The mystery of why birds’ eggs come in so many shapes has long been up in the air. Now new research suggests adaptations for flight may have helped shape the orbs.

Stronger fliers tend to lay more elongated eggs, researchers report in the June 23 Science. The finding comes from the first large analysis of the way egg shape varies across bird species, from the almost perfectly spherical egg of the brown hawk owl to the raindrop-shaped egg of the least sandpiper.
“Eggs fulfill such a specific role in birds — the egg is designed to protect and nourish the chick. Why there’s such diversity in form when there’s such a set function was a question that we found intriguing,” says study coauthor Mary Caswell Stoddard, an evolutionary biologist at Princeton University.

Previous studies have suggested many possible advantages for different shapes. Perhaps cone-shaped eggs are less likely to roll out of the nest of cliff-dwelling birds; spherical eggs might be more resilient to damage in the nest. But no one had tested such hypotheses across a wide spectrum of birds.

Stoddard and her team analyzed almost 50,000 eggs from 1,400 species, representing about 14 percent of known bird species. The researchers boiled each egg down to its two-dimensional silhouette and then used an algorithm to describe each egg using two variables: how elliptical versus spherical the egg is and how asymmetrical it is — whether it’s pointier on one end than the other.

Next, the researchers looked at the way these two traits vary across the bird family tree. One pattern jumped out: Species that are stronger fliers, as measured by wing shape, tend to lay more elliptical or asymmetrical eggs, says study coauthor L. Mahadevan, a mathematician and biologist at Harvard University.
Mahadevan cautions that the data show only an association, but the researchers propose one possible explanation for the link between flying and egg shape. Adapting to flight streamlined bird bodies, perhaps also narrowing the reproductive tract. That narrowing would have limited the width of an egg that a female could lay. But since eggs provide nutrition for the chick growing inside, shrinking eggs too much would deprive the developing bird. Elongated eggs might have been a compromise between keeping egg volume up without increasing girth, Stoddard suggests. Asymmetry can increase egg volume in a similar way.

Testing a causal connection between flight ability and egg shape is tough “because of course we can’t replay the whole tape of life again,” says Claire Spottiswoode, a zoologist at the University of Cambridge who wrote a commentary accompanying the study. Still, Spottiswoode says the evidence is compelling: “It’s a very plausible argument.”

Santiago Claramunt, associate curator of ornithology at the Royal Ontario Museum in Toronto, isn’t convinced that flight adaptations played a driving role in the evolution of egg shape. “Streamlining in birds is determined more by plumage than the shape of the body — high performing fliers can have rounded, bulky bodies” he says, which wouldn’t give elongated eggs the same advantage over other egg shapes. He cites frigate birds and swifts as examples, both of which make long-distance flights but have fairly broad bodies. “There’s certainly more going on there.”

Indeed, some orders of birds showed a much stronger link between flying and egg shape than others did. And while other factors — like where birds lay their eggs and how many they lay at once — weren’t significantly related to egg shape across birds as a whole, they could be important within certain branches of the bird family tree.

The infant moon may have had a thick metal atmosphere, where supersonic winds raised waves in its magma ocean.

That’s the conclusion of a new simulation that calculates how heat from the young sun, the Earth and the moon’s own hot surface could have vaporized lunar metals to give the moon an atmosphere as thick as Mars’. The model, reported online June 22 at arXiv.org, offers a way to test theories of how the moon formed and suggests how researchers could study exoplanets without leaving Earth’s own neighborhood.
Most planetary scientists think the moon formed when a Mars-sized protoplanet slammed into the Earth around 4.5 billion years ago. The collision threw hot, molten material into Earth’s orbit, which coalesced and eventually cooled into the moon.

At first, though, the moon would have been covered in a deep, global ocean of hot liquid rock. The postcollision Earth would have been blisteringly hot as well — upwards of 2000° Celsius — and would have glowed like a red dwarf star.

Prabal Saxena of NASA’s Goddard Spaceflight Center in Greenbelt, Md., and colleagues added up the radiation the early moon would have received from that starlike Earth, plus the sun and the magma ocean itself. Previous models had suggested the early moon should have an atmosphere, but the team believes its model is the first to include all those inputs at once, revealing fresh details about how the atmosphere and ocean may have interacted.

