Animals as small and soft as tardigrades seldom have legs and almost never bother walking. For example, round worms of similar size and body type thrash about, slithering their doughy forms over unpredictable substrates. Yet the water bear, a micro-animal so distinct that scientists were forced to assign it to its own phylum, uses eight stubby legs to improbably propel itself through marine and freshwater sediment, across desert dunes, and beneath the soil.

Now, a new study in PNAS analyzes tardigrade gaits and finds that water bears walk in a manner most closely resembling that of insects 500,000 times their size. The discovery implies the existence of either a common ancestor or an evolutionary advantage that explains why one of the smallest and squishiest creatures evolved to walk just like larger, hard-bodied insects.

“Tardigrades have a robust and clear way of moving — they’re not these clumsy things stumbling around in the desert or in leaf litter,” says Jasmine Nirody, a fellow in Rockefeller’s Center for Studies in Physics and Biology. “The similarities between their locomotive strategy and that of much larger insects and arthropods opens up several very interesting evolutionary questions.”

Smooth runners

Nirody and colleagues first determined how water bears walk and run. “If you watch tardigrades under a light microscope for long enough, you can capture a wide range of behavior,” Nirody says. “We didn’t force them to do anything. Sometimes they would be really chill and just want to stroll around the substrate. Other times, they’d see something they like and run towards it.”

Nirody found that, at their most leisurely, water bears lumber about half a body length per second. At full throttle, their loping strides carried them two body lengths in the same amount of time. But the surprise came when she observed how a water bear’s feet contact the ground as it gains momentum. Unlike vertebrates, which have distinct gaits for each speed — picture a horse’s hooves as it transitions from a walk to a gallop — tardigrades run more like insects, scurrying at increasing speeds without ever changing their basic stepping patterns.

“When vertebrates switch from walking to running, there is a discontinuity,” Nirody says. “With arthropods, all stepping patterns exist along the same continuum.”

Ancient coordination

Why do tardigrades share a locomotive strategy with much larger, hard-bodied insects?

One possible explanation is that tardigrades, long assumed to fit neatly into no existing taxonomy, may share common ancestors — and even a common neural circuit — with insects such as fruit flies, ants, and other segmented scurrying creatures. In fact, some scientists advocate classifying tardigrades within the proposed panarthropod clade, a catchall group that would assign common shelf space to insects, crustaceans, velvet worms, and water bears.

Another possibility is that there is no ancestral connection between tardigrades and arthropods, but that the unrelated groups of organisms independently arrived at the same walking and running strategies because they were evolutionarily advantageous. Perhaps the best way to navigate unpredictable terrain with a microscopic body is to plod like a water bear.

Nirody is equally fascinated by both possibilities. “If there is some ancestral neural system that controls all of panarthropod walking, we have a lot to learn,” she says. “On the other hand, if arthropods and tardigrades converged upon this strategy independently, then there’s much to be said about what makes this strategy so palatable for species in different environments.”

Beyond the implications for evolutionary biology and the study of animal locomotion, the findings may have ramifications for the burgeoning fields of soft and microscale robotics.

By studying how small animals evolved to move across challenging environments, scientists may be able to design robots that can more efficiently squeeze into small spaces or operate at the microscale. “We don’t know much about what happens at the extremes of locomotion — how to make an efficient small walker, or how soft-bodied things should move,” Nirody says.

“Tardigrades are an important porthole into soft-bodied, microscale locomotion.”

Researchers discovered that chlorpyrifos, which is banned for use on foods in Canada but widely sprayed on fruits and vegetables in many other parts of the world, slows down the burning of calories in the brown adipose tissue of mice. Reducing this burning of calories, a process known as diet-induced thermogenesis, causes the body to store these extra calories, promoting obesity.

Scientists made the discovery after studying 34 commonly used pesticides and herbicides in brown fat cells and testing the effects of chlorpyrifos in mice fed high calorie diets. Their findings were published in Nature Communications and could have important implications for public health.

“Brown fat is the metabolic furnace in our body, burning calories, unlike normal fat that is used to store them. This generates heat and prevents calories from being deposited on our bodies as normal white fat. We know brown fat is activated during cold and when we eat,” said senior author Gregory Steinberg, professor of medicine and co-director of the Centre for Metabolism, Obesity, and Diabetes Research at McMaster.

