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Ancient ‘megalake’ covered more than one million square miles 10 million years ago

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The largest lake ever to exist on Earth – the Paratethys megalake – suffered a ‘disaster’ that killed off most of its lifeforms less than 10 million years ago, a new study says. 

At its vastest, Paratethys had a surface area of more than a million square miles (2.8 million square km) – slightly larger than the present-day Mediterranean Sea, according to a team led by experts at Utrecht University, Netherlands. 

For a modern day comparison, Paratethys would stretch from the eastern Alps to what is now Kazakhstan in central Asia. 

It also contained a water volume of more than 1.77 million km3 – representing more than a third the volume of the Mediterranean today. 

But between 9.75 and 7.65 million years ago, up to a third of the megalake water was lost to evaporation, the lake fragmented, and the central basin, now the Black Sea, became particularly toxic and barren. 

Most lifeforms in the lake – including miniature dolphins and seals – became extinct, and those that survived were sick and deformed, the study authors say. 

Location of the Paratethys megalake. For comparison reasons the present-day geography is shown (this was not how Europe appeared at the time)

THE PARATETHYS MEGALAKE 

Paratethys is the largest lake the world has ever known. 

At its vastest, Paratethys had a surface area of more than a million square miles (2.8 million square km) – larger than the Mediterranean Sea today.

It was in initially the Paratethys sea before being closed off by moving tectonic plates around 12 million years ago.

Paratethys succumbed to cataclysms that turned the region into a ‘toxic waste-world’, driven by climate changes.

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The researchers based their estimations on geological and fossil records within the Black Sea, where the Paratethys originally existed. 

As well as the Black Sea, the Caspian Sea, Aral Sea, Lake Urmia, Namak Lake and others are remnants of the Paratethys. 

‘It must have been a post-apocalyptic prehistoric world – an aquatic version of the wastelands from Mad Max’, said study author Wout Krijgsman at Utrecht University.  

Paratethys formed as a lake some 12 million years ago, after a giant sea disconnected from the ocean, and life evolved there over 5 million years – cut-off from the rest of the world. 

Paratethys was previously a sea, connected to the rest of the world’s water, up to 34 million years ago, but the moving tectonic plates closed it off. 

It contained more water than 10 times the volume of all modern lakes combined.  

The megalake’s unique array of creatures included dolphins and whales – among them, the smallest ones in the Earth history – as well as crustaceans and algae.   

Water volume comparison between the Paratethys megalake and other waterbodies (lakes and ice-sheets). Paratethys contained more water than 10 times the volume of all modern lakes combined

The 10-foot (three metre) long Cetotherium riabinini is the best known of these dolphin-sized dwarf baleen whales, researchers say. 

But the fauna were later nearly totally obliterated by cataclysms that turned the region into a salty waste world. 

Over its five million-year lifetime, shifts in climate shrank the lake as it went through ‘desiccation’ – extreme drying and removal of moisture. 

Artist’s impression of the extinct dwarf whale Cetotherium riabinini, compared with a six-foot-tall human

A final period of desiccation – spanning between 7.65 million and 7.9 million years ago – sounded the death knell for the megalake.

This ‘most severe’ drying period, called the Great Khersonian Drying, saw water levels falling by as much as 820 feet (250 metres).

Paratethys lost one-third of its water and 70 per cent of its surface area during this final drying period, researchers reveal. 

As a result, the remaining water was stored in a central, highly salty lake, surrounded by smaller ‘mini lakes’ unsuitable for the lifeforms within. 

As well as the Black Sea, the Caspian Sea, Aral Sea, Lake Urmia, Namak Lake and others are remnants of the Paratethys. Pictured, cliffs on the promontory of Cape Kaliakra on the Black Sea, Bulgaria

‘These crises were similar to the desiccation of lake Aral, but hundreds of times larger in magnitude,’ said lead study author Dan Palcu at University of São Paulo. 

But the demise of Paratethys had some benefits – ancestors of today’s giraffes and elephants would have been forced to migrate towards the present-day African savannah. 

According to Nature, the megalake also likely formed a spectacular waterfall as it drained into the Mediterranean Sea between 6.7 million and 6.9 million years ago. 

The study, entitled ‘Late Miocene megalake regressions in Eurasia’, has been published by Nature in Scientific Reports.  

The Earth is moving under our feet: Tectonic plates move through the mantel and produce Earthquakes as they scrape against each other

Tectonic plates are composed of Earth’s crust and the uppermost portion of the mantle. 

Below is the asthenosphere: the warm, viscous conveyor belt of rock on which tectonic plates ride.

