Rui Tahara

Analyzing primitive extraterrestrial samples from asteroids is key to understanding the evolution of the early solar system. The OSIRIS‐REx mission returned samples from the B‐type asteroid Bennu, providing a valuable opportunity to compare them with the Ryugu samples collected by the Hayabusa2 mission. This study examines the representativeness of a fraction of the Bennu samples, which was allocated from NASA to JAXA, by nondestructive characterization of their physical and spectral properties without atmospheric exposure. The reflectance and observed spectral features in the visible‐to‐infrared range of the Bennu sample resemble those from the spectroscopic analysis of different fractions. Additionally, we found differences in the slope of the visible range and band‐center of ~2.7 μm band between the samples and the asteroid surface, which could be explained by the degree of space weathering. A comparative analysis of the Bennu and Ryugu samples revealed spectral similarities, including absorption features indicative of Mg‐rich phyllosilicates, organics, and carbonates, without any evidence of sampling bias or terrestrial alteration. This finding can be used as a benchmark for subsequent Ryugu–Bennu comparative studies.

NASA's OSIRIS‐REx mission successfully collected and returned ~121.6 g of bulk samples from the B‐type, near‐Earth asteroid (101955) Bennu to Earth in September 2023. Upon returning to Earth, the samples were transported to the NASA Johnson Space Center where most of the samples have been stored and processed. On August 22, 2024, 0.5 wt% of Bennu samples (0.663 g) and a contact pad that collected particles from the surface of Bennu were permanently transferred to JAXA from NASA based on a Memorandum of Understanding and a letter of agreement between the two agencies. Following this, all the Bennu samples have been curated under nitrogen‐purged gloveboxes, called clean chambers in a clean room at the Extraterrestrial Sample Curation Center in Sagamihara. While maintaining the pristinity of samples at the curation, we conduct a series of nondestructive analyses, including near‐infrared spectroscopy within the clean chambers. Bennu curation was conceptualized primarily based on the Hayabusa2 curation, whereas lessons learned from the Hayabusa2 curation were integrated into designing Bennu curation. Here, we describe preparations for the Bennu curation, with an emphasis on the differences from the Hayabusa2 curation.

Pelvic girdles, fins and claspers are evolutionary novelties first recorded in jawed vertebrates. Over the course of the evolution of chondrichthyans (cartilaginous fish) two trends in the morphology of the pelvic skeleton have been suggested to have occurred. These evolutionary shifts involved both an enlargement of the metapterygium (basipterygium) and a transition of fin radial articulation from the pelvic girdle to the metapterygium. To determine how these changes in morphology have occurred it is essential to understand the development of extant taxa as this can indicate potential developmental mechanisms that may have been responsible for these changes. The study of the morphology of the appendicular skeleton across development in chondrichthyans is almost entirely restricted to the historical literature with little contemporary research. Here, we have examined the morphology and development of the pelvic skeleton of a holocephalan chondrichthyan, the elephant shark (Callorhinchus milii), through a combination of dissections, histology, and nanoCT imaging and redescribed the pelvic skeleton of Cladoselache kepleri (NHMUK PV P 9269), a stem holocephalan. To put our findings in their evolutionary context we compare them with the fossil record of chondrichthyans and the literature on pelvic development in elasmobranchs from the late 19th century. Our findings demonstrate that the pelvic skeleton of C. milii initially forms as a single mesenchymal condensation, consisting of the pelvic girdle and a series of fin rays, which fuse to form the basipterygium. The girdle and fin skeleton subsequently segment into distinct components whilst chondrifying. This confirms descriptions of the early pelvic development in Scyliorhinid sharks from the historical literature and suggests that chimaeras and elasmobranchs share common developmental patterns in their pelvic anatomy. Alterations in the location and degree of radial fusion during early development may be the mechanism responsible for changes in pelvic fin morphology over the course of the evolution of both elasmobranchs and holocephalans, which appears to be an example of parallel evolution.

