Shikoku Island Research Articles

Contrasting effects of dams with and without reservoirs on the population density of an amphidromous goby in southwestern Japan

Dam construction affects the distribution and abundance of freshwater fishes, particularly for diadromous species. Amphidromous fishes spawn in rivers, and hatched larvae descend to the sea (or standing water body such as lakes) immediately after hatching, grow there typically for a few months, and then ascend rivers as small juveniles. Landlocked populations of amphidromous fishes above dams and their migration between dam reservoirs and inlet streams (landlocked migration) have often been reported. In these cases, population density in the inlet streams may be increased by dam reservoirs, owing to reduced migration distance, which results in higher return rates. On the other hand, dams without reservoirs do not promote landlocked migration and merely act as a barrier to their upstream migration, resulting in decreased population density. In this study, we examined such contrasting effects of dams with and without reservoirs on the population density of an amphidromous goby, Rhinogobius fluviatilis, in two river systems (the Shigenobu and Yoshino Rivers) of Shikoku Island, Japan. In the Shigenobu River, where more than 300 sediment-control dams and weirs (barriers without reservoirs) have been installed, our analysis showed that the goby density decreased sharply with increasing the number of barriers higher than or equal to 2 m. On the other hand, in the Yoshino River, where we investigated both landlocked populations above water storage dams (with reservoirs) and non-landlocked populations in tributaries without water storage dams, the analysis showed that the goby density increased with decreasing the distance from standing water body (i.e. the sea or dam reservoirs). Furthermore, monthly surveys at sites above and below a water storage dam showed that the recruitment of ascending juveniles above the dam was more abundant and seasonally earlier than that below the dam, probably owing to reduced migration distance and increased return rates. Our results have implications for understanding how dams alter natural distribution patterns of amphidromous fishes.

A new species and new records of goatfishes of the genus Parupeneus (Mullidae) from the Indian Ocean, with updated occurrence information for P.jansenii in the Western Pacific

Goatfishes of the genus Parupeneus (Mullidae), from several areas and countries of the Indo-West Pacific, were studied, focusing on species characterized by a symmetrically rounded rear end of the maxilla, which belong to the so-called heptacanthus group. We examined 62 meristic and morphometric characters and colour patterns from 180 specimens from 11 Parupeneus species, using a comprehensive alpha-taxonomy approach. When possible, the data for species represented by wider size ranges were split into two size classes (small-sized fish, < 110 mm SL, vs. large-sized fish ≥ 110 mm SL) to account for allometric changes in body form. A new species, P. inayatae Uiblein & Fahmi, is described, based on a specimen collected in SW Lom-bok, Indonesia, and new records for four species are reported from the Indian Ocean: Parupeneus fraserorum new for Mozambique, P.jansenii new for Myanmar and the NE Indian Ocean, P. nansen new for Tanzania, and P. procerigena new for the Nazareth Bank and Mauritus (Cargados Carajos Bank), Western Indian Ocean (WIO). The record of P.jansenii for Myanmar was compared in detail to 37 conspecific specimens from the entire distribution range (western Indonesia to Japan and Vietnam to NE Australia). The latter revealed two new Pacific records for the Central Philippines and for Shikoku Island, Japan (northernmost record of the species). For each of the eight heptacanthus-group species, diagnoses are provided along with remarks on intraspecific size- and/or population-related variation and/or other noteworthy observations. The new species can be distinguished from all other 32 congeners as follows: dorsal head margin in front of eyes concave shaped; posterior maxilla margin evenly, symmetrically rounded; body, head, and caudal peduncle moderately deep; pectoral and pelvic fins subequal in length; and caudal peduncle clearly deeper than 9.5 % SL; in life a dusky spot on lateral line below interdorsal space, followed posteriorly by a bright orange blotch. Detailed comparisons among all eight heptacanthus-group species and with three other similar and/or co-occurring congeners revealed considerable similarity between two species pairs, P.jansenii (Eastern Indian Ocean and Western Pacific) and P. nansen (WIO), and P. fraserorum and P. procerigena (both from the WIO). The need to further intensify taxonomie studies and accompanying fisheries-biology and ecological studies of goatfishes in the large realm of the Indo-West Pacific is emphasized.

Shokubai, Sumitomo complete big plants

Nippon Shokubai completed the construction of two facilities: one to produce superabsorbent polymers and the other to produce the key ingredient acrylic acid. Built at a cost of $400 million, both plants at the firm’s site in Antwerp, Belgium, have an annual production capacity of 100,000 metric tons. Separately, Sumitomo Chemical finished building a 100,000-metric-ton methionine plant at its site in Ehime on the southeast island of Shikoku in Japan. The plant brings Sumitomo’s total production capacity for the poultry feed additive to 250,000 metric tons annually.

