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The tremendous diversity of Hymenoptera is commonly attributed to the evolution of parasitoidism in the last common ancestor of parasitoid sawflies (Orussidae) and wasp-waisted Hymenoptera (Apocrita). However, Apocrita and Orussidae differ dramatically in their species richness, indicating that the diversification of Apocrita was promoted by additional traits. These traits have remained elusive due to a paucity of sawfly genome sequences, in particular those of parasitoid sawflies. Here, we present comparative analyses of draft genomes of the primarily phytophagous sawfly Athalia rosae and the parasitoid sawfly Orussus abietinus. Our analyses revealed that the ancestral hymenopteran genome exhibited traits that were previously considered unique to eusocial Apocrita (e.g., low transposable element content and activity) and a wider gene repertoire than previously thought (e.g., genes for CO2 detection). Moreover, we discovered that Apocrita evolved a significantly larger array of odorant receptors than sawflies, which could be relevant to the remarkable diversification of Apocrita by enabling efficient detection and reliable identification of hosts.

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]

The common fruit fly Drosophila melanogaster provides a powerful platform to investigate the genetic, molecular, cellular, and neural circuit mechanisms of behavior. Research in this model system has shed light on multiple aspects of brain physiology and behavior, from fundamental neuronal function to complex behaviors. A major anatomical region that modulates complex behaviors is the mushroom body (MB). The MB integrates multimodal sensory information and is involved in behaviors ranging from sensory processing/responses to learning and memory. Many genes that underlie brain disorders are conserved, from flies to humans, and studies in Drosophila have contributed significantly to our understanding of the mechanisms of brain disorders. Genetic mutations that mimic human diseases-such as Fragile X syndrome, neurofibromatosis type 1, Parkinson's disease, and Alzheimer's disease-affect MB structure and function, altering behavior. Studies dissecting the effects of disease-causing mutations in the MB have identified key pathological mechanisms, and the development of a complete connectome promises to add a comprehensive anatomical framework for disease modeling. Here, we review Drosophila models of human neurodevelopmental and neurodegenerative disorders via the effects of their underlying mutations on MB structure, function, and the resulting behavioral alterations., (© 2024 Stahl and Tomchik; Published by Cold Spring Harbor Laboratory Press.)

How does the brain translate sensory information into complex behaviors? With relatively small neuronal numbers, readable behavioral outputs, and an unparalleled genetic toolkit, the Drosophila mushroom body (MB) offers an excellent model to address this question in the context of associative learning and memory. Recent technological breakthroughs, such as the freshly completed full-brain connectome, multiomics approaches, CRISPR-mediated gene editing, and machine learning techniques, led to major advancements in our understanding of the MB circuit at the molecular, structural, physiological, and functional levels. Despite significant progress in individual MB areas, the field still faces the fundamental challenge of resolving how these different levels combine and interact to ultimately control the behavior of an individual fly. In this review, we discuss various aspects of MB research, with a focus on the current knowledge gaps, and an outlook on the future methodological developments required to reach an overall view of the neurobiological basis of learning and memory., (© 2024 Chan et al.; Published by Cold Spring Harbor Laboratory Press.)

Among animals with visual processing mechanisms, the leech Hirudo verbana is a rare example in which all neurons can be identified. However, little is known about its visual system, which is composed of several pigmented head eyes and photosensitive non-pigmented sensilla that are distributed across its entire body. Although several interneurons are known to respond to visual stimuli, their response properties are poorly understood. Among these, the S-cell system is especially intriguing: it is multimodal, spans the entire body of the leech and is thought to be involved in sensory integration. To improve our understanding of the role of this system, we tested its spectral sensitivity, spatial integration and adaptation properties. The response of the S-cell system to visual stimuli was found to be strongly dependent on the size of the area stimulated, and adaptation was local. Furthermore, an adaptation experiment demonstrated that at least two color channels contributed to the response, and that their contribution was dependent on the adaptation to the background. The existence of at least two color channels was further supported by transcriptomic evidence, which indicated the existence of at least two distinct groups of putative opsins for leeches. Taken together, our results show that the S-cell system has response properties that could be involved in the processing of spatial and color information of visual stimuli. We propose the leech as a novel system to understand visual processing mechanisms with many practical advantages., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2019. Published by The Company of Biologists Ltd.)