Honshu Research Articles

LOCATION OF THE SOUTHERN BOUNDARY OF THE OKHOTSK PLATE BASED ON A SET OF SEISMIC CHARACTERISTICS

The study focuses on determining the position of the southern boundary of the Okhotsk Plate based on the analysis of seismicity distribution in the Hokkaido and Honshu regions as well as adjacent territories according to the Japan Meteorological Agency (JMA) data for a period of 1998–2022. The seismicity distribution data are compared with regional seismic tomography models and the distributions of the directions of principal seismotectonic deformation axes according to data on the focal mechanisms of strong (Mw > 4.7) earthquakes using the International Seismological Center (ISC) data for a period of 1976–2022 and other recent geological–geophysical characteristics, such as gravity field heterogeneities, crustal thickness, volcanic manifestations, etc. It is revealed that the southern boundary of the Okhotsk Plate actually passes along the southern tip of Hokkaido Island (through the Oshima Peninsula and Uchiura Bay) rather than along the Hidaka Ridge or through Honshu Island, as previously assumed by other authors.

1930년대 일본 ｢변호사법｣과 조선 ｢변호사규칙｣의 개정 과정 비교

This study examines the amendment of the Japanese “Lawyer Act” in 1933 and the “Korean Lawyer Regulation” in 1936, highlighting the legal differences between the Japanese mainland and colonial Korea. While Japan aimed to enhance legal professionalism, Korea’s adaptation served as a colonial control tool. However, the reforms also improved Korean lawyers' competence and ethical standards. This study reveals how the colonial legal system selectively adopted elements from Japan, balancing control with professionalization.

Utilization of a wide range of exotic plant species by an exotic, Solidago-specialist aphid, Uroleucon nigrotuberculatum (Hemiptera: Aphididae)

Abstract The Anthropocene epoch is characterized by unprecedented rates of global biological invasions, resulting in the formation of novel ecological assemblages composed of multiple species with different origins. In this study, we focused on the recent expansion of host usage by the red goldenrod aphid, Uroleucon nigrotuberculatum, introduced to Japan from North America. Uroleucon nigrotuberculatum is well known to exclusively feed on Solidago spp in their native range, North America. Based on our observation, we hypothesize that in their introduced region (ie Japan), the aphid U. nigrotuberculatum, recently exhibited a broad host range, capable of exploiting a wide range of exotic plant species beyond the Solidago genus. We collected red aphid colonies from multiple exotic plant species in Hokkaido Island and also collected U. nigrotuberuculatum from multiple populations of S. altissima in Hokkaido and the main island of Japan. Then, we performed a phylogenetic analysis to determine genetic relationships among collected samples. Morphological characteristics were also examined. The phylogenetic analysis revealed no genetic variation among aphids collected from different exotic plants. All specimens clustered with U. nigrotuberculatum were found on S. altissima. Morphological examination confirmed key diagnostic features of U. nigrotuberculatum. We also performed field inoculation experiments. The red aphids collected from S. altissima could survive and reproduce on various exotic plant species, S. gigantea, Taraxacum officinale, and Senecio vulgaris. These results indicate a lack of host-associated genetic differentiation and support the utilization of these novel exotic plants by U. nigrotuberuculatum, potentially facilitating its further spread and ecological impact.

A new species and two new records of the moss-feeding lace bug genus Acalypta (Hemiptera, Heteroptera, Tingidae) from Hokkaido, northern Japan, with an illustrated key to the Japanese species of the genus.