Aurihydrargyrumite, a Natural Au6Hg5 Phase from Japan

Aurihydrargyrumite, a natural Au6Hg5 phase, was found in Iyoki, Uchiko, Ehime Prefecture, Shikoku Island, Japan. Aurihydrargyrumite with a metallic silver luster occurs as a submicron- to 2 μm-thick layer on the outermost surface of the placer gold. A prismatic face may be formed by {001} and {100} or {110}. The streak is also silver white and its Mohs hardness value is ca. 2.5. Its tenacity is ductile and malleable, and its density, as calculated based on the empirical formula and powder unit-cell data, is 16.86 g·cm−3. The empirical formula of aurihydrargyrumite, on the basis of 11 Au + Hg, is Au5.95Hg5.05. Aurihydrargyrumite is hexagonal, P63/mcm, with the lattice parameters a = 6.9960(10) Å, c = 10.154(2) Å and V = 430.40(15) Å3, which is identical with the synthetic Au6Hg5 phase. The seven strongest lines in the powder X-ray diffraction (XRD) pattern [d in Å(I/I0)(hkl)] were 2.877(29)(112), 2.434(42)(113), 2.337(100)(104), 2.234(87)(211), 1.401(39)(314), 1.301(41)(404), and 1.225(65)(217). Aurihydrargyrumite forms through the weathering of mercury-bearing placer gold by involvement of self-electrorefining. This new mineral has been approved by the IMA-CNMNC (2017-003) and it is named for its composition, being a natural amalgam of gold (Latin: aurum) and mercury (Latin: hydrargyrum).

Incidence of infantile spinal muscular atrophy on Shikoku Island of Japan

BackgroundSpinal muscular atrophy (SMA) is an autosomal recessive disorder caused by homozygous mutations in the SMN1 gene. SMA has long been known to be the most common genetic cause of infant mortality. However, there have been no reports on the epidemiology of infantile SMA (types 1 and 2) based on genetic testing in Japan. In this study, we estimated the incidence of infantile SMA on Shikoku Island, which is a main island of Japan and consists of four prefectures: Ehime, Kagawa, Tokushima and Kochi. MethodsA questionnaire was sent to 91 hospitals on Shikoku Island to investigate the number of SMA infants born from 2011 to 2015. A second questionnaire was then sent to confirm the diagnoses of SMA based on clinical and genetic features. ResultsResponses were received from all of the hospitals, and four patients were diagnosed with infantile SMA among 147,950 live births. We estimated the incidence of infantile SMA patients as 2.7 per 100,000 live births (95% confidence interval, 0.1–5.4). A comparison of the four prefectures indicated that the incidence of infantile SMA was significantly higher in Ehime Prefecture than in the other three prefectures; 5.6 per 100,000 live births (95% confidence interval, −0.7 to 11.9) in Ehime Prefecture and 1.1 per 100,000 live births (95% confidence interval, −1.0 to 3.1) in the other prefectures. ConclusionWe estimated the incidence of infantile SMA in an isolated area of Japan. For more precise determination of the incidence of infantile SMA, further studies that include neonatal screening will be needed.

Genetic structure and diversity in relation to the recently reduced population size of the rare conifer, Pseudotsuga japonica, endemic to Japan

Rare species consisting of small populations are subject to random genetic drift, which reduces genetic diversity. Thus, determining the relationship between population size and genetic diversity would provide key information for planning a conservation strategy for rare species. We used six microsatellite markers to investigate seven extant populations of the rare conifer Pseudotsuga japonica, which is endemic to the Kii Peninsula and Shikoku Island regions that are geographically separated by the Kii Channel in southwest Japan. The population differentiation of P. japonica was relatively high (FST = 0.101) for a coniferous species, suggesting limited gene flow among populations. As expected, significant regional differentiation (AMOVA; p < 0.05) indicated genetic divergence across the Kii Channel. A strong positive correlation between census population size and the number of rare alleles (r = 0.862, p < 0.05) was found, but correlations with major indices of genetic diversity were not significant (allelic richness: r = 0.649, p = 0.104, expected heterozygosity: r = 0.361, p = 0.426). The observed order of magnitude of correlation with three genetic diversity indices corresponded with the theoretically expected order of each index’ sensitivity (i.e., the rate of decline per generation) to the bottleneck event. Thus, features that exhibit a faster response, i.e., the number of rare alleles, would have been subject to deleterious effects of the recent decline in population size, which is presumably caused by the development of extensive artificial plantations of other tree species over the last several decades. Finally, we propose a conservation plan for P. japonica based on our findings.

