CO₂ swam towards rock cod’s scent around 90 per cent of the time, whereas those that had enjoyed normal levels of CO₂ avoided the predator’s scent more than 90 per cent of the time.

Sobriety restored

Treating the clownfish bred under CO₂-rich conditions with gabazine, a chemical that blocks the GABA-A receptor, helped them to regain their senses, though: fish treated this way swam towards the predatory smell only 12 per cent of the time.

“The fact that we could use a specific blocker for the GABA-A receptors to reverse the behavioural alterations proves that this receptor is involved in the CO₂ effects,” says Nilsson.

In a second test, using juvenile damselfish () from Lizard Island in the Great Barrier Reef, the team found that high levels of CO₂ destroyed their natural tendency to turn left or right in certain situations – a crucial factor in shoaling. A bath with gabazine restored this “handedness”.

Exciting effect

The GABA-A receptor sits on dendrites, the wiry projections of a neuron that detect chemical signals from other neurons. When the neurotransmitter GABA binds to its receptor, the receptor opens and a flood of negatively charged chloride and bicarbonate ions rush into the cell and prevent it from firing. This means that GABA has an inhibitory effect on the neuron.

When CO₂ accumulates in the fish, it alters the distribution of ions. Now, when the receptor opens, chloride and bicarbonate ions escape out of the cell, exciting the neuron instead. “This would have strong effects on the function of neural circuits in the brain,” says Nilsson, and may make ultimately make the fish behave in a way that increases its likelihood of being eaten.

The influence of CO₂ “is likely to be far broader than just applying to the two species that were considered in this study”, says , a fish ecologist at the South Australian Research and Development Institute in Adelaide, who was not involved in the study. Most animals, both vertebrates and invertebrates, have GABA-A receptors, he says.

Nilsson and Munday suspect that water-breathing animals, such as fish and crustaceans, are especially at risk. These creatures generally have lower blood CO₂ levels than air-breathers, so it is more difficult for them to cope with the acid boost.

Journal reference: , DOI: 10.1038/nclimate1352