Southern Part Of Japan Research Articles

Relationship between the root processing method and quality of herbal medicine of Rauvolfia serpentina cultivated in Japan

Rauvolfia serpentina roots are used as herbal medicine for snake and insect bites, fever, malaria, abdominal pain, hypertension, and dysentery in Southeast Asian countries. This study evaluates the content of reserpine, ajmaline, and ajmalicine in R. serpentina roots obtained with an efficient root processing method. The plants were cultivated in Tanegashima Island in southern part of Japan, where NIBIOHN's experimental farm station is located. We examined both the type of cork layer removal method (manual work, drum mixer washing, and high-pressure washing) and dried roots. We found that the resulting active ingredient contents were not significantly different between manual work and 30 min of drum mixer washing, and high-pressure washing. The washing in a drum mixer for 30 min could be an efficient root processing method. The amount of each active ingredient was compared in each root part (large-, middle-, and small-diameter roots), and there were no significant difference in their contents. In conclusion, R. serpentina roots having a diameter ≥ 0.5 cm contain a similar amount of active ingredients, suggesting that the quality of the crude drug does not vary in the root part. Thus, our study provides significant insights into the use of R. serpentina roots for herbal medicine applications as well as constituents of active ingredients.

Daily geomagnetic variations under variable IMF/solar conditions and their connection with underground conductivity changes in Japan

Fluctuations in Solar Wind (SW) and Interplanetary Magnetic Field (IMF) significantly affect the Geomagnetic Field (GF) measurements particularly during extreme space weather events. The current study investigates the variations of horizontal (H), vertical (Z) geomagnetic components under quiet and disturbed IMF and solar conditions as well as the effect of underground conductivity on the stationary geomagnetic measurements in Japan. Results of data analysis show that the response of the GF to IMF and solar parameters fluctuations is variable. The H- and Z-components were in good harmony with high visual correlation along a latitudinal profile across Japan during quiet times. On the other hand, during the disturbed times related to a Coronal Mass Ejection (CME) launched on 13 May 2005, the GF components varied with the disturbance of IMF and solar parameters. The H-components showed highly correlated variations with a significant reduction along the examined profile due to intensified ionospheric currents, while the Z-components recorded in the northern part of Japan showed abnormal daily variations pattern (positive daily variations) with an enhanced amplitude which is opposite to the normal behavior of daily variations recorded in the central and southern parts of Japan (negative daily variations). The observed enhanced and abnormal daily variation of Z-components in north Japan, which we consider a remarkable observation here, is possibly linked with underground conductivity anomaly in this region.

Statistical Analysis of the Horizontal Phase Velocity Distribution of Atmospheric Gravity Waves and Medium‐Scale Traveling Ionospheric Disturbances in Airglow Images Over Sata (31.0°N, 130.7°E), Japan

AbstractAtmospheric gravity waves (AGWs) and medium‐scale traveling ionospheric disturbances (MSTIDs) in the upper atmosphere affect atmospheric circulation and radio‐wave transmission including satellite positioning and communications, and high‐frequency radio. The 3‐dimensional (3‐D) spectral analysis of airglow images makes it possible to extract wave parameters of AGWs and MSTIDs. Such spectral analysis of long‐term airglow images has not been performed in the southern part of Japan, which is a unique transition latitude from middle to equatorial region. In this study, we calculated the horizontal phase velocity distribution of AGWs in the mesosphere‐lower‐thermosphere (MLT), and MSTIDs in the F‐region ionosphere by applying the 3‐D spectral analysis method to the 557.7 and 630.0‐nm airglow images obtained at Sata (31.0°N, 130.7°E) in Japan over 20 years from 2000 to 2020. The spectra of AGWs in the MLT region in the 557.7‐nm airglow images show that the poleward (northward) power spectral density (PSD) is stronger in summer, suggesting that the tropospheric convection is a possible source of AGWs and the wave ducting propagation occurred. Westward propagation is also observed in winter, suggesting that wind filtering effect by mesospheric jets plays an important role. The PSD of MSTIDs in the 630‐nm airglow images increases during low solar activity periods, suggesting that MSTIDs are produced by ionospheric plasma instability. The westward PSD of MSTIDs is stronger in summer. These results are an important achievement in clarifying the statistical characteristics of AGWs and MSTIDs over Sata, Japan, based on long‐term airglow observations and 3‐D spectral analysis.

