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)
Tuesday, August 02, 2022
Life expectancy drops for Native Americans due to COVID-19
PRINCETON SCHOOL OF PUBLIC AND INTERNATIONAL AFFAIRS
IMAGE: THE PANDEMIC SET NATIVE AMERICANS FURTHER BEHIND OTHER MAJOR RACIAL AND ETHNIC GROUPS IN TERMS OF LIFE EXPECTANCY.view more
CREDIT: EGAN JIMENEZ
Native Americans experienced disproportionately high rates of deaths from COVID-19 due to poverty, crowded housing, high rates of chronic disease, employment in frontline jobs, and limited access to quality health care.
Less is known about the pandemic’s effects on life expectancy for this population, which makes up 2% of the U.S. population.
Noreen Goldman of Princeton University and Theresa AndrasfayPh.D. ’20 of the University of Southern California investigated life expectancy at birth in 2020 and 2021 — when COVID-19 rates were surging — compared to 2019.
Life expectancy is a metric of population-level mortality in a given year, and it is sensitive to deaths at younger ages.
Findings
The pandemic set Native Americans further behind other major racial and ethnic groups in terms of life expectancy. For a high-income country, these figures are shockingly low, the researchers said, and far below every country in the Americas except for Haiti.
The estimated loss in life expectancy at birth for Native Americans is 4.5 years in 2020 and 6.4 years in 2021 relative to 2019.
The pandemic reduced Native American life expectancy at birth from the already low 72 years in 2019 to about 67 years in 2020 and about 65 years in 2021 for both sexes combined.
Men and women each experienced around a six-year drop in life expectancy at birth.
Women’s life expectancy was 69 in 2021, 71 in 2020 — compared to 75 in 2019.
Men’s life expectancy was 62 in 2021, 64 in 2020 — dropping from 69 in 2019.
Native Americans experienced a loss in life expectancy at birth in 2020 that is more than three years above that for whites and 1.5 years above losses for Black and Latino populations.
Although much of this decline resulted directly from COVID-19 deaths, mortality from several chronic diseases also increased substantially for Native Americans during the pandemic. Those with “long COVID” or comorbidities may have been more likely to die from non-COVID causes, and detrimental health behaviors like smoking, drinking, and drug use also became more prevalent during this time — all likely contributing to upticks in mortality rates.
Policy Point
Despite a successful vaccination campaign among Native Americans, the loss in life expectancy at birth in 2021 unexpectedly exceeds that in 2020. There are a few plausible explanations for this disturbing finding:
Vaccines weren’t available to the public in January and February 2021, two of the deadliest months of the pandemic.
Two highly contagious variants (Delta and Omicron), which partially avoided natural and vaccine-acquired immunity, emerged in 2021.
Many Native Americans, like the general U.S. population, are still not vaccinated or did not receive a booster shot.
Deaths from several chronic diseases and drug overdoses increased for all populations during the pandemic, contributing to these dire figures.
Most importantly, Native Americans continue to experience large social, economic, and health inequities, some of which have persisted for centuries, and all of which increase the risk of COVID-19 infection, hospitalization, and death.
“The large financial investment in the American Rescue Plan to enhance identification and treatment of COVID-19 infections and to strengthen the public health infrastructure for the Native American population is a significant step forward.” — Noreen Goldman, Princeton School of Public and International Affairs
Study Authors
Noreen Goldman, Hughes-Rogers Professor of Demography and Public Affairs, Princeton School of Public and International Affairs
Theresa AndrasfayPh.D. ’20, postdoctoral fellow, University of Southern California
IMAGE: RESEARCHERS AT RICE UNIVERSITY AND ELSEWHERE POLLED THOUSANDS OF COACHES AND ATHLETIC DIRECTORS AT TEXAS HIGH SCHOOLS AND COLLEGES ABOUT HOW RISING TEMPERATURES WILL AFFECT THEIR SUMMER PRACTICES. FROM LEFT: TOP ROW, SELENA GUO, BECK MIGUEL SAUNDERS-SHULTZ, GARGI SAMARTH AND EMILY GURWITZ; SECOND ROW, CHELSEA LI, LIZZY GAVIRIA, KAREN LU AND EBRAHIM NABIZADEH; BOTTOM ROW, KATE WEINBERGER, SYLVIA DEE, JANE BALDWIN AND CHRISTINE NITTROUER.view more
CREDIT: THE CLIMATE AND WATER LAB/RICE UNIVERSITY
HOUSTON – (Aug. 1, 2022) – A survey of coaches and athletic officials in Texas indicates many of them would be wise to think harder about the risks their students face as the climate changes, according to Rice University researchers who conducted the statewide study.
