Blogs / 80beats

Elephants, bacteria, and trees may not have much in common besides their status as living organisms that consume energy to power their basic life functions, but a new study has found a remarkable similarity within that commonality. A team of researchers examined over 3,000 organisms from different branches of the tree of life and found that while creatures may vary enormously in size and complexity, their metabolisms use energy at roughly the same rate.

The researchers examined the at-rest metabolisms of all the species and compared their energy usage, pound for pound. While there were some outliers, most species fell within a narrow range, using between 1 and 10 watts per kilogram of biomass. Study coauthor Anastassia Makarieva says that since such a large number of species falls within this narrow range, she hypothesises there may be an optimum metabolic rate for all organisms. “Organisms that lie close to this value may be the fittest to survive,” she says [New Scientist].

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Researchers believe they have found the earliest known animal footprints, left by a centipede-like creature 570 million years ago; if they’re right, the discovery means that animals were walking on the earth 30 million years earlier than previously thought. Researchers say the fossil shows a track of parallel dots, each about two millimeters in diameter, which may have been pressed into the muddy sand by the tiny feet of one of the earliest complex organisms.

But some experts are not convinced by what they’ve seen. Precambrian paleontologist Nick Butterfield said he was “deeply skeptical,” about the conclusions drawn. “From the description—paired rows of dots—it just doesn’t sound like a trackway…. Centipedes and their ilk shuffle along and leave continuous traces in soft (sub-aerially exposed) sediments—they don’t carefully step ahead, lifting each foot out of the mud to place it exactly in a previously made footprint,” he said [National Geographic News].

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In Africa’s Lake Victoria, researchers believe they’ve caught a fish population in the act of splitting into two distinct species. Researchers say this example of evolution-in-action is remarkable because the two sub-populations of fish aren’t geographically isolated and could theoretically interbreed, but adaptations to their vision are causing them to diverge.

Lead researcher Norihiro Okada and his colleagues had previously shown that cichlid fish in Lake Victoria’s shallow waters are bathed in bluer light, while the turbid water of the lake predominantly lets redder light filter down to fish living in deeper water. The researchers showed that the fish’s eyes have adapted to this difference so that fish that live in deeper water have a pigment in their eyes that is more sensitive to red light, while shallow-water fish have a pigment that’s sensitive to blue [Science News]. Okada’s new study, published in Nature [subscription required], shows that those eye adaptations have also affected mating patterns.

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A 33-foot long, carnivorous dinosaur that lived 85 million years ago had a breathing system similar to that used by modern birds, and researchers say the finding is further evidence of the evolutionary link between dinosaurs and birds. A fossil found in a riverbank in Argentina shows evidence of efficient air sacs that pumped air into the dinosaur’s lungs.

Lead researcher Paul Sereno named the new dinosaur Aerosteon riocoloradensis, which means “air bones from the Rio Colorado.” Instead of lungs that expand and contract, Sereno thinks this beast had air sacs that worked like a bellows, blowing air into the beast’s stiff lungs, much like modern birds…. Most paleontologists believe birds evolved from small, feathered meat-eating dinosaurs, and the earliest known birds were strikingly similar to these dinosaurs [Reuters].

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In a striking example of the evolutionary benefits of altruism, researchers have found a species of ants that sends a few workers out each evening on a suicide mission to ensure the continued survival of the colony. The tiny ant Forelius pusillus, which makes its home in sugar cane fields in Brazil, makes a nightly ritual of covering the entrance to its nest with sand. To be sure that the entrance is sealed shut tightly, a few ants remain outside each evening to finish kicking sand over the hole. Those ants, stuck outside in the cold and the wind, die during the night.

“In a colony with many thousands of workers, losing a few workers each evening to improve nest defense would be favored by natural selection,” said co-author Francis Ratnieks…. The ants stuck outside might be old or sick, [co-author Adam] Tofilski conjectured. Thus, they may have essentially sacrificed themselves for the greater good, being more expendable members of the colony [ScienceNOW Daily News].