All of that radiation would have vaporized volatile atoms in the metal-rich magma ocean and formed an atmosphere about one-tenth the thickness of Earth’s, the model showed. To keep things simple, the team used sodium — an easily vaporized element that is abundant on the moon — to represent all the components that could contribute to an atmosphere.

As long as the molten ocean remained liquid, the atmosphere would have received freshly vaporized sodium atoms from the ocean and sent them whipping through the metallic air. An extreme temperature difference — the side of the moon facing Earth would have been heated to temperatures greater than 1700° and the farside would have chilled to a frigid ‒150° — would have raised winds with speeds over a kilometer per second. The winds would probably have blown waves in the magma ocean.
When the winds reached the twilight zone between hot and cold, the atmosphere would have condensed, leaving a band of sodium snow.

After about 1,000 years, the magma ocean would have cooled enough to solidify into a rocky crust. Without a liquid reservoir to draw from, the entire atmosphere would have collapsed.

“The moon’s atmosphere was like a hard-partying rock star,” Saxena says. “It had a really violent, heavy metal existence, but it rapidly just fell apart.”

Kevin Zahnle of NASA’s Ames Research Center in Moffett Field, Calif., thinks this live fast, die young picture of the lunar atmosphere sounds plausible, and might be testable. “Their story is well within the bounds of the possible,” he says. But he’s not sure all of the model’s assumptions are good ones. Both Earth and the moon would have had to be “exceedingly dry” to avoid developing steamy water atmospheres first, for instance.

One way to test the model would be to look for a ring of extra sodium in the rocks around the transition zone. That would show that the atmosphere really did have an extreme temperature gradient and high winds.

Other models of the moon’s formation — for instance, if it formed from several small impacts instead of a single large one — would lead to a cooler atmosphere, less strong winds and ultimately no sodium snow, Saxena says. Finding that extra sodium could help settle the debate about which kind of impact really happened (SN: 4/15/17, p.18).

With its proximity to an Earth that glowed like a star, the early moon could also be a good analog for rocky exoplanets orbiting red dwarfs, Saxena says.

“If we can characterize what the early moon looked like, it can tell us about the physical mechanisms that are operating on these close-in extreme exoplanets,” Saxena says.

Short film is alive and well. Using the current trendy gene-editing system CRISPR, a team from Harvard University has encoded images and a short movie into the DNA of living bacteria.

The work is part of a larger effort to use DNA to store data — from audio recordings and poetry to entire books on synthetic biology. Last year, Seth Shipman and his colleagues at Harvard threw CRISPR into the mix when they used the editing system to record molecular data in the DNA of Escherichia coli.

Now, the team is upping its game with images of a human hand and a short movie, a GIF of a galloping horse from iconic turn-of-the-century photographer Eadweard Muybridge’s Human and Animal Locomotion. In the code, the nucleotide bases that form DNA correspond to black-and-white pixel values. The video was encoded frame by frame. Once the team synthesized the DNA, they used CRISPR and two associated Cas proteins (Cas 1 and 2) to slip the data into the genetic blueprint of E. coli colonies.

After growing the bacteria for several generations, the scientists retrieved the code for the images and film frames and were able to reconstruct the clips. About 90 percent of the encoded information was left intact. Though it’s not a perfect storage system, the results demonstrate CRISPR’s potential for hiding data in the genetic blueprints of bacteria, Shipman and his colleagues write July 12 in Nature.

When my younger daughter was around 6 months old, we gave her mashed up prune. She grimaced and shivered a little, appearing to be absolutely disgusted. But then she grunted and reached for more.

Most babies are ready for solid food around 6 months of age, and feeding them can be fun. One of the more entertaining approaches does not involve a spoon. Called baby-led weaning, it involves allowing babies to feed themselves appropriate foods.

Proponents of the approach say that babies become more skilled eaters when allowed to explore on their own. They’re in charge of getting food into their own mouths, gumming it and swallowing it down — all skills that require muscle coordination. When the right foods are provided (yes to soft steamed broccoli; no to whole grapes), babies who feed themselves are no more likely to choke than their spoon-fed peers.

