SciCombinator

Discover the most talked about and latest scientific content & concepts.

Journal: Current biology : CB

614

Recent climate change on the Antarctic Peninsula is well documented [1-5], with warming, alongside increases in precipitation, wind strength, and melt season length [1, 6, 7], driving environmental change [8, 9]. However, meteorological records mostly began in the 1950s, and paleoenvironmental datasets that provide a longer-term context to recent climate change are limited in number and often from single sites [7] and/or discontinuous in time [10, 11]. Here we use moss bank cores from a 600-km transect from Green Island (65.3°S) to Elephant Island (61.1°S) as paleoclimate archives sensitive to regional temperature change, moderated by water availability and surface microclimate [12, 13]. Mosses grow slowly, but cold temperatures minimize decomposition, facilitating multi-proxy analysis of preserved peat [14]. Carbon isotope discrimination (Δ(13)C) in cellulose indicates the favorability of conditions for photosynthesis [15]. Testate amoebae are representative heterotrophs in peatlands [16-18], so their populations are an indicator of microbial productivity [14]. Moss growth and mass accumulation rates represent the balance between growth and decomposition [19]. Analyzing these proxies in five cores at three sites over 150 years reveals increased biological activity over the past ca. 50 years, in response to climate change. We identified significant changepoints in all sites and proxies, suggesting fundamental and widespread changes in the terrestrial biosphere. The regional sensitivity of moss growth to past temperature rises suggests that terrestrial ecosystems will alter rapidly under future warming, leading to major changes in the biology and landscape of this iconic region-an Antarctic greening to parallel well-established observations in the Arctic [20].

Concepts: Plant, Climate, Weather, Temperature, Antarctica, Cold, Peat, Moss

517

Following the 1986 Chernobyl accident, 116,000 people were permanently evacuated from the 4,200 km(2) Chernobyl exclusion zone [1]. There is continuing scientific and public debate surrounding the fate of wildlife that remained in the abandoned area. Several previous studies of the Chernobyl exclusion zone (e.g. [2,3]) indicated major radiation effects and pronounced reductions in wildlife populations at dose rates well below those thought [4,5] to cause significant impacts. In contrast, our long-term empirical data showed no evidence of a negative influence of radiation on mammal abundance. Relative abundances of elk, roe deer, red deer and wild boar within the Chernobyl exclusion zone are similar to those in four (uncontaminated) nature reserves in the region and wolf abundance is more than 7 times higher. Additionally, our earlier helicopter survey data show rising trends in elk, roe deer and wild boar abundances from one to ten years post-accident. These results demonstrate for the first time that, regardless of potential radiation effects on individual animals, the Chernobyl exclusion zone supports an abundant mammal community after nearly three decades of chronic radiation exposures.

Concepts: Chernobyl disaster, Deer, Zone of alienation, Abundance, Abundance of the chemical elements, Wildlife, Megafauna of Eurasia, Venison

359

In the third trimester of pregnancy, the human fetus has the capacity to process perceptual information [1-3]. With advances in 4D ultrasound technology, detailed assessment of fetal behavior [4] is now possible. Furthermore, modeling of intrauterine conditions has indicated a substantially greater luminance within the uterus than previously thought [5]. Consequently, light conveying perceptual content could be projected through the uterine wall and perceived by the fetus, dependent on how light interfaces with maternal tissue. We do know that human infants at birth show a preference to engage with a top-heavy, face-like stimulus when contrasted with all other forms of stimuli [6, 7]. However, the viability of performing such an experiment based on visual stimuli projected through the uterine wall with fetal participants is not currently known. We examined fetal head turns to visually presented upright and inverted face-like stimuli. Here we show that the fetus in the third trimester of pregnancy is more likely to engage with upright configural stimuli when contrasted to inverted visual stimuli, in a manner similar to results with newborn participants. The current study suggests that postnatal experience is not required for this preference. In addition, we describe a new method whereby it is possible to deliver specific visual stimuli to the fetus. This new technique provides an important new pathway for the assessment of prenatal visual perceptual capacities.

