It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Saturday, August 20, 2022
Harnessing the heart regeneration ability of marsupials
IMAGE: THIS RESEARCH DISCOVERED THAT OPOSSUM HEARTS ARE ABLE TO REGENERATE 2 WEEKS AFTER BIRTH BECAUSE AMPK ACTIVITY WAS STILL INACTIVE. APPLYING THIS KNOWLEDGE TO MICE, RESEARCHERS WERE ABLE TO PROLONG THE PERIOD OF TIME THAT MOUSE HEARTS CAN REGENERATE AFTER BIRTH BY BLOCKING AMPK ACTIVITY.view more
CREDIT: RIKEN
Wataru Kimura and colleagues at the RIKEN Center for Biosystems Dynamics Research (BDR) in Japan have discovered how the hearts of newborn marsupials retain the ability to regenerate for several weeks. Using this knowledge, the team was able to repair mouse hearts that were damaged a week after birth. The findings, published in the scientific journal Circulation, are expected to contribute to the development of regenerative heart medicines.
Heart disease is a leading cause of human death and is associated with numerous other secondary illnesses. For humans and other mammals, damaged heart muscle—such as occurs after a heart attack—cannot be naturally repaired because matured heart-muscle cells do not regenerate. As with all tissue regeneration, heart repair requires the birth of new cells, which can only happen through the process of cell division, when one cell becomes two. In most mammalian hearts, muscle-cell division remains possible just after birth, but disappears quickly after a couple days.
However, unlike other mammals, marsupials like kangaroos and koalas are born in an underdeveloped state and many of their internal organs continue to grow after birth, including their hearts. However, not much is known about their capacity for heart regeneration. The team at RIKEN BDR hypothesized that this post-natal heart growth is possible because marsupial heart-muscle cells retain the ability to divide, and that this would allow their hearts to regenerate after injury. They set out to test this theory in the opossum.
They observed that opossum hearts continued to grow for several weeks after birth. They found that the hearts of two-week-old opossums resembled those of one-day-old mice, and that opossum heart-muscle cells continued to divide for weeks after birth. Experimentally induced heart damage at this age repaired itself within a month, indicating that as long as heart cells continue to divide, the heart can be repaired. These results confirmed their hypothesis, and as Kimura notes, “cardiac regeneration for more than two weeks after birth in the opossum is the longest duration observed among mammals investigated to date.”
The next step was to figure out how this is possible in opossums but not mice. Gene-expression comparisons showed that two-week-old opossums were similar to mice that were only a few days old. The researchers next looked for changes in gene expression that occurred in both animals around the time that heart regeneration was no longer possible. The common factor was a protein called AMPK. Further experiments showed that activation of AMPK in both mice and opossums coincided with the stoppage of cell division in heart muscle. Therefore, the next hypothesis was that inhibiting AMPK or its ability to work could extend the period during which heart regeneration is possible. As Kimura explains, “if we could exploit the molecular pathway that determines the capacity for cardiac regeneration, we should be able to establish novel therapeutic approaches for treating cardiovascular disease.”
They tested this hypothesis in both opossums and mice, and were successful in both cases. In particular, injecting neo-natal mice with AMPK inhibitors allowed hearts that were experimentally damaged a week after birth to regenerate and regain normal function, with minimal scarring. Thus, the researchers were able to use what they learned from marsupials and induce heart regeneration in a regular mammal.
Next on the research agenda is figuring out what triggers AMPK expression at birth in mice but not in opossums. “One important and exciting question is how neonatal marsupials retain regenerative capacity in extrauterine environments, ” says Kimura. “The answers could lead to therapies that can induce heart regeneration in adults.”
