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Ants, like many other animals, use visual memory to follow extended routes through complex environments, but it is unknown how their small brains implement this capability. The mushroom body neuropils have been identified as a crucial memory circuit in the insect brain, but their function has mostly been explored for simple olfactory association tasks. We show that a spiking neural model of this circuit originally developed to describe fruitfly (Drosophila melanogaster) olfactory association, can also account for the ability of desert ants (Cataglyphis velox) to rapidly learn visual routes through complex natural environments. We further demonstrate that abstracting the key computational principles of this circuit, which include one-shot learning of sparse codes, enables the theoretical storage capacity of the ant mushroom body to be estimated at hundreds of independent images. Author Summary We propose a model based directly on insect neuroanatomy that is able to account for the route following capabilities of ants. We show this mushroom body circuit has the potential to store a large number of images, generated in a realistic simulation of an ant traversing a route, and to distinguish previously stored images from highly similar images generated when looking in the wrong direction. It can thus control successful recapitulation of routes under ecologically valid test conditions.

Intratumor heterogeneity is a major challenge in cancer treatment. To decipher patterns of chromosomal heterogeneity, we analyzed six colorectal cancer cell lines by multiplex interphase FISH (miFISH). The mismatch-repair-deficient cell lines DLD-1 and HCT116 had the most stable copy numbers, whereas aneuploid cell lines (HT-29, SW480, SW620 and H508) displayed a higher degree of instability. We subsequently assessed the clonal evolution of single cells in two colorectal carcinoma cell lines, SW480 and HT-29, which both have aneuploid karyotypes but different degrees of chromosomal instability. The clonal compositions of the single cell-derived daughter lines, as assessed by miFISH, differed for HT-29 and SW480. Daughters of HT-29 were stable, clonal, with little heterogeneity. Daughters of SW480 were more heterogeneous, with the single cell-derived daughter lines separating into two distinct populations with different ploidy (hyper-diploid and near-triploid), morphology, gene expression and tumorigenicity. To better understand the evolutionary trajectory for the two SW480 populations, we constructed phylogenetic trees which showed ongoing instability in the daughter lines. When analyzing the evolutionary development over time, most single cell-derived daughter lines maintained their major clonal pattern, with the exception of one daughter line that showed a switch involving a loss of APC. Our meticulous analysis of the clonal evolution and composition of these colorectal cancer models shows that all chromosomes are subject to segregation errors, however, specific net genomic imbalances are maintained. Karyotype evolution is driven by the necessity to arrive at and maintain a specific plateau of chromosomal copy numbers as the drivers of carcinogenesis.

Abstract. The Greenland ice sheet is one of the largest contributors to global meansea-level rise today and is expected to continue to lose mass as the Arcticcontinues to warm. The two predominant mass loss mechanisms are increasedsurface meltwater run-off and mass loss associated with the retreat ofmarine-terminating outlet glaciers. In this paper we use a large ensemble ofGreenland ice sheet models forced by output from a representative subset ofthe Coupled Model Intercomparison Project (CMIP5) global climate models to project ice sheet changes and sea-level risecontributions over the 21st century. The simulations are part of theIce Sheet Model Intercomparison Project for CMIP6 (ISMIP6). We estimate thesea-level contribution together with uncertainties due to future climateforcing, ice sheet model formulations and ocean forcing for the twogreenhouse gas concentration scenarios RCP8.5 and RCP2.6. The resultsindicate that the Greenland ice sheet will continue to lose mass in bothscenarios until 2100, with contributions of 90±50 and 32±17 mm to sea-level rise for RCP8.5 and RCP2.6, respectively. The largestmass loss is expected from the south-west of Greenland, which is governed bysurface mass balance changes, continuing what is already observed today.Because the contributions are calculated against an unforced controlexperiment, these numbers do not include any committed mass loss, i.e. massloss that would occur over the coming century if the climate forcingremained constant. Under RCP8.5 forcing, ice sheet model uncertaintyexplains an ensemble spread of 40 mm, while climate model uncertainty andocean forcing uncertainty account for a spread of 36 and 19 mm,respectively. Apart from those formally derived uncertainty ranges, thelargest gap in our knowledge is about the physical understanding andimplementation of the calving process, i.e. the interaction of the ice sheetwith the ocean. info:eu-repo/semantics/published

