Multiple Species Of Seacows Once Coexisted Say Smithsonian Scientists

Sirenians, or seacows, are a group of marine mammals that include manatees and dugongs; today, only one species of seacow is found in each world region. Smithsonian scientists have discovered that this was not always the case. According to the fossil record of these marine mammals, which dates back 50 million years ago, it was more common to find three, or possibly more, different species of seacows living together at one time. This suggests that the environment and food sources for ancient seacows were also different than today. The team's findings are published in the journal PLoS ONE.

Sirenians, or seacows, are a group of marine mammals that include manatees and dugongs; Today, only one species of seacow is found in each world region. Smithsonian scientists have discovered that this was not always the case. According to the fossil record of these marine mammals, it was more common to find three or more different species of seacows living together at one time. This suggests that the environment and food sources for ancient seacows were also different than today.

 

Credit: Carl Buell

Today there are only four species of seacows―three species of manatees, which are found in different coastal waters of the Atlantic Ocean, and one species of dugong, found along the coasts of the Indo-Pacific Ocean. All seacows are herbivores, and their diet is made up largely of seagrasses.

"The discovery that these multispecies seacow communities once existed revealed answers, but it also created new questions," said Nicholas Pyenson, curator of fossil marine mammals at the Smithsonian's National Museum of Natural History and co-author of the research. "Were these species competing against each other for seagrass resources, or were they avoiding competition by each species feeding in separate areas or on different grasses? Also, were seagrass beds structured differently in the past, or were they dominated by one seagrass species like we see today?"

To answer these questions, the team, lead by Smithsonian predoctoral fellow Jorge Velez-Juarbe, examined three localities from separate time periods, from the late Oligocene (about 23-28 million year ago) in Florida, the early Miocene (about 16-23 million years ago) in India and the early Pliocene (about 3-5 million years ago) in Mexico. All three areas showed conclusive fossil evidence that two or more species of seacow had once coexisted there.

By examining the size and dimensions of the skulls as well as estimating the body sizes, the team deduced that the different species of seacows had characteristics that allowed each to feed on different types of seagrass. Such separation among physical features, the team suggests, reduced any competition for food and allowed multiple species of seacows to coexist. This also suggests that, unlike today's seacow habitats that are dominated by one or two species of seagrass, many species of seagrass once coexisted.

Contacts and sources:

Discovery Of A New Kind Of Neutrino Transformation

Knowing how different kinds of neutrinos mix and change could reveal their masses, explore differences between neutrinos and antineutrinos, and explain why there is any matter at all in the universe

From its beginnings in 2006, the Daya Bay Reactor Neutrino Experiment has established new scientific milestones as the first equal partnership between the U.S. and China in a major physics project. Co-led by personnel from both nations, the collaboration has benefited from monetary support, technical expertise, and intellectual contributions from over 40 institutions in countries around the world.

Initial U.S. participation was guided by James Siegrist, then Associate Laboratory Director for General Sciences and Director of the Physics Division at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab); Siegrist is now Associate Director of DOE’s Office of Science for the Office of High Energy Physics. Other current and former Berkeley Lab members of the Daya Bay Collaboration include Co-spokesperson Kam-Biu Luk, who leads U.S. participation, and Bill Edwards, U.S. Project and Operations Manager, as well as Mike Barry, Ken Chow, Matt Hoff, Matt Kramer, Jason Lee, Nanyang Li, Cheng-Ju Lin, Sa Liu, John Joseph, Yasuhiro Nakajima, Pedro Ochoa, Simon Patton, Alan Smith, Herb Steiner, Mary Stuart, Patrick Tsang, Craig E. Tull, Steve Virostek, Mike Wingert, Henoch Wong, Weili Zhong, and Sergio Zimmerman.

The official Daya Bay Collaboration news release on the first results follows, and is also posted on Interactions.org at http://www.interactions.org/cms/?pid=1031513.

Each antineutrino detector at Daya Bay is lined with photomultiplier tubes to catch the faint trace of antineutrino reactions in the scintillator fluids that fill the detectors. (Photo Roy Kaltschmidt, Lawrence Berkeley National Laboratory)

  The Daya Bay Reactor Neutrino Experiment, a multinational collaboration operating in the south of China, today reported the first results of its search for the last, most elusive piece of a long-standing puzzle: how is it that neutrinos can appear to vanish as they travel? The surprising answer opens a gateway to a new understanding of fundamental physics and may eventually solve the riddle of why there is far more ordinary matter than antimatter in the universe today.