In this study, three species of the moss-feeding lace bug genus Acalypta Westwood, 1840 (Hemiptera, Heteroptera, Tingidae, Tinginae, Acalyptaini) are reported mainly in Hokkaido, northern Japan. The first is Acalyptaalutacea sp. nov. that inhabits mosses growing on the floors of deciduous broad-leaved forests. The second is Acalyptacarinata (Panzer, 1806) that mainly inhabits mosses growing on marshlands and is recorded from Japan for the first time. The third is Acalyptasauteri Drake, 1942 that is widely distributed in three of the four main islands of Japan (Honshu, Shikoku, and Kyushu) and their surrounding islands, but is recorded from the remaining main island (Hokkaido) for the first time. The discovery of A.sauteri in Hokkaido also represents the northernmost record of this species. The following ten species of Acalypta are recognized in Japan: A.alutacea sp. nov., A.carinata, A.cooleyi Drake, 1917, A.gracilis (Fieber, 1844), A.hirashimai Takeya, 1962, A.marginata (Wolff, 1804), A.miyamotoi Takeya, 1962, A.pallidicoronata Souma, 2019, A.sauteri, and A.tsurugisana Tomokuni, 1972. An illustrated key for the identification of the ten species of this genus from Japan is also provided.

Genetic and morphological variation analyses of Dryophytes japonicus (Anura, Hylidae) with description of a new species from northeastern Japan.

Japanese tree frog, Dryophytes japonicus, formerly known as Hyla japonica, is known to include several geographic groups recognized in mitochondrial phylogeny. By analyzing genetic and morphological variations in a large number of individuals of Dryophytes, we studied their taxonomic relationships. A mitochondrial DNA phylogeny was consistent with previous studies in that a high molecular divergence existed between populations from northeastern Japan and Sakhalin (Clade A) and those from southwestern Japan and Korea (Clade B). Nuclear DNA analyses based on SNP data also support such separation, whereas hybrid populations were found at some localities near the border of mitochondrial clades in Honshu Island, forming a hybrid zone. The width of hybrid zone was estimated to be narrow (approx. 25 km) and the migration rates into/beyond it were relatively low. Those results indicate that two genetic groups have long been parapatrically maintained with a narrow hybrid zone in Honshu Island. We examined syntypes of Hyla japonica and designated lectotypes. In adult morphology, the clades could be differentiated mainly by the pattern of rear of thigh, and the lectotypes proved to be Clade B. From these results, we describe the frogs of Clade A as a new species, D. leopardus sp. nov., distinct from D. japonicus.

High Microsatellite but No Mitochondrial DNA Variation in an Invasive Japanese Mainland Population of the Parasitoid Wasp Melittobia sosui.

Invasive populations are predicted to have reduced genetic diversity due to bottleneck events. The parasitoid wasp Melittobia sosui was previously identified only in the subtropical area of the southern Japanese islands and Taiwan but was recently found in the temperate area of the Japanese mainland. The distribution of this species may have recently expanded northward due to factors such as climatic events and global warming. The population genetics of both the native and invasive regions were investigated using mitochondrial and nuclear microsatellite DNA. As expected, mitochondrial variation was observed in the native region but not in the invasive region, which had only one haplotype. However, the two regions exhibited similar levels of microsatellite variation, and an average of 43% and 38% of alleles were uniquely found in the native and invasive populations, respectively. The difference in genetic variation between mitochondrial and microsatellite DNA in the invasive populations may be explained by the faster mutation rate of microsatellites, as well as the population structure of Melittobia, in which the subdivision into small inbreeding lineages may facilitate the accumulation of mutations. The high proportion of private alleles suggests that the mainland population diverged from the native populations at least 100 years ago, ruling out the possibility that the mainland population was established recently. The present study suggests that M. sosui might have already existed on the mainland but at a low frequency or that the mainland population was derived from a ghost population that diverged from the native populations more than 100 years ago.

A new species of the genus Eustigmaeus (Trombidiformes: Prostigmata: Stigmaeidae) and the first record of E. extremiorientalis in Japan.

A new stigmaeid mite species Eustigmaeus imadae sp. nov. (Trombidiformes: Prostigmata: Stigmaeidae) is described from Japan. The species was collected from Shikoku and Honshu Islands. Insights into morphological variation among the specimens collected from different localities are provided. Eustigmaeus extremiorientalis Khaustov, 2016 originally described from Russia is recorded for the first time in Japan and is described based on specimens from the Japanese population. The number of Eustigmaeus species known in Japan has now increased to six.

