At 7mm (0.27 inches) long, Paedophryne amauensis may be the world's smallest vertebrate - the group that includes mammals, fish, birds and amphibians.


World's smallest frog discovered

Richard Black By Richard Black Environment correspondent, BBC News
Frog on coin The tiny frog sits easily on a US dime, whose diameter is 18mm

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A frog species that appears to be the world's smallest has been discovered in Papua New Guinea by a US-based team.


The researchers also found a slightly larger relative, Paedophryne swiftorum.

Presenting the new species in PLoS One journal, they suggest the frogs' tiny scale is linked to their habitat, in leaf litter on the forest floor.

What are amphibians?
Frog eye

First true amphibians evolved about 250 million years ago
Three orders: frogs (inc. toads), salamanders (inc. newts) and the limbless caecilians
Adapted to many aquatic and terrestrial habitats
Present on every continent except Antarctica
Many metamorphose from larvae to adults

Amphibians videos, news and facts: BBC Nature

Finding the frogs was not an easy assignment.

They are well camouflaged among leaves on the forest floor, and have evolved calls resembling those of insects, making them hard to spot.

"The New Guinea forests are incredibly loud at night; and we were trying to record frog calls in the forest, and we were curious as to what these other sounds were," said research leader Chris Austin from Louisiana State University in Baton Rouge, US.

"So we triangulated to where these calls were coming from, and looked through the leaf litter.

"It was night, these things are incredibly small; so what we did after several frustrating attempts was to grab a whole handful of leaf litter and throw it inside a clear plastic bag.

"When we did so, we saw these incredibly tiny frogs hopping around," he told BBC News.
Littering the leaves

The Paedophryne genus was identified only recently, and consists of a number of tiny species found at various points in the eastern forests of Papua New Guinea.
Frog limbs The tiny limbs of amauensis (top) and swiftorum are rendered translucent

"They're occupying the relatively thick leaf litter of tropical forest in low-lying parts of the island, eating incredibly small insects that typically are much smaller than insects that frogs eat," said Professor Austin.

"And they're probably prey for a large number of relatively small invertebrates that don't usually prey on frogs."

Predators may well include scorpions.

Intriguingly, other places in the world that also feature dense, moist leaf litter tend to possess such small frog species, indicating that amphibians are well placed to occupy this ecological niche.

Before the Paedophrynes were found, the title of "world's smallest frog" was bestowed on the Brazilian gold frog (Brachycephalus didactylus) and its slightly larger Cuban relative, the Monte Iberia Eleuth (Eleutherodactylus iberia). They both measure less than 1cm long.

The smallest vertebrates have until now been fish.

Adult Paedocypris progenetica, which dwells in Indonesian swamps and streams, measure 7.9-10.3 mm long.

Male anglerfish of the species Photocorynus spiniceps are just over 6mm long. But they spend their lives fused to the much larger (50mm long) females, so whether they should count in this contest would be disputed.

Paedophryne amaunensis adults average 7.7mm, which is why its discoverers believe it how holds the crown.

The remote expanses of Papua New Guinea rank alongside those of Madagascar as places where hitherto undiscovered amphibian species are expected to turn up, as they are largely undeveloped and not well explored.


http://www.bbc.co.uk/news/science-environment-16491477

Jungle tribes untouched by modern civilisation



http://www.bbc.co.uk/news/magazine-16957988

8 February 2012 Last updated at 23:04 ET Help

They are among the Amazon's last uncontacted tribes and have avoided contact with modern civilisation by hiding in the deepest recesses of the jungle.

Journalist, writer and photographer, Scott Wallace, takes us on a three month journey through the Brazilian Amazon to map the territory of the Arrow People - a rarely glimpsed indigenous group whose life and language remain a mystery and who have repelled previous intruders with deadly arrows.

"The Unconquered - In Search of the Amazon's Last Uncontacted Tribes", explores efforts to protect the rainforest and those who rely on it for survival.

In the book, Brazilian explorer and social activist Sydney Possuelo leads a 34-man team - which includes the author - into the jungle to search for evidence of the Arrow People's range and culture.

In doing so the team must avoid making contact with the tribe, which risks decimation by modern diseases against which it has no protection, should contact be inadvertently made.