Demographic history and conservation aspects of two relict shrubs (Daphnimorpha spp., Thymelaeaceae) showing disjunct and restricted distribution in the southern part of Japan

Climate relicts are of particular importance in evolutionary biology because of the strategies they may adopt for long-term survival despite climatic oscillations. However, because their current distribution is usually restricted and fragmented, many climatic relicts are at risk of extinction. Daphnimorpha (Thymelaeaceae) is a genus endemic to Japan that comprises two species (D. capitellata and D. kudoi) with a disjunct distribution in southern Japan. These two shrub species are endemic to a single mountain range. In this study, we conducted population genetic analyses using genome-wide single nucleotide polymorphisms obtained from multiplexed inter-simple sequence repeats genotyping by sequencing to reveal the phylogeographic history and obtain conservation implications for the two species. The results showed that these two species may have been isolated since the Tertiary period, supporting their status as climate relicts. In addition, D. kudoi showed clear genetic differentiation between the two mountains where it occurred (Mt. Nagata and Mt. Kuromi), with a decline in the effective population sizes inferred during the last glacial period. In contrast, D. capitellata showed no clear intraspecific genetic structure, and its effective population size was relatively stable. These differences could result in contrasting light tolerance between species. For conservation, we recommend managing these species as three evolutionarily significant units (ESUs): D. capitellata, D. kudoi population on Mt. Nagata, and D. kudoi population on Mt. Kuromi. Considering the limited gene flow among subpopulations and small population census, all ESUs require conservation attention to maintain or increase their effective population sizes.

A study on the volatile compounds in Japanese alcoholic beverage (Awamori) produced from Thai rice varieties

Awamori is a famous alcoholic beverage brewed in the Southern part of Japan. Thai rice is well known and there are many varieties of rice including white rice and pigmented rice. This research aimed to study the properties and volatile compounds of Awamori produced from five Thai rice varieties including KDML105, Chainat, RD6, brown KDML105, and riceberry rice. Rice koji was prepared by inoculating the steamed rice with tane-koji from Aspergillus awamori at 0.2% by weight. Then, water and Saccharomyces cerevisiae were added and alcoholic fermentations were performed at around 2 weeks. The production of alcohol and pH changes during the liquid fermentation were monitored, and volatile compounds of the Awamori were determined by gas chromatography-mass spectrophotometry (GC-MS). The highest soluble solid and alcohol content were observed in the fermentation of KDML 105. The alcohol content after 2 weeks of fermentation ranged from 14.5-18 %, with the pH around 4.02-4.5. The same volatile compounds, ethyl alcohol, isobutyl alcohol, isoamyl alcohol, phenylethyl alcohol, isoamyl acetate, ethyl laurate, ethyl linoleate, with the flavor descriptions as alcohol, wine-like, mushroom-like, floral, rose, fruity, banana, sweet, ice-cream, mild fatty, oily, and honey-like odors were detected in all samples from Thai rice while KDML105 presented greater diversity of volatile compounds than the other Thai rice.

Natural attenuation and remobilization of arsenic in a small river contaminated by the volcanic eruption of Mount Iou in southern Kyushu Island, Japan

The active volcano Mount Iou, in the southern part of Japan, erupted in 2018 for the first time in approximately 250 years. Geothermal water discharged from Mount Iou had high concentrations of toxic elements, such as arsenic (As), which could seriously contaminate the adjacent river. In this study, we aimed to clarify the natural attenuation of As in the river through daily water sampling for approximately eight months. The risk of As in the sediment was also evaluated using the sequential extraction procedures. The highest As concentration (2000 μg/L) was observed upstream but typically remained below 10 μg/L downstream. Dissolved As was the main form in the river water on non-rainy days. Arsenic concentration in the river naturally decreased through dilution and sorption/coprecipitation with Fe, Mn, and Al (hydr)oxides during flow. However, peaks in As concentration were frequently observed during rainfall events, possibly due to sediment resuspension. Furthermore, the range of pseudo-total As in the sediment was 4.62–14.3 mg/kg. Total As content was highest upstream before decreasing further along the flow. When using the modified Keon method, 44–70% of the total As existed as more reactive fractions associated with (hydr)oxides.

Early Life History and Recruitment Processes of a Tropical Anguillid Eel Anguilla marmorata to the Pacific Coast, as Revealed by Otolith Sr:Ca Ratios and Microstructure.