“Lifestyle changes around diet and exercise rarely lead to sustained weight loss. We think part of the problem may be this intrinsic dialling back of the metabolic furnace by chlorpyrifos.”

Steinberg said chlorpyrifos would only need to inhibit energy use in brown fat by 40 calories every day to trigger obesity in adults, which would translate to an extra five lbs of weight gain per year.

He said that while several environmental toxins including chlorpyrifos have been linked to rising obesity rates in both humans and animals, most of these studies have attributed weight gain to increases in food intake and not the burning of calories.

While the use of chlorpyrifos on foods is banned in Canada, imported produce may still be treated with it.

“Although the findings have yet to be confirmed in humans, an important consideration, is that whenever possible consume fruits and vegetables from local Canadian sources and if consuming imported produce, make sure it is thoroughly washed,” said Steinberg.

External funding for the study was provided by the Canadian Institutes of Health Research.

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As common as roe deer may seem in Swiss forests, one of their characteristics is unique among deer species. After mating and fertilisation of the egg in midsummer, the pinhead-sized embryo does not implant in the uterus, but enters into a period of dormancy, called embryonic diapause. This period lasts for over four months until December. Only then does the embryo continue its development at normal pace and implants in the uterus. In May, after four and a half months of “real” gestation, the doe gives birth to one to three fawns.

Although the phenomenon has been known for more than 150 years, it still puzzles. Various forms of embryonic diapause are known to occur in over 130 mammalian species. However, they rarely last as long as observed in the roe deer. And, most importantly, almost no other species shows such a pronounced, continuous deceleration instead of a complete halt. In mice, scientists can artificially induce diapause. However, in roe deer it is still unclear which factors control diapause while keeping the embryo alive.

The research group led by Susanne Ulbrich, Professor of Animal Physiology at ETH Zurich, has been investigating the mystery of roe deer diapause for some time. In a new study, the researchers show which molecular processes take place in the embryo while it is dormant: embryonic cells continue to divide during diapause, albeit very slowly. The number of cells, including embryonic stem cells, doubles only every two to three weeks. The study, which has just been published in the journal PNAS, involved not only the ETH group, but also researchers from the Universities of Zurich and Bern, as well as German and French research institutions.

Gene transcripts and signalling molecules studied

To answer the question of what prevents the embryonic cells from dividing at a normal pace, the researchers first examined the molecular composition of the uterine fluid. Next, they took a closer look at the transcriptome, i.e., the sum of all messenger RNA molecules, of the embryos and the uterine epithelial cells.

In the uterine fluid, the researchers found signalling substances that could regulate the cell division rate. The amino acid serine was particularly conspicuous. The ETH researchers showed that towards the end of diapause, the concentration of certain amino acids in the uterine fluid changes. The cell proliferation rate then concomitantly returns to a normal rate.

This process involves the molecular complex mammalian target of rapamycin (mTOR). mTOR reacts to amino acids and plays a crucial role in many metabolic signalling pathways in mammalian cells, including those associated with cancer. mTORC1, for example, regulates protein synthesis and thus cell growth and division.

According to the new findings, the activity of only mTORC1, but not mTORC2, is suppressed in roe deer embryos throughout diapause. This is in contrast to diapausing mice, where cell division is completely halted upon inhibition of both mTORC1 and mTORC2.

Towards the end of diapause, the significant increase in the amino acid level in the uterine fluid activates mTORC1. This, in turn, increases the expression of metabolic and cell cycle genes, driving embryo development forwards. Meanwhile, since mTORC2 is not inhibited during diapause in roe deer embryos, the researchers hypothesise that this could explain why cell division slowly continues.

In this study, the researchers did not investigate whether other signalling molecules are involved alongside the various amino acids. It also remains unclear whether the amino acids are actually responsible for the resumption of embryonic development or whether the embryo itself also secretes molecules that act on maternal cells and signalling pathways. The embryo may indicate its presence to its mother through specific signalling molecules. Ulbrich would like to close this knowledge gap in future studies.

New light on reproductive biology

These new findings shed light on reproductive and developmental biology in general. One fundamental question is how pregnancy is established in mammals. For example, in women and in domestic cattle, embryos often fail to implant in the uterus and die. “This has to do with complex interactions between the embryo and the mother,” Ulbrich says.