Photos: courtesy Scott Wallace and Gleilson Miranda, FUNAI/Survival International

9 February 2012 Last updated at 14:01 ET


Alzheimer's brain plaques 'rapidly cleared' in mice

By James Gallagher Health and science reporter, BBC News

Alzheimer's brain scans Sections of Alzheimer's, left, and healthy brain tissue showing brain shrinkage with the condition


Destructive plaques found in the brains of Alzheimer's patients have been rapidly cleared by researchers testing a cancer drug on mice.

The US study, published in the journal Science, reported the plaques were broken down at "unprecedented" speed.

Tests also showed an improvement in some brain function.

Specialists said the results were promising, but warned that successful drugs in mice often failed to work in people.

The exact cause of Alzheimer's remains unknown, but one of the leading theories involves the formation of clumps of a protein called beta-amyloid. These damage and kill brain cells, eventually resulting in memory problems and the inability to think clearly.

Clearing protein plaques is a major focus of Alzheimer's research and drugs are already being tested in human clinical trials.

In the body, the role of removing beta-amyloid falls to apolipoprotein E - or ApoE. However, people have different versions of the protein. Having the ApoE4 genetic variant is one of the biggest risk factors for developing the disease.
Helping hand

Scientists at the Case Western Reserve University in Ohio were investigating ways of boosting levels of ApoE, which in theory should reduce levels of beta-amyloid.

They tested bexarotene, which has been approved for use to treat cancers in the skin, on mice with an illness similar to Alzheimer's.
Brain plaque Plaques, in brown, form around brain cells, in blue, which kills parts of the brain

After one dose in young mice, the levels of beta-amyloid in the brain were "rapidly lowered" within six hours and a 25% reduction was sustained for 70 hours.

In older mice with established amyloid plaques, seven days of treatment halved the number of plaques in the brain.

The study said there were improvements in brain function after treatment, in nest building, maze performance and remembering electrical shocks.

Researchers Paige Cramer said: "This is an unprecedented finding. Previously, the best existing treatment for Alzheimer's disease in mice required several months to reduce plaque in the brain."
In people?

The research is at a very early stage, and drugs often do not make the leap from animal experiment to human treatment.

Fellow researcher Prof Gary Landreth said the study was "particularly exciting and rewarding" and held the "potential promise of a therapy for Alzheimer's disease".

However, he stressed that the drug had been tested in only three "mouse models" which simulate the early stages of the disease and are not Alzheimer's.
Continue reading the main story
Alzheimer's disease

Alzheimer's disease is the most common cause of dementia
Symptoms include loss of memory, mood changes, and problems with communication and reasoning
No one single factor has been identified as a cause for Alzheimer's disease - a combination of factors, including age, genes, environment, lifestyle and general health are implicated
Source: Alzheimer's Society

He warned people not to "try this at home", as the drug had not been proven to work in Alzheimer's patients and there was no indication of what any dose should be.

"We need to be clear, the drug works quite well in mouse models of the disease. Our next objective is to ascertain if it acts similarly in humans," he said.

His group is preparing to start trials in a small group of people to see if there is a similar effect in humans.

The disease is likely to become more common as people live longer. The Alzheimer's Society predicts the number of people with dementia will reach a million by 2021 in the UK alone.
Continue reading the main story
“Start Quote

There are a number of drugs in development that aim to clear amyloid from the brain, and the jury is still out on whether this approach will be successful as a treatment for Alzheimer's”

Dr Simon Ridley Alzheimer's Research UK

Its research manager, Dr Anne Corbett, said: "This exciting study could be the beginning of a journey towards a potential new way to treat Alzheimer's disease.

"However, this is very early days. People with Alzheimer's should not rush to get this drug, as we need much more research to establish if it has benefits for humans."

Dr Simon Ridley, head of research at Alzheimer's Research UK, said the findings were "promising" but any effect was still unproven in people.

"There are a number of drugs in development that aim to clear amyloid from the brain, and the jury is still out on whether this approach will be successful as a treatment for Alzheimer's."

David Allsop, professor of neuroscience at Lancaster University, said: "I would say that the results should be treated with cautious optimism.

"It looks promising in the mouse model but in recent years, these types of experiments in mice have not translated well into humans."

Balanced on the tip of a scientist's fingernail in Madagascar, the-three centimetre reptile is no bigger than the flies that form his average-sized cousin's lunch. Scientists discovered four new species - called Brookesia micra - on a small islet just off the main island.

Meet mini-meleon! Scientists discover one of the smallest reptiles on the planet

KOOL

Small is good.............................