Rice climate scientist Sylvia Dee led a survey of Texas coaches, trainers and athletic directors showing that while many are aware of the risks of outdoor workouts during the height of summer, not all are on board with adjusting for hotter weather. Dee said that’s concerning in light of recent warnings that climate change is already making Texas’ summers hotter. For example, a 2021 report from the Texas State Climatologist’s office said Texans should expect the number of 100-degree days each summer to nearly double by 2036 compared to the average numbers from 2001-2020.
“It’s one thing to send out a survey, but we need to think ahead and have the tough conversations about what to do if it’s too hot to play football in the summer in the near future (or even now),” said Dee, an assistant professor of Earth, environmental and planetary sciences. “I want to hope that just receiving this survey got these athletic staff thinking about the problem.”
The survey of hundreds of coaches and athletic directors at Texas high schools, colleges and universities found that most are aware of the dangers of intensive workouts and strenuous events when temperatures above 95 degrees Fahrenheit can put athletes at risk of heat-related illnesses.
They indicated they’re keeping a close eye on damaging heat, humidity and wet bulb temperatures and will adjust schedules as necessary. But surprisingly, some indicated they don’t acknowledge climate change or its implications for the health of athletes and their programs.
The results appear in an open-access paper in the American Geophysical Union journal
The 22-question survey, organized and carried out by students starting during the COVID-19 pandemic in 2020, went to 4,701 email contacts, with complete responses from 224 Texas coaches and officials, 51% of whom coach football.
The study relied on state-of-the-art simulations developed at the National Center for Atmospheric Research to compare temperature, heat index, humidity and wet bulb temperature in Texas over two key periods: 1976-2000 and 2076-2100. The projections incorporated estimates for high- and low-carbon emissions scenarios through the end of the century.
They projected average air temperatures, heat index values and wet bulb temperatures will all rise substantially in the future with heat index values regularly exceeding 113 degrees Fahrenheit in Houston, Austin and San Antonio, and exceeding 110 degrees in Dallas, even in the lower-emissions scenario. In West and North Texas cities, including Lubbock, El Paso, Midland/Odessa and Abilene, maximum heat index values could be 30 degrees higher than they are now.
Wet bulb temperature is the temperature of a parcel of air at 100% humidity, basically the point at which athletes -- and everyone else -- can no longer sweat to cool their bodies. According to one study, even the healthiest people would not survive a wet bulb temperature of 95 degrees for more than several hours in the shade.
“It’s quite rare that you would see the wet bulb temperatures on a newscast,” Dee said. “Although a weather forecast usually reports the heat index (the “feels-like” number that combines temperature and humidity), the wet bulb temperature is the one that matters for heat exhaustion, heat stroke and exertional heat illness.”
All of those responding to the survey reported they were aware of heat warnings issued by the National Weather Service, and 88% indicated they factor those warnings into decisions on whether to cancel practice. However, only 54% indicated they take humidity into account when making decisions.
“This discrepancy suggests that there may be a lack of understanding among athletic staff in how humidity affects the perceived temperature,” the researchers wrote.
They noted “athletic staff placed heavier emphasis on and were more concerned about the impact of temperature rather than climate change.” Fully 30% of those who responded were “not concerned at all” about the effects of climate change.
Dee noted there are state-level guidelines that discuss the risks of heat illness for various athletic activities. “But there’s certainly no acknowledgement of increasing risk in the future in any of these documents,” she said.
Dee said the Rice athletes among her intro-level students inspired the project. “I asked them what they do when it’s 100 degrees and humid outside. Where do you go? How do you handle that?” she said. “That got me thinking it would be a neat to start them thinking about the impacts of climate change on student athletes.”
The first pandemic summer of 2020 provided an opportunity to set them to work through online internships, gathering contact data for Texas coaches and officials. Along with designing the survey itself, she said that took nearly two years.
