Archive for the ‘Biology’ Category

Geckos’ new superpower is running on water; now we know how they do it

December 6th, 2018
Geckos’ new superpower is running on water; now we know how they do it

Enlarge (credit: Getty)

Geckos are known for being expert climbers, able to stick to any surface thanks to the billions of tiny hair-like structures on the bottoms of their feet. Now it turns out the little lizards can also zip along the surface of water at high speeds to elude predators. They can't do it for very long; the energy expenditure required is too great. But it's amazing they can do it at all. Scientists think they've pinpointed the mechanisms behind the feat, described in a new paper in Cell Biology.

The project started when co-author Ardian Jusufi, then a postdoc in the lab of University of California, Berkeley biophysicist Robert Full, was on vacation in Singapore during monsoon season. One day, after a big rain storm, he caught a gecko skimming across the water to escape a predator on video. The footage astounded everyone in the lab when he showed it to them. "It was super weird and unexpected, so naturally we had to test this," says co-author Jasmine Nirody, another former Full student who now splits her time between Rockefeller University and the University of Oxford.

There are several creatures in nature capable of walking on water, but they employ different mechanisms depending on their size. Small, lightweight water striders, for instance, rely entirely on surface tension to stay afloat, while the larger, heavier basilisk lizards employ a slapping motion with their feet that creates pockets of air bubbles to keep from sinking. The standard theoretical calculations set very strict boundaries for how small an animal has to be to use surface tension and how large it needs to be before the surface slapping mechanism is viable.

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Posted in Biology, Biomechanics, biophysics, geckos, science, Surface tension | Comments (0)

Medieval European plague genomes hint at of Black Death’s travels

December 5th, 2018
Scanning electron micrograph depicting a mass of <em>Yersinia pestis</em> bacteria (the cause of bubonic plague) in the foregut of the flea vector.

Enlarge / Scanning electron micrograph depicting a mass of Yersinia pestis bacteria (the cause of bubonic plague) in the foregut of the flea vector. (credit: Rocky Mountain Laboratories / Wikimedia)

Barbara Bramanti grew up near Florence, Italy, worked for a while in Mainz, Germany, and is now at the University of Oslo in Norway. Her career has taken her across a decent swath of Western Europe—but not nearly across as big of an area as that ravaged by the plague she studies.

In her latest work, she and her colleagues associate Europe's Black Death plague outbreak with a change in trade policy in Asia.

Where’d they come from?

Yersinia pestis, the subject of her research, is the bacterium responsible for three bubonic plague pandemics over human history. The first was the Justinian Plague, which started in Constantinople around the year 541 CE and devastated the Byzantine Empire until the middle of the eighth century. The second began with the Black Death, which killed at least 30 percent of the population of Western Europe between 1346 and 1353 and then continued rampaging over the next 400-ish years. The third started in 1772 in Yunnan province, in southwest China, and is still currently underway.

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Posted in Biology, disease, evolution, microbiology, science, the plague | Comments (0)

Researchers grow a placenta in a petri dish

December 4th, 2018
Fetus in the womb, computer artwork.

Enlarge / Fetus in the womb, computer artwork. (credit: Science Photo Library - SCIEPRO)

The placenta supports the fetus while it is in utero (and, according to some, a placental can support a rosebush if it's buried under one after delivery).We know a placenta is essential for a successful pregnancy, but we don’t really know exactly how it works because we’ve had no experimental models we can use to study it. Until now.

Researchers in England examined all of the signaling molecules they could find rushing around between the mother and the placenta (which originates from fetal tissue), figuring they might induce the placenta to grow and develop. From this analysis they generated a blend of signaling molecules that they expected could induce placental formation in a culture dish.

They then obtained cells from first trimester placentas from women who had had normal pregnancies but decided to abort. These cells were grown in media that contained the factors identified by this team. Within a week, the cells were growing into organoids—small blobs of tissue similar to organs in mature organisms. The cells seem perfectly happy in this media; at the time this paper was written, they have been stable for a year.

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Posted in Biology, embryology, medicine, science | Comments (0)

Soy milk, almond milk, oat milk. Spider milk?

November 30th, 2018
The spider in question, without its young.

Enlarge / The spider in question, without its young. (credit: Wikimedia Commons)

Milk comes from mammals. It’s kind of a distinctly mammalian thing. Even our government knows that. And yet, Chinese scientists have documented jumping spiders that provide their young with droplets of a nutrient-rich fluid from a furrow on the mother’s body. It is the sole nourishment for the spiderlings until they start foraging, and even then they still drink it until they get slightly more mature. Results are reported in Science.