Concepts: Pregnancy, Childbirth, Infant, Embryo, Fetus, Uterus, Abortion, 3D ultrasound

356

Smallpox holds a unique position in the history of medicine. It was the first disease for which a vaccine was developed and remains the only human disease eradicated by vaccination. Although there have been claims of smallpox in Egypt, India, and China dating back millennia [1-4], the timescale of emergence of the causative agent, variola virus (VARV), and how it evolved in the context of increasingly widespread immunization, have proven controversial [4-9]. In particular, some molecular-clock-based studies have suggested that key events in VARV evolution only occurred during the last two centuries [4-6] and hence in apparent conflict with anecdotal historical reports, although it is difficult to distinguish smallpox from other pustular rashes by description alone. To address these issues, we captured, sequenced, and reconstructed a draft genome of an ancient strain of VARV, sampled from a Lithuanian child mummy dating between 1643 and 1665 and close to the time of several documented European epidemics [1, 2, 10]. When compared to vaccinia virus, this archival strain contained the same pattern of gene degradation as 20(th) century VARVs, indicating that such loss of gene function had occurred before ca. 1650. Strikingly, the mummy sequence fell basal to all currently sequenced strains of VARV on phylogenetic trees. Molecular-clock analyses revealed a strong clock-like structure and that the timescale of smallpox evolution is more recent than often supposed, with the diversification of major viral lineages only occurring within the 18(th) and 19(th) centuries, concomitant with the development of modern vaccination.

Concepts: Infectious disease, Virus, Vaccine, Vaccination, Vaccinia, Poxviridae, Smallpox, Cowpox

336

Misophonia is an affective sound-processing disorder characterized by the experience of strong negative emotions (anger and anxiety) in response to everyday sounds, such as those generated by other people eating, drinking, chewing, and breathing [1-8]. The commonplace nature of these sounds (often referred to as “trigger sounds”) makes misophonia a devastating disorder for sufferers and their families, and yet nothing is known about the underlying mechanism. Using functional and structural MRI coupled with physiological measurements, we demonstrate that misophonic subjects show specific trigger-sound-related responses in brain and body. Specifically, fMRI showed that in misophonic subjects, trigger sounds elicit greatly exaggerated blood-oxygen-level-dependent (BOLD) responses in the anterior insular cortex (AIC), a core hub of the "salience network" that is critical for perception of interoceptive signals and emotion processing. Trigger sounds in misophonics were associated with abnormal functional connectivity between AIC and a network of regions responsible for the processing and regulation of emotions, including ventromedial prefrontal cortex (vmPFC), posteromedial cortex (PMC), hippocampus, and amygdala. Trigger sounds elicited heightened heart rate (HR) and galvanic skin response (GSR) in misophonic subjects, which were mediated by AIC activity. Questionnaire analysis showed that misophonic subjects perceived their bodies differently: they scored higher on interoceptive sensibility than controls, consistent with abnormal functioning of AIC. Finally, brain structural measurements implied greater myelination within vmPFC in misophonic individuals. Overall, our results show that misophonia is a disorder in which abnormal salience is attributed to particular sounds based on the abnormal activation and functional connectivity of AIC.

Concepts: Brain, Cerebrum, Hippocampus, Limbic system, Prefrontal cortex, Ventromedial prefrontal cortex, Insular cortex, Galvanic skin response

328

Noninvasive brain stimulation has shown considerable promise for enhancing cognitive functions by the long-term manipulation of neuroplasticity [1-3]. However, the observation of such improvements has been focused at the behavioral level, and enhancements largely restricted to the performance of basic tasks. Here, we investigate whether transcranial random noise stimulation (TRNS) can improve learning and subsequent performance on complex arithmetic tasks. TRNS of the bilateral dorsolateral prefrontal cortex (DLPFC), a key area in arithmetic [4, 5], was uniquely coupled with near-infrared spectroscopy (NIRS) to measure online hemodynamic responses within the prefrontal cortex. Five consecutive days of TRNS-accompanied cognitive training enhanced the speed of both calculation- and memory-recall-based arithmetic learning. These behavioral improvements were associated with defined hemodynamic responses consistent with more efficient neurovascular coupling within the left DLPFC. Testing 6 months after training revealed long-lasting behavioral and physiological modifications in the stimulated group relative to sham controls for trained and nontrained calculation material. These results demonstrate that, depending on the learning regime, TRNS can induce long-term enhancement of cognitive and brain functions. Such findings have significant implications for basic and translational neuroscience, highlighting TRNS as a viable approach to enhancing learning and high-level cognition by the long-term modulation of neuroplasticity.

Concepts: Psychology, Brain, Cognition, Cerebrum, Perception, Attention versus memory in prefrontal cortex, Dorsolateral prefrontal cortex, Brodmann area

314

While components of the pathway that establishes left-right asymmetry have been identified in diverse animals, from vertebrates to flies, it is striking that the genes involved in the first symmetry-breaking step remain wholly unknown in the most obviously chiral animals, the gastropod snails. Previously, research on snails was used to show that left-right signaling of Nodal, downstream of symmetry breaking, may be an ancestral feature of the Bilateria [1, 2]. Here, we report that a disabling mutation in one copy of a tandemly duplicated, diaphanous-related formin is perfectly associated with symmetry breaking in the pond snail. This is supported by the observation that an anti-formin drug treatment converts dextral snail embryos to a sinistral phenocopy, and in frogs, drug inhibition or overexpression by microinjection of formin has a chirality-randomizing effect in early (pre-cilia) embryos. Contrary to expectations based on existing models [3-5], we discovered asymmetric gene expression in 2- and 4-cell snail embryos, preceding morphological asymmetry. As the formin-actin filament has been shown to be part of an asymmetry-breaking switch in vitro [6, 7], together these results are consistent with the view that animals with diverse body plans may derive their asymmetries from the same intracellular chiral elements [8].