To better understand the responses, Dee and her Rice team collaborated with Christine Nittrouer, formerly a Ph.D. student of Mikki Hebl in Rice’s Department of Psychological Sciences and now a colleague at Texas Tech Universitywho is accustomed to analyzing survey data, as well as colleagues who study extreme weather and epidemiology.
“It’s not surprising that it’s going to get really hot,” Dee said. “But it was a little frightening that, in relation to the physiological limit, there’s a lot of evidence that it’s already too hot for student athletes to safely play sports outdoors.”
She and co-author Nittrouer are interested in a follow-up collaboration that goes beyond the athletic field.
“There’s some interesting work to be done in this field,” she said. “A lot will rely heavily on our colleagues in the social sciences and humanities to think about how we communicate the risks to people in a way that will help them change their minds.”
Co-authors of the paper are Rice Ph.D. student Ebrahim Nabizadeh and undergraduates Chelsea Li, Lizzy Gaviria, Selena Guo, Karen Lu, Beck Miguel Saunders-Shultz and Gargi Samarth; Stanford undergraduate Emily Gurwitz; Jane Baldwin, an assistant professor of Earth system science at the University of California, Irvine, and an adjunct associate research scientist at the Lamont-Doherty Earth Observatory at Columbia University; and Kate Weinberger, an environmental epidemiologist at the University of British Columbia. Nittrouer is an assistant professor of management at Texas Tech.
The Rice Office of Undergraduate Research and Inquiry supported the research.
-30-
Peer-reviewed paper:
“Increasing health risks during outdoor sports due to climate change in Texas: projections vs. attitudes” | GeoHealth | DOI: www.doi.org/10.1029/2022GH000595.
CAPTION: A survey of Texas college and high school coaches, trainers and athletic directors suggests many are not taking climate change into account as they plan their programs’ futures. (Credit: 123rf.com)
CAPTION: Researchers at Rice University and elsewhere polled thousands of coaches and athletic directors at Texas high schools and colleges about how rising temperatures will affect their summer practices. From left: top row, Selena Guo, Beck Miguel Saunders-Shultz, Gargi Samarth and Emily Gurwitz; second row, Chelsea Li, Lizzy Gaviria, Karen Lu and Ebrahim Nabizadeh; bottom row, Kate Weinberger, Sylvia Dee, Jane Baldwin and Christine Nittrouer. (Credit: The Climate and Water Lab/Rice University)
Follow Rice News and Media Relations via Twitter @RiceUNews.
Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation’s top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 4,240 undergraduates and 3,972 graduate students, Rice’s undergraduate student-to-faculty ratio is just under 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for lots of race/class interaction and No. 1 for quality of life by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger’s Personal Finance.
Increasing health risks during outdoor sports due to climate change in Texas: Projections vs. attitudes
ARTICLE PUBLICATION DATE
19-Aug-2022
CAPITALI$T FEMINISM; OVERCOMING CHAUVINISM
Successful women make the best advocates to help other women rise up in the ranks
Job referrals can have different effects depending on the gender and level of experience of who provides them, according to a new study from UC San Diego’s Rady School of Management
IMAGE: ELIZABETH L. CAMPBELL, ASSISTANT PROFESSOR OF MANAGEMENT AT THE RADY SCHOOL OF MANAGEMENTview more
CREDIT: UC SAN DIEGO'S RADY SCHOOL OF MANAGEMENT
New research utilizing data from U.S. Supreme Court law clerk hiring decisions finds that female job applicants with recommendations from other, highly tenured women have the strongest chance of getting a job offer.
The study from the University of California San Diego’s Rady School of Management examines the impact personal references have on hiring decisions because who you know is often just as or more important than what you know when it comes getting hired.
“Personal referrals and recommendations can act as a gatekeeping process in elite and lucrative occupational contexts,” said Elizabeth L. Campbell, assistant professor of management at the Rady School and lead author of the study. “Having the right connections and a powerful informal advocate, also known as a sponsor, has a big impact on job candidates’ success in the hiring process, above and beyond their qualifications alone.”
Referrals and recommendations have been shown to be helpful for women, particularly those in male-dominated professions, where women face even greater biases than the norm. However, Campbell’s study, published in the journal Academy of Management Discoveries, shows that referrals can have different effects depending on who provides them.
