EARTH, ATMOSPHERIC, AND PLANETARY SCIENCES
Researchers performing maintenance on seismometers on the surface of the Glacier d’Argentière in the French Alps.
Seismic observation of subglacial water flow dynamics
Subglacial water flow is known to strongly influence glacier movement, which, in turn, has a direct effect on sea level rise. However, the relationship between subglacial water flow and glacier movement is unclear, due to a lack of observational data. Ugo Nanni et al. deployed a dense array of 98 seismic sensors on the surface of the Argentière glacier in the French Alps and recorded for 1 month seismic noise generated by subglacial water flow during the onset of the 2018 melt season, thus producing a 2D map of the subglacial drainage system and observing the evolution of water flows over time. Early in the observation period, the results revealed a water flow system dominated by multiple subglacial cavities, which produced higher water pressure at the glacier’s base leading to accelerated glacier movement. The seismic data showed a transition to a more efficient channel-like drainage system over time, resulting in decreased basal water pressure and a slight deceleration of the glacier. According to the authors, similar seismic monitoring systems could be adapted to other glaciers and ice sheets to identify locations that are particularly sensitive to the meltwater increases expected from climate change. — M.H.
ECOLOGY
Asian houbara fitted with a satellite transmitter.
Temperature cues for bird migration
Birds have internal cues to prepare for migration. However, the mechanisms by which external cues, such as temperature, fine-tune birds’ migration departure times are unclear. Robert Burnside et al. fitted 48 wild Asian houbaras in Uzbekistan with satellite transmitters to track individuals over multiple migrations between 2011 and 2020. Asian houbaras breeding in Uzbekistan travel up to thousands of kilometers to their wintering grounds in southern Central Asia. Analyzing repeated migration departure decisions of houbaras revealed that individual birds started migration under similar local temperature conditions each year. Although departure responses to temperature varied among individuals, such responses were repeated at the individual level. Because of houbaras’ responses to temperature, spring departures from wintering sites and subsequent arrival at breeding sites occurred earlier during years with warm spring temperatures than during years with cool spring temperatures. Furthermore, individuals typically arrived at their breeding grounds under similar temperature conditions each year. Departure repeatability among individuals was significantly greater with respect to temperature than to daytime length or wind velocity. The findings suggest that houbara populations can adapt their migration timing to annual temperature variability without invoking genetic changes, according to the authors. — M.S.
PSYCHOLOGICAL AND COGNITIVE SCIENCES
Functional connectivity gradients gradually mature across childhood and adolescence.
Cerebral cortex changes from childhood to adolescence
The transition from childhood to adolescence involves myriad changes to brain structure and function. The topography of the cerebral cortex network architecture has been well characterized in adults, but how it changes during development from childhood to adolescence is unclear. Using diffusion mapping, Hao-Ming Dong et al. analyzed 378 resting-state functional MRI scans from 190 healthy school-age children and adolescents to show that the transition from childhood to adolescence is reflected in an age-dependent shift in gradient patterns and macroscale functional organization of the cortex. The overarching connectivity gradient in children was anchored within the unimodal cortex, between somatomotor and visual regions. However, the dominant functional gradient in adolescents transitioned into one more akin to that of adults, with the default network at the opposite end of a spectrum from primary sensory and motor regions. This transition emerged gradually with age, with an inflection point around age 13, along with substantial spatial variability in the sequence of gradient development across the cortex. According to the authors, the topographic organization of the cortex undergoes changes from a functional motif at first dominated by the distinction between sensory and motor circuits in childhood into one balanced through interactions with late-maturing aspects of the association cortex in adolescence. — S.R.
EVOLUTION
An adult male blue dasher (Pachydiplax longipennis) perched on a railing in St. Louis, MO.
