Fish fauna and environmental factors in river estuaries of small and medium-sized rivers on islands significantly influenced by warm currents.

River estuaries are influenced by terrestrial and marine areas, and have a unique environment that is constantly fluctuating. They are also important habitats for biodiversity conservation. Tanegashima Island is significantly influenced by the Kuroshio Current. Although nearby Yakushima Island has been recognized as a World Natural Heritage site and information on many species has been collected, there is little information on species inhabiting the river estuaries of Tanegashima Island. In this study, the river estuarine ichthyofauna of 26 small and medium-sized rivers on Tanegashima Island was surveyed and a total of 2758 individuals of 29 species and one genus belonging to 15 families were collected. The fish fauna of the river estuaries of Tanegashima Island were classified into three groups, namely the river estuaries where coastal terraces are underdeveloped and drowned valleys are formed, the river group where the riverbed gradient at the mouth is high, and other river groups. Environmental factors selected as being important for ordination of fish fauna were the altitude of the headstreams at the watershed scale, the gradient of the river estuarine area, and the presence or absence of rapids in the estuary. The importance of the geohistorical factor of drowned valley formation, in addition to habitat and watershed scale environmental factors, as a factor on river estuarine fish fauna is an important finding for future conservation of local biota diversity.

Cryptic genetic divergence of the red dwarf rasbora, Microrasbora rubescens, in and around Inle Lake: implications for the origin of endemicity in the ancient lake in Myanmar.

Inle Lake, an ancient lake located in the Shan Plateau of Myanmar, is a biogeographically attractive region with high fish endemism. Some endemic species inhabit the lake as well as the surrounding areas. The genetic and ecological relationships between populations in the lake and surrounding areas provide important insights into the process underlying ichthyofaunal formation in Inle Lake. In this study, the authors focused on red dwarf rasbora Microrasbora rubescens, an endemic genus and species in this region, and estimated its population structure and evolutionary scenario based on genome-wide polymorphism, mtDNA and geometric morphometric analyses using samples from Inle Lake and three areas surrounding the lake. The results showed that M. rubescens comprises at least three genetically divergent lineages (Inle, Heho and Hopong) with distinct geographic structures consistent with nuclear and mtDNA data. In contrast, there was no clear regional differentiation in morphology. The divergence time estimation based on mtDNA suggests that the Hopong lineage diverged at 2.7 Ma and the Inle and Heho lineages diverged at 1.9 Ma - consistent with the nuclear DNA results. The deep divergence observed in the endemic species supports the ancient history of ichthyofaunal development in this region. The distinct regional differentiation and morphological conservatism of this species might have been shaped by niche conservatism in stagnant water environments that limit dispersal and morphological diversification. Future comprehensive genetic and morphological analyses and comparisons for other native species should reveal the geographic and ecological processes that shaped the ichthyofauna in this region.

Ecosystem size predicts the probability of speciation in migratory freshwater fish.

Predicting speciation is a fundamental goal of research in evolutionary ecology. The probability of speciation is often positively correlated with ecosystem size. Although the mechanisms driving this correlation are generally difficult to identify, a shared geographical and ecological context provides a suitable condition to study the mechanisms that promote speciation in large ecosystems by reducing the number of factors to be considered. Here, we determined the correlation between speciation and ecosystem size, and discuss the underlying mechanisms of this relationship, using a probable parallel ecotype formation for freshwater fish. Our population genetic analysis revealed that speciation of the landlocked goby, Rhinogobius sp. YB, of the Ryukyu Archipelago, Japan, from its migratory ancestor, R. brunneus, occurred in parallel across five islands. Logistic regression analysis showed that speciation probability could be predicted using island size. The results suggest that ecosystem size predicts the occurrence of adaptation and reproductive isolation, probably through its association with three possible factors: divergent selection strength, population persistence, and occurrence probability of habitat separation.

[Gastric tuberculosis in an elderly patient:a case report].

