Category: 7. Science

  • Team figures out how cavefish lost their eyes

    Team figures out how cavefish lost their eyes



    In a new study, researchers show when cavefishes lost their eyes, which provides a method for dating cave systems.

    Small, colorless, and blind, amblyopsid cavefishes inhabit subterranean waters throughout the eastern United States.

    In an analysis of the genomes of all known amblyopsid species, the researchers found that the different species colonized caves systems independently of each other and separately evolved similar traits—such as the loss of eyes and pigment—as they adapted to their dark cave environments.

    Their findings appear in the journal Molecular Biology and Evolution.

    By studying the genetic mutations that caused the fishes’ eyes to degenerate, the researchers developed a sort of mutational clock that allowed them to estimate when each species began losing their eyes. They found that vision-related genes of the oldest cavefish species, the Ozark cavefish (Troglichthys rosae), began degenerating up to 11 million years ago.

    The technique provides a minimum age for the caves that the fishes colonized since the cavefish must have been inhabiting subterranean waters when their eyesight began devolving, the researchers say.

    “The ancient subterranean ecosystems of eastern North America are very challenging to date using traditional geochronological cave-dating techniques, which are unreliable beyond an upper limit of about 3 to 5 million years,” says Chase Brownstein, a student in Yale’s Graduate School of Arts and Sciences, in the ecology and evolutionary biology department, and the study’s co-lead author.

    “Determining the ages of cave-adapted fish lineages allows us to infer the minimum age of the caves they inhabit because the fishes wouldn’t have started losing their eyes while living in broad daylight. In this case we estimate a minimum age of some caves of over 11 million years.”

    Maxime Policarpo of the Max Planck Institute for Biological Intelligence and the University of Basel is the co-lead author.

    For the study, the researchers reconstructed a time-calibrated evolutionary tree for amblyopsids, which belong to an ancient, species-poor order of freshwater fishes called Percopsiformes, using the fossil record as well as genomic data and high-resolution scans of all living relevant species.

    All the cavefish species have similar anatomies, including elongated bodies and flattened skulls, and their pelvic fins have either been lost or severely reduced. Swampfish (Chologaster cornuta), a sister to cavefish lineage that inhabits murky surface waters, also has a flattened skull, elongated body, and no pelvic fin. While it maintains sight and pigment, there is softening of the bones around its eyes, which disappear in cavefishes. This suggests that cavefishes evolved from a common ancestor that was already equipped to inhabit low-light environments, Brownstein says.

    To understand when the cavefish began populating caves—something impossible to discern from the branches of an evolutionary tree—the researchers studied the fishes’ genomes, examining 88 vision-related genes for mutations. The analysis revealed that the various cavefish lineages had completely different sets of genetic mutations involved in the loss of vision. This, they say, suggests that separate species colonized caves and adapted to those subterranean ecosystems independently of each other.

    From there, the researchers developed a method for calculating the number of generations that have passed since cavefish species began adapting to life in caves by losing the functional copies of vision-related genes.

    Their analysis suggests that cave adaptations occurred between 2.25 and 11.3 million years ago in Ozark cavefish and between 342,000 to 1.70 million years ago (at minimum) and 1.7 to 8.7 million years ago (at maximum) for other cavefish lineages. The findings support the conclusion that at least four amblyopsid lineages independently colonized caves after evolving from surface-dwelling ancestors, the researchers say.

    The maximum ages exceed the ranges of traditional cave-dating methods, which includes isotope analysis of cosmogenic nuclides that are produced within rocks and soils by cosmic rays, the researchers note.

    The findings also suggest potential implications for human health, says Thomas Near, professor of ecology and evolutionary biology at Yale, and senior author of the study.

    “A number of the mutations we see in the cavefish genomes that lead to degeneration of the eyes are similar to mutations that cause ocular diseases in humans,” says Near, who is also the Bingham Oceanographic Curator of Ichthyology at the Yale Peabody Museum.

    “There is the possibility for translational medicine through which by studying this natural system in cavefishes, we can glean insights into the genomic mechanisms of eye diseases in humans.”

    Additional coauthors are from the South Carolina Department of Natural Resources, the American Museum of Natural History, Florida State University, and Paris-Cité University.

    Source: Yale

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  • Extreme Experiments on Perovskite May Offer Insight Into Earth’s Interior and Deep Earthquakes

    Extreme Experiments on Perovskite May Offer Insight Into Earth’s Interior and Deep Earthquakes

    Materials scientists at the University of California San Diego have performed powerful laser shock experiments on a perovskite mineral to better understand the geophysical processes in Earth’s deep interior and the mechanisms behind earthquakes deep within the planet.

    Perovskites are a class of materials used in light-based technologies such as solar cells, LEDs and lasers. They are also the most abundant minerals in Earth’s mantle. Two of the mantle’s most abundant mineral perovskites, bridgmanite and wollastonite, are difficult to study directly because they are unstable under standard laboratory conditions. To get around this, researchers use a chemically different but structurally similar mineral, calcium titanate, as an analogue.

    In a new study, researchers used high power laser shock compression to recreate the extreme pressures and temperatures found deep inside the Earth. They discovered that calcium titanate deforms more like metals by forming dense networks of line and planar defects in contrast to completely disordered amorphization typically found in covalent materials like diamond — that may explain how mantle rocks respond to stress. These findings provide new insights into the processes that drive deep-focus earthquakes, which occur hundreds of kilometers beneath the Earth’s surface, and may also inform the effects of meteorite impacts on planets.

    The study, published in Acta Materialia, was led by UC San Diego researchers Boya Li and Marc Meyers. This research was partially supported by the Department of Energy, National Nuclear Security Administration (award DE-NA0004147).

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  • NASA Scientists Help Maryland County Plan to Beat Summer Heat Risks

    Thousands of Americans are impacted each summer by excessive heat and humidity, some suffering from heat-related illnesses when the body can’t cool itself down. Data from NASA satellites could help local governments reduce the sweltering risks, thanks to a collaboration between NASA scientists and officials in Prince George’s County, Maryland. The effort demonstrates how local officials in other communities could turn to NASA data to inform decisions that provide residents with relief from summer heat.