The Earth has fifteen tectonic plates (pictured) that together have molded the shape of the landscape we see around us today

Earthquakes typically occur at the boundaries of tectonic plates, where one plate dips below another, thrusts another upward, or where plate edges scrape alongside each other. 

Earthquakes rarely occur in the middle of plates, but they can happen when ancient faults or rifts far below the surface reactivate. 

These areas are relatively weak compared to the surrounding plate, and can easily slip and cause an earthquake.

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Maps: Earth ‘officially’ has FIVE oceans as National Geographic finally recognises Southern Ocean

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Cartographers at the National Geographic have finally recognised Antarctica’s Southern Ocean on their maps, bringing their count of Earth’s oceans to five.

The society — which has been releasing maps of the world since 1915 — publicly announced their new policy yesterday, to coincide with World Ocean Day.

National Geographic have defined the ocean as being bound by the current that flows around Antarctica — with a northernmost reach up to the 60th parallel south.

The Southern Ocean joins the Arctic, Atlantic, Indian and Pacific on their charts, although the Antarctica-encircling body’s status remains internationally contested.

Nevertheless, National Geographic hope their revised maps will help people think differently about the Southern Ocean, thereby encouraging its conservation.

Cartographers at the National Geographic have finally recognised Antarctica’s Southern Ocean on their maps, bringing their count of Earth’s oceans to five. Pictured: the Southern Ocean (in red) surrounds Antarctica and abuts against the Atlantic, Indian and Pacific Oceans

National Geographic have defined the ocean (pictured) as being bound by the current that flows around Antarctica — with a northernmost reach up to the 60th parallel south

‘The Southern Ocean has long been recognized by scientists,’ explained National Geographic Society geographer Alex Tait in the announcement.

‘But because there was never agreement internationally, we never officially recognized it. It’s sort of geographic nerdiness in some ways,’ he added.

‘We’ve always labelled it, but we labelled it slightly differently [than the other oceans]. This change was taking the last step and saying we want to recognize it because of its ecological separation.’

The National Geographic said that Mr Tait — who oversees changes to all the maps they publish — and their map policy committee have been debating the merits of acknowledging the Southern Ocean as a body in its own right for years now.

Previously, they had categorised the waters around Antarctica as merely cold, southern extensions of the Atlantic, Indian and Pacific Oceans, even as scientists and members of the press increasingly made use of the term ‘Southern Ocean.’

‘While there is but one interconnected ocean, bravo to National Geographic for officially recognizing the body of water surrounding Antarctica as the Southern Ocean,’ said Marine biologist and National Geographic Explorer at Large Sylvia Earle.

‘Rimmed by the formidably swift Antarctic Circumpolar Current, it is the only ocean to touch three others and to completely embrace a continent rather than being embraced by them.’

Previously, the National Geographic had categorised the waters around Antarctica as merely cold, southern extensions of the Atlantic, Indian and Pacific Oceans, even as scientists and members of the press increasingly made use of the term ‘Southern Ocean.’ Pictured: a National Geographic map of Antarctica from 2009, in which the Southern Ocean is absent

The National Geographic Society — which has been releasing maps of the world since 1915 — publicly announced their new policy yesterday, to coincide with World Ocean Day. Pictured: a new map of the southern hemisphere from the National Geographic, showing the ‘new’ ocean

‘The Southern Ocean has long been recognized by scientists,’ explained National Geographic Society geographer Alex Tait. ‘But because there was never agreement internationally, we never officially recognized it. It’s sort of geographic nerdiness in some ways,’ he added. Pictured: Scientific Base Argentina, which lies in Paradise Bay, on the  Antarctic Peninsula. Until this week, it would have lain on the coast of the Pacific in National Geographic maps

Mr Tait said that he hopes National Geographic’s new policy regarding the Southern Ocean will influence how children using maps in schools will learn to see the world.

‘I think one of the biggest impacts is through education. Students learn information about the ocean world through what oceans you’re studying.’

‘If you don’t include the Southern Ocean then you don’t learn the specifics of it and how important it is,’ he concluded.

THE SOUTHERN OCEAN — A BODY THAT IS DEFINED BY A CURRENT 

Pictured: the Antarctic Circumpolar Current, showing branches connected to the global ‘conveyor belt’ of circulation

Unlike the Arctic, Atlantic, Indian and Pacific Oceans — which are defined by the continents that bound them — the Southern Ocean is instead characterised by the Antarctic Circumpolar Current (ACC).

