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Coelacanth: The Fish That Time Forgot

Often called a living fossil, the coelacanth was long believed to have fallen extinct 70 million years ago, until a specimen was recognized in a fish market in South Africa in 1938. The coelacanth has fleshy, lobed fins that look somewhat like limbs, as does the lungfish, an air-breathing freshwater fish.

 

The coelacanth and the lungfish have long been battling for the honor of which is closer to the ancestral fish that first used fins to walk on land and give rise to the tetrapods, meaning all the original vertebrates and their descendants, from reptiles and birds to mammals.

 

The decoding of the coelacanth genome results in a victory for the lungfish as the closer relative to the first tetrapod. But the coelacanth may have the last laugh because its genome — which, at 2.8 billion bp of DNA, about the same size as a human genome — is decodable, whereas the lungfish genome, a remarkable 100 billion DNA units in length, cannot be cracked with present methods. The coelacanth genome is therefore more likely to shed light on the central evolutionary question of what genetic alterations were needed to change a lobe-finned fish into the first land-dwelling tetrapod.

 

The idea of decoding the coelacanth genome began six years ago when Chris Amemiya, a biologist at the University of Washington in Seattle, acquired some samples of coelacanth tissue. He asked the Broad Institute of Harvard and M.I.T., a biological research institute in Cambridge, Mass., to decode the DNA and invited experts in evolutionary and developmental biology to help interpret the results.

 

Dr. Amemiya’s team has sifted through the coelacanth’s genome for genes that might have helped its cousin species, the ancestor to the first tetrapod, invade dry land some 400 million years ago. They have found one gene that is related to those that, in animal species, build the placenta. Coelacanths have no placenta, but they produce extremely large eggs, with a good blood supply, that hatch inside the mother’s body. This gene could have been developed by land animals into a way of constructing the placenta.

 

Another helpful preadaptation is a snippet of DNA that enhances the activity of the genes that drive the formation of limbs in the embryo. The Amemiya team focused on the enhancer DNA sequence because it occurred in the coelacanth and animals but not in ordinary fish. They then inserted the coelacanth enhancer DNA into mice.

 

“It lit up right away and made an almost normal limb,” said Neil Shubin, meaning that the coelacanth gene enhancer successfully encouraged the mouse genes to make a limb. Dr. Shubin, a member of the team, is a paleontologist at the University of Chicago.

 

Present-day coelacanths are ferocious predators that live in a twilight zone about 500 feet deep where light barely penetrates. They lurk in caves during the day and emerge at night to attack surface fish as they descend and deep-sea fish as they rise to the surface. They have no evident need of fins that might help them walk on land.

 

“This is probably an unusual habitat for this lineage,” said Axel Meyer, an evolutionary biologist at the University of Konstanz in Germany and a member of the team. “Other coelacanths lived in more shallow, estuarylike environments 400 million years ago, and you can envisage them using the fins more like walking legs.”

 

The Amemiya team reports evidence that the coelacanth’s genes have been evolving more slowly than those of mammals, possibly because of “a static habitat and lack of predators.” But its environment must have changed quite considerably over the last 400 million years, Dr. Meyer said. Its principal habitat at present is the caves beneath the Comoro Islands in the Indian Ocean, but since these are extinct volcanoes a mere 5 million to 10 million years old, they must be a quite recent home for the coelacanth.

 

The Amemiya team does not possess a full coelacanth — these are endangered species — and decoded the genome from tissues obtained from Rosemary Dorrington of Rhodes University in South Africa. Dr. Dorrington supplied DNA kits to the Comoro Islands fishermen who occasionally snag coelacanths by accident. When a coelacanth was captured in 2003, they preserved blood and tissues, which were given to Dr. Dorrington and kept frozen, Dr. Amemiya said.

 

The specimen was preserved in Moroni, the capital of the Comoro Islands, but Dr. Amemiya has been unable to find out where it is now because of the constant state of civil war in the islands, he said.

 

Can he be certain, then, that the tissue came from a coelacanth? “Oh, no question,” Dr. Amemiya said. “We have DNA from several other coelacanths, from Africa and Indonesia, which is very similar to this one.” The one caught in 2003 was identified as a coelacanth by Said Ahamada, a South African expert, Dr. Amemiya said.

