Lake Biwa Museum

A lack of information persists on external seed dispersal interactions, despite the rich diversity of potential dispersers. Roadkills offer a unique opportunity to obtain ecological data directly from carcasses. For 18 years, we collected road‐killed mammals in Toyama (Japan) and screened them for seed attachment. We then illustrated species interactions, quantified the number of plant species and seeds individual roadkill carried, and evaluated seasonal variations in the probability of seed attachment. We identified nine mammal species dispersing seeds from 16 distinct plant taxa. Most importantly, medium‐sized mammals (1.5–10.0 kg) accounted for approximately 88% of roadkill carrying seeds, with raccoon dogs Nyctereutes procyonoides dispersing the most seeds. Likely due to seed‐set phenology, we showed a significant increase in seed prevalence for roadkills occurring in autumn. We advocate for future studies in epizoochory to focus on potential animal dispersers community wide.

Recent genetic advancements offer new opportunities for studying natural history museum collections. The genetic analysis of century-old aquatic animal specimens, mostly preserved in ethanol, can provide valuable insights into the changes in genetic diversity caused by anthropogenic impacts. However, knowledge of the characteristics of degraded DNA from such specimens remains limited. In this study, we evaluated the DNA quality of bitterling fish, Tanakia lanceolata (Temminck and Schlegel), collected during the Vega Expedition in Japan in 1879 and preserved in ethanol. We then performed genomic analysis to test its hypothesized translocation-involved population history. The historical DNA was degraded, peaking around 50 bp, but a minor fraction exceeded 300 bp. Mitochondrial genetic analysis revealed high genetic similarity between the eastern and western sides of the Central Highland, typically impeding the dispersal of primary freshwater fish. These findings suggest an unexpected dispersal ability in T. lanceolata or undocumented translocations before the large-scale domestic translocations recorded since the 1910s. The customized workflow for historical ethanol-preserved specimens, based on historical DNA quality in this study, provides a foundation for studying historical archives.

BackgroundFloodplains harbor highly biodiverse ecosystems, which have been strongly affected by both past climate change and by recent human activities, resulting in a high prevalence of many endangered species in these habitats. Understanding the history of floodplain species over a wide range of timescales can contribute to effective conservation planning. We reconstructed the population formation history of the Itasenpara bitterling Acheilognathus longipinnis, an endangered floodplain fish species in Japan, over a broad timescale based on phylogenetic analysis, demographic modeling, and historical demographic analysis using mitogenome and whole-genome sequences. A genome sequence was newly assembled as a reference for the resequencing analysis. This bitterling is distributed in three plains separated by high mountain ranges and exhibits ecological characteristics well adapted to floodplain environments.ResultsOur analyses revealed an unexpected population branching pattern, gene flow, and timing of the differentiation that occurred within a few hundred thousand years, i.e., long after the mountain uplift that was assumed to be the primary geological cause of the population differentiation. The analyses also showed that all local populations experienced a severe decline during the last glacial and post-glacial periods.ConclusionsOur results suggest that the floodplain bitterling was able to disperse through unknown routes after mountain uplift and that its populations were strongly influenced by climatic and geographic changes in glacial–interglacial cycles and subsequent human activities, probably related to its floodplain-dependent ecology. The genomic data highlight the unanticipated distribution process of this species and the magnitude of the impact of human activities, with important implications for its conservation.

Digital archiving of museum collections is a global trend, but web platforms for archival data are not yet well developed. Many of the portal sites developed in Japan lack images and geographical information, making them difficult to use for non-specialists. Therefore, local museums, such as the Lake Biwa Museum, require web platforms that are easy to use for local users. Recently, rapid developments in digital technology have made it easier and cheaper to customize web platforms. Furthermore, the Japanese Government now provides financial support for the digitization of collections. This has made it possible for museum staff, who are not specialized in digital technology, to develop web platforms. Two projects have therefore been set up. Digital Museums using Various Images (DMVI): 3D and high-resolution images of various collections are made available on websites as databases for the museums' collections, which can also be used for exhibitions. Digital Museums using Geographical Information Systems (DMGIS): in addition to distribution maps of specimens and survey data, maps from the past to the present can be superimposed to understand the changes in the habitats of living organisms. The 3D models developed by DMVI can be rotated, enlarged, and reduced, providing a new experience as if you were holding a valuable material that you would not normally be able to touch. The DMVI project is also working towards the development of illustrated databases limited to the organisms found in Shiga Prefecture. Meanwhile, the easy-to-use illustrated search system, DMGIS, is promoting information on bird distributions and cross-disciplinary mapping. For example, specimens and observation data can be plotted and viewed on current maps, and changes in the distribution of birds can be followed along a time axis. This content is intended for use in environmental education and nature conservation. By building an easy-to-use web platform, the aim is to develop a ‘digital museum.’

