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Comment by Dr. Krishna Kumari Challa on July 14, 2023 at 11:54am

Humans' impact on Earth began a new epoch in the 1950s called the Anthropocene, scientists say

From climate change to species loss and pollution, humans have etched their impact on Earth with such strength and permanence since the middle of the 20th century that a special team of scientists says a new geologic epoch began then.

Called the Anthropocene—and derived from the Greek terms for "human" and "new"—this epoch started sometime between 1950 and 1954, according to the scientists. While there is evidence worldwide that captures the impact of burning fossil fuels, detonating nuclear weapons and dumping fertilizers and plastics on land and in waterways, the scientists are proposing a small but deep lake outside of Toronto, Canada—Crawford Lake—to place a historic marker.

It's quite clear that the scale of change has intensified unbelievably and that has to be human impact. This puts the power of humans in a somewhat similar class with the meteorite that crashed into Earth 66 million years ago, killing off dinosaurs and starting the Cenozoic Era, or what is conversationally known as the age of mammals. But not quite. While that meteorite started a whole new era, the working group is proposing that humans only started a new epoch, which is a much smaller geologic time period.

The scientists aims to determine a specific start date of the Anthropocene by measuring plutonium levels at the bottom of Crawford Lake. Crawford Lake, which is 79 feet (29 meters) deep and 258,333 square feet (24,000 square meters) in area, was chosen over 11 other sites because the annual effects of human activity on the earth's soil, atmosphere and biology are so clearly preserved in its layers of sediment. That includes everything from nuclear fallout to species-threatening pollution to steadily rising temperatures.

The remarkably preserved annual record of deposition in Crawford Lake is truly amazing.

The Anthropocene shows the power—and hubris—of humankind. But the reality is that our power to transform the environment has far exceeded our understanding of the consequences and our capacity to change course.

Source: 2023 The Associated Press

https://phys.org/news/2023-07-humans-impact-earth-began-epoch.html?...

Comment by Dr. Krishna Kumari Challa on July 11, 2023 at 11:39am

The latter possibility is particularly intriguing as it suggests that male harvestmen can permanently 'lay down their weapons' and adopt a new lifestyle that doesn't rely on competition. So even when males have fewer legs to stand on, they can still find ways to reproduce.

If that's the case, then Charles Darwin's theory of sexual selection, which puts great emphasis on sexual ornaments and weapons, may not be fully comprehensive; there could be other ways to snag a mate in nature.

In fact, the same male dung beetles that Darwin once used to support his theory of sexual selection over a century ago, turned out to be trimorphic as well. This means that not all male dung beetles possess large mandibles for fighting other males or wooing females.

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While trimorphism can be a result of different genetics, creating various male roles in a society, in the case of dung beetles and harvestmen, the phenomenon seems to have less to do with how animals are born and more to do with how they grow up.

What happens in their youth seems to determine how they develop sexually.

Further research will be needed to explore what sets alpha and beta males apart.

https://academic.oup.com/beheco/article/34/4/613/7160263?login=false

Part 2

Comment by Dr. Krishna Kumari Challa on July 11, 2023 at 11:38am

An Arachnid that has three Different Kinds of Male

Scientists have found a rare species of arachnid in New Zealand that hosts three different types of males. Recent findings on the species are forcing a rethink of animal mating systems and the evolution of reproductive strategies.

We've known since 2020 that while male harvestmen (Forsteropsalis pureora) – or daddy longlegs, as you might better know them – look the same and have similar genes, there seemed to be three distinct types.

At the top of the hierarchy sits the large alpha male, which has short yet strong pincer-like jaws that it uses to pin down competition when fighting for territory or mates.

Next comes the beta male, which has longer and thinner pincers. And in last place is the gamma male, which is seven times smaller than the other two.

Not only do gamma males look different from the others, but they also act differently.

Instead of battling for female mates like their larger peers, researchers found these smaller, weaponless males have all but given up the fight.

Their tactic for survival involves sneaking around and looking for undefended females to reproduce with.

The rare pecking order is known as trimorphism, and researchers only discovered it among animals for the first time in 2009.

Now, researchers at the University of Auckland – many of whom conducted the 2020 study – think they have figured out why trimorphism evolves among harvestmen in particular.

According to the new study, if a male harvestman loses a leg in his youth, voluntarily 'dropping' a limb to avoid a hungry predator, the harvestman can't regrow the lost limb and is 45 times more likely to grow up smaller and weaker than his peers. Perhaps this is because they can't get enough food for their development because their hunting is impeded.

Or maybe there's no point in investing in big fighting weapons when they're already disadvantaged when it comes to fighting. So, the arachnids' resources may be invested in other things, such as testes size, sperm count, or aerobic poise, to ensure they make the most of the mating opportunities they get.

Part 1

Comment by Dr. Krishna Kumari Challa on July 11, 2023 at 11:25am

Fertility Mystery: IVF Success Is Higher if Eggs Harvested in Summer

There's something about the seasons that seems to impact human reproduction for unknown reasons.