 

Because the original specimen is not available and the DNA sequencing is incomplete, the Amemiya team does not know its sex.

 


Via Dr. Stefan Gruenwald
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Earthquake Births New Island off Pakistan : Natural Hazards

Earthquake Births New Island off Pakistan : Natural Hazards | NetGeology | Scoop.it
A piece of seafloor rose out the water after a violent earthquake shook up Earth’s crust in September 2013.
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Geology Page: What set the Earth's plates in motion? "The origin of plate tectonics"

Geology Page: What set the Earth's plates in motion? "The origin of plate tectonics" | NetGeology | Scoop.it
The mystery of what kick-started the motion of our earth's massive tectonic plates across its surface has been explained by researchers at the University of Sydney.

"Earth is the only planet in our solar system where the process of plate tectonics occurs," said Professor Patrice Rey, from the University of Sydney's School of Geosciences.

"The geological record suggests that until three billion years ago the Earth's crust was immobile so what sparked this unique phenomenon has fascinated geoscientists for decades. We suggest it was triggered by the spreading of early continents then eventually became a self-sustaining process."
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The Sahara Is Millions of Years Older Than Thought

The Sahara Is Millions of Years Older Than Thought | NetGeology | Scoop.it
The great desert was born some 7 million years ago, as remnants of a vast sea called Tethys closed up
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Geology Page: Ol Doinyo Lengai Volcano,Tanzania "Video"

Geology Page: Ol Doinyo Lengai Volcano,Tanzania "Video" | NetGeology | Scoop.it
Ol Doinyo Lengai Volcano,Tanzania "Video"
Copyright © BBC Natural History Unit .
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Geology Page: Debris Flow "Video"

Geology Page: Debris Flow "Video" | NetGeology | Scoop.it
Debris flows are fast moving, liquefied landslides of mixed and unconsolidated water and debris that look like flowing concrete. They are defined by their non-newtonian flow dynamics, and behave as Bingham plastics. This characteristic can lead to the formation of levees at the margins of unconstrained debris flows as the margins of the flow freeze.
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Geology Page: Composition of Earth’s mantle revisited

Geology Page: Composition of Earth’s mantle revisited | NetGeology | Scoop.it
Research published last week in Science suggested that the makeup of the Earth's lower mantle, which makes up the largest part of the Earth by volume, is significantly different than previously thought.

The work, performed at the Advanced Photon Source at the U.S. Department of Energy’s Argonne National Laboratory, will have a significant impact on our understanding of the lower mantle, scientists said. Understanding the composition of the mantle is essential to seismology, the study of earthquakes and movement below the Earth's surface, and should shed light on unexplained seismic phenomena observed there.
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Paleontólogos estudam jazida rara em Torres Vedras - Ciência - DN

Paleontólogos estudam jazida rara em Torres Vedras - Ciência - DN | NetGeology | Scoop.it
A Sociedade de História Natural de Torres Vedras anunciou hoje a
descoberta no concelho de uma jazida rara, pela existência de fósseis de
pelo menos dois dinossauros de espécies diferentes e de outros animais.
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First Swimming Dinosaur Was 'Half-Duck, Half-Crocodile'

First Swimming Dinosaur Was 'Half-Duck, Half-Crocodile' | NetGeology | Scoop.it
The iconic Spinosaurus, a dinosaur known largely from bones destroyed in a World War II bombing, was adapted for life in the water, new research finds. This beast was "half-duck, half-crocodile," the researchers added.
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Geology Page: Underwater Volcano Eruption "Video"

Geology Page: Underwater Volcano Eruption "Video" | NetGeology | Scoop.it
Underwater Volcano Eruption "Video"

Copyright © NOAA - National Oceanic and Atmospheric Administration
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New Theory Could Rewrite Our Understanding Of Volcanoes | IFLScience