Recent progress in otolith microchemistry especially in strontium:calcium (Sr:Ca) ratios has revealed significant features of life histories in fishes. A catadromous eel, Anguilla marmorata, has the widest distribution among anguillid eels throughout the Indo-Pacific region. However, its dispersal and recruitment mechanisms in the ocean are still unknown. The temporal and spatial variations of early life history characteristics in a tropical anguillid eel A. marmorata were examined by means of otolith Sr:Ca ratios and microstructure to understand the larval transport and recruitment processes to the coasts in the Pacific region. Durations of the larval stage and age at recruitment to the southern part of Japan ranged from 79 to 157 d and 113 to 192, respectively. No significant differences were found between recruitment months in those parameters. The early life characteristics such as larval duration and age at recruitment were constant throughout the recruitment period in the southern part of Japan. The early life history characteristics in combination with the oceanic current regime possibly determine the larval transportation and dispersion processes and further recruitment dynamics to the Pacific coast of A. marmorata. The present study also provides useful information on its biogeographic distribution in the species as determined by otolith Sr:Ca ratios and microstructure.

Genomic characterization and the prevalence of a novel copiparvovirus in wild sika deer (Cervus nippon) in Japan

A preliminary metagenomic analysis of the virome of wild sika deer (Cervus nippon) blood in Japan resulted in the identification of a novel parvovirus. The virus was closest, but only 44.7-60.7% identical to 17 reported strains belonging to the genus Copiparvovirus within the subfamily Parvovirinae, over the near-entire genomic sequence. The sika deer copiparvovirus DNA was detected in 15% (31/206) of sika deer captured in 7 prefectures of Japan, and a region-dependent prevalence of 0-66.7% was noted, with a biased distribution in the southern part of Japan. The observed biased distribution of sika deer copiparvovirus may be due to the habitat density of deer and the number of ticks, which might play a role in the transmission of the virus.

Conservation of the coral community and local stakeholders’ perceptions of climate change impacts: Examples and gap analysis in three Japanese national parks

Coastal ecosystems consisting of coral communities have high ecosystem services and are important for tourism, fisheries, and the maintenance of biodiversity. Corals are often considered a major tourist resource in national parks located in the southern part of Japan. However, due to global-scale stresses such as climate change and local-scale stresses such as mass outbreaks of coral predators, there is a need to consider appropriate management and countermeasures. Two national parks in the subtropical zone (Keramashoto and Amamigunto national parks) and one national park in the temperate zone (Ashizuri-Uwakai National Park) in Japan were selected as a case study. The objectives of this study were to determine the status of coral conservation/management from websites and reports, and to clarify perceptions/concerns about climate change impacts through interviews with local stakeholders. The overall aim was to identify challenges in achieving sustainable use of coral ecosystems in national parks under climate change. In all of the national parks, the use of the sea area for tourism, such as diving, was very active. At the same time, coral monitoring and culling of predators were being carried out. However, the results of the interviews revealed that each park had different issues in implementing conservation activities, and Ashizuri-Uwakai showed a lack of manpower compared to the other two parks due to the scattered distribution of diving operators. From the interviews on the impacts of climate change, the increases in air and water temperatures were recognized in all parks and were consistent with the actual observed data. In terms of future concerns, increased coral bleaching frequency was common. Text mining showed that perceptions of coastal resources differed among parks and between occupations (tourism, fisheries, and government). Since concerns about climate change varied among regions and conservation activity systems also differed, it is important to consider and implement adaptation measures based on an appropriate understanding of local conditions.

Population-based incidence and outcomes of acute aortic dissection in Japan

Abstract Background The population-based incidence and outcomes of acute aortic dissection (AAD) are still unknown because some patients are already dead on arrival at the hospital, and the accurate diagnosis of AAD is difficult due to the low autopsy rate for patients with cardiopulmonary arrest outside of the hospital. We performed a population-based review of all patients with AAD in a well-defined geographical area in the southern part of Japan between 2016 and 2018. Methods Data of all patients with AAD at our Hospital, which performs medical care for 120,000 residents, were collected retrospectively. The emergency medical service is dedicated to the transfer of all patients in this area to the MPNH. For all patients who were dead on arrival, the diagnosis of AAD was made by autopsy imaging (AI) using computed tomography. The age-adjusted incidence and mortality per 100,000 population were calculated using the Japanese population distribution model in 2015. Results The total incidence of AAD was 79 (type A: 64.5%, n=51). Of those, 60.8% (31/51) of patients with type A and 21.4% (6/28) with type B were dead on arrival and diagnosed by AI. The 30-day mortality rates after the onset of AAD were 74.5% (38/51) in type A and 25.0% (7/28) in type B. Excluding the dead-on-arrival patients, the 30-day mortality rates were 35.0% (7/20) in type A and 4.5% (1/22) in type B. The age-adjusted incidence and mortality of AAD per 100,000 inhabitants were 17.3 (type A: 11.3, type B: 6.0) and 9.6 (type A: 8.4, type B: 1.2), respectively. Both values were significantly higher in men than in women. Conclusions The population-based survey of emergency medical care for AAD showed that the age-adjusted incidence of AAD was two-fold higher than in previous reports, and the actual mortality rates after AAD onset were markedly higher due to the high incidence of dead-on-arrival. Funding Acknowledgement Type of funding sources: None. Representative CT images of type A AAD