ASSOCIATION OF UNIVERSITIES FOR RESEARCH IN ASTRONOMY (AURA)
IMAGE: NESTLED IN THE CENTER OF THE TARANTULA NEBULA IN THE LARGE MAGELLANIC CLOUD IS THE LARGEST STAR YET DISCOVERED. WITH THE HELP OF THE ZORRO IMAGER AND THE POWER OF THE 8.1-METER GEMINI SOUTH TELESCOPE IN CHILE, ASTRONOMERS HAVE PRODUCED THE SHARPEST IMAGE EVER OF THIS STAR. THIS NEW IMAGE CHALLENGES OUR UNDERSTANDING OF THE MOST MASSIVE STARS AND SUGGESTS THAT THEY MAY NOT BE AS MASSIVE AS PREVIOUSLY THOUGHT.view more
CREDIT: INTERNATIONAL GEMINI OBSERVATORY/NOIRLAB/NSF/AURA ACKNOWLEDGMENT: IMAGE PROCESSING: T.A. RECTOR (UNIVERSITY OF ALASKA ANCHORAGE/NSF’S NOIRLAB), M. ZAMANI (NSF’S NOIRLAB) & D. DE MARTIN (NSF’S NOIRLAB)
By harnessing the capabilities of the 8.1-meter Gemini South telescope in Chile, which is part of the International Gemini Observatory operated by NSF’s NOIRLab, astronomers have obtained the sharpest image ever of the star R136a1, the most massive known star in the Universe. Their research, led by NOIRLab astronomer Venu M. Kalari, challenges our understanding of the most massive stars and suggests that they may not be as massive as previously thought.
Astronomers have yet to fully understand how the most massive stars — those more than 100 times the mass of the Sun — are formed. One particularly challenging piece of this puzzle is obtaining observations of these giants, which typically dwell in the densely populated hearts of dust-shrouded star clusters. Giant stars also live fast and die young, burning through their fuel reserves in only a few million years. In comparison, our Sun is less than halfway through its 10 billion year lifespan. The combination of densely packed stars, relatively short lifetimes, and vast astronomical distances makes distinguishing individual massive stars in clusters a daunting technical challenge.
By pushing the capabilities of the Zorro instrument on the Gemini South telescope of the International Gemini Observatory, operated by NSF’s NOIRLab, astronomers have obtained the sharpest-ever image of R136a1 — the most massive known star. This colossal star is a member of the R136 star cluster, which lies about 160,000 light-years from Earth in the center of the Tarantula Nebula in the Large Magellanic Cloud, a dwarf companion galaxy of the Milky Way.
Previous observations suggested that R136a1 had a mass somewhere between 250 to 320 times the mass of the Sun. The new Zorro observations, however, indicate that this giant star may be only 170 to 230 times the mass of the Sun. Even with this lower estimate, R136a1 still qualifies as the most massive known star.
Astronomers are able to estimate a star's mass by comparing its observed brightness and temperature with theoretical predictions. The sharper Zorro image allowed NSF's NOIRLab astronomer Venu M. Kalari and his colleagues to more accurately separated the brightness of R136a1 from its nearby stellar companions, which led to a lower estimate of its brightness and therefore its mass.
“Our results show us that the most massive star we currently know is not as massive as we had previously thought,” explained Kalari, lead author of the paper announcing this result. “This suggests that the upper limit on stellar masses may also be smaller than previously thought.”
This result also has implications for the origin of elements heavier than helium in the Universe. These elements are created during the cataclysmicly explosive death of stars more than 150 times the mass of the Sun in events that astronomers refer to as pair-instability supernovae. If R136a1 is less massive than previously thought, the same could be true of other massive stars and consequently pair instability supernovae may be rarer than expected.
The star cluster hosting R136a1 has previously been observed by astronomers using the NASA/ESA Hubble Space Telescope and a variety of ground-based telescopes, but none of these telescopes could obtain images sharp enough to pick out all the individual stellar members of the nearby cluster.
Gemini South’s Zorro instrument was able to surpass the resolution of previous observations by using a technique known as speckle imaging, which enables ground-based telescopes to overcome much of the blurring effect of Earth’s atmosphere [1]. By taking many thousands of short-exposure images of a bright object and carefully processing the data, it is possible to cancel out almost all this blurring [2]. This approach, as well as the use of adaptive optics, can dramatically increase the resolution of ground-based telescopes, as shown by the team’s sharp new Zorro observations of R136a1 [3].
“This result shows that given the right conditions an 8.1-meter telescope pushed to its limits can rival not only the Hubble Space Telescope when it comes to angular resolution, but also the James Webb Space Telescope,” commented Ricardo Salinas, a co-author of this paper and the instrument scientist for Zorro. “This observation pushes the boundary of what is considered possible using speckle imaging.”