A new study  has found in vitro fertilization (IVF) is most successful when eggs are harvested in the summer.

It doesn't seem to matter when the frozen embryo is actually transferred to a person's womb, only when it is originally collected.

If eggs are retrieved in summer, the live birth rate is 31 percent; if eggs are collected in autumn, the live birth rate is 26 percent.

Meanwhile, eggs collected in winter and spring sit between these two success rates.

While previous IVF studies found seasons have no consistent impact on embryo transfers, implantation, pregnancy, or live birth rates, egg collection seems to be a different matter.

Of all these embryos, those collected on days with more than 10 hours of sunshine were 28 percent more likely to result in a live birth than those collected when the sun showed its face for less than 7 hours a day.

However, the actual temperature of the day didn't seem to have an impact.

The research was done in hindsight, so it can't reveal a direct cause and effect.

 a similar 2022 study in the Northern Hemisphere found that the season and temperature at the time of egg retrieval significantly impacted the subsequent live birth rate.

Specifically, eggs collected during summer in Boston were 42 percent more likely to result in a live birth than those collected during winter. Meanwhile, eggs collected on the warmest days were 34 percent more likely to result in a live birth than eggs collected on the coldest days.

The findings suggest that seasons can have an important effect on a person's ovarian function, although not necessarily the receptiveness of their uterus or the early development of a fetus.

The two studies disagree, however, on whether ambient temperature or the duration of bright sunshine is the more important seasonal factor impacting embryo retrieval, possibly via vitamin D or the production of melatonin.

Maybe it's neither.

https://academic.oup.com/humrep/advance-article/doi/10.1093/humrep/...

Comment by Dr. Krishna Kumari Challa on July 10, 2023 at 1:49pm

Animals who mate during a heat wave less likely to reproduce successfully, new study shows

As the planet continues to warm due to global climate change, the frequency and intensity of extreme weather events, such as heat waves, is rising. Heat waves are not just uncomfortable for humans; they also pose significant challenges for animals. Heat stress caused by these extreme events can disrupt all aspects of animal reproduction. The findings also show that when a heat wave occurs during mating, offspring are smaller and have lower survival rates.

Understanding how animals are affected by climate change is vital, and the research looked at the potential effects of heat waves, and in particular, the role of the timing of a heat wave event, within an organism's reproductive cycle.

Researchers  found that the timing of the heat wave really matters: when it occurs a few days before or after mating, it has little to no effect on reproductive processes. In contrast, when the heat wave occurs during mating, parents are less likely to reproduce successfully, and their offspring are smaller and have lower survival.

The research provides novel insights and can improve the ability to make informed predictions about the ecological consequences of heat waves under climate change.

The implications of these findings extend well beyond this specific insect species, and they highlight the need to investigate these effects more broadly.

Predicting how wild populations will be affected by climate change is a challenging endeavor. This study provides another piece of the puzzle and helps us form a more complete picture of how heat waves might shape animal reproduction and population survival.

Natalie Pilakouta et al, The consequences of heatwaves for animal reproduction are timing‐dependent, Functional Ecology (2023). DOI: 10.1111/1365-2435.14386

Comment by Dr. Krishna Kumari Challa on July 10, 2023 at 1:02pm

The pressures of being a precocial baby bird that had to keep itself warm, while undergoing a rapid molt, might have been a factor in the ultimate doom of the Enantiornithines. Enantiornithines were the most diverse group of birds in the Cretaceous, but they went extinct along with all the other non-avian dinosaurs.

When the asteroid hit, global temperatures would have plummeted and resources would have become scarce, so not only would these birds have even higher energy demands to stay warm, but they didn't have the resources to meet them.

Both the amber specimen and the study of molting in modern birds point to a common theme: prehistoric birds and feathered dinosaurs, especially ones from groups that didn't survive the mass extinction, molted differently from today's birds.

 Yosef Kiat et al, Rarity of molt evidence in early pennaraptoran dinosaurs suggests annual molt evolved later among Neornithes, Communications Biology (2023). DOI: 10.1038/s42003-023-05048-x

Jingmai O'Connor et al, Immature feathers preserved in Burmite provide evidence of rapid molting in enantiornithines, Cretaceous Research (2023). DOI: 10.1016/j.cretres.2023.105572

Part 2

Comment by Dr. Krishna Kumari Challa on July 10, 2023 at 1:02pm

Fossils reveal how ancient birds molted, could explain why modern birds survived while other dinosaurs died
Every bird you've ever seen—every robin, every pigeon, every penguin at the zoo—is a living dinosaur. Birds are the only group of dinosaurs that survived the asteroid-induced mass extinction 66 million years ago. But not all the birds alive at the time made it. Why the ancestors of modern birds lived while so many of their relatives died has been a mystery that paleontologists have been trying to solve for decades. Two new studies point to one possible factor: the differences between how modern birds and their ancient cousins molt their feathers.