FPGA Based Tsunami Wave Propagation Calculator

The authors continue to use hardware acceleration to calculate tsunami wave propagation in a few seconds at modern PC. The goal of this work is to develop original implementation the FPGA-based algorithm for nested-grids computations of tsunami wave propagation. The FPGA-based Calculator, for regular grid has been proposed and numerically tested earlier. Use of the nested grid approach makes it possible to calculate wave propagation almost until the shore line. Numerical tests are based on the real digital bathymetry at southern part of Japan. Mesh step variation of the gird is from 180 m to just 7 m. Realistic shape of the initial sea surface displacement at tsunami source was used. The detailed distribution of wave height maxima around and inside the Onahama port have been issued as a result of tsunami generated by a model source located along the Japan deep-water trench. The superfast FPGA calculator provides an opportunity to obtain the calculated wave parameters inside ports and harbours even before arrival of tsunami wave.

Infrasonic Earthquake Detectability Investigated in Southern Part of Japan, 2019.

The Kochi University of Technology (KUT) Infrasound Sensor Network contains 30 infrasound sensors which are distributed all over Japan especially in Shikoku Island. At all infrasound stations installed with three-axis accelerometers to measure the peak ground acceleration (PGA). Many earthquakes were detected by our system after establishing of the network since 2016. In this study we will focus on all the possibilities for infrasound detection generated from earthquakes using KUT sensor network and International Monitoring system (IMS) stations for the earthquakes which were detected in southern part of Japan during 2019. As for earthquakes with strike-slip mechanisms the P-waves could not be detected by our sensors. In addition, The conversion from seismic to acoustic waves can be happened through the generating of the T-phase from oceanic earthquakes. On 9 May 2019, progressive multi-channel cross correlation (PMCC) method applied infrasound and hydroacoustic waves from two earthquakes happened in west of Kyushu Island as the T-phase was well-recorded at H11N station near Wake Island. Moreover, infrasound propagation modeling is applied to the reconstructed atmosphere profile by Ground to Space Model (AVO-G2S) to confirm the infrasound arrivals, furthermore the 3D ray tracing process and the calculations by using the transmission loss equation with normal modes and parabolic equation methods are investigated. The study confirmed the infrasound generation scenario from the T-phase of oceanic propagation.

Detection of Mycoplasma wenyonii and "Candidatus Mycoplasma haemobos" from Japanese Black breeding cows in Kyushu and Okinawa region, southern part of Japan.

This study aimed to elucidate the epidemiological status of hemoplasma infection and investigate the interaction between Theileria orientalis and hemoplasmas in Japanese Black breeding cows raised in the Kyushu and Okinawa regions. Blood samples were collected from 400 cows from 80 different farms in eight prefectures (five samples per farm and 10 farms per prefecture). Mycoplasma wenyonii (Mw), “Candidatus Mycoplasma haemobos” (CMh), and T. orientalis were examined by polymerase chain reaction (PCR) assay using whole blood samples. PCR results showed that 91.5% (366/400) of cows were positive for bovine hemoplasma: 40.3% were infected with Mw only, 9.5% with CMh only, and 41.8% with both species. T. orientalis was detected in 36% (144/400) of cows. The infection rate of T. orientalis was higher in the grazing group (P<0.001) than in the housed group, while the rate of CMh infection was higher (P<0.05) in the housed group than in the grazing group, suggesting that not only the tick but also other arthropod vectors may contribute to hemoplasma transmission. Although the cows with hemoplasma dual infection showed higher (P<0.05) white blood cell counts compared with hemoplasma-negative cows, there was no difference in hematologic parameters related to the anemia between the hemoplasma-positive and -negative animals. This may indicate that Japanese Black cattle could have resistance to the anemia caused by infection with hemoplasma.