New Theory Could Rewrite Our Understanding Of Volcanoes | IFLScience | NetGeology | Scoop.it
The theory that volcanoes are driven by mantle plumes—narrow jets of magma originating within the Earth’s core—is a staple of geology. Aspiring geologists, like everyone else, learn in high school that volcanoes far from plate boundaries lie above such plumes. Subsequent education builds on this like layers of strata. So when the theory is challenged, a field of science quakes. "Mantle plumes have never had a sound physical or logical basis," says Caltech's Professor Don Anderson. "They are akin to Rudyard Kipling's 'Just So Stories' about how giraffes got their long necks." 
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Massive Extinct Volcano Discovered Beneath Pacific Ocean

Massive Extinct Volcano Discovered Beneath Pacific Ocean | NetGeology | Scoop.it
Lurking some 3.2 miles (5.1 kilometers) beneath the Pacific Ocean, a massive mountain rises up from the seafloor, say scientists who discovered the seamount using sonar technology.
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Incredible Photos of Volcanic Eruption in Iceland | IFLScience

Incredible Photos of Volcanic Eruption in Iceland | IFLScience | NetGeology | Scoop.it
A fountain of lava surged into the air on August 29 after a fissure in the Holuhraun lava field between Iceland’s Bardarbunga and Askja volcanoes erupted. The lava gushed from the fissure at 15.9 million gallons per minute (1,000 cubic meters per second) at 7 a.m. local time, three hours after the eruption began.
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Smithsonian Channel | Facebook

The Grand Prismatic Spring pumps out over 4,000 gallons of boiling water every minute. Learn what gives this natural wonder its beauty on Aerial America:...
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Strangest Prehistoric Creatures To Ever Appear on Earth | IFLScience

Strangest Prehistoric Creatures To Ever Appear on Earth | IFLScience | NetGeology | Scoop.it
Ask any kid what his or her favorite prehistoric animal is, and you’ll probably get an answer like T. rex, Triceratops, or Stegosaurus. While those are certainly among the most popular, they aren’t the strangest creatures that paleontologists have dug up.
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Explosive Rock Exfoliation Caught On Film | IFLScience

Explosive Rock Exfoliation Caught On Film | IFLScience | NetGeology | Scoop.it
Catching geologic processes in the act can be tricky business. Many are rare and over in a jiffy, so witnessing them is unlikely. Some are so slow you’d never notice them happening, whereas others are too dangerous for observers to get close enough. But lucky for us, an ongoing geological marvel is going on in the Sierra Nevada that someone managed to capture on film.
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‘Manuelino’, o pequeno dinossauro que viveu no tempo dos gigantes

‘Manuelino’, o pequeno dinossauro que viveu no tempo dos gigantes | NetGeology | Scoop.it
Viveu em Portugal há 152 milhões de anos e só há 15 foi extraído das rochas para se dar a conhecer. Hoje sabe-se finalmente qual é o seu b.i: conheça Eousdryosaurus, ou 'Manuelino' para os amigos.
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Microscopic Diamonds Suggest Cosmic Impact Responsible for Younger Dryas Climate Change 12,800 Years Ago

Microscopic Diamonds Suggest Cosmic Impact Responsible for Younger Dryas Climate Change 12,800 Years Ago | NetGeology | Scoop.it

A new study published in The Journal of Geology provides support for the theory that a cosmic impact event over North America some 13,000 years ago caused a major period of climate change known as the Younger Dryas stadial, or “Big Freeze.”

 

Around 12,800 years ago, a sudden, catastrophic event plunged much of the Earth into a period of cold climatic conditions and drought. This drastic climate change—the Younger Dryas—coincided with the extinction of Pleistocene megafauna, such as the saber-tooth cats and the mastodon, and resulted in major declines in prehistoric human populations, including the termination of the Clovis culture.

 

With limited evidence, several rival theories have been proposed about the event that sparked this period, such as a collapse of the North American ice sheets, a major volcanic eruption, or a solar flare.

 

However, in a study published in The Journal of Geology, an international group of scientists analyzing existing and new evidence have determined a cosmic impact event, such as a comet or meteorite, to be the only plausible hypothesis to explain all the unusual occurrences at the onset of the Younger Dryas period.

 

Researchers from 21 universities in 6 countries believe the key to the mystery of the Big Freeze lies in nanodiamonds scattered across Europe, North America, and portions of South America, in a 50-million-square-kilometer area known as the Younger Dryas Boundary (YDB) field.