Some baby-led weaning proponents also suspected that the method might ward off obesity, and a small study suggested as much. The idea is that babies allowed to feed themselves might better learn how to regulate their food intake, letting hunger and fullness guide them to a reasonable calorie count. But a new study that looked at the BMIs of babies who fed themselves and those who didn’t found that babies grew similarly with either eating style.

A clinical trial of about 200 mother-baby pairs in New Zealand tracked two different approaches to eating and their impact on weight. Half of the moms were instructed to feed their babies as they normally would, which for most meant spoon-feeding their babies purees, at least early on. The other half was instructed that only breast milk or formula was best until 6 months of age, and after that, babies could be encouraged to feed themselves. These mothers also received breastfeeding support.

At the 1- and 2-year marks, the babies’ average BMI z-scores were similar, regardless of feeding method, researchers report July 10 in JAMA Pediatrics. (A BMI z-score takes age and sex into account.) And baby-led weaning actually produced slightly more overweight babies than the other approaches, but not enough to be meaningful. At age 2, 10.3 percent of baby-led weaning babies were considered overweight and 6.4 percent of traditionally-fed babies were overweight. The two groups of babies seemed to take in about the same energy from food, analyses of the nutritional value and amount of food eaten revealed.

The trial found a few other differences between the two groups. Babies who did baby-led weaning exclusively breastfed for longer, a median of about 22 weeks. Babies in the other group were exclusively breastfed for a median of about 17 weeks. Babies in the baby-led weaning group were also more likely to have held off on solid food until 6 months of age.

While baby-led weaning may not protect babies against being overweight, the study did uncover a few perks of the approach. Parents reported that babies who fed themselves seemed less fussy about foods. These babies also reportedly enjoyed eating more (though my daughter’s prune fake-out face is evidence that babies’ inner opinions can be hard to read). Even so, these data seem to point toward a more positive experience all around when using the baby-led weaning approach. That’s ideal for both experience-hungry babies and the parents who get to savor watching them eat.

Type 2 diabetes and prion disease seem like an odd couple, but they have something in common: clumps of misfolded, damaging proteins.

Now new research finds that a dose of corrupted pancreas proteins induces normal ones to misfold and clump. This raises the possibility that, like prion disease, type 2 diabetes could be triggered by these deformed proteins spreading between cells or even individuals, the researchers say.

When the deformed pancreas proteins were injected into mice without type 2 diabetes, the animals developed symptoms of the disease, including overly high blood sugar levels, the researchers report online August 1 in the Journal of Experimental Medicine.
“It is interesting, albeit not super-surprising” that the deformed proteins could jump-start the process in other mice, says Bruce Verchere, a diabetes researcher at the University of British Columbia in Vancouver. But “before you could say anything about transmissibility of type 2 diabetes, there’s a lot more that needs to be done.”

Beta cells in the pancreas make the glucose-regulating hormone insulin. The cells also produce a hormone called islet amyloid polypeptide, or IAPP. This protein can clump together and damage cells, although how it first goes bad is not clear. The vast majority of people with type 2 diabetes accumulate deposits of misfolded IAPP in the pancreas, and the clumps are implicated in the death of beta cells.

Deposits of misfolded proteins are a hallmark of such neurodegenerative diseases as Alzheimer’s and Parkinson’s as well as prion disorders like Creutzfeldt-Jakob disease (SN: 10/17/15, p. 12).

Since IAPP misfolds like a prion protein, neurologist Claudio Soto of the University of Texas Health Science Center at Houston and his colleagues wondered if type 2 diabetes could be transmitted between cells, or even between individuals. With this paper, his group “just wanted to put on the table” this possibility.