    NASA researchers and their Prince George’s County collaborators reported in Frontiers in Environmental Science that they used the Landsat 8 satellite, jointly operated by NASA and the US Geological Survey, and NASA’s Aqua satellite, to gain insight into surface temperature trends across the county over the past few decades. The data also show how temperatures have responded to changing land use and construction. It is information that county planners and environmental experts hope can aid them in their attempts to remediate and prevent heat dangers in the future. The collaboration may also help the county’s first responders anticipate and prepare for heat-related emergencies and injuries.

    Cooperation with Prince George’s County expands on NASA’s historic role, said Stephanie Schollaert Uz, an applications scientist with NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and one of the study authors. “Applying government satellite data to county-level problems is new here. We’re trying to make it easier for people outside of NASA to use our data, in part by including how-to guides referenced at the end of our paper,” Schollaert Uz said.

    In the long run, county officials hope to use NASA satellites to track the negative health impacts that arise from land use and modification. Removal of tree cover and the construction of non-permeable roads, parking lots, and structures that lead to water runoff are among the factors that create heat islands, where temperatures in localized areas soar relative to the surrounding landscape. In addition to the direct dangers of heat for county residents and workers, areas with higher-than-normal temperatures can drive intense local weather events.

    “There’s potentially a greater incidence of microbursts,” said Mary Abe of Prince George’s County’s sustainability division. “The atmosphere can become supercharged over hot spots,” causing high winds and flood-inducing rains.

    Prince George’s County planners anticipate relying on NASA satellites to determine where residents and county employees are at greater risk, predict how future construction could impact heat dangers, and develop strategies to moderate heat in areas currently experiencing elevated summer temperatures. Efforts might include protecting existing trees and planting new ones. It could include replacing impermeable surfaces (cement, pavement, etc.) with alternatives that let water soak into the ground rather than running off into storm drains. To verify and calibrate the satellite observations crucial for such planning, county experts are considering enlisting residents to act as citizen scientists to collect temperature and weather data on the ground, Abe said.

    Eventually, the NASA satellite temperature data could also lead to strategies to curb insect-borne diseases, said Evelyn Hoban, associate director for the Prince George’s County division of environmental health and communicable disease. “Once we know where the higher temperatures are, we can check to see if they create mosquito or tick breeding grounds,” said Hoban, who coauthored the study. “We could then focus our outreach and education, and perhaps prevention efforts, on areas of greater heat and risk.”

    A NASA guide is available to aid other communities who hope to duplicate the Prince George’s County study. The guide provides introductions on a variety of NASA satellite and ground-based weather station data. Instructions for downloading and analyzing the data are illustrated in an accompanying tutorial that uses the Prince George’s County study as an example for other communities to follow on their own.

    One of the greatest benefits of the collaboration, Abe said, is the boost in credibility that comes from incorporating NASA resources and expertise in the county’s efforts to improve safety and health. “It’s partly the NASA brand. People recognize it and they’re really intrigued by it,” she said. “Working with NASA builds confidence that the decision-making process is based firmly in science.”

    By James Riordon
    NASA Goddard Space Flight Center

    Media contact: Elizabeth Vlock
    NASA Headquarters

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  • Neurodevelopmentally rooted epicenters in schizophrenia: sensorimotor-association spatial axis of cortical thickness alterations

    Neurodevelopmentally rooted epicenters in schizophrenia: sensorimotor-association spatial axis of cortical thickness alterations

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  • Perseverance Mars rover stumbles upon wind-carved ‘megaripples’ on the Red Planet

    Perseverance Mars rover stumbles upon wind-carved ‘megaripples’ on the Red Planet

    NASA’s Perseverance rover has captured a striking new image of massive, wind-carved sand formations known as “megaripples” during its latest exploration stop on the Red Planet.

    The photo, taken on Aug. 13, reveals a field of these ridges at a site called Kerrlaguna, where Perseverance is investigating how Martian winds continue to shape the landscape. According to a recent NASA statement, this work is part of a broader effort to better understand Mars’ modern environment.

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  • Aging dynamics in captive sea turtles reflect conserved life-history patterns across the testudine phylogeny

    Aging dynamics in captive sea turtles reflect conserved life-history patterns across the testudine phylogeny

    Reproductive output does not decline with age in captive green turtles

    At the population level, cumulative reproductive output increased by 13% of its current value per unit time (θ = 0.13; 95% CI: 0.12–0.14), which approximated an almost linear increase in reproduction from age 17 to 38 years of age (Fig. 1A; SI Appendix, Fig. S1). This reproductive pattern is consistent with other testudines, such as Blanding’s turtle Emydoidea blandingii23 and painted turtles Chrysemys picta24, which tend not to show age-related declines in clutch size and reproductive frequency (but see ref. 25). Longitudinal data on Mediterranean green turtles suggest a similar pattern, where the cumulative number of clutches increases linearly with time since their first breeding season26. Unfortunately, the animals used in their study were of unknown age, complicating direct comparisons with our results.

    Fig. 1: Despite mortality increasing exponentially, multi-season nesters (MSN) show no decline in cumulative reproductive output.

    A Solid line represents the average change in cumulative reproductive output (number of eggs) with age and associated 95% CI (dashed line). Horizontal dashed line indicates the equilibrium value, ({{rm{kappa }}}). B Solid line shows age-specific changes in mortality and associated 95% CI (shaded area). Vertical dashed line represents the minimum age at first reproduction (AFR).