Regional genetic differences among Japanese populations and performance of genotype imputation using whole-genome reference panel of the Tohoku Medical Megabank Project

BackgroundGenotype imputation from single-nucleotide polymorphism (SNP) genotype data using a haplotype reference panel consisting of thousands of unrelated individuals from populations of interest can help to identify strongly associated variants in genome-wide association studies. The Tohoku Medical Megabank (TMM) project was established to support the development of precision medicine, together with the whole-genome sequencing of 1070 human genomes from individuals in the Miyagi region (Northeast Japan) and the construction of the 1070 Japanese genome reference panel (1KJPN). Here, we investigated the performance of 1KJPN for genotype imputation of Japanese samples not included in the TMM project and compared it with other population reference panels.ResultsWe found that the 1KJPN population was more similar to other Japanese populations, Nagahama (south-central Japan) and Aki (Shikoku Island), than to East Asian populations in the 1000 Genomes Project other than JPT, suggesting that the large-scale collection (more than 1000) of Japanese genomes from the Miyagi region covered many of the genetic variations of Japanese in mainland Japan. Moreover, 1KJPN outperformed the phase 3 reference panel of the 1000 Genomes Project (1KGPp3) for Japanese samples, and IKJPN showed similar imputation rates for the TMM and other Japanese samples for SNPs with minor allele frequencies (MAFs) higher than 1%.Conclusions1KJPN covered most of the variants found in the samples from areas of the Japanese mainland outside the Miyagi region, implying 1KJPN is representative of the Japanese population’s genomes. 1KJPN and successive reference panels are useful genome reference panels for the mainland Japanese population. Importantly, the addition of whole genome sequences not included in the 1KJPN panel improved imputation efficiencies for SNPs with MAFs under 1% for samples from most regions of the Japanese archipelago.

Tsunami evacuation simulation using geographic information systems for homecare recipients depending on electric devices.

Tsunamis cause direct damage to property and destroy infrastructure. In addition, power outages can lead to death, especially for patients who rely on medical equipment requiring a power supply. Recently, Nankai Trough Earthquakes have been predicted, and much effort has been put into developing countermeasures in Japan. Kochi City on Shikoku Island is expected to suffer in the event of a large tsunami. The present study identifies individuals living in Kochi who need evacuation assistance and depend on electrical medical devices, simulates evacuation behavior and inundation during a tsunami using a geographic information system (GIS), and considers the usefulness of such a GIS. We asked caregivers, including visiting nurses, to introduce us to homecare recipients who rely on a ventilator, an endotracheal suction device, or other medical devices requiring electric power. We received introductions to 52 homecare recipients. Using a GIS, we plotted the area of predicted inundation and the locations of homecare recipients, nursing stations, and welfare evacuation shelters. We predicted evacuation routes, and then analyzed the time difference between the time required for evacuation and tsunami arrival at a welfare evacuation shelter. To measure the effects of the main parameters, we conducted both one-way and multi-way sensitivity analysis. In the event of a tsunami, eight of the homecare recipients living in the forecasted inundation areas in Kochi may face delayed evacuation. Among homecare recipients facing a high possibility of escape delay, 95.2% lived more than 1,800 m from the nearest welfare evacuation shelter. We found that individual evacuation behavior can be simulated by specifying the residence of a homecare recipient and the evacuation route using a GIS.

A preliminary molecular phylogeny shows Japanese and Austrian populations of the red mite Balaustium murorum (Acari: Trombidiformes: Erythraeidae) to be closely related

The red mite Balaustium murorum (Hermann) inhabits the Western Palaearctic realm and is well adapted to man-made structures. In Japan, B. murorum had been reported more frequently after the 1980s. A molecular phylogeny based on the nuclear 18S rRNA and mitochondrial COI genes, and including B. murorum individuals from Japan and Austria and representatives of related species from Japan showed four Balaustium species-level lineages in Japan (B. murorum, Balaustium sp. 1, Balaustium sp. 2, Balaustium sp. 3). The B. murorum lineage shared identical 18S sequence and COI haplotype with the Austrian population. Balaustium sp. 1 was detected from the Tokyo and Misaki area (Honshu Island) and was the sister group to B. murorum; the other two lineages inhabited coastal environments of Erimo, Hokkaido Island (Balaustium sp. 2) and Ainan, Shikoku Island (Balaustium sp. 3). The high genetic distances among these four lineages indicate that each lineage is a distinct species, with three of the lineages representing undescribed species. Our results are compatible with the conclusion that B. murorum was introduced to Japan from Europe, although our study did not resolve the polarity or timing of migration events.