Regional range extension of two xanthid crab species (Decapoda, Brachyura) to the mid-Sanriku Coast, the coldest waters off Honshu, Japan

Abstract This paper reports the first occurrences of two brachyuran crab species of the family Xanthidae MacLeay, 1838, viz., Actaea semblatae Guinot, 1976 and Gaillardiellus orientalis (Odhner, 1925), from the mid-Sanriku Coast, along the Pacific coast of northeastern Japan. While these records do not represent the northern limit of distribution of these species, they do show a range extension into the coldest waters of Honshu, the main island of Japan, probably due to global warming and changes in flow patterns of the local sea currents.

Vincetoxicumnakaianum (Asclepiadoideae, Apocynaceae), a new species from Japan for Cynanchummagnificum Nakai, nomen nudum.

Vincetoxicum Wolf is the third largest genus in Asclepiadoideae, and 23 species are distributed in Japan. We discovered that an erect herb species, distributed in the eastern part of the Honshu island, was invalidly named Vincetoxicummagnificum (Nakai) Kitag. based on Cynanchummagnificum Nakai, nomen nudum. Therefore, we presently name this species Vincetoxicumnakaianum K.Mochizuki & Ohi-Toma, and we give a detailed description in this study. Additionally, we provide photographs that demonstrate its ecology and diagnostic characteristics.

Description of Ixodeslanigeri sp. nov., a new hard tick species (Acari, Ixodidae) collected from mouse-eared bats (Vespertilionidae, Myotis) in Vietnam.

Historically, for more than one and a half centuries, only one so-called "long-legged bat tick" species, i.e., Ixodesvespertilionis Koch was known to science. However, during the past decade, it was recognized on a molecular basis that long-legged ixodid ticks associated with bats may represent at least six species. Of these, until recently, five have been morphologically described. In this study, Ixodes ticks were collected from two Myotis species in southeastern Asia, Vietnam. Based on the morphological and molecular characteristics of the female, nymph and larva, Ixodeslanigeri Hornok, sp. nov. is described here. The male is unknown. Like other members of the Ixodesariadnae complex, I.lanigeri Hornok apparently shows a preference for vesper bats as its typical hosts. In this context, host-association and geographical separation may explain the evolutionary divergence of I.lanigeri Hornok from its closest relative occurring on Murinahilgendorfi Peters in East Asia, Japan, because no Myotis or Murina spp. have overlapping distribution between Vietnam and the main islands of Japan. On the other hand, supposing that (similarly to I.ariadnae) I.lanigeri Hornok probably occurs on other myotine bats and knowing that several Myotis species indigenous in Vietnam have a broad geographical range in southern and southeastern Asia, the new tick species most likely has a widespread distribution in this area.

Global earthquakes in the first half of 2024 according to the GS RAS

Description of the Earth seismicity at the level of mb (MS)≥6.0 in the first half of 2024 is pro-vided. А total of 60 earthquakes are included in the list with such magnitudes. Also information on 77 earthquakes felt on the territory of the Russian Federation according to the Alert Service of the Geophysical Survey RAS is given. For the eight strongest events, information messages were published within one to two days after their occurrence, and parameters of their focal mecha-nisms were calculated. During the period under review, the strongest global earthquake with MS=7.7 (Mw=7.3) occurred on April 2 on the northeast coast of Taiwan Island. As a result, twelve people died and about a thousand were injured. The greatest human casualties and materi-al damage were caused by the catastrophic earthquake on January 1 with MS=7.3 (Mw=7.3) on the west coast of Honshu Island, Japan, which caused 240 deaths and 1,036 injuries. On the terri-tory of Russia, the most noticeable (intensity Ii=5 in the nearest settlements) were two earth-quakes: on January 15 with mb=5.5 (Mw=5.2) in the area of Lake Baikal in Buryatia and on May 6 with MS=5.0 (Mw=5.3) in the Chukotka Autonomous Okrug. The seismic energy released on the globe for the first half of 2024 (sum(E0.5)=1.29≥∙1017 J) increased compared to that in the 2023 second half, but remained below the average semi-annual value for the period of 2010–2023 (sum(E0.5)=2.24≥∙1017 J).