The International Ocean Discovery Program (IODP) Expedition 386, Japan Trench Paleoseismology, represents the first utilization of giant piston coring (GPC) within scientific ocean research drilling. This allowed for a Mission Specific Platform (MSP) multi-site, multi-hole, shallow subsurface coring in an ultra-deep water subduction zone trench. The primary objective of the expedition was to investigate the concept of submarine paleoseismology in the Japan Trench, which involves studying long-term records of deposits in the deep sea that can provide insights into past earthquake events. In this paper, we compile and interpret initial shipboard data and results to (1) establish first-order event stratigraphic correlation of thick event beds (> 50 cm in thickness) between sites, (2) test previously published event-stratigraphic predictions of earthquake-related event deposits as proposed based on high-resolution hydro-acoustic subbottom profiler (SBP) data, and (3) derive SBP-scale event deposits age estimates to (4) discuss the advantages and limitations of giant piston coring for scientific drilling operations and the potential of new event stratigraphy results for advancing submarine paleoseismology.The findings of the study identified a total of 77 SBP-scale event beds across 15 sites along a trench-parallel transect spanning over 600 km. These event beds exhibit clear expressions in SBP data, with approximately 49 % matching precisely with SBP units previously identified by Kioka et al. (2019a). For the remaining 51 % of SBP-scale event beds, thin, acoustically-transparent bodies were observed between high-amplitude horizons, for which SBP-based seismic interpretation alone would not be definitive. Consequently, the study concluded that the SBP-scale event-stratigraphy observed in IODP 386 cores validates the event-bed mapping conducted by Kioka et al. (2019a) and improves SBP interpretation for event beds in the 0.5 to 1 m thickness range.The initial age constraints obtained from shipboard radiolarian biostratigraphy enable us to provide rough estimates of event ages by linearly interpolating between previously dated events occurring less than 2000 years ago and a datum around 11,000 years ago reported in four boreholes from trench basins in the Southern, Central, and Northern Japan Trench. Inter-site stratigraphic correlation reveals distinct SBP-scale event stratigraphies for the trench segments located to the north and south of the structurally complex “boundary area” at approximately 39.3–39.4°N, which is hypothesized to potentially act as a persistent rupture barrier for megathrust earthquakes. We observe more frequent but thinner event deposits in the Southern and Central Japan Trench, and fewer but thicker event beds in the Northern Japan Trench. This spatial variation may be related to the different seismogenic behavior of the various asperities along the Japan Trench megathrust and/or to differences in the response of slope sediments to earthquake shaking. However, here-presented investigations at the SBP-scale level are deemed too simplistic for robust application of the “submarine paleoseismology” approach. The extensive and high-quality dataset from IODP GPC, coupled with the encouraging initial correlation results presented here, leads us to hypothesize that further detailed studies can identify and characterize event deposition dynamics at the micro-facies level, refine sediment provenance, and constrain precise event ages necessary for evaluating synchronicity in paleoseismological interpretation. These studies will also enable robust exploration of along-strike correlations or variations, facilitating the extraction of paleo-earthquake signals from Japan Trench event stratigraphies.

Two new diatom species, Praestephanos tokaiensis sp. nov. and P. miensis sp. nov. are described from lacustrine deposits in the Pliocene Ueno Formation of the Kobiwako Group in Iga City, Mie Prefecture, Japan. The stratigraphic ranges of P. tokaiensis and P. miensis are approximately 3.9–3.8 Ma and 3.8–3.7 Ma, respectively. The morphology of these species is mainly characterized by a slightly doubly undulating central area; this feature is not found in previously described Praestephanos species or similar Stephanodiscus species. The stratigraphic distribution and morphology of the two new species suggest that P. tokaiensis and P. miensis have an ancestor–descendant relationship.