四国におけるツキノワグマの個体情報の収集 : 体毛をもちいた遺伝学的手法による個体識別(実践報告)

四国におけるツキノワグマの個体情報の収集 : 体毛をもちいた遺伝学的手法による個体識別(実践報告)

First record of the rare spoon worm &lt;i&gt;Ikedosoma elegans&lt;/i&gt; (Annelida: Echiura: Thalassematidae) from Shikoku Island, Japan

Ikedosoma elegans (Ikeda, 1904) (Annelida: Echiura: Thalassematidae) is a rare, large deep-burrowing spoon worm that has been observed only in Japan. This species was first described based on the specimens collected from Misaki, Sagami Bay (Kanagawa Prefecture), eastern Japan, in 1902. Since the first description, this species has not been collected until the recent studies, which reported that I. elegans was collected from Hamana Lake (Shizuoka Prefecture), Boso Peninsula (Chiba Prefecture), and probably Amakusa, Ariake Sea (Kumamoto Prefecture). Furthermore, the specimen collected from Takasu, Seto Inland Sea (Okayama Prefecture) in 1975 was identified to be I. elegans. In this study, we present a new locality of this species in Japan. We collected a large individual of I. elegans with a probably commensal scale worm (Polynoidae: Polynoinae) by using a yabby pump in a mud flat in the Doki River Estuary, which is facing the Seto Inland Sea, in Marugame (Kagawa Prefecture), northern Shikoku Island. To the best of our knowledge, the present study is the first record of I. elegans from Shikoku Island and the second record from the Seto Inland Sea, following a 42-year-old record from Takasu, Okayama.

Bird species observed by automatic cameras on Shikoku Island

Bird species observed by automatic cameras on Shikoku Island

Ichinokawa Mine and Antimon deposits in Shikoku island

Ichinokawa Mine and Antimon deposits in Shikoku island

Naturalization of the Red-billed Blue Magpie in western Shikoku Island, Japan

Naturalization of the Red-billed Blue Magpie in western Shikoku Island, Japan

Impacts of two super typhoons on the Kuroshio and marginal seas on the Pacific coast of Japan

High-resolution downscaling ocean modeling was conducted to investigate the impacts of two super typhoons on the Kuroshio in the fall of 2014 off the Kyushu and Shikoku Islands, Japan. The model result was compared with field observations and satellite altimetry. The synoptic and mesoscale oceanic structures around the Kuroshio exhibit a good reproducibility. The typhoons generated near-inertial oscillations (NIOs) and near-inertial internal waves (NIIWs) around the Kuroshio path, particularly on the right side of the typhoon tracks. The NIOs developed in the mixed layer to alter the direction of the Kuroshio by ~30°. The associated velocity off the Shikoku and Kyushu Islands was significantly decelerated by ~0.2ms−1. The velocity almost vanished off Kyushu Island and thus induced an unstable fluctuating path shortly after both typhoons passed over that region. The NIIWs were also excited at the thermocline, resulting in the oscillation of the Kuroshio path occurred in the entire water column. In contrast, off Shikoku Island, the typhoons shifted the Kuroshio path northward to enhance the interactions with the topographies. This shift caused considerable eddy shedding from the capes that resulted in mesoscale counterclockwise circulations as cyclonic quasi-standing eddies with a shedding period of ~3 days in the north of the Kuroshio path. The magnitude, direction, and meridional location of the path of the Kuroshio prominently fluctuated with the propagation of these eddies, manifested off Shikoku Island. Furthermore, these eddies induced sporadic northward intrusions of the Kuroshio warm water through the Kii Channel into the Seto Inland Sea (SIS), where a weak but persisting southward outflow prevails under normal conditions. Therefore, the process could collectively be called the “typhoon-Kuroshio-eddy interaction”, which conceptually differs from the “typhoon-eddy-Kuroshio interaction” in the previous studies, where the Kuroshio was modulated by eddy collision. The wind stress curl and intrusions associated with the typhoons jointly provoked the inversion of the counterclockwise SIS residual circulation. The resultant spatially averaged volume flux was ~8 times as high as that under normal conditions.