Formed some 34 million years ago, when Antarctica and South America were separated by the action of continental drift, the ACC flows counter-clockwise around Antarctica in a fluctuating band that lies at around a latitude of 60°.

Inside the current — which stretches from the surface to the ocean floor — the waters are both colder and less salty than the waters of the Atlantic, Indian and Pacific Oceans to the both.

These three bodies, however, do feed the ACC, which transports more water than any other current and helps to drive a global circulation known as ‘the conveyor belt’ which serves to shunt heat around the globe.

This means that the current has a significant impact on the Earth’s climate — as does the Southern Ocean itself, with the cold, dense water than sinks off the coast of Antarctica helping to store carbon in the deep ocean. 

Pictured: Emperor penguins, which are endemic to the southernmost continent

And by surrounding these chilly southern waters, the ACC helps to keep Antarctica cold — and provides an ecologically distinct environment for thousands of species that are unique to the Southern Ocean.

According to National Geographic Explorer in Residence Enric Sala, the Southern Ocean ‘encompasses unique and fragile marine ecosystems that are home to wonderful marine life such as whales, penguins, and seals.’ 

National Geographic hope their revised maps will help people think differently about the Southern Ocean, thereby encouraging its conservation.

Recently studies have shown that human-driven climate change is warming the waters that move through the Antarctic Circumpolar Current.

It is unclear to what extent this is impacting the southernmost continent — but experts have noted that some of the most rapid melting of Antarctica’s ice sheets and shelves has occurred where the ACC is closest to land.

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Native Australian mammal are known for having the ‘weirdest penises’ in the animal kingdom

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The ‘very strange and unusual’ echidna penis remains a mystery to researchers who still don’t understand why it has four heads.

The ‘very long’ phallus makes up a third of the mammal’s body while erect, is bright red, and has four prongs, which can all be used for reproduction.

University of Queensland researcher Dr Steve Johnson co-authored a study on the short-beaked echidna’s impressive member, but said only ‘the creator God’ knows why it is so bizarrely shaped.

It may be to please the insatiable female echidna, who scientists think may mate multiple times with up to a dozen males while ovulating.

The echidna is native to Australia, has spiky pines, a bird-like beak, a pouch like a kangaroo and also lays eggs.

The ‘very strange and unusual’ echidna penis remains a mystery to researchers who still don’t understand why it has four heads 

When the echidna has sex, two of the four prongs are engorged while the others are flaccid.

The female has two separate reproductive tracts which take a penis head each during sex.

It is possible she could mate with up to a dozen partners while ovulating, as  scientists have found sperm from eleven different males inside one deceased female echidna.

Researchers also predicted the pair may have intercourse multiple times, possibly using all prongs during a session.

‘It does look like they do it more than once, but there’s still a bit of debate… we’re not quite sure whether these guys are induced ovulators or not,’ Dr Johnson said.  

The penis is also unusual because it is not used for urinating.

‘Not only is the [echidna] penis strange in the way it looks, it’s also strange in terms of they don’t actually urinate through their penis,’ said Dr Johnson.

‘[This is unlike] all other species of mammals expect for the platypus and the other species of echidna. These animals urinate not through their penis, but at the base of the penis.’

Researchers want to understand the short-beaked echidna reproductive system to help breed the short-beaked echidna, a critically endangered species found in New Guinea.

Dr Johnston said the ‘unique animal’ is poorly understood, despite being found across the country.  

‘They’re very common. You’ll find echidnas nearly all over Australia, across Mt Kosciuszko right through to the desert, on the coastline, even here in suburban Brisbane,’ he said. 

The ‘very long’ phallus makes up a third of the mammal’s body while erect, is bright red and has four prongs which can all ejaculate

HOW DO ECHIDNAS MATE?

  • Males follow the female before the female signals it is ready to mate by digging its legs and head into the ground. The male will then dig a rut next to the female 
  • A male has a four-headed penis, but only uses two of those heads at a time to ejaculate sperm when mating with a female
  • The male will then use the other two heads the next time it mates
  • A female echidna typically has a 20-day gestation period before laying an egg directly into her temporary pouch that develops when she is pregnant and regresses when her baby no longer needs it 
  • The puggles hatch about 10 days after the egg is laid, and stay in the pouch for two to three months
  • When the puggles hatch they are only 1.5 centimetres long and will travel further down their mother’s pouch to get milk
  • At seven months old the mother echidna leaves and the puggles are left to fend for themselves

Source: ABC Science 

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Young clownfish living closest to the shore die FASTER than those further out

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Young clownfish living closest to the shore die faster than those further out because they are being exposed to artificial lighting from streetlights, piers and ports, a new study has warned. 

