News & Current Affairs

September 1, 2008

Experts poised for rare frog hunt

Experts poised for rare frog hunt

Golden toads mating

The golden toad has vanished from Costa Rica’s rainforests

Scientists are set to begin a hunt for the some of the world’s rarest frogs in Costa Rica, including the iconic golden toad, last seen some 20 years ago.

A team from Manchester University and Chester Zoo are in Costa Rica to track down the highly endangered creatures.

News will follow their trek deep into the cloud forests of Monteverde.

Amphibians numbers around the world have crashed, in part because of a deadly fungus. Costa Rica has been particularly badly hit.

Expedition leader Andrew Gray, from the University of Manchester’s Manchester Museum, said: “Costa Rica’s highlands used to be major biodiversity hotspots – but in many areas amphibian populations have been completely decimated.”

Killer fungus

Yellow-eyed leaf frog

The killer fungus

In the late 1980s, herpetologists around the world found that amphibian populations were suffering unprecedented declines, but they struggled to understand exactly why.

A decade later, researchers isolated a previously unknown fungus, Batrachochytrium dendrobatidis, which was infecting amphibians, effectively suffocating them by making it impossible for them to breathe across their skin.

Recently, the scientists working on the Global Amphibian Assessment estimated that one-third of all amphibians were threatened by extinction and about 120 species had already become extinct since the 1980s.

Many believe the disease caused by the chytrid fungus is a key factor for this crash. Other causes are thought to include habitat destruction and changes in climate.

Frog rediscovery

Countries in Central America have been particularly badly affected by the deadly chytrid fungus, which is now widespread there. A great deal of effort is now being put into place to safeguard any remaining species.

Ithsmohyla rivularis
To find this species last year that was thought to be extinct at the same times as the golden toad was incredible
Andrew Gray

Andrew Gray said: “For the last 10 years, I’ve been working with others to ensure the future for frogs that have so far escaped extinction.

“One of the main things I have been doing is establishing breeding populations in Manchester Museum for a number of very, very rare species – including the splendid leaf frog (Cruziohyla calcarifer), the yellow-eyed leaf frog (Agalychnas annae) and the lemur leaf frog (Hylomantis lemur).

“I’ve also been working with the Costa Rican authorities and scientists to put conservation measures into place at the sites where any rare frogs are found.”

Last year, Mr Gray caught a glimpse of the Ithsmohyla rivularis in the cloud forests of Monteverde – a frog that was thought to have gone extinct about 20 years ago.

Splendid Leaf frog

Manchester Museum has a splendid leaf captive breeding population

He said: “To find this species last year that was thought to have become extinct at the same time as the golden toad was incredible – it is the rarest tree frog in the world.”

He has now been given special permission by the Costa Rican authorities to collect some of the frogs to take back to Manchester.

He told : “We are returning to thoroughly search the site in the hope of finding more specimens.

“It’s not going to be easy – they live deep in the Monteverde rainforest, they are only a couple of centimetres in size and they only come out in the dead of night – and while the males do call, the females don’t make a sound.”

‘Never say never’

The rediscovery of Ithsmohyla rivularis has spurred the team on to also try to seek out a golden toad (Bufo pereglines).

This colourful amphibian, which scientists only discovered in 1966, became the iconic symbol of amphibian decline. In 1987 there were approximately 1,500 of the toads, but just two years later it had vanished from the face of the rainforest.

Mr Gray said: “We are going to be trekking through an area where the golden toad used to thrive. It is very unlikely we will find one – but as last year’s discovery showed us, never say never.”

While in the rainforest, the team will also trying to track down the miniature red-eyed tree frog (Duellmanohyla uranochroa) – a species on the brink of extinction – to investigate how some frogs may be able to prevent the chytrid fungus from taking hold.

This is a unique opportunity to study the frogs in their natural habitat
Mark Dickinson

Previous research has shown that some species of tree frog have a special pigment in their skin that enables them to reflect light, allowing them to “sunbathe” without drying out.

Physicist Mark Dickinson, from Photon Science Institute at the University of Manchester, will be taking a spectrometer into the field to investigate how different frog species reflect light.

He said: “So far, I’ve only been able to investigate captive frogs in the lab. This is a unique opportunity to study the frogs in their natural habitat.”

The team believes that the ability to sit out in the Sun may allow the frogs’ skin to heat up just enough to kill off chytrid – preventing the disease from taking its grip.

Some of the team will also be heading to the last known breeding site of the green-eyed frog (Lithobates vibicarius) where Chester Zoo is helping to support a conservation programme.

August 30, 2008

New giant clam species discovered

New giant clam species discovered

Giant clam (M.Naumann)

The new giant clam species has a deeply folded shell outline

A new species of giant clam has been discovered in the Red Sea.

Fossils suggest that, about 125,000 years ago, the species Tridacna costata accounted for more than 80% of the area’s giant clams.

The species may now be critically endangered, researchers report in Current Biology journal.

The scientists believe their findings may represent one of the earliest examples of the over-exploitation of marine organisms by humans.

T. costatahas “very peculiar characteristics” that set it apart from two other species of giant clam that are also found in the area.

The Latin word costatus means “ribbed” and T. costata has a distinctive, zig-zag outline to its shell.

“The new species are mid-sized clams – up to 40cm long and a couple of kilograms heavy,” explained co-author Dr Claudio Richter, from the Alfred-Wegener Institute for Polar and Marine Research, Germany.

The new species has a distant relative, T. gigas, which can grow up to 1.4m long.

Live specimens of T. costata appear to be restricted to very shallow waters. Other species were also found in deeper reef zones.

The clam has an earlier and shorter breeding season that coincides with the seasonal plankton bloom. Genetic analysis confirmed the status of the new species.

‘Time travel’

“One of the great features of the desert-enclosed Red Sea is that you can literally time-travel from the present, several hundred thousand years into the past,” said Dr Richter.

The research team uncovered well-preserved fossil evidence that suggested stocks of these giant clams plummeted some 125,000 years ago – during an interval between Ice Ages.

They believe this period coincides with the appearance of modern humans in the Red Sea area.

Giant clams were abundant, large in size and easily accessible – making them an attractive food source for hunter-gatherers.

In “pre-human times”, T. costata may have been up to 60cm long. Since then, shell size has also decreased dramatically.

“The overall decline in giant clam stocks – with the striking loss of large specimens – is a smoking gun indicating over-harvesting,” said Dr Richter.

The scientists were not expecting to find a new species in an area as well studied as the Red Sea.

The research highlights how little is known about marine biodiversity in general, the scientists said.

“The coral reefs in particular… may still harbour very large surprises,” said Dr Richter.

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