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This study presents evidence of stably trapped electrons at Jupiter's moon Ganymede. We model energetic electron pitch angle distributions and compare them to observations from the Galileo Energetic Particle Detector to identify signatures of trapped particles during the G28 encounter. We trace electron trajectories to show that they enter Ganymede's mini‐magnetospheric environment, become trapped, and drift around the moon for up to 30 min, in some cases stably orbiting the moon multiple times. Conservation of the first adiabatic invariant partially contributes to energy changes throughout the electrons' orbits, with additional acceleration driven by local electric fields, before they return to Jupiter's magnetosphere or impact the surface. These trapped particles manifest as an electron population with an enhanced flux compared to elsewhere within the mini‐magnetosphere that are detectable by future spacecraft. Plain Language Summary: The magnetized planets of the solar system are known to possess a population of high‐energy, orbiting electrons that are sustained for extended timescales. By comparison, Ganymede, the only moon in the solar system confirmed to have its own permanent magnetic field, should also retain a similar population of trapped particles. Observations from the Galileo mission hint at the existence of electrons that may be locally trapped at the moon, but information regarding their origin and the mechanism behind trapping these electrons is unknown. Furthermore, there are no constraints on the processes that help sustain such a trapped population, and the timescales over which they are maintained at Ganymede remain unknown. In this study, we provide evidence that trapped electrons exist at Ganymede, identify the mechanisms driving their dynamics, and answer open questions about the moon's local energetic particle environment. Key Points: We compare Galileo G28 energetic electron data with test particle tracing to identify a population of trapped electrons at GanymedeWe achieve a robust match between the energetic electron pitch angle distributions from our model compared to those observed by GalileoElectrons follow stable orbits that can encircle the moon multiple times before being lost to the surface or to Jupiter's magnetosphere [ABSTRACT FROM AUTHOR]

Based on a hybrid model of Europa's magnetospheric interaction, we provide context for the magnetic field perturbations observed by the Juno spacecraft during its only close flyby of the moon in September 2022. By systematically varying the incident flow conditions and the density profile of Europa's atmosphere, we demonstrate that the observed, large‐scale signatures of magnetic field draping are consistent with a dawn‐dusk asymmetry in the moon's neutral envelope. During the flyby, such an asymmetry would have enhanced the magnetic perturbations in Europa's anti‐Jovian hemisphere, explaining why the spacecraft already detected strong field line draping while still several moon radii away. Conversely, a reduced neutral density in the sub‐Jovian hemisphere can explain why the perturbations in the flow‐aligned field component remained nearly constant as Juno approached Europa. While a dawn‐dusk asymmetry in Europa's atmosphere has been predicted by theoretical work, our results provide the first in situ hints of its presence. Plain Language Summary: Located within Jupiter's magnetosphere, the small Galilean moon Europa is continuously exposed to a flow of magnetized plasma, traveling at a relative velocity of about 100 km/s. The deflection of this plasma around Europa generates perturbations to Jupiter's magnetic field, as observed for the first time in two decades during the flyby of the Juno spacecraft in 2022. The magnitude and extension of these magnetic perturbations are largely determined by the shape of Europa's atmosphere and ionosphere which represent obstacles to the incident magnetospheric plasma. To provide three‐dimensional context for the structure of Europa's magnetic environment at the time of the Juno flyby, we have applied a computer simulation to study the moon's interaction with the plasma flow. Comparison between modeled and observed magnetic fields suggests that, at the time when Juno collected these data, Europa's atmosphere may have been denser in the anti‐Jovian than in the Jupiter‐facing hemisphere. Theoretical predictions suggest such an asymmetry to be present in Europa's neutral envelope, partially generated by centrifugal and Coriolis forces acting on the gas molecules during the moon's rotation around Jupiter. Our study reveals first hints from a spacecraft flyby that such a hemispheric asymmetry may indeed exist in Europa's atmosphere. Key Points: By applying a hybrid model (kinetic ions, fluid electrons), we study Europa's interaction with Jupiter's magnetosphere during the Juno flybyA dawn‐dusk asymmetry in Europa's atmosphere can reproduce the large‐scale structure of the draping signatures seen by the Juno magnetometerThe spacecraft encountered the center of Europa's southern Alfven wing during ingress and the periphery of the northern wing during egress [ABSTRACT FROM AUTHOR]