She adds that a successful pregnancy calls for precise timing. The embryo must make itself known at the right time through appropriate (molecular) signals and interrupt the mother’s cycle. “We want to better understand this interaction between embryo and mother,” Ulbrich explains. For this, she says, the roe deer is an ideal model. Embryonic development in roe deer is very similar to that of cattle but takes place in slow motion. “This allows us to better temporally resolve the sequence of events and find causal relationships.”

The findings could also help improve in vitro fertilisation in humans so that embryos may no longer need to be frozen. Moreover, natural factors could be used to control the rate at which cells, including embryonic stem cells, divide.

However, important seabed habitats and species recover more quickly following extreme storms than in the wake of such fishing activity.

That is one of the key findings of a first-of-its-kind study which examined the impact of the 2013/14 winter storms on the Lyme Bay Marine Protected Area (MPA), off the coast of southern England.

Academics from the University of Plymouth have been monitoring the area using underwater cameras and other techniques since 2008, when a ban on bottom towed fishing was introduced as part of a range of conservation measures.

They have previously demonstrated that several species have returned to the area since the MPA was introduced, resulting in the significant recovery of seabed life and fish and shellfish stocks.

However, there have been no previous studies looking at how extreme storms impact seabed habitats or the potential for MPAs to increase ecosystem resilience from storms.

To address that, researchers analysed the impacts of the 2013/14 series of storms, which separate studies by the University found to be the most energetic to hit western Europe since 1948.

Through annual surveys of seabed life in the MPA, they were able to see the immediate impact of the storms but also how the seabed was able to recover in subsequent years.

Writing in Frontiers in Marine Science, the researchers say that with extreme events likely to become more frequent and severe as a result of climate change, up to 29% of coastal reef MPAs around the UK may be similarly impacted by extreme storms.

Dr Emma Sheehan, Associate Professor of Marine Ecology at the University of Plymouth, is the study’s lead author. She said: “In our assessments in 2014, it appeared the previous winter’s storms had devastated the MPA. Loose sediments and other debris were prolific where life and biogenic reef habitat had been observed the year before. However, by 2016, large numbers of adult pink sea fans and other species were being observed once again with more juvenile pink sea fans than ever before. It showed the MPA’s recovery had begun almost immediately whereas, by contrast, it took more than three years for such patterns to be seen following its initial designation.”

The University’s work in Lyme Bay has been carried out in conjunction with local fishers and other community groups along the Dorset and Devon coastline.

In addition to assessing the effects of a ban on bottom-towed fishing, it has shown that limits on crab and lobster pot fishing could offer long-term benefits to fishermen and the environment.

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A research team from Tohoku University has unveiled more about the evolutionary process of the Marinoan-Ediacaran transition. Using biomarker evidence, they revealed possible photosynthetic activity during the Marinoan glaciation. This was followed by photosynthetic organisms and bacteria entering a period of low productivity. However, as eukaryotes expanded during the early Ediacaran period, they blossomed.

Dr. Kunio Kaiho, who co-authored a paper with Atena Shizuya, said, “Our findings help clarify the evolution of primitive to complex animals in the aftermath of the Snowball Earth.” Their paper online was published in the journal Global and Planetary Change on August 8, 2021.

The late Neoproterozoic era (650-530 million years ago) witnessed one of the most severe ice ages in the Earth’s 4.6-billion-year history. Researchers believe that ice sheets covered the entire earth since glaciogenic units, such as ice-rafted debris, are distributed globally. Overlaying these glaciogenic formations are cap carbonates. These precipitate under warm conditions and therefore suggest that the glacial environment changed rapidly into a greenhouse environment.

The Snowball Earth hypothesis purports the atmospheric carbon dioxide concentration controlled the change from a frozen state to an ice-free state. Ice sheet-covered oceans prevented the dissolution of carbon dioxide into seawater during the Marinoan ice age, meaning greenhouse gas concentration, emitted by volcanic activity, increased gradually. Once the extreme greenhouse effect kicked in, glaciers melted and excess carbon dioxide precipitated on glaciogenic sediments as cap carbonates.