“We began this work as an exploratory observation to see how well Zorro could observe this type of object,” concluded Kalari. “While we urge caution when interpreting our results, our observations indicate that the most massive stars may not be as massive as once thought.”
Zorro and its twin instrument `Alopeke are identical imagers mounted on the Gemini South and Gemini North telescopes, respectively. Their names are the Hawaiian and Spanish words for “fox” and represent the telescopes’ respective locations on Maunakea in Hawai‘i and on Cerro Pachón in Chile. These instruments are part of the Gemini Observatory’s Visiting Instrument Program, which enables new science by accommodating innovative instruments and enabling exciting research. Steve B. Howell, current chair of the Gemini Observatory Board and senior research scientist at the NASA Ames Research Center in Mountain View, California, is the principal investigator on both instruments.
“Gemini South continues to enhance our understanding of the Universe, transforming astronomy as we know it. This discovery is yet another example of the scientific feats we can accomplish when we combine international collaboration, world-class infrastructure, and a stellar team,” said NSF Gemini Program Officer Martin Still.
This comparison image shows the exceptional sharpness and clarity of the Zorro imager on the 8.1-meter Gemini South telescope in Chile (left) when compared to an earlier image taken with the NASA/ESA Hubble Space Telescope (right). The new Gemini South image allowed astronomers to clearly distinguish the star R136a1 from its nearby stellar companions, providing the data needed to reveal that – while still the most massive star known in the Universe – it is less massive than previously thought.
CREDIT
International Gemini Observatory/NOIRLab/NSF/AURA Acknowledgment: Image processing: T.A. Rector (University of Alaska Anchorage/NSF’s NOIRLab), M. Zamani (NSF’s NOIRLab) & D. de Martin (NSF’s NOIRLab); NASA/ESA Hubble Space Telescope
This is an illustration of R136a1, the largest known star in the Universe, which resides inside the Tarantula Nebula in the Large Magellanic Cloud. By harnessing the capabilities of the 8.1-meter Gemini South telescope in Chile, a team of astronomers has obtained the sharpest image ever of this colossal star.
CREDIT
NOIRLab/NSF/AURA/J. da Silva/Spaceengine
Notes
[1] The blurring effect of the atmosphere is what makes stars twinkle at night, and astronomers and engineers have devised a variety of approaches to dealing with atmospheric turbulence. As well as placing observatories at high, dry sites with stable skies, astronomers have equipped a handful of telescopes with adaptive optics systems, assemblies of computer-controlled deformable mirrors and laser guide stars that can correct for atmospheric distortion. In addition to speckle imaging, Gemini South is able to use its Gemini Multi-Conjugate Adaptive Optics System to counteract the blurring of the atmosphere.
[2] The individual observations captured by Zorro had exposure times of just 60 milliseconds, and 40,000 of these individual observations of the R136 cluster were captured over the course of 40 minutes. Each of these snapshots is so short that the atmosphere didn’t have time to blur any individual exposure, and by carefully combining all 40,000 exposures the team could build up a sharp image of the cluster.
[3] When observing in the red part of the visible electromagnetic spectrum (about 832 nanometers), the Zorro instrument on Gemini South has an image resolution of about 30 milliarcseconds. This is slightly better resolution than NASA/ESA/CSA’s James Webb Space Telescope and about three-times sharper resolution achieved by the Hubble Space Telescope at the same wavelength.
More information
This research was presented in the paper “Resolving the core of R136 in the optical” to appear in The Astrophysical Journal.
The team is composed of Venu M. Kalari (Gemini Observatory/NSF's NOIRLab and Departamento de Astronomia, Universidad de Chile), Elliott P. Horch (Department of Physics, Southern Connecticut State University), Ricardo Salinas (Gemini Observatory/NSF's NOIRLab), Jorick S. Vink (Armagh Observatory and Planetarium), Morten Andersen (Gemini Observatory/NSF's NOIRLab and the European Southern Observatory), Joachim M. Bestenlehner (Department of Physics and Astronomy, University of Sheffield), and Monica Rubio (Departamento de Astronomia, Universidad de Chile).