Study on inter-taxon population structure and diversity variation of hosta inferring from trnG-trnS regional cpDNA

Diversity studies are now a key tool in genetic conservation work. The perennial herb genus Hosta showed a complex radiation of numerous species in mountains and riversides around the Shikoku Island, Japan. The purpose of this study was to evaluate trnS-trnG regional genetic structure and the genetic divergence within hosta taxa populations in this area. We sequenced trnS-trnG regional (chloroplast DNA) cpDNA in 81 populations comprising 399 individuals of 11 Hosta taxa collected from Shikoku area. The different numbers of haplotypes were found in different taxon. The divergences of population of Hosta genus and individual taxon were shown in NJ phylogenetic tree. The highest number of haplotypes (14) was found in H. longipes var. gracillima. H. sieboldiana and H. kiyosumiensis populations showed the maximum haplotype diversity (1.0), and H. alismifolia showed maximum nucleotide diversity (π: 0.012). The genetic structures of the H. tardiva with H. kikutii var. caput-avis (FST divergence: 52.7%) and H. sieboldiana with H. tardiva (FST divergence: 52.2%) populations were greatly differentiated from each other (FST value: >0.15 to 0.25). We found maximum evolutionary divergence (0.009) between H. alismifolia and H. kikutii var. polyneuron populations. The significant negative neutrality test values are the evidence of expansion of the total population. H. sieboldiana and H. kiyosumiensis are more widely distributed than other taxa. H. sieboldiana, H. alismifolia, H. longipes var. gracillima and H. kikutii var. polyneuron showed the excessive low frequency variants.

Objective detection of long-term slow slip events along the Nankai Trough using GNSS data (1996\u20132016)

This paper presents a method for objective detection of long-term slow slip events with durations on the order of years, on the plate boundary along the Nankai Trough, relying on global navigation satellite system daily coordinate data. The Chugoku region of Japan was held fixed to remove common mode errors, and a displacement component was calculated relative to the direction of plate subduction. Correlations were then calculated between this displacement component and a 3-year ramp function with a 1-year slope. Nearly all periods of strong correlation coincide with periods of previously reported long-term slow slip events. A period of strong correlation around the Kii Channel in 2000–2002 is attributed to a previously undocumented long-term slow slip event beneath the Kii Channel and the eastern part of Shikoku Island with an equivalent moment magnitude of 6.6. This detection method reveals variation among long-term slow slip events along the Nankai Trough.

High resolution record of Quaternary explosive volcanism recorded in fluvio-lacustrine sediments of the Uwa basin, southwest Japan

The identification of widespread tephras is important, not only for understanding volcanic processes but also for age estimation and establishing stratigraphic relationships. Many widespread tephras have been erupted from six active and buried caldera volcanoes in the SW Japan-Ryukyu volcanic arcs. To reconstruct high-resolution tephrostratigraphy, we analyzed core UT from the Uwa basin on western Shikoku Island and correlated the tephras in the core with the proximal source deposits that we sampled. This 120 m-long core composed of fluvio-lacustrine deposits, spanning the middle Pleistocene to Holocene. We recognized and characterized 52 visible tephra and tephric sediment layers in the core on the basis of their stratigraphy, the petrographic features and the major-element composition of glass shards. We successfully correlated 15 tephras with the following previously identified widespread tephras, mainly from volcanoes on Kyushu: Kikai-Akahoya (7.3 ka), Aira-Tn (29 ka), Aso-4 (87 ka), Kikai-Tozurahara (95 ka), Aso-ABCD (100 ka), Ata (105-110 ka), Aso-3 (112.7 ka, calculated in this study), Aso-2 (140 ka), Ata-Toihama (240 ka), Aso-1 (250-270 ka), Tky-Ng1 (290-300 ka), Kakuto (330-340 ka), Oda (420-450 ka), Hiwaki (570-580 ka), and Yufugawa (600 ka). Above 50 m depth, all known widespread tephras from Kyushu younger than 350 ky were included in the sequence that has a fairly constant sedimentation rate of about 0.14 mm/yr. This high-resolution tephrostratigraphy was correlated with those of regional long-core records from the Lake Biwa in the central Japan and offshore of Shikoku that contributes to establish onshore-onshore and onshore-offshore correlations in southwest Japan. In the sediments, each of the following tephras from caldera-forming eruptions, Aso-4, Aso-ABCD, Ata, Aso-3, Aso-2 and Aso-1 occurred above multiple, compositionally similar tephra layers erupted from the same volcano over a long time period. This high-resolution record is therefore an important contribution to the correlation of regional stratigraphy and reconstruction of both the long-term eruptive history and the magma evolution of volcanoes in the SW Japan and -Ryukyu volcanic arcs.

瀬戸内鹽業の發展 (「日本資本主義成立期の諸問題」 : 四國地方を中心として)

瀬戸内鹽業の發展 (「日本資本主義成立期の諸問題」 : 四國地方を中心として)

明治時代の阿波藍 (「日本資本主義成立期の諸問題」 : 四國地方を中心として)

明治時代の阿波藍 (「日本資本主義成立期の諸問題」 : 四國地方を中心として)