A paper describing the new reconstruction, which used microcomputed tomography (micro-CT) to scan the fossil and reveal vertebrae and ribs of the fish that were previously hidden beneath rock, appeared April 2 in the journal Proceedings of the National Academy of Sciences.

“Tiktaalik was discovered in 2004, but key parts of its skeleton were unknown,” said Tom Stewart, assistant professor of biology in the Eberly College of Science at Penn State and one of the leaders of the research team. “These new high-resolution micro-CT scans show us the vertebrae and ribs of Tiktaalik and allow us to make a full reconstruction of its skeleton, which is vital to understanding how it moved through the world.”

Unlike most fish, which have vertebrae and ribs that are the same along the length of the trunk, the axial skeletons of limbed vertebrates show dramatic differences in the vertebrae and ribs from the head region to the tail region. The evolution of this regionalization allowed the performance of specialized functions, one of which was a mechanical linkage between ribs in the sacral region to the pelvis that enabled support of the body by the hind limbs.

The pelvic fins of fish are evolutionarily related to hind limbs in tetrapods — four-limbed vertebrates, including humans. In fish, the pelvic fins and bones of the pelvic girdle are relatively small and float freely in the body. For the evolution of walking, the researchers explained, the hind limbs and pelvis became much larger and formed a connection to the vertebral column as a way of bracing the forces related to supporting the body.

“Tiktaalik is remarkable because it gives us glimpses into this major evolutionary transition,” Stewart said. “Across its whole skeleton, we see a combination of traits that are typical of fish and life in water as well as traits that are seen in land-dwelling animals.”

The original description of Tiktaalik focused on the front portion of the skeleton. Fossils were meticulously prepared to remove the surrounding matrix of rock and expose the skull, shoulder girdle and pectoral fins. The ribs in this area were large and expanded, suggesting that they may have supported the body in some way, but it was unclear exactly how they would have functioned. In 2014, the fish’s pelvis, discovered in the same location as the rest of the skeleton, was also cleaned of matrix and described.

“From past studies, we knew that the pelvis was large, and we had a sense that the hind fins were large too, but until now couldn’t say if or how the pelvis interacted with the axial skeleton,” Stewart said. “This reconstruction shows, for the first-time, how it all fit together and gives us clues about how walking might have first evolved.”

The researchers explained that, unlike our own hips where our bones fit tightly together, the connection between the pelvis and axial skeleton of Tiktaalik was likely a soft-tissue connection made of ligaments.

“Tiktaalik had specialized ribs that would have connected to the pelvis by a ligament,” Stewart said. “It’s astonishing really. This creature has so many traits — large pair of hind appendages, large pelvis, and connection between the pelvis and axial skeleton — that were key to the origin of walking. And while Tiktaalik probably wasn’t walking across land, it was definitely doing something new. This was a fish that could likely prop itself up and push with its hind fin.”

The new reconstruction of the skeleton also sheds light on specializations for head mobility in Tiktaalik and new details of the fish’s pelvic fin anatomy.

“It’s incredible to see the skeleton of Tiktaalik captured in such vivid detail,” said Neil Shubin, Robert R. Bensley Distinguished Service Professor of Organismal Biology and Anatomy at the University of Chicago and one of the authors of the paper. “This study sets the stage for ones that explore how the animal moved about and interacted with its environment 375 million years ago.”

In addition to Stewart and Shubin, the research team includes Justin B. Lemberg, Emily J. Hillan, and Isaac Magallanes at The University of Chicago, and Edward B. Daeschler at Academy of Natural Sciences of Drexel University.

Support from the Brinson Foundation, the Biological Sciences Division of The University of Chicago, an anonymous donor to the Academy of Natural Sciences of Drexel University, and the U.S. National Science Foundation funded this research. Fieldwork was made possible by the Polar Continental Shelf Project of Natural Resources, Canada; the Department of Heritage and Culture, Nunavut; the hamlets of Resolute Bay and Grise Fiord of Nunavut; and the Iviq Hunters and Trappers of Grise Fiord.