Tilia trees are preferred hosts of several ectomycorrhizal Ascomycota – New insights supported by the first community study of the endemic Tilia kiusiana

Asia is the center of Tilia (Malvaceae) species diversity. However, the ectomycorrhizal (ECM) relations of Asian Tilia are scarcely studied. This study provides the first description of ECM communities of Tilia kiusiana, a rare tree endemic to southwestern Japan. Across the natural distribution of T. kiusiana, ECM fungal communities hosted by the species were investigated in three study sites: Hyōgo (H) and Yamaguchi (Y) on Honshu Island, and Ōita (O) on Kyushu Island. Using molecular methods, T. kiusiana was revealed to host a high diversity of fungi belonging to 25 ECM lineages (16, 17, and 14 lineages on sites H, Y, and O, respectively). The ECM communities of T. kiusiana and the previously studied endemic T. japonica were compared to the available data on other ECM tree genera in Japan, revealing that three Ascomycota ECM lineages (/genea-humaria, marcelleina-peziza gerardii, /tuber-helvella) show a preference towards Tilia hosts. While the total lineage richness did not differ among the compared host tree genera, Tilia communities exhibited higher effective lineage richness at higher (less sensitive to rare taxa) diversity orders. Despite their relative rarity, Tilia trees might play an important role in mixed forests: maintaining the diversity of ECM Ascomycota and potentially buffering the ECM fungal biodiversity loss in cases of ECM tree host diversity decline.

Age-Related Changes in the Body Size and Weight of Sika Deer (Cervus nippon): A Comparison between Northern and Southern Populations of Honshu, The Main Island of Japan

Age-Related Changes in the Body Size and Weight of Sika Deer (Cervus nippon): A Comparison between Northern and Southern Populations of Honshu, The Main Island of Japan

Public health nurses leaving remote islands: An investigation into the turnover rate of remote island PHNs in Japan.

This study investigated the number of public health nurses (PHNs) and the turnover rates of PHNs working in small municipal administrations on remote islands throughout Japan. A questionnaire survey was administered on 359 remote islands, each with a population of less than 5000, including islands connected to the Japanese mainland by a bridge or road. The survey questionnaire asked about the number of PHNs stationed on the remote islands, their length of service, the number of retirees, and the ages of those who had retired. Of the 353 islands which responded, 30 islands had a total of 77 PHNs. Of those 30 islands, 29 were isolated islands that were not connected to the mainland by a bridge or road. The turnover rate of PHNs on the 29 islands was 13.3%. The turnover rate of 13.3% for PHNs on remote islands (with no bridge or road) with a population of less than 5000 was higher than the 7.9% turnover rate for PHNs in municipalities of equal size. To maintain the quality of life of island residents, preventingPHNs from leaving their jobs is an important challenge.

Microbiome of psyllids of the family Aphalaridae, including Aphalara itadori, a biocontrol agent against Reynoutria spp.

AbstractSeveral European and North American countries have started releasing the Japanese knotweed psyllid, Aphalara itadori (Shinji) (Hemiptera: Aphalaridae), to control the Japanese knotweed, Reynoutria japonica Houtt. (Polygonaceae), and its relatives, which are among the worst invasive exotic plants. However, establishing populations of the currently released strains in the field has not been successful, desiring newly collected lineages. Moreover, little is known about the microbiome of the current strains, which potentially impacts properties as biocontrol agents. Hence, this study analyzed the microbiota of an A. itadori strain newly collected on Honshu Island, Japan, along with related species of the family Aphalaridae, using amplicon sequencing of 16S rRNA genes. The localization of symbionts identified in A. itadori was further analyzed using fluorescence in situ hybridization. The results demonstrated that the A. itadori bacteriome, a specialized organ for microbial symbiosis, maintains a dual symbiotic system with the primary symbiont “Candidatus Carsonella ruddii” (Gammaproteobacteria: Oceanospirillales: Halomonadaceae) and the secondary symbiont Sodalis sp. (Gammaproteobacteria: Enterobacterales: Pectobacteriaceae), suggesting that they are evolutionarily stable obligate mutualists for A. itadori. The central area of the bacteriome containing Sodalis comprised uninucleate bacteriocytes with nuclei larger than those of bacteriocytes harboring Carsonella. This observation contrasted previous reports on various psyllid lineages in which secondary symbionts are housed in a central syncytium with nuclei smaller than those of bacteriocytes for Carsonella. No known plant pathogens or parasitic manipulators of insect reproduction were identified in the analyzed A. itadori strain, indicating its suitability as a biocontrol agent, posing a minimum risk to the ecosystem. Besides distinct Carsonella lineages, Sodalis independently acquired by Craspedolepta miyatakeai Klimaszewski and an ambiguous Enterobacterales symbiont in Epheloscyta kalopanacis Loginova were identified. Only Carsonella was found in Togepsylla matsumurana Kuwayama. These results indicate repeated infections and replacements of bacterial symbionts during the evolution of Psylloidea, providing deeper insights into the microbe‐psyllid interactions.