“We find that overall candidates who are recommended by male sponsors are more likely to be hired than those recommended by female sponsors,” Campbell said. “Yet, when we dig deeper into the data, we find that the story is a bit more complicated. When you factor in how long the sponsor has been working in their respective position, also known as their tenure or seniority, this pattern changes. Female candidates who are sponsored by highly tenured female sponsors are the most likely to be hired.”
While this research suggests that male sponsors are perceived as more persuasive overall, women who are highly tenured in their careers may have more power than they think.
“Growing awareness of gender inequalities may explain this,” Campbell said. “People now better appreciate how challenging it is for women to reach high levels of rank and tenure in their careers, relative to men. Knowing it was harder for women to get to the same place as their male peers changes the assumptions people make about those women who have achieved seniority in their fields.”
The authors utilized field data on real hiring decision for U.S. Supreme Court clerkships because they are elite early career positions in the legal field, which remains male-dominated despite an abundant pool of highly qualified female candidates.
Campbell and co-authors theorize higher levels of tenure boosts perceptions of female sponsors’ credibility specifically when it comes to identifying high-quality female candidates. This is because highly tenured female sponsors, who likely faced challenges advancing in their own careers, might be seen as better able to identify junior women poised to succeed in the field over the long term, compared to male sponsors.
“A takeaway is that highly tenured and high-ranking women, who have been successful in their careers, should feel empowered to use their influence,” Campbell said. “Our research suggests they can have a meaningful impact on helping early-career women achieve their goals, particularly in spaces where highly tenured women are notable exceptions.”
The authors obtained data for the study from a combination of sources, including the Public Information Office at the Supreme Court and the Judicial Yellow Book, which includes records of judges and the clerks they hire each year.
Using different statistical modeling techniques, the authors examine gender differences in clerkship hiring decisions while also controlling for other important factors like the candidate’s qualifications and the sponsor’s prior success with getting candidates hired as clerks.
“While we found evidence of gender differences in hiring decisions, our results also underscore that there are actions professionals can take to help address gender inequity,” Campbell said. “Sponsorship is something that leaders can do to help talented junior employees succeed. Organizations still need to do their part in trying to eliminate bias from formal hiring and promotion processes. But informal advocacy will continue to play a role in hiring decisions and our research suggests successful female leaders can wield influence in this domain to help talented junior women advance in their career.”
The study, “From Exception to Exceptional: How Gender and Tenure Impact Sponsor Effectiveness” can be found here and is co-authored by Brandy Aven and Rosalind M. Chow, both of the Tepper School of Business at Carnegie Mellon University.
“What do you think of when you picture a scientist? For many people, the image of a scientist is influenced by things like movies and TV shows, like ‘The Big Bang Theory,’ where scientists — especially women scientists — are highly stereotyped,” said Phillips, who also serves as NCEAS’s science communication and policy officer.
Indeed, popular culture still has the tendency to typecast females in STEM fields, which, among other things, pits femininity and female attractiveness against intelligence and seriousness, and casts doubt on women’s competence. Add to that a dearth in representations of diversity, and there’s a connection to be made between prevailing stereotypes and lack of role models, and the significant gender disparity in the U.S. STEM workforce. According to statistics from the National Science Board, women make up almost half of the employed U.S. population, but only about a third of the STEM workforce, a proportion that has changed little since 2010.
So in 2018, while pursuing her doctoral degree in organic geochemistry at the California Institute of Technology, Phillips turned to Instagram and started Women Doing Science, a site that features photos and profiles of female scientists all over the world in their elements, be they labs, lecture halls or the field.
“I started Women Doing Science because social media, unlike regular media, can show so many versions of what a scientist looks like, highlighting many potential role models for women in STEM that they may lack in their everyday lives or professional institutions,” Phillips said.
What started as a creative endeavor and a bit of activism quickly evolved into an international movement as submissions rolled in from female scientists all over the world. There are women doing science underwater, peering through microscopes, examining rocks, studying animals, testing robots, giving lectures. They range in appearance and dress, and they all look like they’re enjoying their work. The site currently has almost 100,000 followers and has gained a large crew of volunteers who help recruit more scientists and write about their work.