Crocodylia has an extensive epithelial pneumatic space in the middle ear, paratympanic sinus system. Although fossil and extant crocodylian paratympanic sinus systems have been studied recently using the computed tomography (CT) and three‐dimensional (3D) reconstruction data, due to the soft tissue nature of the pneumatic system and presence of its surrounding soft tissue structures, some boundaries, and definitions of each extension remain ambiguous. We describe the comprehensive paratympanic sinus system in posthatched alligator using soft tissue enhanced CT data with 3D reconstructions. The data are compared to the available data to discuss the ontogenetic pattern in alligator. We introduce further divided entities of the pneumatic system based on their associated bony and soft tissue structures and epithelial membrane and clarify the pneumatic terminologies. We then re‐visit the potential homology of the paratympanic sinus in Archosauria. Epithelial boundaries of the ventral portion of the pneumatic system from the histological data suggest that the dual origin of the basioccipital diverticulum derived from the tympanic sinus and basicranial diverticulum medially. The presence of the epithelial boundary and pneumatic changes in ontogeny suggests that the middle ear may function differently in developmental stages. Lastly, a morphogenetic tree is constructed to help future work of comparative developmental studies of the paratympanic sinus system between crocodiles and birds.

The growth of imaginal discs in holometabolous insects is coordinated with larval growth to ensure the symmetrical and proportional development of the adult appendages. In ants, the differential growth of these discs generates distinct castes – the winged male and queen castes and the wingless worker caste. In the hyperdiverse ant genus Pheidole , the worker caste is composed of two morphologically distinct subcastes: small minor workers and larger, big-headed soldiers. Although these worker subcastes are completely wingless, soldier larvae develop rudimentary forewing discs that are necessary for generating the disproportionate head-to-body scaling of the big-headed soldier subcaste. However, it remains unclear whether rudimentary forewing discs in soldier larvae are coordinated with other imaginal discs, and whether disc growth and coordination patterns vary between the minor worker and soldier subcastes. Here we show, using quantitative nano-CT three-dimensional analyses, that growth of the soldier rudimentary forewing discs is coordinated with the increase in volume of the leg and eye-antennal (head) discs as well as with larval size. We found that the growth rate of the rudimentary forewing discs differs from the leg discs but is similar to the growth of the head (eye-antennal) discs relative to larval size, suggesting that growth of each type of imaginal disc may be differentially regulated. In addition to their larger size, the soldier eye-antennal discs increase in width as they undergo morphogenesis to generate the characteristic shape of the large soldier head, suggesting that the rudimentary forewing discs may regulate their patterning in addition to their growth. Finally, we observe little growth of the leg and eye-antennal discs during the bipotential stage, while in minor worker development these discs grow at similar rates to one another in coordination with larval size to generate the smaller minor worker subcaste. Our results suggest that rudimentary organs with regulatory functions may participate in new patterns of inter-organ coordination and regulation to produce novel phenotypes and complex worker caste systems. We provide characterization of larval development and imaginal disc growth and morphogenesis with the aim of highlighting this as an emerging system for the study of rudimentary organs during development and evolution.

Microplastics and nanoplastics are emerging contaminants in aquatic and terrestrial environments. Due to the challenges in detecting these small plastics in complex soil matrices, data about their abundance in terrestrial environments are scarce and our knowledge of their impacts on terrestrial organisms is severely lacking. Here, we introduced a well-established terrestrial model organism – the fruit fly (Drosophila melanogaster) – to study the chronic adverse effects of model micro- and nanoplastics. The toxicity of model dialyzed polystyrene spheres (1 μm and 20 nm) was assessed via dietary exposures to a wide range of concentrations (0.01 to 100 ppm). In a first experiment, flies were exposed from larval to adult stage for 13 days. Uptake of both particle sizes in the gastrointestinal tract of larvae was observed, with depuration times of 1 and 24 h for 20 nm and 1 μm particles, respectively. In adults, only 1 μm particles accumulated to detectable levels and nano computed tomography imaging revealed intestinal damage. Both micro- and nanoplastics significantly affected locomotion while mortality, development, and fertility were not significantly affected. A second 8 day experiment focused on the daily behavior of adults exposed to micro- and nanoplastics. We observed no effect on circadian rhythms but an increase in daily activity after micro- and nanoplastic exposure at 50 ppm, likely in response to a reduction in nutrient absorption due to the change in diet or intestinal damage. Overall, dietary exposures to clean spherical polystyrene micro- and nanoplastics caused low toxicity but significant sublethal effects in the fruit fly. This study establishes a baseline understanding of the impacts of model micro- and nanoplastic exposure to the fruit fly and motivates the need for further work focusing on naturally weathered plastic debris.