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In the middle of the Australian outback along a mountain chain called the Flinders Ranges, researchers have discovered a 650 million year old reef that was once underwater. Researchers say the tiny fossils they’ve already found in the ancient reef may be the earliest examples of multicellular organisms ever found, and may answer questions about how animal life evolved.

Researcher Malcolm Wallace explains that the oldest-known animal fossils are 570 million years old. The reef in the Flinders Ranges is 80 million years older than that and was, he said, “the right age to capture the precursors to animals” [The Times]. The first fossils discovered in the reef appear to be sponge-like multicellular organisms that resemble tiny cauliflowers, measuring less than an inch in diameter, but Wallace cautions that the creatures haven’t been thoroughly studied yet. The reef’s discovery was announced at a meeting of the Geological Society of Australia this week.

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Researchers have found the first small finger-like bones in the fins of a fish that lived 380 million years ago, about 15 million years before the first four-footed creatures, called tetrapods, clambered onto the land.

The finding upends the most recent theory of the evolution of digits: The need to adapt to swampy marshlands and terra firma, the theory went, is what drove the gradual shift through natural selection from fish fins suitable only for swimming to weight-bearing limbs with articulated joints. The study, however, reveals that rudimentary fingers were already present inside the fins of the shallow-water Panderichthys, a transitional species that was nonetheless more fish than tetrapod [The Daily Telegraph].

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A newly discovered ant from the Amazon rainforest is so strange that researchers have named it “the ant from Mars.” Found in Brazil, the ant has a pale body and no eyes, says [lead researcher] Christian Rabeling…. Its mouthparts stick out like sharp forceps and are longer than the rest of its head. Its DNA may be even more interesting. Genetic analysis puts the new ant so far from other species that it deserves its own subfamily [Science News].

Researchers named the subterranean ant Martialis heureka, which translates to “eureka ant from Mars,” because of the new species‘ odd morphology and because of their own excitement over finding it. Researchers say that a DNA analysis suggests that the M. heureka evolved earlier than any other living ant, and that it has changed little over 50 million years. “This discovery lends support to the idea that blind, subterranean predator ants arose at the dawn of ant evolution,” Rabeling said [LiveScience].

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Almost 150 years since Charles Darwin published his ideas in The Origin of Species, a senior Anglican clergyman has written that the Church of England owes Darwin an apology for misunderstanding his theories of evolution. The church official, Reverend Malcolm Brown, was writing Monday on a church Web site launched to mark Darwin’s bicentenary next year. The Church of England says his statement reflects its position but does not constitute an official apology [AP].

The apology may be a bit late, but Brown wrote that it’s both relevant and necessary, as some religious groups continue to scoff at evolution. “Charles Darwin - 200 years from your birth (1809) the Church of England owes you an apology for misunderstanding you and, by getting our first reaction wrong, encouraging others to misunderstand you still,” he wrote on the Church of England website. “We try to practise the old virtues of ‘faith seeking understanding’ and hope that makes some amends” [The Independent].

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A new fossil study has pinpointed the moment when whales lost their distinct legs and tail and developed flukes, sometimes called tail fins, instead: Flukes are the two wide, flat triangular lobes on a whale’s back end and are made of skin and connective tissue, with bones in the middle [National Geographic News]. Researchers say that the Georgiacetus vogtlensis, whose fossil was found in Alabama, was one of the last whales to have powerful back legs and a tail like a dog’s, and that whales evolved flukes between 40 and 38 million years ago.

Paleontologists already knew that the ancestors of whales once strode on land on four legs, just as other mammals do. Over time, as they evolved to dwell in water, their front legs became flippers while they lost their back legs and hips, although modern whales all still retain traces of pelvises, and occasionally throwbacks are born with vestiges of hind limbs [LiveScience].