    During a typical breeding season, female green turtles laid an average of 393 ± 238 eggs, distributed across 4.5 ± 2.0 clutches, though some individuals produced over 1000 eggs per season. Over their lifetime, females averaged a total reproductive output of 2602 eggs, with this distribution highly right-skewed and heavy-tailed. Importantly, new clutches were not clumped over time (Fig. 1A). As a result, the Poisson distribution provided a better fit to the reproductive data over competing models ((Delta {{{rm{SIC}}}}_{{{rm{GP}}}-{{rm{Poisson}}}}=2253.4); (Delta {{{rm{SIC}}}}_{{{rm{NB}}}-{{rm{Poisson}}}}=2.2)). A major factor affecting the temporal spread of reproduction is the duration between breeding seasons. In the wild, it is uncommon for females to reproduce in consecutive years27, but green turtles at the CTC have an average inter-breeding interval of 1.7 years (wild inter-breeding intervals: 2.9 and 3.2 years28,29). Factors associated with captivity – ad libitum feeding, higher quality resources, and access to suitable mates – may significantly reduce the physiological costs of reproduction but accelerate reproductive schedules. For instance, captive green turtles have a younger age at first reproduction (AFR) but reach maturity at a similar body size (measured via curved carapace length; CCL)30 to wild populations (CTC: CCL = 98.5 cm, AFR = 12.01 years; Australia (wild): CCL = 102.1 cm, AFR = 32 years31; Hawaii (wild): CCL = 94.0 cm, AFR = 27.3 years32). Only 29 of the 118 captive green turtles in Fig. 1 had an AFR less than 10 years old (range: 7–32).

    At the population-level, we did not find evidence that a higher allocation to reproduction per year or a younger age at maturity33 led to an earlier deceleration in cumulative egg production. These findings are broadly consistent with Dynamic Energy Budget (DEB) models for Australian green turtles after the removal of resource limitation34. The main difference between captive and wild green turtles appears to be reproductive frequency, whereby predator-free, resource-rich captive conditions support the upper limit of their reproductive potential. However, such accelerated reproductive rates, in combination with accelerated growth rates30 could have contributed to a lower expected longevity post-maturity35 (see mortality results), which aligns with a well-supported prediction by Williams10,36. Rapid development is correlated with rapid senescence. On the other hand, the removal of environmental constraints may dampen or decouple trade-offs expected under natural conditions37,38, such as the correlation between longevity and aging rate39 or the covariance between lifespan, growth, and reproduction40,41. As such, any comparison with wild green turtle populations is currently speculative.

    Observed differences in reproductive trajectories among captive turtles were mostly a result of individual heterogeneity (SI Appendix, Fig. S2). For example, four turtles laying over 10,000 eggs averaged two more clutches per year and returned to breed half a year sooner. While some individuals maintain high reproductive functioning at older ages, this may ultimately be curtailed by a rising probability of catastrophic death rather than a gradual decline in fitness42. In such cases, their reproductive lifespan is effectively truncated by mortality. The contribution of older turtles to the next generation could also decrease if developmental problems are more prevalent in elderly animals23,25. Thus, the actual number of offspring produced may decline with increasing egg production40,43. Unfortunately, we were unable to relate egg output to offspring production because hatchling data collection and egg incubation conditions were not consistent over the study period. Investigating the link between age-specific changes in egg production and offspring fitness is a critical area for future research.

    Beyond 60 years old, average egg production was projected to stop, reaching a lifetime plateau at about (kappa =) 13,545 eggs (Fig. 1A; SI Appendix, Table S1). Yet, it is unknown if captive green turtles will live this long. Other environmental threats that are an indirect result of aging, such as increased susceptibility to disease44, may induce mortality in elderly females. Conversely, females reproducing into old age may be a result of the selective disappearance of low-quality individuals, i.e., selective disappearance effects45. Mortality selection alters the composition of older age classes by removing frailer individuals from the population. The strength of this mortality filter depends on the overall risk of death46. When the risk of death is high, fitter individuals disproportionately represent the oldest age classes. In captivity, mortality filters are generally weak, extending the lifespan of every individual40. However, a filter for reproductive lifespan could mirror a mortality filter in which the oldest individuals reproducing represent a specific subpopulation remaining after selective disappearance47. As natural selection weakens with age, it creates a window of optimal fertility, which varies in duration across individuals48. As a result, infertility in late life may arise from complex hormonal changes48, irrespective of increases in longevity.

    Females experiencing a single reproductive season (Fig. 2), hereafter termed one-time nesters (OTN), are not an artifact of captivity but are also regularly observed in wild populations49. For instance, 35% of 1770 female loggerhead turtles Caretta caretta nesting on the South-Eastern US had only one observed reproductive event50. In our study, OTN accounted for 24% of the 156 females. Compared to multi-season nesters (MSN), OTN did not differ in age at first reproduction (∆MSN-OTN = 0.5 years, t59.8 = 0.7, p = 0.5). Notably, their single reproductive event incurred no detectable survival cost. OTN experienced a reproductive lifespan 52% shorter than MSN (see survival results below) but laid significantly fewer eggs in their first breeding season (∆MSN-OTN = 76.9 eggs, t72.1 = −2.5, p = 0.02) – a difference equivalent to nearly one full clutch. The fate of short-lived OTN may further point to a selective filter favoring an intrinsic physiological resilience needed for sustained reproduction, a capacity that remains crucial even in captive conditions.

    Fig. 2: One-time nesters (OTN) incur no survival cost from reproduction.
    figure 2

    A Points represent observed annual reproductive output. Since each female only had one observed breeding season, the associated ages for each point represents age at first reproduction (AFR). Individuals that laid less than the average clutch size of 100 eggs are below the dashed line. B Solid lines show age-specific changes in mortality and associated 95% CI (shaded area). Vertical dashed line represents the minimum AFR.

    Mortality rates in captive green turtles increase exponentially with age

    Survival patterns for captive green turtles follow the Gompertz law, which posits that adult mortality rises exponentially – or linearly on the log-scale – with age after maturity51. This mortality pattern has also been observed in captive3 and wild4 testudines. As expected, captive green turtles have a low initial mortality rate (({{{rm{beta }}}}_{0}): 0.01 – 0.04) and a slow aging rate (({{{rm{beta }}}}_{1}): 0.09–0.10), similar to other testudine species3 and orders of magnitude lower than rates typical for birds and mammals (See Fig. 1 in refs. 4,40). However, aging rates for both groups [OTN and MSN] were strictly positive (Fig. 3) and significantly different from zero (p < 0.001), revealing green turtles can experience actuarial senescence even in protected environments. This may relate to growth slowing to an asymptotic size rather than continuing indefinitely throughout life. Female green turtles at the CTC reach 95% of their maximum mass and 85% of their maximum length at AFR30, limiting any potential benefits from increasing size on fecundity.