Climate and wing coloration in dragonflies
Organisms often adapt to changing climates. However, whether climatic adaptation includes the evolution of traits related to mating is unclear. Michael Moore et al. examined field guides and citizen-science observations of dragonflies, created a database of melanin wing ornaments and habitat climates for 319 dragonfly species, and evaluated the relationship between ornaments and temperatures. Although ornamental patches of melanin on dragonfly wings are advantageous in courtship and rival intimidation, they can increase body temperatures to more than 2 °C above ambient temperatures. Such a rise in body temperature benefits dragonflies in cool climates but may damage wing tissues, reduce fighting abilities, or prove lethal to dragonflies in warm climates. Male dragonflies in the coolest parts of North America have consequently evolved larger and darker melanin wing patches than male dragonflies in the warmest regions of the continent. During the warmest years between 2005 and 2019, the authors report, male dragonflies exhibited the smallest melanin wing patches. However, climate did not significantly affect wing ornaments of female dragonflies. Climate-warming projections suggested that male dragonflies will likely evolve even smaller melanin wing patches by 2070 as global warming increases. The findings suggest that mating-related traits of male, but not female, dragonflies consistently evolve to adapt to local climates, according to the authors. — M.S.
PHYSIOLOGY
Improved stem cell model for Duchenne muscular dystrophy
Duchenne muscular dystrophy (DMD) is a disabling genetic disease that causes the degeneration of skeletal muscles and premature death. The disease lacks a cure, and standard-of-care treatment with glucocorticoids can cause side effects such as obesity and mood disorders. Ziad Al Tanoury, John Zimmerman, Jyoti Rao, Daniel Sieiro, Harold McNamara, Thomas Cherrier, et al. developed an improved preclinical model for testing alternative candidate therapies. The optimized protocol differentiates human induced pluripotent stem cells (iPSCs) to skeletal muscle fibers. First, cells from healthy adults are genetically reprogrammed into iPSCs, which are immature and can turn into multiple cell types. Next, CRISPR-Cas9–mediated gene editing is used to introduce DMD mutations in the iPSCs, which are then exposed to a chemical cocktail to induce the formation of skeletal muscle cells. The resulting cells are more mature than those generated by previously reported iPSC-based DMD approaches. As a result, the new DMD-mutant, iPSC-derived muscle fibers recapitulate major features of the disease. For example, the mutant muscle fibers show excessive branching and fusion, contraction defects, and increased calcium signaling, when compared with nonmutant iPSC-derived muscle fibers. According to the authors, the preclinical model could be used to examine the molecular mechanisms underlying DMD, advance personalized medicine applications, and develop effective treatments with few side effects. — J.W.
ANTHROPOLOGY
European settlers and mortality of Indigenous people
The decline of Indigenous populations in the Americas following the arrival of European settlers is among the most severe demographic collapses. However, the timing and scale of the collapse in some regions, such as California, remain unclear. To determine the impact of diseases in the Americas before and after 1769, Terry Jones et al. analyzed age-at-death records of 33,715 Indigenous people who lived in central California between 3050 BCE and 1870 CE. The data included 10,256 records from excavated human burial sites and 23,459 records created by missionaries from Spain and retained by missions in central California. From 1770 CE to 1800 CE, Indigenous populations in central California exhibited a mortality profile similar to that of populations experiencing an epidemic plague. Beginning around 1770 CE, Indigenous people likely had sustained contact with individuals from Spain, who established permanent settlements and missions in central California during this period. Mortality records also showed that more females than males died near Spanish missions. The findings suggest that extreme social disruption, including increased violence, enslavement, and food insecurity, caused by Spanish settlers increased the vulnerability of Indigenous people to disease, while also increasing mortality in general, according to the authors. — M.S.
EARTH, ATMOSPHERIC, AND PLANETARY SCIENCES
Inhabitants of the deep sea, such as this deep sea angler, could soon see their homes transformed by mining. Survey data suggest that many of the people who care about the ecosystem’s fate see it as a mystical place. Image credit: Dante Fenolio/Science Source.
Emotional associations, more than knowledge, determine how much people care about the deep sea
Posted on July 6, 2021
Carolyn Beans
With new technological advances in deep-sea mining, the ocean floor’s trove of valuable metals and rare earth elements is coming within reach of commercial mining operations. The impending reality of this practice, and its associated environmental risks, raises the question of how we, as a society, assess the value of a place we may never see to guide environmental decisions.