 

Microscopic nanodiamonds, melt-glass, carbon spherules, and other high-temperature materials are found in abundance throughout the YDB field, in a thin layer located only meters from the Earth’s surface. Because these materials formed at temperatures in excess of 2200 degrees Celsius, the fact they are present together so near to the surface suggests they were likely created by a major extraterrestrial impact event.

 

In addition to providing support for the cosmic impact event hypothesis, the study also offers evidence to reject alternate hypotheses for the formation of the YDB nanodiamonds, such as by wildfires, volcanism, or meteoric flux.

 

The team’s findings serve to settle the debate about the presence of nanodiamonds in the YDB field and challenge existing paradigms across multiple disciplines, including impact dynamics, archaeology, paleontology, limnology, and palynology.

 


Via Dr. Stefan Gruenwald
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Bernhard H. Schmitz's curator insight, September 16, 6:33 AM

And where is the center of the YDB field?

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Geology Page: Plate Tectonics Map

Geology Page:  Plate Tectonics Map | NetGeology | Scoop.it
Plate Tectonics Map
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Geology Page: Researchers say a major quake may occur off the coast of Istanbul

Geology Page: Researchers say a major quake may occur off the coast of Istanbul | NetGeology | Scoop.it
When a segment of a major fault line goes quiet, it can mean one of two things: The "seismic gap" may simply be inactive—the result of two tectonic plates placidly gliding past each other—or the segment may be a source of potential earthquakes, quietly building tension over decades until an inevitable seismic release.

Researchers from MIT and Turkey have found evidence for both types of behavior on different segments of the North Anatolian Fault—one of the most energetic earthquake zones in the world. The fault, similar in scale to California's San Andreas Fault, stretches for about 745 miles across northern Turkey and into the Aegean Sea.
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Geology Page: Deep mission: Japan takes aim at the source of megaquakes

Geology Page: Deep mission: Japan takes aim at the source of megaquakes | NetGeology | Scoop.it
Even in port, it's easy to see how the research vessel Chikyu got its nickname. From the waterline to the top of its drilling derrick, the vessel also known as "Godzilla-Maru" towers nearly 30 stories tall.

It's longer than two football fields.

A helicopter landing pad juts over the bow. The two midship cranes are powerful enough to hoist a Boeing 787.

The Japanese government spent more than $500 million to build this monster of a ship with one goal in mind: to decipher the inner workings of a fault capable of unleashing a disaster far worse than the 2011 Tohoku earthquake and tsunami.
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L'eruzione in Islanda si intensifica molto: video da aereo

L'eruzione in Islanda si intensifica molto: video da aereo | NetGeology | Scoop.it
Le straordinarie immagini aeree appena girate in volo sull'area dove sta sgorgando una grossa quantità di lava. Ci sono enormi fontane lungo la fessura che continua ad estendersi. L'area ricoperta dalla lava è ora superiore a 4 km quadrati.
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Watch A Man Climb Into An Active Volcano | IFLScience

Watch A Man Climb Into An Active Volcano | IFLScience | NetGeology | Scoop.it
George Kourounis rappelled nearly 400 meters (1,300 feet) into an active volcano to have the adventure of a lifetime and, of course, take a selfie. 
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Placas tectônicas dobram velocidade de movimento

Placas tectônicas dobram velocidade de movimento | NetGeology | Scoop.it
Estudo recente sobre placas tectônicas da Terra indica que elas estão se movendo mais rápido agora d...
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Tornado of hot gas caught emerging from fiery volcano - environment - 05 September 2014 - New Scientist

Tornado of hot gas caught emerging from fiery volcano - environment - 05 September 2014 - New Scientist | NetGeology | Scoop.it
A huge gas tornado has been photographed spewing from Iceland's Bardarbunga volcano on an infrared camera designed to let pilots see volcanic ash clouds
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See Iceland's Spectacular Eruption From Space (Photo)

See Iceland's Spectacular Eruption From Space (Photo) | NetGeology | Scoop.it
Satellites finally caught a view of Iceland's spectacular eruption from space.
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Volcano continues fiery lava eruption

Volcano continues fiery lava eruption | NetGeology | Scoop.it
A dramatic lava eruption that began early on Sunday near Iceland's Bardarbunga volcano has continued into Monday.
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