Traveling at close to the speed of light, the three basic neutrino “flavors” – electron, muon, and tau neutrinos, as well as their corresponding antineutrinos – mix together and oscillate (transform), but this activity is extremely difficult to detect. From Dec. 24, 2011, until Feb. 17, 2012, scientists in the Daya Bay collaboration observed tens of thousands of interactions of electron antineutrinos, caught by six massive detectors buried in the mountains adjacent to the powerful nuclear reactors of the China Guangdong Nuclear Power Group. These reactors, at Daya Bay and nearby Ling Ao, produce millions of quadrillions of elusive electron antineutrinos every second.

The copious data revealed for the first time the strong signal of the effect that the scientists were searching for, a so‑called “mixing angle” named theta one-three (written θ13), which the researchers measured with unmatched precision. Theta one-three, the last mixing angle to be precisely measured, expresses how electron neutrinos and their antineutrino counterparts mix and change into the other flavors. The Daya Bay collaboration’s first results indicate that sin2 2 θ13 is equal to 0.092 plus or minus 0.017.

“This is a new type of neutrino oscillation, and it is surprisingly large,” says Yifang Wang of China’s Institute of High Energy Physics (IHEP), co-spokesperson and Chinese project manager of the Daya Bay experiment. “Our precise measurement will complete the understanding of the neutrino oscillation and pave the way for the future understanding of matter-antimatter asymmetry in the universe.”

Neutrinos, the wispy particles that flooded the universe in the earliest moments after the big bang, are continually produced in the hearts of stars and other nuclear reactions. Untouched by electromagnetism, they respond only to the weak nuclear force and even weaker gravity, passing mostly unhindered through everything from planets to people. The challenge of capturing these elusive particles inspired the Daya Bay collaboration in the design and precise placement of its detectors.

“Although we’re still two detectors shy of the complete experimental design, we’ve had extraordinary success in detecting the number of electron antineutrinos that disappear as they travel from the reactors to the detectors two kilometers away,” says Kam-Biu Luk of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California at Berkeley. Luk is co-spokesperson of the Daya Bay Experiment and heads U.S. participation. “What we didn’t expect was the sizable disappearance, equal to about six percent. Although disappearance has been observed in another reactor experiment over large distances, this is a new kind of disappearance for the reactor electron antineutrino.”

The Daya Bay experiment counts the number of electron antineutrinos detected in the halls nearest the Daya Bay and Ling Ao reactors and calculates how many would reach the detectors in the Far Hall if there were no oscillation. The number that apparently vanish on the way (oscillating into other flavors, in fact) gives the value of theta one-three. Because of the near-hall/far-hall arrangement, it’s not even necessary to have a precise estimate of the antineutrino flux from the reactors.

“Even with only the six detectors already operating, we have more target mass than any similar experiment, plus as much or more reactor power,” says William Edwards of Berkeley Lab and UC Berkeley, the U.S. project and operations manager for the Daya Bay Experiment. Since Daya Bay will continue to have an interaction rate higher than any other experiment, Edwards explains, “it is the leading theta one-three experiment in the world.”

The first Daya Bay results show that theta one-three, once feared to be near zero, instead is “comparatively huge,” Kam-Biu Luk remarks, adding that “Nature was good to us.” In coming months and years the initial results will be honed by collecting far more data and reducing statistical and systematic errors.

“The Daya Bay experiment plans to stop the current data-taking this summer to install a second detector in the Ling Ao Near Hall, and a fourth detector in the Far Hall, completing the experimental design,” says Yifang Wang.

Refined results will open the door to further investigations and influence the design of future neutrino experiments – including how to determine which neutrino flavors are the most massive, whether there is a difference between neutrino and antineutrino oscillations, and, eventually, why there is more matter than antimatter in the universe – because these were presumably created in equal amounts in the big bang and should have completely annihilated one another, the real question is why there is any matter in the universe at all.

“It has been very gratifying to be able to work with such an outstanding international collaboration at the world’s most sensitive reactor neutrino experiment,” says Steve Kettell of Brookhaven National Laboratory, the chief scientist for the U.S. effort. “This moment is exciting because we have finally observed all three mixing angles, and now the way is cleared to explore the remaining parameters of neutrino oscillation.”