    Fig. 3: Adult life expectancies and aging rates across captive and wild testudines.
    figure 3

    Shaded bars represent either 95% credible intervals (non-sea turtle species3,4) or 95% confidence intervals (sea turtle species). Uncertainty estimates were computed using either Bayesian survival trajectory analysis (BaSTA) or the Delta Method. Tree tip color indicates family, and shapes and colors for aging rates and life expectancies show environment (i.e., captive (blue circles) versus wild (red squares)).

    Differences in reproductive dynamics between OTN and MSN translated into distinct mortality functions (Figs. 1B and 2B). This distinction was captured by including a covariate for reproductive status (SI Appendix, Table S2), which provided a better fit to the data over assuming additional unobserved heterogeneity (via a Gamma-Makeham frailty model52,53). Initial mortality rates, which were 25% lower for MSN, shaped these differences. Both life expectancy (KLD = 1.0) and lifespan inequality (KLD = 1.0) were significantly different between OTN and MSN (SI Appendix, Fig. S3 and Table S3–4), with OTN having a 52% shorter reproductive lifespan (({e}_{x}^{{OTN}}) = 10.2; ({e}_{x}^{{MSN}}) = 19.6) and greater variance in age at death (({H}_{x}^{{OTN}}) = 0.6; ({H}_{x}^{{MSN}}) = 0.4). We estimated 5% of captive green turtles will survive beyond 23.4 (OTN) and 35.5 (MSN) years old, and 1% will live past 27.6 (OTN) to 39.6 (MSN) years old. Their respective aging rates correspond to a mortality doubling time of 6.7 years for OTN and 7.4 years for MSN. Whether mortality and reproductive estimates for MSN and OTN reflect individual variation in response to captivity remains unclear40. However, since individuals in the study primarily reflect the original, diverse genetic founder stock, our results are unlikely a result of inbreeding depression54.

    The most common age at death (modal age; estimation based on method in ref. 55) was 10 years for OTN and 24 years for MSN. This earlier modal death age for OTN, coupled with a significantly greater variance (see ({H}_{x}^{{OTN}}) above) suggests that deaths occur earlier on average but are more dispersed. In contrast, the narrower age range of death for MSN may indicate a more consistent timing of when late-life physiological decline leads to mortality. The earlier modal age for OTN aligns with an earlier onset of actuarial senescence post-maturity, although we could not attribute this to reproductive costs. Contrary to predictions about the timing of peak mortality36, significant increases did not begin shortly after sexual maturity for MSN but occurred approximately 12 years post-maturity (at 24 years of age), indicating a substantially delayed period before peak mortality risks manifested. This phenomenon of deferred actuarial senescence in MSN, where the primary escalation of mortality risk is postponed, has also been reported in endotherms56 and ectotherms3,4.

    To explore the interplay between survival and reproduction further, we focused solely on MSN, as these individuals not only actualized the most common reproductive strategy of green turtles but also allowed us to evaluate how reproductive costs impact survival over successive breeding seasons. Recalling that cumulative reproductive output increased linearly through much of early to mid-adulthood and given that their peak mortality (modal age at death) occurs at around 24 years, the later inflection point in their reproductive trajectory (27 years; Fig. 1) suggests that mortality risk begins to accelerate before any observable decline in reproductive output. While we found no evidence that a higher annual reproductive rate or earlier maturity led to an earlier decline in egg production, the mortality pattern in MSN points to a potential trade-off between current reproduction and future survival.

    Comparing mortality and reproductive patterns between captive and wild green turtles

    Surprisingly, our estimate for reproductive longevity for captive green turtles (19.6 years post-maturity) closely matches those reported for wild Australian green turtle populations (18–19 years)57. Differences in longevity between captive and wild populations seem to be related to maturity time. Although green turtles may remain reproductively active for ~19 years, the waiting time to first reproduction is reduced by around 32% in captivity. Wild green turtles spend almost half their lives gathering the necessary resources to reach a minimum body size needed to meet the requirements for long-distance migration and reproduction, which is related to environmental, developmental, and physiological constraints58. Once mature, differences in reproductive rates relate to the time required to gather resources for a subsequent breeding season. In captivity, turtles do not need to migrate thousands of kilometers between breeding and foraging grounds, significantly reducing their energetic costs and increasing their reproductive rate. However, in wild leatherback turtles the stress of reproducing at a higher frequency had negative physiological effects59, suggesting a trade-off between current and future reproduction that influences lifetime reproductive success60.

    Limited resources compounded by extensive migrations result in wild green turtles having fewer reproductive seasons compared to those in captivity. If wild populations follow a similar reproductive trajectory as shown in Fig. 1A, we project a 20-year reproductive lifespan with an inter-breeding interval of two and four years would result in a lifetime output of between 1324 and 4080 eggs – a figure close to the estimated lifetime reproductive output in wild Australian green turtles ( ~ 2000 eggs61). Yet, such projections from captive populations are speculative. Data from known-aged sea turtles would greatly enhance comparative analyses. Despite the hundreds of global projects monitoring sea turtle populations, several operational since the early 1960s, no long-term longitudinal data exist for known-age sea turtles of any species, rendering the estimation of age-specific mortality and reproductive rates particularly challenging62. The inability to accurately determine the absolute chronological age of living wild sea turtles remains the single most significant impediment to precisely understanding their life history63. This limitation impedes the employment of typical demographic tools64 to understand phenotypic variation and plasticity in wild populations experiencing vastly differing ecological pressures.

    Alternative approaches have emerged that circumvent the need for aging live animals and allow for the construction of age- and size-specific reaction norms65. While undoubtedly valuable, such methods cannot translate into direct, individual-level changes in reproductive output and survival over a full lifespan, nor can they fully capture the dynamic interplay of environmental factors. For instance, if aging rates are environmentally modulated, as observed in other testudines3 rather than an underlying change in juvenile mortality as seen in primates66, wild populations of sea turtles may experience mortality rates that vary with local selective pressures, such as foraging ground productivity67, predation, disease, temperature regimes, and climate change68. These factors are known to strongly influence species-specific vital rates across testudines. In painted turtles, aging rates vary between and within wild and captive populations (captivity: 0.0919, 0.103; wild: 0.044, 0.014, 0.1025). Comparable results have been reported in pond sliders Trachemys scripta3,4, as well as European pond turtles Emys orbicularis4. This environmental sensitivity has important implications in understanding selection for lifespan-extending mechanisms in long-lived species, which is expected to be strong. When extrinsic mortality is low and aging-related mortality is high, as is the case in certain birds and mammals42,69, extending lifespan further would likely come at a high evolutionary cost. Life extending mechanisms may be less costly in terms of evolutionary fitness for testudines when actuarial senescence is not the primary source of mortality42, but this needs to be evaluated with empirical data. While direct longitudinal studies of known-aged individuals in the wild remain paramount, at present, research on the paradoxical life history of sea turtles can be most effectively advanced by tracking individuals from their first breeding season, employing breeding age rather than absolute age.