The mouse version of the IAPP protein cannot clump — and mice don’t develop type 2 diabetes, a sign that the accumulation of IAPP is important in the development of the disease, says Soto. To study the disease in mice, the animals need to be engineered to produce a human version of IAPP. When pancreas cells containing clumps of misfolded IAPP, taken from an engineered diabetic mouse, were mixed in a dish of healthy human pancreas cells, it triggered the clumping of IAPP in the human cells.
The same was true when non-diabetic mice got a shot made with the diabetic mouse pancreas cells. The non-diabetic mice developed deposits of clumped IAPP that grew over time, and the majority of beta cells died. When the mice were alive, more than 70 percent of the animals had blood sugar levels beyond the healthy range.

Soto’s group plans to study if IAPP could be transmitted in a real world scenario, such as through a blood transfusion. They’ve already begun work on transfusing blood from mice with diabetes to healthy mice, to see if they can induce the disease. “More work needs to be done to see if this ever operates in real life,” Soto says.

Even if transmission of the misfolded protein occurs only within an individual, “this opens up a lot of opportunities for intervention,” Soto says, “because now you can target the IAPP.”

Verchere also believes IAPP is “a big player” in the progression of type 2 diabetes, and that therapies that prevent the clumps of proteins from forming are needed. Whether or not future research supports the idea that the disease is transmissible, the study is “good for appreciating the potential role of IAPP in diabetes.”

Cross two flashlight beams and they pass right through one another. That’s because particles of light, or photons, are mostly antisocial — they don’t interact with each other. But now scientists have spotted evidence of photons bouncing off other photons at the Large Hadron Collider at CERN, the European particle physics lab in Geneva.

“This is a very basic process. It’s never been observed before, and here it is finally emerging from the data,” says theoretical physicist John Ellis of King’s College London who was not involved with the study. Researchers with the ATLAS experiment at the LHC report the result August 14 in Nature Physics.
Because photons have no electric charge, they shouldn’t notice one another’s presence. But there’s an exception to that rule. According to quantum mechanics, photons can briefly transform into transient pairs of electrically charged particles and antiparticles — such as an electron and a positron — before reverting back to photons. Predictions made more than 80 years ago suggest that this phenomenon allows photons to interact and ricochet away from one another.

This light-by-light scattering is extremely rare, making it difficult to measure. But photons with more energy interact more often, providing additional chances to spot the scattering. To produce such energetic photons, scientists slammed beams of lead nuclei together in the LHC. Photons flit in and out of existence in the lead nuclei’s strong electromagnetic fields. When two nuclei got close enough that their electromagnetic fields overlapped, two photons could interact with one another and be scattered away.

To measure the interaction, ATLAS scientists sifted through their data to find collisions in which only two photons — the two that scattered away from the collision — appeared in the aftermath. “That’s the trickiest part of the whole thing,” says physicist Peter Steinberg of Brookhaven National Laboratory in Upton, N.Y., a member of the ATLAS collaboration. The scientists had to ensure that, in their enormous, highly sensitive particle detector, only two photons appeared, and convince themselves that no other particles had gone unaccounted for. The researchers found 13 such events over 19 days of data collection. Although other processes can mimic light-by-light scattering, the researchers predict that only a few such events were included in the sample.

The number of scattering events the researchers found agrees with the predictions of the standard model, physicists’ theory of particle physics. But a more precise measurement of the interaction might differ from expectations. If it does, that could hint at the existence of new, undiscovered particles.

Spacecraft have gone bite-sized. On June 23, Breakthrough Starshot, an initiative to send spacecraft to another star system, launched half a dozen probes called Sprites to test how their electronics fare in outer space. Each Sprite, built on a single circuit board, is a prototype of the tiny spacecraft that Starshot scientists intend to send to Alpha Centauri, the trio of stars closest to the sun. Those far-flung probes would be the smallest working spacecraft yet.

“We’re talking about launching things that are a thousand times lighter than any previous spacecraft,” says Avi Loeb, an astrophysicist at Harvard University who is part of the committee advising the initiative. A Sprite is only 3.5 centimeters square and weighs four grams, but packs a solar panel, radio, thermometer, magnetometer for compass capabilities and gyroscope for sensing rotation.