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The dinosaurs that held dominion over the Earth in the Jurassic Period didn’t rule the lands because they out-competed every rival, a new study says. Researchers studied fossil evidence from an earlier epoch, the Triassic Period, and say that dinosaurs showed no evidence of being better adapted to their environment than their challengers. “For a long time it was thought that there was something special about the dinosaurs that helped them become more successful during the Triassic, the first 30 million years of their history, but this isn’t true,” said lead author of the study, Steve Brusatte [LiveScience].

Instead they may have just been lucky enough to survive a drastic climate shift when their rivals didn’t. Researchers compared fossils from the 30 million years in the Triassic when dinosaurs coexisted with crurotarsan archosaurs, a group whose only living relative is crocodiles. They found that not only did the groups evolve at the same rate, but the crurotarsans even developed a wider range of body types than dinosaurs, suggesting that the group as a whole was more successful at developing to live in different habitats and ecosystems [Telegraph].

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Researchers have discovered a stretch of “junk” DNA that may have contributed to humanity’s evolution of opposable thumbs. When genetically engineered into mice, the human DNA seems to activate genes in the budding wrist and thumb. Chimp and monkey versions, on the other hand, seem only capable of switching on genes in the developing shoulder [New Scientist].

In a new study, the research team combed through the vast regions of human DNA that do not contain code for making proteins. Formerly dissed as “junk DNA,” sections of these non-gene regions are now known to play a regulatory role, dialing down or cranking up the activity of actual genes [Science News]. Researchers first found a long sequence of DNA that had barely changed during the entire evolution of backboned creatures, and then zeroed in on a smaller stretch of code that had accumulated 16 changes since the ancestors of humans and chimpanzees split, about 6 million years ago.

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Ninety years after the discovery of the first antibiotic, penicillin, researchers have found an entirely new tactic in the fight against bacteria that cause infectious diseases. Instead of hunting for new ways to kill bacteria, researchers have developed a drug, called LED209, that disarms them, preventing them from releasing the toxins that cause illness.

“The sensors in bacteria are waiting for the right signal to initiate the expression of virulent genes,” [said lead researcher] Vanessa Sperandio…. “Using LED209, we blocked those sensing mechanisms and basically tricked the bacteria to not recognize that they were within the host” [Reuters]. The new technique, which has only been demonstrated in mice so far, could be a boon for researchers who are worried about creating more antibiotic-resistant “superbugs.”

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A mouse’s nose has a cluster of specialized cells that respond to the chemical signals sent out by fellow mice that are in distress, researchers report, meaning that mice can literally smell fear. A lump of nerve cells in the nose tip called the Grueneberg ganglion responds to the “fear pheromones” of imperiled creatures, sending a signal straight to the brain. As Grueneberg ganglia are known to exist in rodents, cats, apes, and humans, researchers say it’s likely that the cells perform the same function in all mammals.

In a new study, researchers dosed water dishes with mouse alarm pheromones, and put the dishes in cages with both normal mice and mice whose ganglia had been removed. The contrast was very striking, [lead researcher Marie-Christine] Broillet said. “The normal mouse immediately gets scared and goes to the corner of the box and freezes,” she said. But mice without the ganglia carried on as before, seemingly unaware of the danger signals. Both groups were able to sniff out cookies hidden in their cages, however, suggesting the altered group’s sense of smell was otherwise unaffected [National Geographic News].

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Some clever magpies can recognize themselves in a mirror, leading researchers to include them among the ranks of self-aware animals—an elite group that is generally thought to include only humans, great apes, bottlenose dolphins, and elephants. This new study suggests that a brain capable of surprisingly sophisticated intelligence developed in a few birds long after they split from the mammalian evolutionary tree, about 300 million years ago.

Says lead researcher Helmut Prior: “It shows that the line leading to humans is not as special as many thought…. After finding this kind of intelligence in apes, many people thought it had developed once in one evolutionary line with humans at the end. The bird studies show it has developed at least twice”[Reuters].

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