    Comparing mortality and reproductive patterns across captive and wild testudines

    To situate our findings on captive green turtles within the broader evolutionary landscape, we conducted a comparative analysis across testudines. Captive green turtles exhibit aging rates similar to those of other testudines (Fig. 3), and the relationships among fitness-related traits in testudines (including sea turtles) generally align with established life-history patterns3,4,19, irrespective of environment. For instance, an earlier age at first reproduction is linked to a shorter lifespan and body mass is positively correlated with life expectancy (SI Appendix, Fig. S4A, B). A notable divergence, however, emerges in their reproductive investment: green turtles produce a disproportionately heavier reproductive mass relative to their aging rate, life expectancy, and AFR (Fig. 4A–C). Despite this difference, the allometric relationship between reproductive mass and body mass in green turtles matches theoretical expectations (Fig. 4D), a pattern that also holds across wild sea turtle species70. Extensive migrations between foraging and breeding grounds impose strict physiological constraints, making the large body size of sea turtles an evolutionary prerequisite for their highly migratory, oceanic lifestyle71. In general, a larger body size offers significant adaptive advantages, including reduced predation risk, a lower mass-specific metabolic rate, and greater starvation tolerance. However, these benefits are balanced by higher resource requirements, a longer maturation period, and increased susceptibility to extinction due to longer generation times.

    Fig. 4: Body mass predicts annual reproductive mass (RM), but RM does not vary with other life-history traits.
    figure 4

    Solid lines indicate the fitted model, and shaded areas are 95% CI. Estimates for captive green turtles in plots (A–D) are shown by the green turtle silhouette, sourced from PhyloPic. AFR denotes age at first reproduction.

    Across testudines, we found aging rates do not strongly vary along a slow-fast continuum as typically defined by other life-history traits. Notably, the relationship between aging rates and body mass, AFR, and annual fecundity are substantially weaker than in other reptiles4 (Fig. 5A–C). Collectively, these traits explained only 8% of the variation in aging rates (Table 1A). While the direction of these relationships is similar to other reptiles (excluding testudines), the effect sizes are trivial, yielding nearly flat lines across taxa with different fecundities (slope: testudines = 0.01, reptiles = 0.11), ages at first reproduction (slope: testudines = −0.01, reptiles = −0.18), and body masses (slope: testudines = 0.00, reptiles = −0.03). Furthermore, while wild populations in our dataset exhibit slightly faster aging rates, this difference was not statistically significant (Table 1A, Fig. 5).

    Fig. 5: Aging rates across testudines do not follow a fast-slow continuum.
    figure 5

    Solid lines indicate the fitted model, and shaded areas are 95% confidence intervals. Predictions for aging rates from Reinke et al. 4 including (teal dashed line) and excluding (teal solid line) their testudine data. Estimates for captive green turtles in plots (A–C) are shown by the green turtle silhouette, sourced from PhyloPic. AFR denotes age at first reproduction.

    Table 1 Slow-fast continuum results for the effect of (A) aging rate and (B) reproductive mass on different life-history traits

    Consistently slow aging rates across testudines, despite substantial differences in body size, environmental conditions, and habitat use, likely stem from a weakening of life-history trade-offs. Shared protective phenotypes (e.g., shells) and physiological adaptations, such as the ability to endure food scarcity while keeping maintenance costs low relative to energy storage72, may buffer testudines against selective pressures that typically drive diverse aging trajectories in other groups. The stronger relationships reported by Reinke et al.4 appear predominantly driven by high variation in squamates, with crocodilians and tuataras showing aging patterns more aligned with testudines. Similarly, the correlation between mortality and AFR in Shine and Iverson73 arises from methodological distinctions between age-specific mortality and instantaneous adult mortality ((-{mathrm{ln}}({{rm{S}}})), where S is a point estimate for adult survival probability). Our results suggest that, within testudines, the expected covariance among life-history traits with aging rates along a slow-fast continuum is not evident because they collectively occupy the slow extreme of this broader spectrum (see also Fig. 4 in ref. 4).

    While variation in reproductive mass does not directly align with the slow-fast continuum, it correlates strongly with body mass – a trait that itself is indicative of a species’ position on that continuum (SI Appendix, Fig. S4A, B). Female body mass in testudines explained 81% of the variation in annual reproductive mass (Fig. 4D). Other life-history traits, such as life expectancy, AFR, aging rate, and environment, did not explain the residual variation, and their effect actually became trivial once body mass was prioritized in a sequential decomposition of variance (Type I ANOVA). The dominant role of body size is anticipated, given its fundamental importance to organismal fitness, and it is both heritable74 and exhibits plastic responses to changing environments75, particularly during ontogeny30. In line with scaling laws76, which predict reproductive mass should follow a power function of the form (alpha cdot {M}_{F}^{beta }), we estimate the scaling exponent ((beta)) to be 0.89 (95% CI: 0.77–1.02), suggesting hypoallometric scaling. This result aligns closely with findings across sea turtles70 and testudines in general77, whereby larger species produce relatively lighter clutches (slope ≈ 0.77 in ref. 77). Interestingly, among individuals of the same species, this pattern is reversed (hyperallometric scaling)70,78.