NSF’s NOIRLab (National Optical-Infrared Astronomy Research Laboratory), the US center for ground-based optical-infrared astronomy, operates the international Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), Kitt Peak National Observatory (KPNO), Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and Vera C. Rubin Observatory (operated in cooperation with the Department of Energy’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona. The astronomical community is honored to have the opportunity to conduct astronomical research on Iolkam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence that these sites have to the Tohono O'odham Nation, to the Native Hawaiian community, and to the local communities in Chile, respectively.
IMAGE: THE ERUPTION CREATED AN INITIAL WAVE 90 METRES HIGHview more
CREDIT: UNIVERSITY OF BATH
Wave created by Tonga volcano eruption reached 90 metres - nine times taller than 2011 Japan tsunami
New research reveals more about the magnitude of January eruption, as researchers call for better preparedness
The eruption of the Hunga Tonga-Hunga Ha’apai volcano in January created an initial wave 90 metres high – almost the height of the Statue of Liberty (93m)
University of Bath tsunami expert calls for better warning systems to detect volcanic eruptions, saying systems are 30 years behind comparable earthquake detection tools
The initial tsunami wave created by the eruption of the underwater Hunga Tonga Ha’apai volcano in Tonga in January 2022 reached 90 metres in height, around nine times taller than that from the highly destructive 2011 Japan tsunami, new research has found.
An international research team says the eruption should serve as a wake-up call for international groups looking to protect people from similar events in future, claiming that detection and monitoring systems for volcano-based tsunamis are ’30 years behind’ comparable tools used to detect earthquake-based events.
Dr Mohammad Heidarzadeh, Secretary-General of the International Tsunami Commission and a senior lecturer in the University of Bath’s Department of Architecture & Civil Engineering, authored the research alongside colleagues based in Japan, New Zealand, the UK and Croatia.
By comparison, the largest tsunami waves due to earthquakes before the Tonga event were recorded following the Tōhoku earthquake near Japan in 2011 and the 1960 Chilean earthquake, reached 10 metres in initial height. Those were more destructive as they happened closer to land, with waves that were wider.
Dr Heidarzadeh says the Tonga tsunami should serve as a wake-up call for more preparedness and understanding of the causes and signs of tsunamis cause by volcanic eruptions. He says: “The Tongan tsunami tragically killed five people and caused large scale destruction, but its effects could have been even greater had the volcano been located closer to human communities. The volcano is located approximately 70 km from the Tongan capital Nuku'alofa – this distance significantly minimized its destructive power.
“This was a gigantic, unique event and one that highlights that internationally we must invest in improving systems to detect volcanic tsunamis as these are currently around 30 years behind the systems we used to monitor for earthquakes. We are under-prepared for volcanic tsunamis.”
The research was carried out by analysing ocean observation data recordings of atmospheric pressure changes and sea level oscillations, in combination with computer simulations validated with real-world data.
The research team found that the tsunami was unique as the waves were created not only by the water displaced by the volcano’s eruption, but also by huge atmospheric pressure waves, which circled around the globe multiple times. This ‘dual mechanism’ created a two-part tsunami – where initial ocean waves created by the atmospheric pressure waves were followed more than one hour later by a second surge created by the eruption’s water displacement.
This combination meant tsunami warning centres did not detect the initial wave as they are programmed to detect tsunamis based on water displacements rather than atmospheric pressure waves.
The research team also found that the January event was among very few tsunamis powerful enough to travel around the globe – it was recorded in all world’s oceans and large seas from Japan and the United States’ western seaboard in the North Pacific Ocean to the coasts within the Mediterranean Sea.
The paper, co-authored by colleagues from New Zealand’s GNS Science, the Association for the Development of Earthquake Prediction in Japan, the University of Split in Croatia and at London’s Brunel University, was published this week in Ocean Engineering.
Dr Aditya Gusman, Tsunami Modeller at the New Zealand-based geoscience service, says: “The 2018 Anak Krakatau volcano and 2022 Hunga Tonga-Hunga Ha'apai volcano eruptions clearly showed us that coastal areas surrounding volcano islands are at risk of being hit by destructive tsunamis. Although it may be preferable to have low-lying coastal areas completely clear from residential buildings, such a policy may not be practical for some places as volcanic tsunamis can be considered infrequent events.”