Made famous by ‘Finding Nemo’, the iconic reef-dwellers feed, reproduce, defend their territories and interact with other fish during the day before sleeping at night.

Like humans, this period of inactivity is crucial for their well-being because they need it to recharge, researchers said.

But when the down time is interrupted by artificial light the effect on clownfish can be catastrophic.

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In need of sleep: Young clownfish living closest to the shore die faster than those further out because they are being exposed to artificial lighting from piers and ports, a study has warned

Clownfish were monitored for almost two years in the reefs around Moorea in French Polynesia

Why do clownfish need moonlight rather than artificial light to thrive?

The survival and growth rates of clownfish are negatively affected by long-term exposure to artificial light at night, a study has found. 

This may be due to the potential for light to attract natural predators, as well as the harmful effects on physiology of the fish, the team of international researchers said.

Clownfish need a period of inactivity at night to recharge but the lack of sleep caused by artificial light may also result in increased metabolism, with a subsequent higher demand for energy.

This could be part of the reason why the growth of young clownfish was stunted.

By comparison, those living further from the shore and enjoying natural moonlight had higher survival rates and increased growth.

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A team of international scientists from France, the UK, Chile and Australia found that young clownfish had higher rates of death when exposed to light pollution close to the coast.

This is because of the harmful effects it has on the physiology of the fish, as well as the potential for artificial light to attract natural predators. 

The juvenile clownfish also grew 44 per cent slower than those in natural lighting conditions.

‘The impacts of light pollution found here are probably underestimated and mitigation measures and policy changes are urgently required,’ said marine ecology expert Stephen Swearer.

The clownfish were monitored for almost two years in the reefs around Moorea in French Polynesia.

Professor Swearer, from the University of Melbourne, said researchers exposed 42 clownfish in their host anemones to either artificial light at night (ALAN) or natural light in the lagoon. 

‘Thirty six per cent of the clownfish exposed to light pollution were more likely to die than fish under natural light cycles,’ said lead author, Jules Schligler, from the École Pratique des Hautes Études PSL Université Paris.

He said clownfish can be found in shallow coastal waters and are easily impacted by light at night from streetlights, piers or ports because they are highly sedentary living in anemones. 

In the research paper, the scientists said that ‘even those fish that survived didn’t entirely escape the effects of artificial light at night as they grew less than fish from the control group.’ 

Reef-dwellers: Researchers exposed 42 clownfish to either artificial light or natural moonlight

The study from the University of Melbourne produced this graphic to summarise its findings

‘This is the first time that the impacts of ALAN have been tested on a coral reef fish in the wild and over such a long time,’ said Daphne Cortese, a post-doctoral fellow at the University of Glasgow. 

‘As 12 per cent of all coral reef fish live in close association with another sedentary species, such as a coral or anemone, light pollution could already be having severe negative impacts on a fifth of fringing reef fish populations.’

Scientists hope the research will help raise awareness of the impacts of ALAN on coastal marine ecosystems.

‘Many marine protected areas are impacted by light pollution at night, and authorities are not taking this pollution into account,’ said Ricardo Beldade, associate professor at the Pontificia Universidad Católica de Chile. 

‘We hope that policymakers take this threat much more seriously for future management strategies.’

The study is published by the University of Melbourne in the journal Proceedings of the Royal Society B.

CLOWNFISH FATHERS HAVE STRONG NURTURING INSTINCTS BECAUSE OF A ‘LOVE HORMONE’

Nurturing: Clownfish parenting instincts are so strong that even if you place eggs from an unrelated nest near a bachelor anemonefish, he will take care of them

One area where Finding Nemo had things right is the great lengths clownfish dads go to to support their offspring, just like Marlin.

Their parenting instincts are so strong that even if you place clownfish eggs from an unrelated nest near a bachelor anemonefish, he will take care of them. 

Researchers previously found the love hormone behind this fathering behaviour.

And it’s very similar to oxytocin, the hormone that facilitates bonding between human mothers and their babies after childbirth.

Scientists, based at the University of Illinois at Urbana-Champaign, decided to study the brain chemistry behind this parental care.

So they took individual anemonefish that were fathering and gave them an injection of antagonists.

They then analysed how these drugs might either promote or inhibit male parental care.

They found that anemonefish rely on isotocin, a signalling molecule that is almost identical to oxytocin. 

When the researchers blocked this hormone, they found that the anemonefish fathers stopped tending to their eggs.

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