Cockroaches and doves also provide their young with a substance described as “milk,” because it comes from their bodies and provides the exclusive source of sustenance to the young. Cockroach moms deposit this substance into the brood sac where their embryos are developing.

Dove parents—mothers and fathers both—generate crop milk and feed it to the baby birds for their first few days of life, until the babies can digest real food. Crop milk consists of nutrient-filled cells sloughed off in flakes from the inside of the parent birds’ crops, which are under their necks.

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Posted in Biology, lactation, science, spiders | Comments (0)

Scientists, ethicists slam decisions behind gene-edited twins

November 30th, 2018
Chinese geneticist He Jiankui speaks during the Second International Summit on Human Genome Editing at the University of Hong Kong days after the Chinese geneticist claimed to have altered the genes of the embryo of a pair of twin girls before birth, prompting outcry from scientists of the field.

Enlarge / Chinese geneticist He Jiankui speaks during the Second International Summit on Human Genome Editing at the University of Hong Kong days after the Chinese geneticist claimed to have altered the genes of the embryo of a pair of twin girls before birth, prompting outcry from scientists of the field. (credit: S.C. Leung/SOPA Images/LightRocket via Getty Images)

As more details regarding the first gene-edited humans are released, things continue to look worse. The researcher who claimed the advance, He Jiankui, has now given a public talk that includes many details on the changes made at the DNA level. The details make a couple of things clear: we don't know whether the editing will protect the two children from HIV infections, and we can't tell whether any areas of the genome have been damaged by the procedure.

All of that raises even further questions as to whether He followed ethical guidelines when performing the work and getting consent from the parents. And, more generally, nobody is sure why He chose to ignore a strong consensus that the procedure wasn't yet ready for use in humans. In response to the outcry, the Chinese government has shut down all further research by He, even as it was revealed that a third gene-edited baby may be on the way.

While the US already has rules in place that are intended to keep research like He's from happening, a legal scholar Ars spoke with suggested there may be a loophole that could allow something similar here. In light of that, it's important to understand the big picture He has potentially altered. What exactly happened in China and why does it concern so many in the scientific community?

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Posted in Biology, CRISPR, ethics, Features, gene editing, medicine, science, stem cells | Comments (0)

DNA data from Africans reveals sequences that we’d missed

November 24th, 2018
The first printout of the human genome to be presented as a series of books, displayed in the 'Medicine Now' room at the Wellcome Collection, London.

Enlarge / The first printout of the human genome to be presented as a series of books, displayed in the 'Medicine Now' room at the Wellcome Collection, London. (credit: Russ London at English Wikipedia)

The human genome sequence, first published in 2001, has some important information missing. The latest version of it, called GRCh38, has a monstrous 3.1 gigabases of information—but that's still not enough. A letter published in Nature Genetics this week finds that the reference genome is missing a colossal 10 percent of the genetic information found in the genomes of hundreds of people with African ancestry—information that also appears in other human populations.

Get the reference

The "human genome" is in fact assembled from the genomes of just a handful of people, with the majority of GRCh38 coming from just one person. It's not a snapshot of what's in human DNA so much as a kind of template and roadmap, giving a sense of what's in there and allowing comparisons between individuals and the "reference genome."

We've known this is a limitation and have been making constant additions to the reference genome, which has improved its ability to represent the huge range of variation that's present in modern humans. But because its source is so limited, write the authors of this week's letter, so is its usefulness: "In recent years, a growing number of researchers have emphasized the importance of capturing and representing sequencing data from diverse populations."

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Posted in Biology, Genetics, life sciences, science | Comments (0)

Some clues about why male Guinea baboons fondle each other’s genitals

November 18th, 2018
Two baboons out for a walk carrying a third, infant baboon.

Enlarge / A baby Guinea baboon in its pre-diddling days goes for a ride. (credit: Michelle Bender / Flickr)

Male Guinea baboons have a curious habit. They will walk—or sometimes run—to another male baboon and say a quick hello in a very enthusiastic way: with a “mutual penis diddle”. Or sometimes it’s a quick mount from behind. Other times, they do a short dance-like “polonaise,” facing the same way, on their hind legs, hand on the other’s hip, and a few steps forward.