The healthy dataset naturally lent itself to a case study.
“We wanted to determine if Women Doing Science was successful in its goal of highlighting diverse and international scientists, and if yes, what the impact was to the followers of the page,” Phillips said.
In their analysis, the Women Doing Science team found that the site was indeed successful in its scope, with 37% of their posts featuring women of color and a third with bilingual captions. In fact, the site’s representation of diversity is a large draw.
“In a survey, followers mentioned that the diversity of posts was a main reason they engaged with the page,” Phillips said, “along with finding role models and generally getting inspiration.” Followers also noted the power that images of female scientist had in helping with impostor syndrome and alleviating the loneliness of being a woman in a STEM field.
But there was a downside, too. Upon examination of three particularly viral posts, two subjects received a lot of approval from followers for being “trailblazers,” while the third stimulated heated debate. It was a photo of a biology doctoral student in the lab, in heels, with hair down and makeup on.
“The third went viral for a bad reason, because the scientist was depicted as highly feminine and conforming to traditional stereotypes,” Phillips said. The angry comments and direct messages to the featured scientist came down to harassment, she added. Meanwhile, other commenters came to the doctoral student’s defense, criticizing others for gatekeeping the image of a female scientist. The admins decided to remove the post temporarily to defuse the situation.
But that feedback was important as well, highlighting pitfalls in the ongoing struggle of women to develop STEM identities.
“That experience had always been on my mind while running the page,” Phillips said. “But getting to formally analyze it was really insightful for myself in processing what was happening. I realized how fragile the identities are of women in STEM, that an image of a female scientist that is beautiful and wants to be taken seriously has such a hard time doing so, even today. We just have so much more work to do for STEM to be a truly inclusive space for women, and especially for women with marginalized identities.”
The team hopes that this case study will provide valuable information to universities and research institutions as they work toward evening the STEM playing field for incoming researchers and add dimensionality to the image of female scientists.
Drought-resistant crops, hydropower, AI for atomic measurement, controlling refrigerants and recycling e-waste
IMAGE: THE MELTON HILL DAM ON THE CLINCH RIVER IN EAST TENNESSEE CAN GENERATE UP TO 79 MEGAWATTS OF ENERGY FOR THE TENNESSEE VALLEY AUTHORITY.view more
CREDIT: JASON RICHARDS/ORNL, U.S. DEPT. OF ENERGY
Orchestrating rhythms of the light
A team of scientists led by Oak Ridge National Laboratory developed a theory that thylakoids, membrane networks key to plant photosynthesis, also function as a defense mechanism to harsh growing conditions, which could aid the development of hardier plants.
Thylakoids contain grana, structures resembling stacked coins that expand and contract when water flows in and out, like the bellows of an accordion. The action mirrors the movement of guard cells, structures on plant leaves that act like accordion buttons, allowing carbon dioxide in and water vapor out.
These structures harmonize the flow of electrons with carbon uptake during photosynthesis. Scientists have questioned why such a complicated network exists in hardier plants. ORNL researchers theorize that it helps plants tolerate fluctuating conditions such as too little or too much water and sunlight.
The theory was developed as scientists studied large-scale photosynthesis and will help refine global carbon cycling models, said ORNL’s Lianhong Gu. — Stephanie Seay
Caption: The bellows-like action of the thylakoid membrane inside plant chloroplasts harmonizes the flow of electrons to power photosynthesis. A team of scientists led by ORNL theorize the thylakoid can help plants respond to stressful growing conditions such as drought. Credit: Nathan Armistead and Jacquelyn DeMink/ORNL, U.S. Dept. of Energy
The facts behind hydropower
To further the potential benefits of the nation’s hydropower resources, researchers at Oak Ridge National Laboratory have developed and maintain a comprehensive water energy digital platform called HydroSource that informs key stakeholders of development and operational costs, environmental concerns and licensing requirements.
Hydropower accounts for nearly 7% of all electricity generated in the United States and provides quick-start capabilities during blackouts and the ability to store power for high-demand periods.
HydroSource provides updated information on hydropower facilities and infrastructure, models and visualizations for future development, and analytical tools to better understand how and where hydropower can be implemented throughout the U.S.