“This is really remarkable,” says Wenlong Zhan, vice president of the Chinese Academy of Sciences and president of the Chinese Physical Society. “We hoped for a positive result when we decided to fund the project, but we never imagined it could come so quickly!”

“Exemplary teamwork among the partners has led to this outstanding performance,” says James Siegrist, DOE Associate Director of Science for High Energy Physics. “These notable first results are just the beginning for the world’s foremost reactor neutrino experiment.”

The Daya Bay collaboration consists of scientists from the following countries and regions: China, the United States, Russia, the Czech Republic, Hong Kong, and Taiwan. The Chinese effort is led by co-spokesperson, chief scientist, and project manager Yifang Wang of the Institute of High Energy Physics, and the U.S. effort is led by co-spokesperson Kam-Biu Luk and project and operations manager William Edwards, both of Berkeley Lab and UC Berkeley, and by chief scientist Steve Kettell of Brookhaven.

Contacts and sources: 
DOE/Lawrence Berkeley National Laboratory

What Have We Got In Common With A Gorilla?

Researchers announce today that they have completed the genome sequence for the gorilla – the last genus of the living great apes to have its genome decoded. While confirming that our closest relative is the chimpanzee, the team show that much of the human genome more closely resembles the gorilla than it does the chimpanzee genome.

Credit: Wikipedia

This is the first time scientists have been able to compare the genomes of all four living great apes: humans, chimpanzees, gorillas and orang-utans. This study provides a unique perspective on our own origins and is an important resource for research into human evolution and biology, as well as for gorilla biology and conservation.

"The gorilla genome is important because it sheds light on the time when our ancestors diverged from our closest evolutionary cousins. It also lets us explore the similarities and differences between our genes and those of gorilla, the largest living primate," says Aylwyn Scally, first author from the Wellcome Trust Sanger Institute. "Using DNA from Kamilah, a female western lowland gorilla, we assembled a gorilla genome sequence and compared it with the genomes of the other great apes. We also sampled DNA sequences from other gorillas in order to explore genetic differences between gorilla species."

The team searched more than 11,000 genes in human, chimpanzee and gorilla for genetic changes important in evolution. Humans and chimpanzees are genetically closest to each other over most of the genome, but the team found many places where this is not the case. 15% of the human genome is closer to the gorilla genome than it is to chimpanzee, and 15% of the chimpanzee genome is closer to the gorilla than human.

In all three species, genes relating to sensory perception, hearing and brain development showed accelerated evolution – and particularly so in humans and gorillas.

"Our most significant findings reveal not only differences between the species reflecting millions of years of evolutionary divergence, but also similarities in parallel changes over time since their common ancestor," says Dr Chris Tyler-Smith, senior author from the Wellcome Trust Sanger Institute. "We found that gorillas share many parallel genetic changes with humans including the evolution of our hearing. Scientists had suggested that the rapid evolution of human hearing genes was linked to the evolution of language. Our results cast doubt on this, as hearing genes have evolved in gorillas at a similar rate to those in humans."

This research also illuminates the timing of splits between species. Although we commonly think of species diverging at a single point in time, this does not always reflect reality: species can separate over an extended period of time.

The team found that divergence of gorillas from humans and chimpanzees occurred around ten million years ago. The split between eastern and western gorillas was much more recent, in the last million years or so, and was gradual, although they are now genetically distinct. This split is comparable in some ways to the split between chimpanzees and bonobos, or modern humans and Neanderthals.

"Our research completes the genetic picture for overall comparisons of the great apes," says Dr Richard Durbin, senior author from the Wellcome Trust Sanger Institute, "After decades of debate, our genetic interpretations are now consistent with the fossil record and provide a way for palaeontologists and geneticists to work within the same framework.

"Our data are the last genetic piece we can gather for this puzzle: there are no other living great ape genera to study."

Gorillas survive today in just a few isolated and endangered populations in the equatorial forests of central Africa. They are severely threatened and their numbers are diminishing. This research not only informs us about human evolution, but highlights the importance of protecting and conserving the full diversity of these remarkable species.


Contacts and sources: 
Aileen Sheehy
Wellcome Trust Sanger Institute