Blue whales, the largest animals on Earth, can eat about four tons of food a day—and when they’re done digesting, there’s still a whole lot of stuff left over. This aerial shot, taken by oceanographic consultant Eddie Kisfaludy off the Southern California coast, shows a blue whale and a truly enormous plume of its poop, the same vibrant orange as the krill on which the whales feed.
Whale feces, it turns out, plays a substantial role in ocean ecosystems. Since it floats to the surface, it brings nitrogen whales have taken in when they fed in the ocean’s depths to shallow waters, providing a much-needed nutrient for plankton there. The massive mammals’ poop also serves as a significant carbon sink; one study estimated that excrement from sperm whales in the Southern Ocean alone sequestered 400,000 tons of carbon dioxide a year.
Rhesus macaques live in social hierarchies, and for those at the bottom, well, life is not so great. After extensive studies on these macaques, scientists have found that low rank is correlated with poor health as well as physiological changes in stress-related hormones, sex hormones, and white blood cell counts.
In this week’s Proceedings of the National Academy of Sciences, a new study went one step further to show that gene expression, especially that of immune-related genes, was also dependent on social rank. By following female rhesus macaques as their ranks changed over time, the researchers gathered evidence for causal link’s direction, too. It wasn’t that poor health lead to low social rank; it was falling on the social ladder that led to physiological and gene-regulation changes.
If having kids has made you feel like less of a party animal, men, you now have some science backing you up. A new study following men from their single salad days through the early years of their children’s lives found that fathers had a steeper decline in testosterone levels than men who remained single and childless. Though previous studies had indicated that fathers had lower testosterone, this is the first study to look at men before and after fatherhood, showing that it’s not just that lower-testosterone males are more likely to become dads. (In fact, this study shows the opposite—it’s the hormone-pumped guys who are more likely to settle down with a partner and have kids.)
But testosterone declines naturally with age, and stress is known to contribute to cellular aging. Is the accelerated decline because zero sleep, frayed nerves, and other byproducts of procreating are making men old before their time? That’s a question for next time—this study doesn’t address the decline’s cause.
Image courtesy of edenpictures / flickr
Life at the top ain’t easy.
What’s the News: In the hardscrabble world of a baboon troop, being the alpha male has its perks: power, food, ample opportunities to woo the ladies. But all that status brings with it a great deal of stress, a new study shows, as the alpha male constantly scrambles to stay atop the social pyramid. The life of a second-in-command beta male—somewhat fewer perks but, the researchers found, a whole lot less stress—is starting to sound like the better deal.
It was a stroke of serendipity that may one day help those who hide under comb overs or wear wigs: scientists studying how mice bowels react to a stress-reducing chemical have inadvertently discovered a cure to baldness. But unfortunately, it looks like this cure won’t apply to genetic baldness, which is by far the main cause of most hairless pates. Still, researchers hope the lucky find will eventually be used to battle at least some of the bare heads of humans.
The story begins with mice that were genetically modified to produce too much corticotrophin-releasing factor, or CRF–a type of stress hormone. Normally, as these stressed-out rodents age, their backs lose hair. But a group of researchers from the Veterans Administration and the University of California at Los Angeles didn’t care about hair, they just wanted to study the effects of a chemical on the modified mice.
Researchers at the Salk Institute developed a peptide called “astressin-B”, which blocks the action of CRF, and the teams injected the peptide into the bald mice. They weren’t thinking about baldness at all — they wanted to test whether the astressin had any impact on the mice’s gastrointestinal tracts. The first injection did nothing, so the team gave the mice additional injections over five days, and then measured the effects on the newly de-stressed mice’s colons. [Popular Science]
With most of the experiment done, the researchers forgot about the mice for three months. Then they returned for some follow-up tests:
A little stress can do a mouse good, a new cancer study suggests.
Matthew During wanted to see whether stressing out mice by messing with their environment would affect the rate of tumor growth. So, for a study that now appears in Cell, he and his team divided up their mice into two groups. Some mice lived quiet, peaceful lives in cages shared between five mouse roommates, while the other group lived in a stressful cluttered cacophony, where the cages held 18 to 20 animals plus numerous distractions and challenges like toys, mazes, and wheels.
Mice were then injected with tumor cells, which led to malignancies in all of the control animals within 15 days… The rate of tumor formation in animals living in the enriched environment was significantly delayed, and 15 percent had not developed tumors after nearly three weeks; when tumors were visible, they were 43 percent smaller than the lesions on control animals [Scientific American].
Because the “enriched environment” gave those mice so much more to do, an obvious conclusion would be that it’s the uptick in physical activity—not the effect of added stress—that kept tumors at bay. So During’s team tested the mice to see if just giving them more time on the running wheel, independent of the other factors, was enough to see the effect. It wasn’t.
Last week DISCOVER brought you the sad and somewhat counter-intuitive study that suggested loneliness could actually be “contagious” and spread across a social network. Now more bad news for the lonely. In a study (in press) in the Proceedings of the National Academy of Sciences, another team of researchers argues that, in rats at least, loneliness can increase cancer incidence.
The scientists separated their test rats at birth, keeping them either in groups of five or alone. Those kept alone had a 135% increase in the number of mammary tumours, a 8,391% increase in the size of tumours and a 3.3-fold increase in the relative risk of malignancy [Nature News]. They also showed higher levels of the hormone corticosterone, which is connected to stress.