New research from Lan Yang, the Edwin H. & Florence G. Skinner Professor in the Preston M. Green Department of Electrical & Systems Engineering in the McKelvey School of Engineering at Washington University in St. Louis, unlocks the power of exceptional points (EPs) for advanced optical sensing. In a study published April 5 in Science Advances, Yang and first author Wenbo Mao, a doctoral student in Yang’s lab, showed that these unique EPs — specific conditions in systems where extraordinary optical phenomena can occur — can be deployed on conventional sensors to achieve a striking sensitivity to environmental perturbations.

Yang and Mao developed an EP-enhanced sensing platform that overcomes the limitations of previous approaches. Unlike traditional methods that require modifications to the sensor itself, their innovative system features an EP control unit that can plug into physically separated external sensors. This configuration allows EPs to be tuned solely through adjustments to the control unit, allowing for ultrahigh sensitivity without the need for complex modifications to the sensor.

“We’ve implemented a novel platform that can impart EP enhancement to conventional optical sensors,” Yang said. “This system represents a revolutionary extension of EP-enhanced sensing, significantly expanding its applicability and universality. Any phase-sensitive sensor can acquire improved sensitivity and reduced detection limit by connecting to this configuration. Simply by tuning the control unit, this EP configuration can adapt to various sensing scenarios, such as environmental detection, health monitoring and biomedical imaging.”

By decoupling the sensing and control functions, Yang and Mao have effectively skirted the stringent physical requirements for operating sensors at EPs that have so far hindered their widespread adoption. This clears the way for EP enhancement to be applied to a wide range of conventional sensors — including ring resonators, thermal and magnetic sensors, and sensors that pick up vibrations or detect perturbations in biomarkers — vastly improving the detection limit of sensors scientists are already using. With the control unit set to an EP, the sensor can operate differently — not at an EP — and still reap the benefits of EP enhancement.

As a proof-of-concept, Yang’s team tested a system’s detection limit, or ability to detect weak perturbations over system noise. They demonstrated a six-fold reduction in the detection limit of a sensor using their EP-enhanced configuration compared to the conventional sensor.

“With this work, we’ve shown that we can significantly enhance our ability to detect perturbations that have weak signals,” Mao said. “We’re now focused on bringing that theory to broad applications. I’m specifically focused on medical applications, especially working to enhance magnetic sensing, which could be used to improve MRI technology. Currently, MRIs require a whole room with careful temperature control. Our EP platform could be used to enhance magnetic sensing to enable portable, bedside MRI.”

A new study led by scientists at the University of Alaska Fairbanks and the University of Reading calls into question Bergmann’s rule, an 1800s-era scientific principle stating that animals in high-latitude, cooler climates tend to be larger than close relatives living in warmer climates.

The fossil record shows otherwise.

“Our study shows that the evolution of diverse body sizes in dinosaurs and mammals cannot be reduced to simply being a function of latitude or temperature,” said Lauren Wilson, a UAF graduate student and a lead author of a paper published today in the journal Nature Communications. “We found that Bergmann’s rule is only applicable to a subset of homeothermic animals (those that maintain stable body temperatures), and only when you consider temperature, ignoring all other climatic variables. This suggests that Bergmann’s ‘rule’ is really the exception rather than the rule.”

The study started as a simple question Wilson discussed with her undergraduate advisor: Does Bergmann’s rule apply to dinosaurs?

After evaluating hundreds of data points gleaned from the fossil record, the answer seemed a solid “no.”

The dataset included the northernmost dinosaurs known to scientists, those in Alaska’s Prince Creek Formation. They experienced freezing temperatures and snowfall. Despite this, the researchers found no notable increase in body size for any of the Arctic dinosaurs.

Next the researchers tried the same evaluation with modern mammals and birds, the descendants of prehistoric mammals and dinosaurs. The results were largely the same: Latitude was not a predictor of body size in modern bird and mammal species. There was a small relationship between the body size of modern birds and temperature, but the same was not the case for prehistoric birds.

The researchers say the study is a good example of how scientists can and should use the fossil record to test current-day scientific rules and hypotheses.

“The fossil record provides a window into completely different ecosystems and climate conditions, allowing us to assess the applicability of these ecological rules in a whole new way,” said Jacob Gardner, a postdoctoral researcher at the University of Reading and the other lead author of the paper.

Scientific rules should apply to fossil organisms in the same way they do modern organisms, said Pat Druckenmiller, director of the University of Alaska Museum of the North and one of the co-authors of the paper.