Avian heads are characterized as having two extensive air‐filled systems lined with epithelia; the paranasal and paratympanic sinuses. Many diverticula derived from the paratympanic sinus system are known to reticulate with each other to form a single merged pneumatic space within the adult braincase. However, the development of these complex branching and reticulating epithelia has not been examined in detail. In this study, we describe the comprehensive developmental pattern of the paratympanic sinus and its associated soft tissues in a model bird, Japanese quail (Coturnix japonica). The data are derived from three‐dimensional reconstructions based on histological sections and soft tissue enhanced micro‐CT data. Those data provide the foundation of the complex hierarchical developmental pattern of the paratympanic sinus system. Moreover, associations with other tissues help establish key morphologies that identify each pneumatic entity. This study clarifies the developmental relationships of the ventral portions of the paratympanic sinus system, the siphoneal diverticulum and marginal sinus, based on the ligaments associated with the Eustachian tube. In addition, detailed histological pneumatic morphologies reveal hitherto unknown epithelial diversity, which may be indicative of equally complex developmental processes. We use the pneumatization of the quadrate as an example to support a close relationship with vascular growth and pneumatic epithelia invasion into ossified bone. We confirm pneumatic diverticula never enter into cartilages, possibly due to the absence of vasculature in these tissues. Lastly, we use the concept of a morphogenetic tree as a tool to help present the complex developmental pattern of the paratympanic sinus system and apply it toward inferring pneumatic morphologies in a nonavian theropod braincase.

Avian skulls exhibit extensive pneumatic spaces lined with epithelia from the paranasal and paratympanic sinus systems. However, limited detailed studies of these sinuses in extant birds, and the soft tissue associations of major portions of the paranasal sinuses, have made it difficult to accurately reconstruct their evolutionary history from the fossil record. We describe the complete head pneumatic system of two phylogenetically distant model species, Japanese quail (Coturnix coturnix japonica) and zebra finch (Taeniopygia guttata), from a combination of soft tissue enhanced microscopic computed tomography with three-dimensional reconstructions of various soft tissues and histological sections. Conserved and differing pneumatic morphologies are emphasized in this study. Common morphologies, such as the shared topologies of the ostium associated with the suborbital diverticulum, are used to propose that this diverticulum may be the primary paranasal sinus in birds, implying an evolutionary origin of this diverticulum prior to the antorbital sinus in avian antecedents. Differences in pneumatic extensions about the jaw adductor muscles and palatal bones imply physical constrains to the extensions of the suborbital and maxillary diverticula in both taxa. Unique morphologies, such as the marginal sinus in the paratympanic sinus in the zebra finch suggest specialized functions for further investigation. We highlight the importance of this study to help in establishing the foundation of avian head sinuses towards modelling these complex anatomies and understanding their functions.

Rapid three‐dimensional imaging of embryos to better understand the complex process of morphogenesis has been challenging. Recently introduced iodine staining protocols (I₂KIand alcoholic iodine stains) combined with microscopic X‐ray computed tomography allows visualization of soft tissues in diverse small organisms and tissue specimens.I₂KIprotocols have been developed specifically for small animals, with a limited number of quantitative studies of soft tissue contrasts. To take full advantage of the low X‐ray attenuation of ethanol and retain bound iodine while dehydrating the specimen in ethanol, we developed an ethanolI₂KIprotocol. We present comparative microscopic X‐ray computed tomography analyses of ethanolI₂KIand I₂KIstaining protocols to assess the performance of this new protocol to visualize soft tissue anatomy in late stage Japanese quail embryos using quantitative measurements of soft tissue contrasts and sample shrinkage. Both protocols had only 5% shrinkage compared with the original harvested specimen, supporting the use of whole mounts to minimize tissue shrinkage effects. Discrimination within and among the selected organs with each staining protocol and microscopic X‐ray computed tomography imaging were comparable to those of a gray scale histological section. Tissue discrimination was assessed using calibratedcomputed tomographyvalues and a newdiscriminationindex to quantify the degree ofcomputed tomographyvalue overlaps between selected soft tissue regions. Tissue contrasts were dependent on the depth of the tissue within the embryos before the embryos were saturated with each stain solution, and optimal stain saturations for the entire embryo were achieved at 14 and 28 days staining forI₂KIand ethanolI₂KI, respectively. EthanolI₂KIprovided superior soft tissue contrasts by reducing overstaining of fluid‐filled spaces and differentially modulating staining of some tissues, such as bronchial and esophageal walls and spinal cord. Delineating the selected soft tissues using optimal threshold ranges derived from the quantitative analyses of the contrast enhancement in optimally stained embryos is possible. The protocols presented here are expected to be applicable to other organisms with modifications to staining time and contribute toward rapid and more efficient segmentation of soft tissues for three‐dimensional visualization.