Concepts: DNA, Gene, Gene expression, Animal, Symmetry, Mollusca, Gastropod shell, Snail

313

Predator-prey dynamics are an important evolutionary driver of escalating predation mode and efficiency, and commensurate responses of prey [1-3]. Among these strategies, camouflage is important for visual concealment, with countershading the most universally observed [4-6]. Extant terrestrial herbivores free of significant predation pressure, due to large size or isolation, do not exhibit countershading. Modern predator-prey dynamics may not be directly applicable to those of the Mesozoic due to the dominance of very large, visually oriented theropod dinosaurs [7]. Despite thyreophoran dinosaurs' possessing extensive dermal armor, some of the most extreme examples of anti-predator structures [8, 9], little direct evidence of predation on these and other dinosaur megaherbivores has been documented. Here we describe a new, exquisitely three-dimensionally preserved nodosaurid ankylosaur, Borealopelta markmitchelli gen. et sp. nov., from the Early Cretaceous of Alberta, which preserves integumentary structures as organic layers, including continuous fields of epidermal scales and intact horn sheaths capping the body armor. We identify melanin in the organic residues through mass spectroscopic analyses and observe lighter pigmentation of the large parascapular spines, consistent with display, and a pattern of countershading across the body. With an estimated body mass exceeding 1,300 kg, B. markmitchelli was much larger than modern terrestrial mammals that either are countershaded or experience significant predation pressure as adults. Presence of countershading suggests predation pressure strong enough to select for concealment in this megaherbivore despite possession of massive dorsal and lateral armor, illustrating a significant dichotomy between Mesozoic predator-prey dynamics and those of modern terrestrial systems.

Concepts: Predation, Crypsis, Reptile, Mammal, Cretaceous, Dinosaur, Carnivore, Ankylosauria

280

Balance arises from the interplay of external forces acting on the body and internally generated movements. Many animal bodies are inherently unstable, necessitating corrective locomotion to maintain stability. Understanding how developing animals come to balance remains a challenge. Here we study the interplay among environment, sensation, and action as balance develops in larval zebrafish. We first model the physical forces that challenge underwater balance and experimentally confirm that larvae are subject to constant destabilization. Larvae propel in swim bouts that, we find, tend to stabilize the body. We confirm the relationship between locomotion and balance by changing larval body composition, exacerbating instability and eliciting more frequent swimming. Intriguingly, developing zebrafish come to control the initiation of locomotion, swimming preferentially when unstable, thus restoring preferred postures. To test the sufficiency of locomotor-driven stabilization and the developing control of movement timing, we incorporate both into a generative model of swimming. Simulated larvae recapitulate observed postures and movement timing across early development, but only when locomotor-driven stabilization and control of movement initiation are both utilized. We conclude the ability to move when unstable is the key developmental improvement to balance in larval zebrafish. Our work informs how emerging sensorimotor ability comes to impact how and why animals move when they do.

Concepts: Developmental biology, Fish, Force, Centrifugation, Stability, Instability

276

Ants can navigate over long distances between their nest and food sites using visual cues [1, 2]. Recent studies show that this capacity is undiminished when walking backward while dragging a heavy food item [3-5]. This challenges the idea that ants use egocentric visual memories of the scene for guidance [1, 2, 6]. Can ants use their visual memories of the terrestrial cues when going backward? Our results suggest that ants do not adjust their direction of travel based on the perceived scene while going backward. Instead, they maintain a straight direction using their celestial compass. This direction can be dictated by their path integrator [5] but can also be set using terrestrial visual cues after a forward peek. If the food item is too heavy to enable body rotations, ants moving backward drop their food on occasion, rotate and walk a few steps forward, return to the food, and drag it backward in a now-corrected direction defined by terrestrial cues. Furthermore, we show that ants can maintain their direction of travel independently of their body orientation. It thus appears that egocentric retinal alignment is required for visual scene recognition, but ants can translate this acquired directional information into a holonomic frame of reference, which enables them to decouple their travel direction from their body orientation and hence navigate backward. This reveals substantial flexibility and communication between different types of navigational information: from terrestrial to celestial cues and from egocentric to holonomic directional memories.

Concepts: Earth, Navigation, Classical mechanics, Rotation, Walking, Rigid body, Frame of reference, Drag-and-drop