Paleontologists have long debated whether the dinosaurs were cold-blooded, soaking up heat from their surroundings like today’s reptiles, or warm-blooded, able to generate their own heat the way modern birds and mammals do. Some scientists pointed to dark bands called lines of arrested growth in dinosaur bones as evidence that the animals were cold-blooded. These lines, much like tree rings, show times when growth slowed down due to limited resources—perhaps, researchers suggested, during off seasons when the heat-absorbing animal wasn’t able to get enough energy from its environment.
A new study in Nature, however, examined the bones of 40 species of present-day ruminants—many-stomached, very much warm-blooded mammals—from around the globe, and found these animals’ bones show these same lines of arrested growth. Even mammals, it seems, slow down enough in tough times to leave these telltale marks in their bones. (Archaeologists have found similar bands, called Harris lines, in human bones from periods of malnutrition.) While this doesn’t prove dinos were warm-blooded, it knocks down an oft-cited piece of evidence that they weren’t. It’s possible that the dinosaurs evolved high body temperature, and passed the adaptation onto their descendants, today’s birds.
What’s the News: Dinosaur metabolism is one of the biggest mysteries in paleontology. Ever since the giant creatures were first unearthed, scientists have been wondering whether dinosaurs drew their heat from the environment, like the cold-blooded modern reptiles they resemble, or whether they generated heat themselves, like warm-blooded mammals.
Using a geoscience technique to see at what temperature dinosaur tooth enamel formed, scientists have found that at least two large dinosaurs, Brachiosaurus and Camarasaurus, had body temperatures similar to our own. While this study on its own doesn’t explain where the heat came from, it does add to paleontologists’ toolboxes a new, reliable way to probe temperature, which will lead to better inputs into the computational models that may eventually answer the question of whether dinosaurs were warm- or cold-blooded.
What’s the News: Bats have to use twice as much energy to fly when they’re wet as when they’re dry, a new study in Biology Letters found, which may help explain why many bats refrain from flying in heavy rain.
What’s the News: Anxiety. Insomnia. Hallucinations. Methamphetamine’s effects on the human brain are well documented, but researchers know relatively little about how the drug affects the body on the molecular scale. Looking at fruit flies (Drosophila melanogaster), scientists have detailed how meth disrupts chemical reactions associated with generating energy, creating sperm cells, and regulating muscles. Most interestingly, they discovered that meth-exposed fruit flies may live longer when they eat sugar. “We know that methamphetamine influences cellular processes associated with aging, it affects spermatogenesis, and it affects the heart,” says University of Illinois entomologist Barry Pittendrigh. “One could almost call meth a perfect storm toxin because it does so much damage to so many different tissues in the body.”
A hibernating bear might appear to be the perfect metaphor for laziness, laying around half the year in carefree slumber. But in fact, it is a marvel of efficiency. New research in the journal Science shows that bears can drop their metabolic rate all the way down to 25 percent of normal while losing only about 10 degrees in body temperature.
Øivind Tøien and colleagues got lucky when a few black bears came a little too close to residents of Alaska for the Alaskans’ comfort. The state’s Department of Fish and Game intended to remove them as a “nuisance,” so the researchers got their hands on the bears and did a little hibernation experiment. They built artificial dens for the large mammals, complete with cameras and observational equipment including radio transmitters, allowing them to track the bears’ body temperatures and other vitals.
It was thought that, like most animals, the bears would have to drop their body temperatures to put the brakes on metabolism—each 18-degree Fahrenheit (10-degree Celsius) drop in temperature should equal a 50-percent reduction in the chemical activity. [National Geographic]
The fact that bears were so much more efficient than other hibernators came as a big surprise, Tøien says:
Standard human body temperature is 98.6 degrees Fahrenheit: It’s one of those numbers from grade school science textbooks—like 65 million years since the dinosaur extinction or nine eight planets in the solar system—that just gets stuck in your head. But why should it be that balmy temperature and no other?
According to a study by researchers at Albert Einstein College of Medicine, the 98-degree range is in perfect balance.
Every one degree Celsius rise in body temperature wards off about 6 percent more fungal species. So tens of thousands of fungi can infect reptiles and amphibians, but we can only be invaded by a few hundred fungi. In the new work, the researchers created a mathematical model that weighed the fungal protection benefits versus the metabolic cost of high body temperature. And the optimal temperature was 98.1, quite close to what evolution figured out. [Scientific American]
Next time you’re at the pub with friends, take it easy on the lightweights—the ones who are getting a little silly after just a couple of drinks. That might be a blessing in disguise, according to a new study, because the 10 to 20 percent of people whose genetics make them especially sensitive to booze might also be at greatly reduced risk to develop alcoholism.
In the journal Alcoholism: Clinical and Experimental Research, Kirk Wilhelmsen and colleagues identified a particular gene associated with the easily intoxicated. The gene in question encodes an enzyme called CYP2E1, responsible for metabolizing not just alcohol in the brain, but also other substances like acetaminophen (Tylenol).
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].