“You can’t understand modern ecosystems if you ignore their evolutionary roots,” he said. “You have to look to the past to understand how things became what they are today.”

The paper is the first clear evidence demonstrating an effect of climate change on this charismatic species. Specifically, the paper shows that July rainfall results in reduced July water clarity in loon territories. Reduced water clarity, in turn, makes it difficult for adult loons to find and capture their prey (mainly small fishes) under water, so they are not able to meet their chicks’ metabolic needs. The result is low chick weight and higher chick mortality. Since loons use the same foraging mode across their breeding range, the impact of water clarity on loon breeding success found in Wisconsin is likely to be echoed from Alaska to Iceland.

Piper, in collaboration with Max Gline and Kevin Rose from Rensselaer Polytechnic Institute, reports several important findings. Over the past 25 years, there has been a consistent decline in water clarity. During the same period, body weights of adult males, adult females, and chicks have also declined. By searching among a large number of environmental variables, the authors were able to pinpoint mean water clarity during the month of July — the month of most rapid growth in chicks — as the strongest predictor of body weight. In a separate analysis, the authors found that rainfall in July impacts water clarity negatively. That is, heavy rainfall in July results in reduced water clarity, whereas light rainfall leads to high clarity and good foraging conditions for loons. Consequently, the rise in rainfall observed in recent decades, attributed to climate change, poses challenges for adult loons in feeding their offspring and diminishes chick survival rates.

The precise way in which rainfall leads to reduced water clarity is currently under investigation. The authors suggest that rain might carry dissolved organic matter (DOM) into lakes from adjacent streams and shoreline areas. But it is also possible that nutrients (such as fertilizers used on lawns by lake residents), pet waste, or even leaks from septic systems might be to blame.

This study represents a unique partnership between diverse fields. Piper’s three-decade-long study of loon behavioral ecology in northern Wisconsin intersects with Gline and Rose’s use of Landsat imagery to calculate freshwater lake clarity. Combining data from these sources has illuminated the cause behind the sharp decline in breeding success in northern Wisconsin. It is now evident that both the loss of water clarity — as well as increasing populations of black flies, which have increased due to greater rainfall — are to blame for the population downturn.

“Few animals on Earth are at once so beloved and so poorly understood as Common Loons,” Piper said. “This partnership between a loon behaviorist and lake ecologists who collect satellite data on water clarity has given us a unique and powerful window onto foraging efficiency and the loon population as a whole that might help us conserve the species.”

Piper is in the process of establishing a second marked study population of loons, equal in size to the first, in Minnesota. There he will determine whether the recent decline in loon breeding success recorded by the Minnesota Department of Natural Resources results from a loss of water clarity, as in Wisconsin.

“We found several proteins important for vision that were affected by thermal stress,” says Dr Qiaz Hua, a recent PhD graduate from the University of Adelaide’s School of Biological Sciences.

“One of them is a structural protein found in high abundance in animal eye lenses to preserve lens transparency and optical clarity, and another is responsible for the regeneration of visual pigments in the photoreceptors of the eyes.

“The levels of both of these proteins were significantly reduced under projected ocean warming conditions, which suggests that octopus vision is likely to be impaired under thermal stress.”

Octopuses are highly visual animals, with 70 per cent of the octopus brain dedicated to vision — which is 20 per cent more than in humans.

“The primary functions of vision include but are not limited to visual acuity, discrimination of brightness, depth perception, motion detection and polarisation, and it is crucial for detecting predator and prey as well as for communication,” says Dr Hua.

“Having impaired vision will affect an octopus’s chances of survival in the wild through increased predator risk as well as lower foraging success.”

To make this finding, the research team, including academics from the University of South Australia, University of California Davis, and the South Australian Research and Development Institute’s aquatic sciences division, exposed Octopus berrima embryos to different temperature treatments, a control 19°C exposure, 22°C to model current summer temperatures, and 25°C to model projected summer temperatures.

“The future-projected temperature was based on the Intergovernmental Panel on Climate Change’s projected increase of about 3°C of warming by 2100,” Dr Hua says.

In addition to impaired vision, Dr Hua found increased ocean water temperatures would have a negative effect on octopus broods.

“We found a high mortality rate under future warming conditions. Out of three replicate octopus broods, none of the eggs hatched for two of them and less than half of the eggs hatched for the remaining brood,” Dr Hua says.