    Although inter-specific hypoallometry might imply reproduction carries a proportionally higher allometric cost for smaller species, we found no detectable direct effect of reproductive mass itself on aging rates (p = 0.87), AFR (p = 0.86), or life expectancy (p = 0.21). Reproductive mass was slightly heavier in captivity (Table 1B and Fig. 4), but this difference was not significant (∆captive-wild = 0.05; p = 0.77). Although univariate tests detected a strong phylogenetic signal for both reproductive mass and body mass (Pagel’s λ; SI Appendix, Fig. S5 and Table S5), evolutionary relatedness did not explain the residual variance for reproductive mass, nor aging rates in the PGLS models (SI Appendix, Table S6). Instead, life-history trade-offs associated with the magnitude of reproductive investment primarily manifest through adjustments in other life-history components (SI Appendix, Fig. S4), such as age at first reproduction and overall life expectancy (as suggested by correlations with body mass). For instance, turtles and tortoises are constrained by the size of their body cavity, which is affected by their overall body plan. As such, there is a trade-off between the number of eggs and egg size79. Egg size is expected to be subject to stronger directional selection than clutch size, as each egg must provision all essential resources required for hatchling survival. Empirical data support this hypothesis, finding that clutch size shows greater phenotypic variance relative to egg size80. Patterns of reproductive allocation may largely reflect these allometric and anatomical constraints, especially as both clutch and egg size generally increase with body size across testudines81, rather than being strongly lineage-specific72.

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  • Physicists Discover Universal Laws Governing Quantum Entanglement

    Physicists Discover Universal Laws Governing Quantum Entanglement

    Researchers used thermal effective theory to uncover universal patterns in quantum entanglement across all dimensions. Credit: Stock

    Scientists uncovered universal laws of entanglement in any dimension. The results strengthen links between particle physics, quantum theory, and gravity.

    A group of theoretical physicists has shown that quantum entanglement obeys universal principles in every dimension by applying thermal effective theory. Their findings were recently published in the journal Physical Review Letters, where the paper was selected as an Editors’ Suggestion.

    “This study is the first example of applying thermal effective theory to quantum information. The results of this study demonstrate the usefulness of this approach, and we hope to further develop this approach to gain a deeper understanding of quantum entanglement structures,” said lead author and Kyushu University Institute for Advanced Study Associate Professor Yuya Kusuki.

    Quantum entanglement and Rényi entropy

    In classical physics, particles that are far apart act independently. In contrast, quantum physics shows that two particles can remain strongly correlated even at great distances, a phenomenon known as quantum entanglement. This effect is central to quantum technologies such as quantum computing and quantum communication, making its study essential for both theoretical insight and practical applications.

    Quantum Entanglement in 1+1 and 2+1 Dimensions
    Quantum entanglement in 1+1 and 2+1 dimensions. Credit: Yuya Kusuki

    One of the main tools for characterizing entanglement is the Rényi entropy, which measures the complexity of quantum states and how information is distributed. It plays a key role in classifying quantum states, evaluating whether complex quantum systems can be simulated, and is also widely used in theoretical research on the black hole information loss paradox and quantum gravity.

    Despite its importance, uncovering the structure of quantum entanglement remains a major challenge for both physics and quantum information science. Most investigations so far have been restricted to (1+1)-dimensional models, meaning one spatial dimension plus time. Extending this work to higher dimensions has proven much more complex.

    A team led by Yuya Kusuki at the University of Tokyo’s Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), together with Caltech Professor Hirosi Ooguri and researcher Sridip Pal, has now demonstrated that quantum entanglement exhibits universal patterns even in higher dimensions. They achieved this by adapting theoretical methods originally developed in particle physics to the study of quantum information.

    Applying the thermal effective theory

    The research team focused on the thermal effective theory, which has recently led to major advances in the analysis of higher-dimensional theories in particle physics. This is a theoretical framework designed to extract universal behavior from complex systems, based on the idea that observable quantities can often be characterized by only a small number of parameters.

    By introducing this framework into quantum information theory, the team analyzed the behavior of Rényi entropy in higher-dimensional quantum systems. Rényi entropy is characterized by a parameter known as the replica number.

    The team demonstrated that, in the regime of small replica number, the behavior of the Rényi entropy is universally governed by only a few parameters, such as the Casimir energy, a key physical quantity within the theory. Furthermore, by leveraging this result, the team clarified the behavior of the entanglement spectrum in the region where its eigenvalues are large.

    Thermal Effective Theory and Quantum Entanglement
    Looking a quantum entanglement in a quantum many-body system using thermal effective theory, which uncovers universal features of quantum entanglement. Credit: Yuya Kusuki

    They also investigated how universal behavior changes depending on the method used to evaluate the Rényi entropy. These findings hold not only in (1+1) dimensions, but in arbitrary spacetime dimensions, marking a significant step forward in the understanding of quantum entanglement structures in higher dimensions.

    The next step for the researchers is to further generalize and refine this framework. This work represents the first demonstration that thermal effective theory can be effectively applied to the study of quantum entanglement structures in higher dimensions, and there remains ample room to further develop this approach. By improving the thermal effective theory with quantum information applications in mind, researchers could gain a deeper understanding of quantum entanglement structures in higher-dimensional systems.

    On the applied side, the theoretical insights gained from this research may lead to improvements in numerical simulation methods for higher-dimensional quantum systems, propose new principles for classifying quantum many-body states, and contribute to a quantum-information-theoretic understanding of quantum gravity. These developments hold promise for broad and impactful future applications.

    Reference: “Universality of Rényi Entropy in Conformal Field Theory” by Yuya Kusuki, Hirosi Ooguri and Sridip Pal, 5 August 2025, Physical Review Letters.
    DOI: 10.1103/fsg7-bs7q

    This research was supported in part by the U.S. Department of Energy, Office of Science, Office of High Energy Physics, under Award Number DE-SC0011632 and by the Walter Burke Institute for Theoretical Physics at Caltech. Hirosi Ooguri is also supported in part by the Simons Investigator Award (MP-SIP-00005259) and by JSPS Grants-in-Aid for Scientific Research 23K03379. His work was performed in part at the Kavli Institute for the Physics and Mathematics of the Universe at the University of Tokyo, which is supported by the World Premier International Research Center Initiative, MEXT, Japan, at the Kavli Institute for Theoretical Physics (KITP) at the University of California, Santa Barbara, which is supported by grant NSF PHY-2309135, and at the Aspen Center for Physics, which is supported by NSF grant PHY-1607611. Yuya Kusunoki is also supported by the INAMORI Frontier Program at Kyushu University and JSPS KAKENHI Grant Number 23K20046.