“We created this digital platform to enable stakeholders, including hydropower developers and operators, non-governmental agencies and advocacy groups, and policy makers to make data-driven decisions,” said ORNL’s Debjani Singh. “We all want the same thing – to develop reliable, sustainable energy while protecting the environment.” — Mimi McHale
Media Contact: Kimberly A. Askey, 865.576.2841, askeyka@ornl.gov
Caption: The Melton Hill Dam on the Clinch River in East Tennessee can generate up to 79 megawatts of energy for the Tennessee Valley Authority. Credit: Jason Richards/ORNL, U.S. Dept. of Energy
Automating neutron experiments with AI
Oak Ridge National Laboratory researchers are developing a first-of-its-kind artificial intelligence device for neutron scattering called Hyperspectral Computed Tomography, or HyperCT. The fully automated, AI-driven platform can rotate a sample in almost any direction, eliminating the need for human intervention and significantly reducing lengthy experiment times.
The design enables scientists using neutron scattering, a technique that measures atoms inside materials, to complete characterizations of samples without pauses for adjustments. The AI software determines the optimal angles to measure based on a sample’s shape, greatly reducing the amount of unnecessary data that could slow down experimental results.
“With only a few input parameters, HyperCT will give us more accurate data roughly four times faster than conventional methods,” said ORNL’s Hassina Bilheux.
Once developed, the technology can be used on any neutron scattering instrument, which will significantly increase the number of experiments and improve the quality of scientific data that only neutrons can provide. (video)
Caption: The AI-driven HyperCT platform has three primary points of articulation that can rotate a sample in almost any direction, eliminating the need for human intervention and significantly reducing lengthy experiment times. Credit: Genevieve Martin, ORNL/U.S. Dept. of Energy
Steady as it goes and flows
Oak Ridge National Laboratory researchers demonstrated that microchannel heat exchangers in heating, ventilation and air conditioning units can keep refrigerants evenly and continually distributed by inserting a device called a piezoelectric-driven magnetic actuator, or PEDMA.
Heat exchangers are shells or pipes that use metal tubing to transfer heat from one place to another. In contrast, a microchannel exchanger uses a maze of smaller pathways, making it low weight and lower cost while providing superior performance. However, these small channels can cause refrigerant maldistribution, putting extra pressure on the compressor.
In a study, the team developed a prototype PEDMA insert consisting of 3D printed resin parts and small permanent magnets.
“The magnets work to actively change the geometry inside the exchanger once inserted into the equipment,” ORNL’s Joseph Rendall said. “Testing showed significant improvement of refrigerant flow. This represents a new method for controlling flow distribution in microchannel heat exchangers.”
Caption: Oak Ridge National Laboratory researchers developed a device called a piezoelectric-driven magnetic actuator, or PEDMA, that can be inserted into the header of a microchannel heat exchanger to keep refrigerants flowing evenly and the HVAC unit running efficiently. Credit: ORNL, U.S. Dept. of Energy
Saving e-waste scraps
Researchers at Oak Ridge National Laboratory and Momentum Technologies have piloted an industrial-scale process for recycling valuable materials in the millions of tons of e-waste generated annually in the United States.
Rare earth elements, or REEs, are strategic resources in high demand but in limited supply for advanced clean energy and defense technologies. Domestic pathways for securing supply chains are needed.
Researchers previously demonstrated a method for recycling scrap permanent magnets in consumer electronics using membrane solvent extraction. Now the technology has met a critical step toward deployment. The system has been scaled up to achieve high-purity separations, as reported in Advanced Engineering Materials.
“The system is modular and scalable with a small footprint and minimal waste,” said ORNL’s Ramesh Bhave.
“We’re working with partners toward commercialization and exploring applications to recycle REEs used in growing technology areas, such as wind power and electric vehicles,” said ORNL’s Syed Islam.
Caption: Oak Ridge National Laboratory’s Ramesh Bhave and team partnered with Momentum Technologies to develop a modular, scalable system for recycling scrap permanent magnets in e-waste. Credit: Carlos Jones/ORNL, U.S. Dept. of Energy
IMAGE: THE FRESHWATER CRUSTACEAN DAPHNIA (WATER FLEA) IS A COMMON RESEARCH ORGANISM IN ECOLOGY, TOXICOLOGY, EVOLUTIONARY DEVELOPMENTAL BIOLOGY, AND OTHER FIELDS.view more
CREDIT: PROYECTO AGUA
WOODS HOLE, Mass. – Many crustaceans, including lobster, crabs, and barnacles, have a cape-like shell protruding from the head that can serve various roles, such as a little cave for storing eggs, or a protective shield to keep gills moist.