These spacecraft are designed to fly solo, but for this test, they hitched a ride into low Earth orbit on satellites named Max Valier and Venta-1. Each satellite has one Sprite permanently riding sidecar, and the Max Valier craft has another four it could fling out into space. Unfortunately, as of August 10, ground controllers haven’t yet been able to reach the Max Valier satellite to send a “Release the Sprites!” command. One of the permanently attached Sprites — probably the one on Venta-1 — is in radio contact.

Before sending next-gen Sprites off to Alpha Centauri, scientists plan to equip them with cameras, actuators for steering and other tools. “This was really just the first step in a long journey for Starshot,” Loeb says.

With its bright hue, this snake was bound to stand out sooner or later.

A newly discovered subspecies of sea snake, Hydrophis platurus xanthos, has a narrow geographic range and an unusual hunting trick. The canary-yellow reptile hunts at night in Golfo Dulce off Costa Rica’s Pacific coast. With its body coiled up at the sea surface, the snake points its head under the water, mouth open. That folded posture “creates a buoy” that stabilizes the snake so it can nab prey in choppy water, says study coauthor Brooke Bessesen, a conservation biologist at Osa Conservation, a biodiversity-focused nonprofit in Washington, D.C. In contrast, typical Hydrophis platurus, with a black back and yellow underbelly, hunts during the day, floating straight on calm seas.
The newly described venomous snake has been reported only in a small, 320-square-kilometer area of Golfo Dulce. After analyzing 154 living and preserved specimens, the researchers described the reptile’s characteristics July 24 in Zookeys. The scientists hope that the subspecies designation will enable the Costa Rican government to protect the sunny serpent, which they worry is already at risk from overzealous animal collectors.

Viking warriors have a historical reputation as tough guys, with an emphasis on testosterone. But scientists now say that DNA has unveiled a Viking warrior woman who was previously found in a roughly 1,000-year-old grave in Sweden. Until now, many researchers assumed that “she” was a “he” buried with a set of weapons and related paraphernalia worthy of a high-ranking military officer.

If the woman was in fact a warrior, a team led by archaeologist Charlotte Hedenstierna-Jonson of Uppsala University in Sweden has identified the first female Viking to have participated in what was long considered a male pursuit.
But the new report, published online September 8 in the American Journal of Physical Anthropology, has drawn criticism from some researchers. All that’s known for sure, they say, is that the skeleton assessed in the new report belonged to a woman who moved to the town where she was interred after spending her youth elsewhere.

“Have we found the Mulan of Sweden, or a woman buried with the rank-symbols of a husband who died abroad?” asks archaeologist Søren Sindbæk of Aarhus University in Denmark. There’s no way to know what meanings Vikings attached to weapons placed in the Swedish grave, Sindbæk says.

Although the new paper dubs the long-dead woman “a high-ranking female Viking warrior,” other interpretations of her identity are possible, Hedenstierna-Jonson acknowledges. But she notes that the Viking woman “was an exception in a sphere dominated by men, either if she was an active warrior or if she was ‘only’ buried in full warrior dress with a complete set of weapons.”

Excavations in the late 1800s at Birka, a Scandinavian trading center from the 700s to around 1000 (SN: 4/18/15, p. 8), uncovered the woman’s grave. Remains of Birka lie on the island of Björkö, about 30 kilometers west of present-day Stockholm. About 1,100 of more than 3,000 graves that encircle Birka have been unearthed.

Excavators noted that the body lay among a warrior’s gear. This equipment included an ax, a spear, arrows, a large knife, two shields and two horses. Playing pieces found in the grave, apparently for some type of board game, suggest the woman may have been a high-ranking officer with knowledge of military tactics and strategy, Hedenstierna-Jonson’s team speculates.
Researchers have typically assumed that Viking-era graves with weapons contain male warriors. Curiously, though, many skeletons in these graves, including that of the Birka woman, display no battle injuries.

Biological anthropologist Anna Kjellström of Stockholm University, a coauthor of the new study, reported at a meeting in 2013 that the Birka individual was a woman, based on pelvic shape and bone sizes. DNA from the Birka skeleton now confirms its female status and reveals many genetic similarities to present-day northern Europeans.