Whilst the Snowball Earth theory explains the wide distributions of glacial formations, it fails to shed light on the survival of living organisms. To counteract this, some researchers argue that sedimentary organic molecules, a molecular clock, and fossils from the late Neoproterozoic era are evidence that primitive eukaryotes such as sponges survived this severe ice age. Alternative models also propose that an ice-free open sea existed during the glaciation and acted as an oasis for marine life.

But what is understood is that the Marinoan glaciation and the succeeding extreme climatic transition likely had a marked impact on the biosphere. Shortly after the ice age, the Lantian biota, the earliest-known complex macroscopic multicellular eukaryotes, emerged. The Lantian biota includes macrofossils that are phylogenetically uncertain but morphologically and taxonomically diverse. Meanwhile, pre-Marinoan species have simple body plans with limited taxonomic variety.

Bacteria and eukaryote biomarkers demonstrate that bacteria dominated before the glaciation, whereas steranes/hopanes ratios illustrate that eukaryotes dominated just before it. However, the relationship between the biosphere changes and the Marinoan glaciation is unclear.

In 2011, Kaiho and his team traveled to Three Gorges, China under the guidance of China University of Science’s Dr. Jinnan Tong to take sedimentary rock samples from the deeper outcrops of marine sedimentary rocks. From 2015 onwards, Shizuya and Kaiho analyzed the biomarkers of algae, photosynthetic activity, bacteria, and eukaryotes from the rock samples.

They found photosynthetic activity based on n-C₁₇ + n-C₁₉ alkanes for algae and pristane + phytane during the Marinoan glaciation. Hopanes within the early and late carbonate deposition showed photosynthetic organisms and other bacteria entering a state of low productivity before recovering. And steranes from carbonates and mudstones after the cap carbonate deposition from the early Ediacaran period indicated the expansion of eukaryotes. The expansion of eukaryotes corresponded to the Lantian biota being morphologically diverse when compared to pre-Marinoan species.

Kaiho believes we are one step closer to understanding the evolutionary process that occurred before and after Snowball Earth. “The environmental stress of closed ocean environments for the atmosphere followed by high temperatures around 60°C may have produced more complex animals in the aftermath.” Their findings show that bacterial recovery preceded eukaryotes’ domination.

Kaiho’s team is doing further studies to clarify the relationship between climate change and the biosphere in other locations. They are also studying the relationship between atmospheric oxygen increases and animal evolution from the late Cryogenian to early Cambrian (650 to 500 million years ago).

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Soon after the Big Bang 13.8 billion years ago, the Universe was an unruly place. Galaxies constantly collided. Stars formed at an enormous rate inside gigantic gas clouds. However, after a few billion years of intergalactic chaos, the unruly, embryonic galaxies became more stable and over time matured into well-ordered spiral galaxies. The exact course of these developments has long been a mystery to the world’s astronomers. However, in a new study published in Monthly Notices of the Royal Astronomical Society, researchers have been able to provide some clarity on the matter.

“Using a supercomputer, we have created a high-resolution simulation that provides a detailed picture of a galaxy’s development since the Big Bang, and how young chaotic galaxies transition into well-ordered spirals” says Oscar Agertz, astronomy researcher at Lund University.

In the study, the astronomers, led by Oscar Agertz and Florent Renaud, use the Milky Way’s stars as a starting point. The stars act as time capsules that divulge secrets about distant epochs and the environment in which they were formed. Their positions, speeds and amounts of various chemical elements can therefore, with the assistance of computer simulations, help us understand how our own galaxy was formed.

“We have discovered that when two large galaxies collide, a new disc can be created around the old one due to the enormous inflows of star-forming gas. Our simulation shows that the old and new discs slowly merged over a period of several billion years. This is something that not only resulted in a stable spiral galaxy, but also in populations of stars that are similar to those in the Milky Way,” says Florent Renaud, astronomy researcher at Lund University.

The new findings will help astronomers to interpret current and future mappings of the Milky Way. The study points to a new direction for research in which the main focus will be on the interaction between large galaxy collisions and how spiral galaxies’ discs are formed. The research team in Lund has already started new super computer simulations in cooperation with the research infrastructure PRACE (Partnership for Advanced Computing in Europe).

“With the current study and our new computer simulations we will generate a lot of information which means we can better understand the Milky Way’s fascinating life since the beginning of the Universe,” concludes Oscar Agertz.

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