This shell (carapace), it’s been proposed, didn’t evolve from any similar structure in the crustacean ancestor, but appeared de novo (or out of the blue) through somewhat random co-option of the genes that also specify insect wings.
However, in a new study from the Marine Biological Laboratory (MBL), Research Associate Heather Bruce and Director Nipam Patel provide evidence for an alternate view: The carapace, along with other plate-like structures in arthropods (crustaceans, insects, arachnids, and myriapods) all evolved from a lateral leg lobe in a common ancestor.
This evidence buttresses their proposal for a new concept of how novel structures evolve – one which suggests that they aren’t so novel, after all. The study, on the carapace of the crustacean Daphnia, appears online inCurrent Biology.
“How novel structures arise is a central question in evolution,” Bruce says. “The prevailing idea, called gene co-option, is that genes that are functioning in one context, say to make insect wings, end up in an unrelated context, where they make, say, a carapace,” says Bruce. “But here we show that the Daphnia carapace didn’t just pop out of nowhere.”
Rather, they propose the ancestral, plate-like leg lobe that evolved into both the wing and the carapace was likely present in the ancestor of all living arthropods. But because the wing and carapace look so different from this ancestral plate, and from other plates in neighboring arthropod lineages, no one realized that they were all the same thing.
“We are starting to realize that structures that don’t look anything alike – wings, carapaces, tergal plates – are actually homologous,” Bruce says. “That suggests they have a single origin that is way more ancient than anyone would have thought, way back in the Cambrian period, [500 million] years ago.”
It was there all along (cryptic persistence)
Bruce calls her model for how novel structures emerge “cryptic persistence of serial homologs.”
“Serial homologs are things like hands and feet, or the vertebrae of our spine, or the many legs repeating down a centipede’s body,” she says. “The [repeats] can look really different, but you can see similarities, and they are all built using the same initial genetic pathways. In some cases, the full structure doesn’t grow out – you may get a truncated centipede leg, or it’s really subtle and tiny. While the cells have been programmed to form the leg, they aren’t actually growing out the leg.”
In Bruce’s view, these dormant rudiments - legs, plates, etc - can persist over millions of years, as long as another repeat of the structure is still present somewhere else in the animal. And when the time is right, the structure may grow out again and take different forms in different species – a wing in an insect, say, or a carapace in a crustacean.
“If an ancestral structure is no longer needed, nature probably just truncates or reduces that tissue rather than deleting it completely. But the tissue is still there and can be elaborated again in later lineages, and appear to us to be novel,” Bruce says.
“This kind of truncation is probably common in evolution because genetic networks are so interdependent, “Bruce explains. “if a genetic pathway or tissue were to be deleted, some other pathway or tissue would be affected.”
“I think cryptic persistence can be an explanation for a lot of ‘novel’ structures,” Bruce says.
The authors drew their conclusions by analyzing gene expression patterns in several arthropod species, and by eliminating other hypotheses of how the carapace may have evolved.
“The ancient, common origin of all these plate-like structures [in arthropods] suggests the gene networks that pattern these structures are very evolvable and plastic. They are capable of generating an awesome amount of diversity,” Bruce says.
CAPTION
The ancestral arthropod had multiple plates on each leg on every body segment, similar to the living crustacean Parhyale. Later arthropods repress most of these, but any plate can be derepressed on any body segment to form what appears to be novel structures. The Daphnia carapace evolved by de-repressing and elaborating the blue head plate and the insect wing evolved by de-repressing and elaborating the pink thoracic plate.
CREDIT
Bruce and Patel, Current Biology, 2022.
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The Marine Biological Laboratory (MBL) is dedicated to scientific discovery – exploring fundamental biology, understanding marine biodiversity and the environment, and informing the human condition through research and education. Founded in Woods Hole, Massachusetts in 1888, the MBL is a private, nonprofit institution and an affiliate of theUniversity of Chicago.