Hardware Acceleration of Tsunami Wave Propagation Modeling in the Southern Part of Japan

In order to speed up the calculation of tsunami wave propagation, the field-programmable gate array (FPGA) microchip is used. This makes it possible to achieve valuable performance gain with a modern regular personal computer. The two half-step MacCormack scheme was used herein for numerical approximation of the shallow water system. We studied the distribution of tsunami wave maximal heights along the coast of the southern part of Japan. In particular, the dependence of wave maximal heights on the particular tsunami source location was investigated. Synthetic 100 × 200 km sources have realistic parameters corresponding to this region. As observed numerically, only selected parts of the entire coast line are subject to dangerous tsunami wave amplitudes. The particular locations of such areas strongly depend on the location of the tsunami source. However, the extreme tsunami heights in some of those areas can be attributed to local bathymetry. The proposed hardware acceleration to compute tsunami wave propagation can be used for rapid (say, in a few minutes) tsunami wave danger evaluation for a particular village or industrial unit on the coast.

Notes on Forefoot Characteristics of the Ryukyu Long-Furred Rat, Diplothrix legata, for Its Arboreal Lifestyle

Forefoot characteristics of the Ryukyu long-furred rat, Diplothrix legata, in the Amami-oshima, Tokunoshima, and Okinawajima Islands of the southern part of Japan (the Nansei Archipelago), were analyzed morphologically considering its arboreal lifestyle. The presence of a nail on the pollex was confirmed and seemed to be regarded as an arboreal feature, based on the presence of nails in other arboreal murids reported in previous studies. In addition, a linear palmar groove was confirmed between the interdigital pads and the thenar-hypothenar pads. We tried to allow the forefoot to take hold of a thin stick at this groove; the stick fit well in the groove, and it seemed to be possible to grip by the fingers except for pollex. Thus, the sizes and positions of palmar swollen pads forming the linear groove were considered to be useful for gripping a thin twig in an arboreal lifestyle. In addition, the entire unguis size tended to be larger in Okinawajima Island than in Amami-oshima Island as a geographical variation.

Upper Triassic shallow–water carbonates from the Naizawa Accretionary Complex, Hokkaido (Japan): New insights from Panthalassa

Due to their accretion on the Circum–Pacific area during the Jurassic and the Cretaceous, Upper Triassic carbonates from the Panthalassa occur very scarcely and with relatively poor preservation in accretionary complexes. However, they represent a unique opportunity to improve our knowledge of the depositional conditions in tropical regions of the Panthalassa. Recognized as a cradle of life, shallow–water carbonates are also of great importance to understand of how life evolved out of the Tethyan domain during the Triassic. Since 2007, several sedimentological and biostratigraphic studies, focused on the Upper Triassic shallow water limestone from the Circum–Pacific area, have been carried out as part of the REEFCADE project at the University of Geneva. Carbonates were thus reported in the southern part of Japan and in the Russian Far East. Hokkaido Island, in northern Japan, represents the missing link between those two areas. To fill this gap, five limestone outcrops, so far poorly described in the literature, were identified and sampled in the Pippu and Esashi areas (central and northern part of Hokkaido Island, respectively). Their related microfacies are presented in detail as well as their foraminiferal associations. The obtained age, based on foraminiferal biostratigraphy from both areas, is defined as Carnian and the facies similarities, associated with specific modes of occurrence, identify the outcrops from the two areas as part of the same depositional system. Based on microfacies interpretations, a hypothetical depositional model is presented. It corresponds to a intra–oceanic depositional system developed on the flanks of an emergent volcanic seamount. The strong similarity with synchronous systems from the Sambosan Accretionary Complex (southwestern Japan) is discussed.