Using a hybrid model (kinetic ions, fluid electrons), we provide context for plasma and magnetic field observations from Juno's PJ34 flyby of Ganymede on 07 June 2021. We consider five model configurations that successively increase the complexity of Ganymede's atmosphere and ionosphere by including additional particle species and ionization mechanisms. We examine the density and flow patterns of pick‐up ions with small H2+ $\left({\mathrm{H}}_{2}^{+}\right)$, intermediate (H2O+), and large O2+ $\left({\mathrm{O}}_{2}^{+}\right)$ masses in Ganymede's interaction region. The results are validated by comparing the modeled magnetic field and ion densities against time series from Juno's magnetometer and plasma instruments. Our major findings are: (a) Ganymede's internal dipole dominated the magnetic field signature observed inside the moon's magnetosphere, while plasma currents shaped the field perturbations within the "wake" region detected along the Jupiter‐averted magnetopause. (b) Ganymede's pick‐up tail leaves a subtle, but clearly discernible imprint in the magnetic field downstream of the moon. (c) Heavy pick‐up ions dominate ionospheric outflow and form a tail with steep outer boundaries. (d) During the flyby, the position of Ganymede's Jupiter‐facing magnetopause varied in time due to Kelvin‐Helmholtz waves traveling along the boundary layer. As such, the location of the Jupiter‐facing magnetopause observed by Juno represents only a single snapshot of this time‐dependent process. (e) Ionospheric hydrogen ions are partially generated outside of Ganymede's magnetopause, forming a dilute H2+ ${\mathrm{H}}_{2}^{+}$ corona that surrounds the moon's magnetosphere. (f) Most H2O+ ions are produced at low latitudes where field lines are closed, resulting in a very dilute pick‐up tail for this species. Key Points: Using a hybrid model, we provide three‐dimensional context for plasma and magnetic field observations from the Juno PJ34 flyby of GanymedeEscaping heavy ions from Ganymede's ionosphere cause subtle, but discernible modifications to the magnetic field in the vicinity of the moonGanymede's sub‐Jovian magnetopause is susceptible to Kelvin‐Helmholtz instabilities, causing the location of the boundary layer to oscillate [ABSTRACT FROM AUTHOR]

Recent years have witnessed significant progress in understanding how memories are encoded, from the molecular to the cellular and the circuit/systems levels. With a good compromise between brain complexity and behavioral sophistication, the fruit fly Drosophila melanogaster is one of the preeminent animal models of learning and memory. Here we review how memories are encoded in Drosophila, with a focus on short-term memory and an eye toward future directions. Forward genetic screens have revealed a large number of genes and transcripts necessary for learning and memory, some acting cell-autonomously. Further, the relative numerical simplicity of the fly brain has enabled the reverse engineering of learning circuits with remarkable precision, in some cases ascribing behavioral phenotypes to single neurons. Functional imaging and physiological studies have localized and parsed the plasticity that occurs during learning at some of the major loci. Connectomics projects are significantly expanding anatomical knowledge of the nervous system, filling out the roadmap for ongoing functional/physiological and behavioral studies, which are being accelerated by simultaneous tool development. These developments have provided unprecedented insight into the fundamental neural principles of learning, and lay the groundwork for deep understanding in the near future. [ABSTRACT FROM AUTHOR]

The dioptric visual system relies on precisely focusing lenses that project light onto a neural retina. While the proteins that constitute the lenses of many vertebrates are relatively well characterized, less is known about the proteins that constitute invertebrate lenses, especially the lens facets in insect compound eyes. To address this question, we used mass spectrophotometry to define the major proteins that comprise the corneal lenses from the adult Drosophila melanogaster compound eye. This led to the identification of four cuticular proteins: two previously identified lens proteins, drosocrystallin and retinin, and two newly identified proteins, Cpr66D and Cpr72Ec. To determine which ommatidial cells contribute each of these proteins to the lens, we conducted in situ hybridization at 50% pupal development, a key age for lens secretion. Our results confirm previous reports that drosocrystallin and retinin are expressed in the two primary corneagenous cells-cone cells and primary pigment cells. Cpr72Ec and Cpr66D, on the other hand, are more highly expressed in higher order interommatidial pigment cells. These data suggest that the complementary expression of cuticular proteins give rise to the center vs periphery of the corneal lens facet, possibly facilitating a refractive gradient that is known to reduce spherical aberration. Moreover, these studies provide a framework for future studies aimed at understanding the cuticular basis of corneal lens function in holometabolous insect eyes. [ABSTRACT FROM AUTHOR]