What is a dialect? What is a standard?: shifting indexicality and persistent ideological norms

Abstract This paper examines the ways in which the indexical meanings that attach to enregistered speaking styles are debated and contested in interaction by younger Japanese adults. Contested meanings include discourses of so-called hyoojungo ‘Standard Japanese’ and the speaking styles that are collectively described as ‘Okinawan dialect’, which are associated with the islands of Okinawa Prefecture in Japan. This paper uses data from casual conversations between younger male adults who were all born and raised in Okinawa Prefecture but moved to the main island of Honshu for university. Discourse analysis of these conversations demonstrates how these younger adults negotiate the social meanings attached to Okinawan speaking styles, linking them to broader ideologies of so-called hyoojungo as well as gendered styles, and reproducing normative ideologies of ‘good’ and ‘bad’ speech. Homing in on moments in which these speech styles are negotiated, the results of this paper emphasize the persistence of normative linguistic ideologies even as the meaning and content of linguistic styles are being re-imagined.

Archaeological Collections from the Jōmon Period in the Peter the Great Museum of Anthropology and Ethnography (Kunstkamera)

Archaeological Collections from the Jōmon Period in the Peter the Great Museum of Anthropology and Ethnography (Kunstkamera)

Traditional Meiyu-Baiu has been suspended by global warming.

More than 1000 years, the Meiyu-Baiu have shaped the uniqueness of natural resources, civilization and culture in the Yangtze River Basin of China and the main islands of Japan. In recent decades, frequent rainstorms and droughts have seemingly diminished the misty features of traditional Meiyu-Baiu rainfall. However, there is still no consensus on whether their traditional nature is suspended. In this study, we quantitatively demonstrate that the Meiyu-Baiu almost completely lost their traditional features during 1961-2023, ∼80% of which can be attributed to anthropogenic warming. Furthermore, in a warmer future, the traditional Meiyu-Baiu will be more unlikely to appear. This study underscores the urgency in adapting to climate shift because destructive extremes are measurably taking the place of mild and maternal rains.

Unexpected discovery of the Australian seed bug Brentiscerus putoni (White, 1878) (Hemiptera, Heteroptera, Lygaeoidea, Rhyparochromidae, Drymini) in Japan suggests the possibility of a recent introduction due to human activity

The genus Brentiscerus Scudder, 1962 (Hemiptera, Heteroptera, Lygaeoidea, Rhyparochromidae, Drymini) is widely distributed in the Australian Region; however, no species have been recorded in the Palaearctic Region. Here, we report Brentiscerus putoni (White, 1878) from Japan, based on materials collected from Honshu, Kyushu, and Kamikoshiki-shima Island. This discovery represents the first Palaearctic record of the genus and suggests that B. putoni may be an alien species in Japan. All 25 specimens were collected in a well-investigated region of Japan since 2013.

The early last glacial fill terrace along the upper reach of the Sotoyama River (Ooishi River), in the Northern Kitakami Mountains, northeast Honshu Island, Japan

The early last glacial fill terrace along the upper reach of the Sotoyama River (Ooishi River), in the Northern Kitakami Mountains, northeast Honshu Island, Japan