The maintenance for present infrastructures in southern part of Japan

In general, governments used to increase the number of public works for their economic recovery. In United State, huge number of bridges, roads and tunnels were constructed in 1920’s. The lifetime of infrastructures is regarded as fifty years in general. In addition, the budget for maintenance of infrastructure had been decreased from the latter half of 1960s to 1970s. Therefore, most of these infrastructures were decayed in 1980’s and this period is called as ‘America in Ruins’. In Japan, enough number of power generators were required to launch heavy industries after World War II. To export these products, ports and highways were constructed. Furthermore, the bullet train ‘Shinkansen’ and urban expressways in Tokyo were constructed for Olympic game held in 1964. In 2010’s, most of these infrastructures seem to reach their life time. However, government doesn’t have enough budget for renovations. Therefore, new standards and technologies for repair and inspections are being required. Nowadays, huge number of infrastructures are under construction in Malaysia. Similar issues of United States or Japan may be occurred in this fifty years. In this paper, recent policy of government and new technologies including methods and equipment for maintenance of infrastructures in southern part of Japan are shown.

Climatological characteristics of planetary boundary layer height over Japan

Based on the 30‐year (1988–2017) radiosonde observations, the climatological characteristics of the planetary boundary layer height (PBLH) over Japan, as well as the long‐term changes, are investigated. We firstly compared four different methods to determine the PBLH. Results show that the bulk Richardson number method has the best performance among all these methods. At all studied stations, monthly median PBLHs in the morning are generally higher than the ones in the evening. Bimodal structure of seasonal PBLHs are found over Japan. Daytime PBLH peaks in spring and autumn and achieves the minimum in summer and winter. Night‐time PBLH shows less seasonal variations. It is found that the PBLHs in the central and southern part of Japan could be dominant by the variations of surface temperature, while the variations of surface relative humidity (RH) may be responsible for the PBLHs in the northern part of Japan. Moreover, sea fog which is associated with high RH and temperature inversion also has an obvious influence on PBLHs in northern Japan. Trend study shows that PBLHs in most stations slightly increased during the past 30 years.

Molecular discrimination and phylogeographic patterns of clones of the parthenogenetic gecko Lepidodactylus lugubris in the Japanese Archipelago

AbstractVertebrates usually reproduce sexually in which males and females contribute their offspring genome and produce genetically diverse offspring. However, some of them are asexual without genetic contribution from males. The nocturnal gecko, Lepidodactylus lugubris, is all females and reproduces parthenogenetically. This gecko is known to consist of diploid and triploid clones in the tropical and subtropical regions, which can be identified by their dorsal marking patterns, ploidy, and protein polymorphism. This gecko is also distributed in the southern parts of Japan, and several clones have been reported. In this study, we investigated the origins and genetic diversity of Japanese L. lugubris by clonal discrimination using microsatellite and mitochondrial DNA analyses. A total of 748 individuals were collected from 21 islands of five island groups (Ogasawara, Okinawa, Miyako, Yaeyama and Daito Islands) and 17 clones were distinguished genetically. Mitochondrial cyt b sequences of these clones suggested that they were all closely related and differentiated recently. Clonal diversity was much higher (14 clones) in the Daito Islands than in the other island groups in which only one or two clones coexisted. Judging from the dorsal marking patterns and ploidy known so far, six clones were cosmopolitan and may be colonized from the outside of Japan. However, other 11 clones were endemic to the Daito Islands and explained by possible hybridization between the one female diploid clone and one male diploid clone because other 9 clones were triploid and all had the combinations of polymorphic microsatellite alleles of these female and male diploid clones. Although the males have never been recorded in the Daito Islands, males might appear in the past. These findings contribute to understanding of clonal diversity and dynamics of asexually reproducing animals. If diploid parthenogenetic geckos can produce triploid clones by mating with the diploid males, clonal diversity would increase rapidly in a small island, and such newly produced triploid clones would expand widely.

Microflora of Mycotoxigenic Fungi in Rice Grains in Kyushu Region of Japan and Their Changes during Storage under non-Controlled Conditions.

Contamination of agricultural crops by mycotoxins has increased because of the expansion of mycotoxin-producing fungi along with global warming. In this study, the fungal microflora of brown rice grains cultivated in Kyushu region in the southern part of Japan was investigated. A total of 75% of rice samples examined in this study showed less than 30% of fungal contamination rates with a median rate of 12.5%. Some isolates of Aspergillus flavus showed the ability to produce aflatoxins (AFs) (AFB1 production was 62.5-70.4 ng/mL) . Furthermore, AF-producing Aspergillus flavus survived during storage and Aspergillus creber, which produced sterigmatocystin, was detected in a stored rice sample. Although AFs or sterigmatocystin-contamination was not detected in any rice samples, these mycotoxin-producing fungi are distributed and can survive during storage under the natural conditions in Japan. Employing suitable storage conditions is important for preventing mycotoxin contamination of brown rice grains.