The highly specialized evolution of Strepsiptera has produced one of the most unusual eyes among mature insects, perhaps in line with their extremely complex and challenging life cycle. This relatively rare insect order is one of the few for which it has been unclear what spectral classes of photoreceptors any of its members may possess, an even more apt question given the nocturnal evolution of the group. To address this question, we performed electroretinograms on adult male Xenos peckii: we measured spectral responses to equi-quantal monochromatic light flashes of different wavelengths, and established VlogI relationships to calculate spectral sensitivities. Based on opsin template fits, we found maximal spectral sensitivity (λmax) in the green domain at 539 nm. Application of a green light to `bleach' green receptors revealed that a UV peak was contributed to by an independent UV opsin with a λmax of 346 nm. Transcriptomics and a phylogenetic analysis including 50 other opsin sequences further confirmed the presence of these two opsin classes. While these findings do not necessarily indicate that these unorthodox insects have color vision, they raise the possibility that UV vision plays an important role in the ability of X. peckii males to find the very cryptic strepsipteran females that are situated within their wasp hosts. [ABSTRACT FROM AUTHOR]

SUMMARY Stemmata, the larval eyes of holometabolous insects are extremely diverse, ranging from full compound eyes, to a few ommatidial units as are typical in compound eyes, to sophisticated and functionally specialized image-forming camera-type eyes. Stemmata evolved from a compound eye ommatidial ancestor, an eye type that is morphologically well conserved in regards to cellular composition, and well studied in regards to development. However, despite this evolutionary origin it remains largely unknown how stemmata develop. In addition, it is completely unclear how development is altered to give rise to some of the functionally most complex stemmata, such as those of the sunburst diving beetle, Thermonectus marmoratus. In this study, we used histological methods to investigate the embryonic development of the functionally complex principal stemmata Eye 1 and Eye 2 of the larval visual system of T. marmoratus. To gain insights into how cellular components of their sophisticated camera-type eyes might have evolved from the cellular components of ommatidial ancestors, we contrast our findings against known features of ommatidia development, which are particularly well understood in Drosophila. We find many similarities, such as the early presence of a pseudostratified epithelium, and the order in which specific cell types are recruited. However, in Thermonectus each cell type is represented by a large number of cells from early on and major tissue re-orientation occurs as eye development progresses. This study provides insights into the timing of morphological features and represents the basis for future molecular studies. [ABSTRACT FROM AUTHOR]

[Display omitted] The constitutive androstane receptor (CAR) controls xenobiotic clearance, regulates liver glucose, lipid metabolism, and energy homeostasis. These functions have been mainly discovered using the prototypical mouse-specific CAR ligand TCPOBOP in wild-type or CAR null mice. However, TCPOBOP is reported to result in some off-target metabolic effects in CAR null mice. In this study, we compared the metabolic effects of TCPOBOP using lipidomic, transcriptomic, and proteomic analyses in wild-type and humanized CAR-PXR-CYP3A4/3A7 mice. In the model, human CAR retains its constitutive activity in metabolism regulation; however, it is not activated by TCPOBOB. Notably, we observed that TCPOBOP affected lipid homeostasis by elevating serum and liver triglyceride levels and promoted hepatocyte hypertrophy in humanized CAR mice. Hepatic lipidomic analysis revealed a significant accumulation of triglycerides and decrease of its metabolites in humanized CAR mice. RNA-seq analysis has shown divergent gene expression levels in wild-type and humanized CAR mice. Gene expression regulation in humanized mice is mainly involved in lipid metabolic processes and in the PPAR, leptin, thyroid, and circadian clock pathways. In contrast, CAR activation by TCPOBOP in wild-type mice reduced liver and plasma triglyceride levels and induced a typical transcriptomic proliferative response in the liver. In summary, we identified TCPOBOP as a disruptor of lipid metabolism in humanized CAR mice. The divergent effects of TCPOBOP in humanized mice in comparison with the prototypical CAR-mediated response in WT mice warrant the use of appropriate model ligands and humanized animal models during the testing of endocrine disruption and the characterization of adverse outcome pathways. [ABSTRACT FROM AUTHOR]