“In the broods where none of the eggs hatched, the mothers died naturally while the eggs were still in early development stages.

“Because maternal care of embryos occurs in octopuses, global warming could have a simultaneous impact on multiple generations, with the low survival rate of the embryos caused by the direct effect of thermal stress as well as the indirect effect of thermal stress on the mothers.

“Our study shows that even for a highly adaptable taxon like octopuses, they may not be able to survive future ocean changes.”

Other effects of higher temperatures which have been observed in octopuses include a higher metabolic rate, reduced size at maturity, and even a range shift in the distribution of some species.

“We hope that future research would examine a combination of environmental stressors including ocean acidification, warming, and deoxygenation,” Dr Hua says.

“It would also be useful to do a transgenerational experiment to see if sensitivity or tolerance to the environmental stressors is passed down from one generation to the next, which help us understand the impacts on the continuation of the species.”

WASP-76b is an ultra-hot giant planet. Orbiting its host star twelve times closer than Mercury orbits our Sun, it receives more than 4,000 times the Sun’s radiation on Earth. ”The exoplanet is ‘inflated’ by the intense radiation from its star. So, although it is 10% less massive than our cousin Jupiter, it is almost twice as big,” explains Monika Lendl, assistant professor in the Department of Astronomy of the UNIGE Faculty of Science, and co-author of the study.

Since its discovery in 2013, WASP-76b has been the subject of intense scrutiny by astronomers. A strangely hellish picture has emerged. One side of the planet is always facing its star, reaching temperatures of 2,400 degrees Celsius. Elements that would form rocks on Earth melt and evaporate here, before condensing on the slightly cooler night side, creating clouds of iron that drip molten iron rain.

The crucial contribution of CHEOPS

One of the most disturbing observations for astronomers is the asymmetry between the planet’s two terminators. The terminator is the imaginary line that separates the day and night sides of a planet. In the case of WASP-76b, the observations show an increase in the amount of light from the terminator to the east of the planet compared with the one to the west.

To solve this mystery, astronomers used no fewer than twenty-three observations with the CHEOPS space telescope, spread over three years. The ESA satellite, which is piloted by Switzerland and has its scientific operations centre at the UNIGE Department of Astronomy, observed numerous secondary eclipses of the planet (when it passes behind its star) and several phase curves (continuous observation during a complete revolution of the planet).

Combining these new data with those from other telescopes (TESS, Hubble and Spitzer), the astronomers were able to put forward a surprising hypothesis to explain the excess luminous flux on the eastern side of the planet: ”This unexpected glow could be caused by a strong, localised and anisotropic reflection — i.e. one that depends on direction — what we call a glory,” explains Olivier Demangeon, researcher at the Instituto de Astrofísica e Ciências do Espaço in Portugal and lead author of the study.

A first outside our solar system

Glories are common phenomena on Earth. They have also been observed on Venus. The effect, similar to a rainbow, occurs when light is reflected by clouds made up of perfectly uniform droplets. In the case of Earth, the droplets are made out of water, but the nature of these droplets on WASP-76b remains mysterious. It could be iron, as this has already been detected in the planet’s extremely hot atmosphere. The detection of this phenomenon on WASP-76b is the first of its kind outside our solar system.

”The reason why no such glory has ever been observed outside our solar system is that this phenomenon requires very specific conditions. First of all, the atmospheric particles must be almost perfectly spherical, completely uniform and sufficiently stable to be observed throughout a long time. These droplets have to be directly illuminated by the planet’s host star, and the observer — in this case CHEOPS — must be in the right position,” explains Olivier Demangeon.

Results to be confirmed

Further data will be needed to confirm with certainty that this intriguing excess of light on the eastern terminator of WASP-76b is a glory. This confirmation would attest to the presence of clouds made up of perfectly spherical droplets that have existed for at least three years, or that are constantly renewing themselves. For such clouds to persist, the temperature of the atmosphere would also have to be stable over time — a fascinating and detailed insight into what could be happening on WASP-76b.

Detecting such tiny phenomena at such a great distance will enable scientists and engineers to identify others that are just as crucial. For example, the reflection of starlight off liquid lakes and oceans — a necessary condition for habitability.