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  • NASA’s Chandra Reveals Star’s Inner Conflict Before Explosion

    NASA’s Chandra Reveals Star’s Inner Conflict Before Explosion

    The inside of a star turned on itself before it spectacularly exploded, according to a new study from NASA’s Chandra X-ray Observatory. Today, this shattered star, known as the Cassiopeia A supernova remnant, is one of the best-known, well-studied objects in the sky.

    Over three hundred years ago, however, it was a giant star on the brink of self-destruction. The new Chandra study reveals that just hours before it exploded, the star’s interior violently rearranged itself. This last-minute shuffling of its stellar belly has profound implications for understanding how massive stars explode and how their remains behave afterwards.

    Cassiopeia A (Cas A for short) was one of the first objects the telescope looked at after its launch in 1999, and astronomers have repeatedly returned to observe it.

    “It seems like each time we closely look at Chandra data of Cas A, we learn something new and exciting,” said Toshiki Sato of Meiji University in Japan who led the study. “Now we’ve taken that invaluable X-ray data, combined it with powerful computer models, and found something extraordinary.”

    As massive stars age, increasingly heavy elements form in their interiors by nuclear reactions, creating onion-like layers of different elements. Their outer layer is mostly made of hydrogen, followed by layers of helium, carbon and progressively heavier elements – extending all the way down to the center of the star. 

    Once iron starts forming in the core of the star, the game changes. As soon as the iron core grows beyond a certain mass (about 1.4 times the mass of the Sun), it can no longer support its own weight and collapses. The outer part of the star falls onto the collapsing core, and rebounds as a core-collapse supernova.

    The new research with Chandra data reveals a change that happened deep within the star at the very last moments of its life. After more than a million years, Cas A underwent major changes in its final hours before exploding.

    “Our research shows that just before the star in Cas A collapsed, part of an inner layer with large amounts of silicon traveled outwards and broke into a neighboring layer with lots of neon,” said co-author Kai Matsunaga of Kyoto University in Japan. “This is a violent event where the barrier between these two layers disappears.”

    This upheaval not only caused material rich in silicon to travel outwards; it also forced material rich in neon to travel inwards. The team found clear traces of these outward silicon flows and inward neon flows in the remains of Cas A’s supernova remnant. Small regions rich in silicon but poor in neon are located near regions rich in neon and poor in silicon. 

    The survival of these regions not only provides critical evidence for the star’s upheaval, but also shows that complete mixing of the silicon and neon with other elements did not occur immediately before or after the explosion. This lack of mixing is predicted by detailed computer models of massive stars near the ends of their lives.

    There are several significant implications for this inner turmoil inside of the doomed star. First, it may directly explain the lopsided rather than symmetrical shape of the Cas A remnant in three dimensions. Second, a lopsided explosion and debris field may have given a powerful kick to the remaining core of the star, now a neutron star, explaining the high observed speed of this object.

    Finally, the strong turbulent flows created by the star’s internal changes may have promoted the development of the supernova blast wave, facilitating the star’s explosion.

    “Perhaps the most important effect of this change in the star’s structure is that it may have helped trigger the explosion itself,” said co-author Hiroyuki Uchida, also of Kyoto University. “Such final internal activity of a star may change its fate—whether it will shine as a supernova or not.”

    These results have been published in the latest issue of The Astrophysical Journal and are available online.

    To learn more about Chandra, visit:

    https://science.nasa.gov/chandra

    Learn more about the Chandra X-ray Observatory and its mission here:

    chandra

    https://chandra.si.edu

    This release features a composite image of Cassiopeia A, a donut-shaped supernova remnant located about 11,000 light-years from Earth. Included in the image is an inset closeup, which highlights a region with relative abundances of silicon and neon.

    Over three hundred years ago, Cassiopeia A, or Cas A, was a star on the brink of self-destruction. In composition it resembled an onion with layers rich in different elements such as hydrogen, helium, carbon, silicon, sulfur, calcium, and neon, wrapped around an iron core. When that iron core grew beyond a certain mass, the star could no longer support its own weight. The outer layers fell into the collapsing core, then rebounded as a supernova. This explosion created the donut-like shape shown in the composite image. The shape is somewhat irregular, with the thinner quadrant of the donut to the upper left of the off-center hole.

    In the body of the donut, the remains of the star’s elements create a mottled cloud of colors, marbled with red and blue veins. Here, sulfur is represented by yellow, calcium by green, and iron by purple. The red veins are silicon, and the blue veins, which also line the outer edge of the donut-shape, are the highest energy X-rays detected by Chandra and show the explosion’s blast wave.

    The inset uses a different color code and highlights a colorful, mottled region at the thinner, upper left quadrant of Cas A. Here, rich pockets of silicon and neon are identified in the red and blue veins, respectively. New evidence from Chandra indicates that in the hours before the star’s collapse, part of a silicon-rich layer traveled outwards, and broke into a neighboring neon-rich layer. This violent breakdown of layers created strong turbulent flows and may have promoted the development of the supernova’s blast wave, facilitating the star’s explosion. Additionally, upheaval in the interior of the star may have produced a lopsided explosion, resulting in the irregular shape, with an off-center hole (and a thinner bite of donut!) at our upper left.

    Megan Watzke
    Chandra X-ray Center
    Cambridge, Mass.
    617-496-7998
    mwatzke@cfa.harvard.edu

    Corinne Beckinger
    Marshall Space Flight Center, Huntsville, Alabama
    256-544-0034
    corinne.m.beckinger@nasa.gov

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  • NASA Is Exploring Alternative Ways To Retrieve Samples From Mars

    NASA Is Exploring Alternative Ways To Retrieve Samples From Mars

    Bringing samples from Mars back to Earth is one of NASA’s most ambitious goals. The plan goes back to the 1970s, with NASA’s robotic exploration program, when the first spacecraft landed on the surface of the Red Planet. This planetary exploration program gained momentum with the launch of the Mars rover missions, including Spirit, Opportunity, and Curiosity. In 2021, the rover named Perseverance made history by collecting and caching environmental samples from the Jezero Crater, a site where scientists believe they might find evidence of past life. These samples are sealed in titanium tubes and are stored on the surface of Mars, waiting for the opportunity to reach Earth.