A comparison of two forms of radioactive strontium in teeth from the Birka woman, 15 other individuals excavated at Birka and pre-Viking age people from several parts of Sweden indicated that the woman moved to the trading center as a teenager or young woman. Humans absorb strontium from local rock formations through water and plant foods, leaving a chemical signature in teeth that approximately maps where these people grew up. The researchers estimate the woman was at least 30 years old when she died.

Findings in the new paper don’t demonstrate that the Birka woman was a Viking warrior, writes archaeologist Judith Jesch in a Sept. 9 post on her Norse and Viking Ramblings blog. Perhaps all alleged warriors in Viking-era warrior graves who lack serious wounds didn’t actually fight, contends Jesch, of the University of Nottingham in England. Hedenstierna-Jonson’s group provides no evidence that the Birka woman’s bones contain traces of strenuous physical activity expected from a warrior adept enough to avoid severe injuries, she writes.

“A certain amount of confusion” surrounds the original locations of bones excavated at Birka and then bagged for storage, including those of the proposed woman warrior, Jesch adds. Sloppy excavation practices at Birka more than 100 years ago sometimes accidentally lumped together bones from different graves, she says in her post.

Women could have been warriors during the Viking age, whether or not the Birka woman fought alongside men, says archaeologist Marianne Moen of the University of Oslo. Research over the past 30 years shows that Viking women were landowners, farmers, merchants, traders and participants in legal proceedings. Graves of two other Viking-era women, both in Norway, contain various weapons.

What’s important is not to hold women to a different standard than men when assessing comparable weapons placed in their graves, Moen asserts. The Birka find “was a warrior grave until it was sexed as female,” she says. “Now a lot of people would like to call it something else. That is where the danger lies here.”

A new species of hermit crab discovered in the shallow waters of southern Japan has been enjoying the perks of living like a peanut worm. Like the worms, the 7- to 8-millimeter-long hermit crab uses corals as a covering, researchers report September 20 in PLOS ONE.

Other kinds of hermit crabs live in coral reefs, but typically move in and out of a series of mollusk shells as the crabs grow. Diogenes heteropsammicola is the first hermit crab known to form a mutually beneficial relationship with two species of mobile corals called walking corals. Unlike more familiar coral species, these walking corals don’t grow in colonies and aren’t attached to the seafloor. Instead, each host coral grows with and around a crab, forming a cavity in the coral skeleton that provides a permanent home for the crustacean. In exchange, the crab helps the coral “walk.”
Walking corals are already known to be in a symbiotic relationship with a different sea creature — flexible, marine peanut worms called sipunculids. A symbiotic shift between such distantly related species as the worms and the crab is rare because organisms in a mutualistic relationship tend to be specialized and completely dependent on one other, says study coauthor Momoko Igawa, an ecologist at Kyoto University in Japan.
But similar to the worms, D. heteropsammicola appears to be well-adapted to live in the corals. Its extra slim body can slip inside the corals’ narrow cavity. And unlike other hermit crabs — whose tails curve to the right to fit into spiral shells — D.heteropsammicola’ s tail is symmetrical and can curl either way, just like the corals’ opening.
“Being able to walk around in something that is going to grow larger as you grow larger, that’s a big plus,” says Jan Pechenik, a biologist at Tufts University in Medford, Mass., who was not involved in the study. A typical hermit crab that can’t find a larger shell to move into “really is in trouble.”

D. heteropsammicola’s relationship with walking corals may begin in a similar way as it does with sipunculan worms, Igawa says. A walking coral larva latches onto a tiny mollusk shell containing a juvenile hermit crab and starts to grow. When the hermit crab outgrows the shell, the crustacean moves into the readily available host coral’s crevice, and the shell remains encapsulated in the coral.

By observing the hermit crab in an aquarium, Igawa and coauthor Makoto Kato, also an ecologist at Kyoto University, determined that the crab provides the corals with the same services as the worms: transportation and preventing the corals from being overturned by currents or buried in sediment.

Igawa hopes to search for this new hermit crab in Indonesia, a region where walking corals are normally found. Plus, because walking coral fossils are easy to come by in Japan, she also wants “to reveal the evolutionary history of the symbioses of walking corals [with] sipunculans and hermit crabs by observing these fossils.”