Co-author Dr Jadranka Šepić, from the University of Split, Croatia, adds: “What is important is to have efficient warning systems, which include both real-time warnings and education on what to do in a case of a tsunami or warning - such systems save lives. In addition, at volcanic areas, monitoring of volcanic activity should be organized, and more high-quality research into volcanic eruptions and areas at hazard is always a good idea.”
Snapshots of tsunami propagation at different times for the 15 January 2022 Tonga tsunami from our source model S6.
CREDIT
University of Bath
The paper Estimating the eruption-induced water displacement source of the 15 January 2022 Tonga volcanic tsunami from tsunami spectra and numerical modelling is published in Ocean Engineering. https://doi.org/10.1016/j.oceaneng.2022.112165
For more information or to request an interview, contact Will McManus at the University of Bath at wem25@bath.ac.uk / press@bath.ac.uk or on +44 (0)1225 385798.
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HARVARD UNIVERSITY, DEPARTMENT OF ORGANISMIC AND EVOLUTIONARY BIOLOGY
IMAGE: ARTISTIC RECONSTRUCTION OF THE REPTILE ADAPTIVE RADIATION IN A TERRESTRIAL ECOSYSTEM DURING THE WARMEST PERIOD IN EARTH'S HISTORY. IMAGE DEPICTS A MASSIVE, BIG-HEADED, CARNIVOROUS ERYTHROSUCHID (CLOSE RELATIVE TO CROCODILES AND DINOSAURS) AND A TINY GLIDING REPTILE AT ABOUT 240 MILLION YEARS AGO. THE ERYTHROSUCHID IS CHASING THE GLIDING REPTILE AND IT IS PROPELLING ITSELF USING A FOSSILIZED SKULL OF THE EXTINCT DIMETRODON (EARLY MAMMALIAN ANCESTOR) IN A HOT AND DRY RIVER VALLEY.view more
CREDIT: IMAGE CREATED BY HENRY SHARPE
Studying climate change-induced mass extinctions in the deep geological past allows researchers to explore the impact of environmental crises on organismal evolution. One principal example is the Permian-Triassic climatic crises, a series of climatic shifts driven by global warming that occurred between the Middle Permian (265 million years ago) and Middle Triassic (230 million years ago). These climatic shifts caused two of the largest mass extinctions in the history of life at the end of the Permian, the first at 261myo and the other at 252myo, the latter eliminating 86% of all animal species worldwide.
The end-Permian extinctions are important not only because of their magnitude, but also because they mark the onset of a new era in the history of the planet when reptiles became the dominant group of vertebrate animals living on land. During the Permian, vertebrate faunas on land were dominated by synapsids, the ancestors of mammals. After the Permian extinctions, in the Triassic Period (252-200 million years ago), reptiles evolved at rapid rates, creating an explosion of reptile diversity. This expansion was key to the construction of modern ecosystems and many extinct ecosystems. These rapid rates of evolution and diversification were believed by most paleontologists to be due to the extinction of competitors allowing reptiles to take over new habitats and food resources that several synapsid groups had dominated before their extinction.
However, in a new study in Sciences Advancesresearchers in the Department of Organismic and Evolutionary Biology and the Museum of Comparative Zoology at Harvard University and collaborators reveal the rapid evolution and radiation of reptiles began much earlier, before the end of the Permian, in connection to the steadily increasing global temperatures through a long series of climatic changes that spanned almost 60 million years in the geological record.
“We found that these periods of rapid evolution of reptiles were intimately connected to increasing temperatures. Some groups changed really fast and some less fast, but nearly all reptiles were evolving much faster than they ever had before,” said lead author postdoctoral fellow Tiago R Simões.
Previous studies on the impacts of these changes have often neglected terrestrial vertebrates due to limited data availability, focusing mostly on the response from marine animals
In this study, Simões and senior author Professor Stephanie E. Pierce (both at Harvard) worked alongside collaborators Professor Michael Caldwell (University of Alberta, Canada) and Dr. Christian Kammerer (North Carolina Museum of Natural Sciences) to examine early amniotes, which represent the forerunners of all modern mammals, reptiles, birds, and their closest extinct relatives, at the initial phase of their evolution. At this point in time the first groups of reptiles and mammal ancestors were splitting from each other and evolving along their own separate evolutionary paths.