AbstractA trade‐off between current and future fitness potentially explains variation in life‐history strategies. A proposed mechanism behind this is parasite‐mediated reproductive costs: individuals that allocate more resources to reproduction have fewer to allocate to defence against parasites, reducing future fitness. We examined how reproduction influenced faecal egg counts (FEC) of strongyle nematodes using data collected between 1989 and 2008 from a wild population of Soay sheep in the St. Kilda archipelago, Scotland (741 individuals). Increased reproduction was associated with increased FEC during the lambing season: females that gave birth, and particularly those that weaned a lamb, had higher FEC than females that failed to reproduce. Structural equation modelling revealed future reproductive costs: a positive effect of reproduction on spring FEC and a negative effect on summer body weight were negatively associated with overwinter survival. Overall, we provide evidence that parasite resistance and body weight are important mediators of survival costs of reproduction.

The North Sea Last Interglacial sea level is sensitive to the fingerprint of mass loss from polar ice sheets. However, the signal is complicated by the influence of glacial isostatic adjustment driven by Penultimate Glacial Period ice-sheet changes, and yet these ice-sheet geometries remain significantly uncertain. Here, we produce new reconstructions of the Eurasian ice sheet during the Penultimate Glacial Maximum (PGM) by employing large ensemble experiments from a simple ice-sheet model that depends solely on basal shear stress, ice extent, and topography. To explore the range of uncertainty in possible ice geometries, we use a parameterised shear-stress map as input that has been developed to incorporate bedrock characteristics and the influence of ice-sheet basal processes. We perform Bayesian uncertainty quantification, utilising Gaussian process emulation, to calibrate against global ice-sheet reconstructions of the Last Deglaciation and rule out combinations of input parameters that produce unrealistic ice sheets. The refined parameter space is then applied to the PGM to create an ensemble of constrained 3D Eurasian ice-sheet geometries. Our reconstructed PGM Eurasian ice-sheet volume is 48±8 m sea-level equivalent (SLE). We find that the Barents–Kara Sea region displays both the largest mean volume and volume uncertainty of 24±8 m SLE while the British–Irish sector volume of 1.7±0.2 m SLE is the smallest. Our new workflow may be applied to other locations and periods where ice-sheet histories have limited empirical data.

Changes in the volume and extent of land ice of the Svalbard archipelago have been the subject of considerable research since their sensitivity to changes in climate was first noted. However, the measurement of these changes is often necessarily based on point or profile measurements which may not be representative if extrapolated to a whole catchment or region. Combining high-resolution elevation data from contemporary laser-altimetry surveys and archived aerial photography makes it possible to measure historical changes across a glacier's surface without the need for extrapolation. Here we present a high spatial resolution time-series for six Arctic glaciers in the Svalbard archipelago spanning 1961 to 2005. We find high variability in thinning rates between sites with prevalent elevation changes at all sites averaging −0.59 ± 0.04 m a⁻¹ between 1961–2005. Prior to 1990, ice surface elevation was changing at an average rate of −0.52 ± 0.09 m a⁻¹ which decreased to −0.76 ± 0.10 m a⁻¹ after 1990. Setting the elevation changes against the glaciers' altitude distribution reveals that significant increases in thinning rates are occurring most notably in the glaciers' upper reaches. We find that these changes are coincident with a decrease in winter precipitation at the Longyearbyen meteorological station and could reflect a decrease in albedo or dynamic response to lower accumulation. Further work is required to understand fully the causes of this increase in thinning rates in the glaciers' upper reaches. If on-going and occurring elsewhere in the archipelago, these changes will have a significant effect on the region's future mass balance. Our results highlight the importance of understanding the climatological context of geodetic mass balance measurements and demonstrate the difficulty of using index glaciers to represent regional changes in areas of strong climatological gradients.