Feathers are one of the key traits that all birds share. They're made of a protein called keratin, the same material as our fingernails and hair, and birds rely on them to fly, swim, camouflage, attract mates, stay warm, and protect against the sun's rays.

But feathers are complex structures that can't be repaired, so as a means of keeping them in good shape, birds shed their feathers and grow replacements in a process called molting. Baby birds molt in order to lose their baby feathers and grow adult ones; mature birds continue to molt about once a year.

A paper in the journal Cretaceous Research detailed the discovery of a cluster of feathers preserved in amber from a baby bird that lived 99 million years ago.

Today, baby birds are on a spectrum in terms of how developed they are when they're born and how much help they need from their parents. Altricial birds hatch naked and helpless; their lack of feathers means that their parents can more efficiently transmit body heat directly to the babies' skin. Precocial species, on the other hand, are born with feathers and are fairly self-sufficient.

All baby birds go through successive molts— periods when they lose the feathers they have and grow in a new set of feathers, before eventually reaching their adult plumage. Molting takes a lot of energy, and losing a lot of feathers at once can make it hard for a bird to keep itself warm. As a result, precocial chicks tend to molt slowly, so that they keep a steady supply of feathers, while altricial chicks that can rely on their parents for food and warmth undergo a "simultaneous molt," losing all their feathers at roughly the same time.

The amber-preserved feathers in this study are the first definitive fossil evidence of juvenile molting, and they reveal a baby bird whose life history doesn't match any birds alive today.

"This specimen shows a totally bizarre combination of precocial and altricial characteristics. All the body feathers are basically at the exact same stage in development, so this means that all the feathers started growing simultaneously, or near simultaneously."

However, this bird was almost certainly part of a now-extinct group called the Enantiornithines, which   were highly precocial.

Part 1

Comment by Dr. Krishna Kumari Challa on July 10, 2023 at 12:51pm

Physicists develop a metamaterial that can count

A block of rubber that can count to ten and even remember the order in which it is pressed—physicists  have published about this latest metamaterial in the journal Physical Review Letters.

A beam counter: rubber that can count to ten

Lennard J. Kwakernaak et al, Counting and Sequential Information Processing in Mechanical Metamaterials, Physical Review Letters (2023). DOI: 10.1103/PhysRevLett.130.268204

Comment by Dr. Krishna Kumari Challa on July 10, 2023 at 12:46pm

Chemists discover why photosynthetic light-harvesting is so efficient

When photosynthetic cells absorb light from the sun, packets of energy called photons leap between a series of light-harvesting proteins until they reach the photosynthetic reaction center. There, cells convert the energy into electrons, which eventually power the production of sugar molecules.

This transfer of energy through the light-harvesting complex occurs with extremely high efficiency: Nearly every photon of light absorbed generates an electron, a phenomenon known as near-unity quantum efficiency.

A new study by chemists offers a potential explanation for how proteins of the light-harvesting complex, also called the antenna, achieve that high efficiency. For the first time, the researchers were able to measure the energy transfer between light-harvesting proteins, allowing them to discover that the disorganized arrangement of these proteins boosts the efficiency of the energy transduction.

In order for that antenna to work, you need long-distance energy transduction. The key finding of this work is that the disordered organization of the light-harvesting proteins enhances the efficiency of that long-distance energy transduction.

Wang, Dihao et al, Elucidating interprotein energy transfer dynamics within the antenna network from purple bacteria, Proceedings of the National Academy of Sciences (2023). DOI: 10.1073/pnas.2220477120. doi.org/10.1073/pnas.2220477120

Comment by Dr. Krishna Kumari Challa on July 10, 2023 at 12:29pm

Native to North America, the American mink has been domesticated for the fur trade for over a century. After they were bred in Europe for fur farming, captive animals escaped to form feral populations that have spread throughout Europe. This natural history thus provided the separated populations that researchers needed. 

To explore changes in brain size, the team turned to a proxy: skulls. "Braincase size is a good proxy for brain size in mink, and this allows us to take measurements from existing skull collections without the need for living animals. A museum collection from Cornell University was used to study skulls of wild American mink while European fur farms provided skulls of domesticated animals.

The team took measurements from skulls to calculate relative brain size of the animals. They found that, according to the well-documented domestication process, the brains of captive-bred mink had shrunk by 25% compared to their wild ancestors. But, in contrast to expectations, the brains of feral mink grew almost back to wild size within 50 generations.

Researchers think  tehy know why this animal, in particular, has achieved what was thought to be unlikely. American mink belong to a family of small mammals with a remarkable ability to seasonally change their brain size in a process known as Dehnel's phenomenon. 

While other domesticated animals seem to lose brain size permanently, it's possible that mink can regain their ancestral brain sizes because they have flexible brain size built into their system. This flexibility could have offered advantages to the mink that re-entered the wild.

 Ann-Kathrin Pohle et al, Domestication effect of reduced brain size is reverted when mink become feral, Royal Society Open Science (2023). DOI: 10.1098/rsos.230463

Part 2

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