“Reptiles represent an ideal and rare terrestrial system to study this question as they have a relatively good fossil record and survived a series of climatic crises including the ones leading up to the largest extinction in the history of complex life, the Permian-Triassic mass extinction,” said Simões.
Reptiles were relatively rare during the Permian compared to mammalian ancestors. However, things took a major shift during the Triassic when reptiles underwent a massive explosion in the number of species and morphological variety. This lead to the appearance of most of the major living groups of reptiles (crocodiles, lizards, turtles) and several groups that are now entirely extinct.
The researchers created a dataset based on extensive first-hand data collection of more than 1,000 fossil specimens from 125 species of reptiles, synapsids, and their closest relatives during approximately 140 million years before and after the Permian-Triassic extinction. They then analyzed the data to detect when these species first originated and how fast they were evolving using state-of-the-art analytical techniques such as Bayesian evolutionary analysis, which is also used to understand the evolution of viruses such as SARS-COVID 19. The researchers then combined the new dataset with global temperature data spanning several million years in the geological record to provide a broad overview of the animals’ major adaptive response towards climatic shifts.
“Our results reveal that periods of fast climatic shifts and global warming are associated with exceptionally high rates of anatomical change in most groups of reptiles as they adapted to new environmental conditions,” said Pierce, “and this process started long before the Permian-Triassic extinction, since at least 270 million years ago, indicating that the diversification of reptile body plans was not triggered by the P-T extinction event as previously thought, but in fact started tens of million years before that.”
“One reptile lineage, the lepidosaurs, which gave rise to the first lizards and tuataras, veered in the opposite direction of most reptile groups and underwent a phase of very slow rates of change to their overall anatomy,” said Simões, “essentially, their body plans were constrained by natural selection, instead of going rogue and radically changing like most other reptiles at the time.” The researchers suggest this is due to pre-adaptations on their body size to better cope with high temperatures.
“The physiology of organisms is really dependent on their body size,” said Simões, “small-bodied reptiles can better exchange heat with their surrounding environment. The first lizards and tuataras were much smaller than other groups of reptiles, not that different from their modern relatives, and so they were better adapted to cope with drastic temperature changes. The much larger ancestors of crocodiles, turtles, and dinosaurs could not lose heat as easily and had to quickly change their bodies in order to adapt to the new environmental conditions.”
Simões, Pierce, and collaborators also mapped out how body size changed across geographical regions during this timeframe. They revealed that climatic pressures on body size were so high there was a maximum body size for reptiles to survive in tropical regions during the lethally hot periods of this time.
“Large-sized reptiles basically took two routes to deal with these climate shifts,” said Pierce, “they either migrated closer to temperate regions or invaded the aquatic world where they didn’t need to worry about overheating because water can absorb heat and maintain its temperature much better than air.”
“This strong association between rising temperatures in the geological past and a biological response by dramatically different groups of reptiles suggests climate change was a key factor in explaining the origin and the explosion of new reptile body plans during the latest Permian and Triassic,” said Simões.
Evolutionary response from reptiles to global warming and fast climatic changes. Rates of evolution (adaptive anatomical changes) in reptiles start increasing early in the Permian (at about 294 million years ago), which also marks the onset of the longest period of successive fast climatic shifts in the geological record. From 261 until 235 million years ago, increased global warming from massive volcanic eruption contributed to further climate change and led to the hottest period in Earth’s history. This resulted in two mass extinctions and the demise of reptile competitors on land (mammalian ancestors). The most intensive period of global warming coincided with the fastest rates of evolution in reptiles, marking the diversification of reptile body plans and the origin of modern reptile groups
CREDIT
Figure by Tiago Simões
The researchers would like to thank the Museum of Comparative Zoology (MCZ), Harvard University, vertebrate paleontology staff and the curators across 50+ natural history collections worldwide for their help with specimen access. Funding was provided by: Alexander Agassiz Postdoctoral Fellowship, MCZ; National Sciences and Engineering Research Council of Canada (NSERC) postdoctoral fellowship; Grant KA 4133/1-1 from the Deutsche Forschungsgemeinschaft; NSERC Discovery Grant #23458 and NSERC Accelerator Grant; Faculty of Science, Chairs Research Allowance, University of Alberta; Lemann Brazil Research Fund; Funds made available through Harvard University.