Clearly, this behavior needs an explanation. In some ways, it’s not all that much of a mystery: ritual greeting is actually fairly widespread among many primate species and takes many colorful forms. It's a behavior that's “common among males living in multi-male groups,” write the authors of a new paper exploring Guinea baboons’ greeting behavior.

So it’s no surprise that the Guinea baboons greet each other. But the intimacy of their behavior stands out. Unlike other species, where ritual greetings serve to cool down a tense or aggressive moment, for Guinea baboons, it seems to be more about keeping their social bonds strong.

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Posted in Behavioral science, Biology, cooperation, science | Comments (0)

Whales are stressed out by climate change, and it shows in their earwax

November 16th, 2018
A graph next to what looks like a tree sliced down the middle but is actually whale earwax.

Enlarge / A whale earplug, showing the layers accumulated across a lifetime, and the corresponding cortisol levels. (credit: Nature Communications)

In a whale’s earwax lie clues to its entire life. Some species of whale build up large “earplugs” of fatty, waxy material that can trap hints about the hormones that coursed through the beast and the pollutants it swam through.

In a paper published this month in Nature Communications, researchers used earplugs recovered from 20 whales to explore how their stress levels have responded to changes over the last 200 years. They found that the whales’ stress levels moved in concert with being hunted, rising as whaling levels reached fever pitch, and plummeting as whaling levels reduced. But since the 1970s, stress levels have been steadily climbing again, keeping step with warming ocean waters.

The ear is the window to a whale’s soul

Tracking even the most obvious behaviors in wild animals can be a tricky business—for instance, nobody knows for sure where great white sharks go to breed. Even knowing how many animals there are in a population can be difficult. Figuring out how stressed whales have been is a near-impossible task, but a crucial one: stress affects the health of individual whales, which in turn affects the health of the population. So tracking stress levels could be useful for developing a comprehensive whale conservation strategy.

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Posted in Biology, climate change, conservation, science | Comments (0)

Chimps have different cultural norms about friendliness, too

November 9th, 2018
The extent that chimps engage in social grooming is different between groups.

Enlarge / The extent that chimps engage in social grooming is different between groups. (credit: flickr user: Tambako The Jaguar)

Human cultures have widely varying norms when it comes to friendliness and politeness. Make accidental eye contact with a Londoner on public transport and suffer mutual horror, but go to South Africa and find yourself routinely embraced by complete strangers. For researchers studying human behavior, there’s a strong push to study a wider variety of different populations around the world in an effort to expand focus beyond rich westerners. But when it comes to animal behavior, differences between populations have come under less scrutiny.

A paper in PNAS this week explored differences in social behavior between four different populations of chimpanzees, finding that the groups had very different norms when it came to hanging out together and grooming one another. They point out that this means studying one population of chimps might not always be enough for accurate claims about the species as a whole.

Midwestern vs. New Yorker chimps

The Chimfunshi Wildlife Orphanage Trust in Zambia is an ideal place to investigate differences between chimpanzee groups. It's home to 120 chimpanzees, some of whom were wild-born but needed to be rescued and some of whom were born in the orphanage. The sanctuary has distinct populations separated from each other but all living in the same ecological environment.

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Posted in Behavioral science, Biology, primates, science | Comments (0)

Low-caste men in India cooperate like college students

November 7th, 2018
Cartoon of hunters with stags and hares

A diagram of the options in game theory's Stag Hunt. (credit: Wikimedia Commons)

In the Discourses on the Origin of Inequality, the political philosopher Jean-Jacques Rousseau imagines a hypothetical prehistoric Stag Hunt. Each hunter working alone can catch a hare, but hares aren’t very meaty. Working together a group can cooperate to take down a stag—but only if everyone is committed. If someone spots a hare and decides to go after it, the stag escapes and everyone else ends up hungry.

Economic studies in which university students in the US played simulated versions of the Stag Hunt indicated that at some point, pairs would realize that it was in both of their best interests to commit to hunting the stag and they would fall into “an efficient and cooperative equilibrium.” But it turns out that American university students are not a particularly representative subset of humanity and cannot necessarily grant deep insights into human nature. They are too WEIRD: Western, Educated, Industrial, Rich, and Developed.

When Indian men in the rural northern Indian state of Uttar Pradesh played the game, only low-caste men acted like the American students. High-caste men decidedly did not fall into an efficient cooperation.

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Posted in behavioral economics, Behavioral science, Biology, game theory, Human behavior, science | Comments (0)