    NASA’s original Mars Sample Return (MSR) plan involves a complex, multi-mission campaign. It includes launching a Sample Retrieval Lander that would be equipped with a small rocket and a robotic arm that can gather the sample tubes. Then, the samples would be launched into the orbit of Mars, where an ESA orbiter would intercept them and return to Earth. All this would be achieved by 2033. However, this intricate plan comes with some great challenges. One particular challenge made NASA reassess the feasibility of this project — the budget. According to estimates, it’d cost nearly $11 billion, but it would also involve lots of technical problems and delays. In 2024, the space agency acknowledged that the current MSR project is no longer viable. Now, NASA is exploring cheaper and faster alternatives, including collaboration with some commercial partners like SpaceX and Lockheed.

    Read more: How Many Meteors Actually Hit Earth Every Year?

    Launching From The Surface Of Mars

    Concept image of MAV launching from Mars – NASA/JPL-Caltech

    One of the main problems scientists encountered during their Mars Sample Return mission planning was how they would lift the samples off the surface of Mars. At the heart of the original MSR plan was the Mars Ascent Vehicle (MAV), a small rocket designed to launch the sealed sample tubes into the orbit of the Red Planet. While launching a rocket from Earth is no easy task, it has become routine. Launching it from the surface of another planet would mean doing it from a long distance, with no margin for error. The MAV would need to safely land on Mars, endure months of the planet’s harsh environment while remaining dormant, and then perform a flawless vertical launch into Mars’ orbit successfully. Designing a rocket that would be light enough to deliver to Mars, and powerful enough to reach the orbit of Mars from the planet’s surface, is a delicate engineering job. There’s also the concern of stability, propulsion reliability, and designing guidance systems for the unpredictable Martian environment.

    Another concern for NASA scientists is the Martian atmosphere. While it’s lighter than Earth’s atmosphere, it comes with some specific challenges. It’s still thick enough that any spacecraft would simply burn upon entry into the Martian atmosphere if not protected by a special thermal shielding. On the other hand, it’s also thin enough that no spacecraft can rely on a parachute alone to be slowed down enough to land safely.

    Two Ways Forward

    Concept of Mars rover's entry, descent, and landing

    Concept of Mars rover’s entry, descent, and landing – NASA/JPL-Caltech

    NASA is now reevaluating its approach, and two alternative strategies are already outlined and still under review as of 2025.

    The first is NASA’s original MSR plan, but significantly simplified. It would rely on the already proven Sky Crane landing system. This is the same technology used to safely deliver the Curiosity and Perseverance rovers to the surface of Mars. A scaled-down lander would be equipped with the new version of MAV. To make the vehicle lighter, the scientists opted for a Radioisotope Power System instead of solar panels. This new system is capable of providing reliable power and heat to the MAV. Instead of launching a new rover, this plan involves relying on Perseverance to deliver the samples directly to the MAV. This reduces the mission complexity while still retaining the key elements of NASA’s original plan.

    The second strategy involves looking towards companies such as SpaceX, Blue Origin, and Lockheed. NASA has accepted 11 studies from the scientific community and space industry, each proposing the best way to return Mars samples to Earth. Some of these studies include modular systems, novel propulsion techniques, or entirely new vehicle designs. What’s common to these proposals is that their costs are estimated between $5.5 and $7.5 billion. By the end of 2026, NASA should be able to concentrate on one Mars Sample Return plan, and they’re confident they will reach Earth by 2040.

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  • Outstanding Photos Show First Baby Planet Growing In The Grooves Of A Stellar Disk

    Outstanding Photos Show First Baby Planet Growing In The Grooves Of A Stellar Disk

    For several years, astronomers have been seeing the hallmark of planet formation around stellar protoplanetary disks. A baby star is surrounded by a disk of gas and dust, and to observatories like ALMA, grooves in the disk appear as dark rings. These grooves are believed to be formed by fledgling planets, but no planets have been seen in them. Until now.

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    Researchers report revolutionary observations of WISPIT 2, which show – both in infrared light and optical – a planet among the dark rings. WISPIT 2b, as it is called, is estimated to be very young, but a lot more massive than the planets in the Solar System – around five times the mass of Jupiter, orbiting 56 times further away from its star than Earth is from the Sun.

    “Dozens of theory papers have been written about these observed disk gaps being caused by protoplanets, but no one’s ever found a definitive one until today,” co-lead author Laird Close, professor of astronomy at the University of Arizona, said in a statement.

    “It’s been a point of tension, actually, in the literature and in astronomy in general, that we have these really dark gaps, but we cannot detect the faint exoplanets in them. Many have doubted that protoplanets can make these gaps, but now we know that in fact, they can.”

    But that is not the only find in this system. The team also found evidence of a second candidate planet, currently named CC1, which is about nine times the mass of Jupiter but orbiting a lot closer, about 15 times the Earth-Sun distance. In Solar System terms, that’s between Saturn and Uranus.

    “Capturing an image of these forming planets has proven extremely challenging, and it gives us a real chance to understand why the many thousands of older exoplanet systems out there look so diverse and so different from our own solar system. I think many of our colleagues who study planet formation will take a close look at this system in the years to come,” co-author Dr Christian Ginski from the University of Galway said in a statement.

    This whole system is like looking back into the past of the Solar System. While we do not have planets quite as big around the Sun, we are seeing the birth of a planetary system not too dissimilar.

    “Discovering this planet was an amazing experience – we were incredibly lucky. WISPIT 2, a young version of our Sun, is located in a little-studied group of young stars, and we did not expect to find such a spectacular system. This system will likely be a benchmark for years to come,” co-lead author Richelle van Capelleveen, from Leiden University, explained.

    The work was possible thanks to the MagAO-X extreme adaptive optics system at the Magellan Telescope in Chile, the Large Binocular Telescope in Arizona, and the Very Large Telescope at the European Southern Observatory in Chile.

    The study is published in two papers in The Astrophysical Journal Letters.

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