Just over 250 million years ago during the end of the Permian period and start of the Triassic, reptiles had one heck of a coming out party.
Their rates of evolution and diversity started exploding, leading to a dizzying variety of abilities, body plans, and traits, and helping to firmly establish both their extinct lineages and those that still exist today as one of the most successful and diverse animal groups the world has ever seen. For the longest time, this flourish was explained by their competition being wiped out by two of the biggest mass extinction events (around 261 and 252 million years ago) in the history of the planet.
A new Harvard-led study has rewritten that explanation by reconstructing how the bodies of ancient reptiles changed and by comparing it against millions of years of climate change.
Harvard paleontologist Stephanie Pierce’s lab shows that the morphological evolution and diversification seen in early reptiles not only started years before these mass extinction events but instead were directly driven by what caused them in the first place — rising global temperatures due to climate change.
“We are suggesting that we have two major factors at play — not just this open ecological opportunity that has always been thought by several scientists — but also something that nobody had previously come up with, which is that climate change actually directly triggered the adaptive response of reptiles to help build this vast array of new body plans and the explosion of groups that we see in the Triassic,” said Tiago R. Simões, a postdoctoral fellow in the Pierce lab and lead author on the study.
“Basically, [rising global temperatures] triggered all these different morphological experiments — some that worked quite well and survived for millions of years up to this day, and some others that basically vanished a few million years later,” Simões added.
In the paper, which published Friday in Science Advances, the researchers lay out the vast anatomical changes that took place in many reptile groups, including the forerunners of crocodiles and dinosaurs, in direct response to major climate shifts concentrated between 260 to 230 million years ago.
The study provides a close look at how a large group of organisms evolve because of climate change, which is especially pertinent today as temperatures continually rise. In fact, the rate of carbon dioxide released into the atmosphere today is about nine times what they were during the timeframe that culminated in the biggest climate change-driven mass extinction of all time 252 million years ago: the Permian-Triassic mass extinction.
“Major shifts in global temperature can have dramatic and varying impacts on biodiversity,” said Stephanie E. Pierce, Thomas D. Cabot Associate Professor of Organismic and Evolutionary Biology and curator of vertebrate paleontology in the Museum of Comparative Zoology. “Here we show that rising temperatures during the Permian-Triassic led to the extinction of many animals, including many of the ancestors of mammals, but also sparked the explosive evolution of others, especially the reptiles that went on to dominate the Triassic period.”
The study involved close to eight years of data collection and took a heavy dose of camerawork, CT scanning, and loads of passport stamps as Simões traveled to more than 20 countries and more than 50 different museums to take scans and snapshots of more than 1,000 reptilian fossils.
With all the information, the researchers created an expansive dataset that was analyzed with state-of-the-art statistical methods to produce a diagram called an evolutionary time tree. Time trees reveal how early reptiles were related to each other, when their lineages first originated, and how fast they were evolving. They then combined it with global temperature data from millions of years ago.
Diversification of reptile body plans started about 30 million years before the Permian-Triassic extinction, making it clear these changes weren’t triggered by the event as previously thought. The extinction events did help put them in gear though.
The dataset also showed that rises in global temperatures, which started at about 270 million years ago and lasted until at least 240 million years ago, were followed by rapid body changes in most reptile lineages. For instance, some of the larger cold-blooded animals evolved to become smaller so they could cool down easier; others evolved to life in water for that same effect. The latter group included some of the most bizarre forms of reptiles that would go on to become extinct such as a giant, long-necked marine reptile once thought to be the Loch Ness monster, a tiny chameleon-like creature with a bird-like skull and beak, and a gliding reptile resembling a gecko with wings. It also includes the ancestors of reptiles that still exist today like turtles and crocodiles.
Smaller reptiles, which gave rise to the first lizards and tuataras, went on a different path than their larger reptile brethren. Their evolutionary rates slowed down and stabilized in response to the rising temperatures. The researchers believe it was because the small-bodied reptiles were already better adapted to the rising heat since they can more easily release heat from their bodies compared to larger reptiles when temperatures got hot very quickly all-around Earth.
The researchers say they are planning to expand on this work investigating the impact of environmental catastrophes on evolution of organisms with abundant modern diversity, such as the major groups of lizards and snakes.