A woman in her 70s presented to our hospital with epigastric pain, back pain, and weight loss. Esophagogastroduodenoscopy was performed, and numerous protuberances, which were suspected to be submucosal tumors, were found at the gastric corpus. The patient was diagnosed with gastric tuberculosis based on the biopsy results of these protuberances. Histopathological analysis demonstrated non-caseating epithelioid granuloma. A positive culture for Mycobacterium tuberculosis was also obtained on gastric juice analysis and confirmed using polymerase chain reaction assay. In the rapidly aging population in Japan, our findings emphasize on the importance of differentiating gastrointestinal tuberculosis, including gastric tuberculosis, from other diseases. This case may provide information about the development of gastric tuberculosis.

Detour canal, a civil engineering heritage created through historical struggle for water resources, now provides the habitats for a rare freshwater fish.

The Ariake catfish, Tachysurusaurantiacus, is a freshwater fish endemic to Kyushu Island, Japan. However, these catfish are now endangered owing to environmental changes. Despite their status, there is scant quantitative research on the Ariake catfish regarding their potential conservation. The Yabe River is a typical catfish habitat situated in the northern part of Kyushu Island (Ariake Area) and has a unique civil engineering heritage, as represented by the so-called 'detour canal'. The canals were created owing to competition by two Domains to divert additional water resources into their own territory for rice cultivation during the Edo Period (1603-1867). To fill the research gap on the Ariake catfish and assess the ecological value of detour canals, in this study, we conducted a survey of local catfish populations and nine environmental parameters that can affect them. We found that the population volume of the Ariake catfish was significantly higher in canals than in ordinary branch rivers. Although the detour canals were not originally constructed for biodiversity conservation, they nonetheless unintentionally provide catfish habitat at present. As these canals represent a remarkable example of a contribution by a civil engineering heritage structure to biodiversity conservation, our study should be used as a potential justification for preserving the canals, as well as conserving the aquatic species that utilise them as vital habitat.

The complete mitochondrial genome of freshwater gammarid Gammarus nipponensis (Crustacea: Amphipoda: Gammaridae).

This study presents the complete mitochondrial genome sequence of Gammarus nipponensis, a freshwater crustacean found in the western regions of Honshu, Shikoku and Kyushu in Japan. The entire genome is 16,429 bp in length, encoding a standard set of 13 protein-coding genes, two ribosomal RNA genes and 22 transfer RNA genes, as well as the putative control regions. The mitochondrial genome of G. nipponensis is characterized by a high concentration of A and T nucleotides (67.1%). Notably, the mitogenome contains long TATTTTA repeats in the control region 2 at 686 bp long. This newly available genome information will be useful for studying the evolutionary relationships within the genus Gammarus and for understanding diversification among G. nipponensis populations.

What is the appropriate method of pathological specimen collection for cholangiocarcinoma detection in primary sclerosing cholangitis?

BACKGROUND: In primary sclerosing cholangitis (PSC), it is important to understand the cholangiographic findings suggestive of malignancy, but it is difficult to determine whether cholangiocarcinoma is present due to modifications caused by inflammation. This study aimed to clarify the appropriate method of pathological specimen collection during endoscopic retrograde cholangiopancreatography for surveillance of PSC. METHODS: A retrospective observational study was performed on 59 patients with PSC. The endpoints were diagnostic performance for benign or malignant on bile cytology and transpapillary bile duct biopsy, cholangiographic findings of biopsied bile ducts, diameters of the strictures and upstream bile ducts, and their differences. RESULTS: The sensitivity (77.8% vs. 14.3%, P = 0.04), specificity (97.8% vs. 83.0%, P = 0.04), and accuracy (94.5% vs. 74.1%, P = 0.007) were all significantly greater for bile duct biopsy than for bile cytology. All patients with cholangiocarcinoma with bile duct stricture presented with dominant stricture (DS). The diameter of the upstream bile ducts (7.1 (4.2-7.2) mm vs. 2.1 (1.2-4.1) mm, P < 0.001) and the diameter differences (6.6 (3.1-7) mm vs. 1.5 (0.2-3.6) mm, P < 0.001) were significantly greater in the cholangiocarcinoma group than in the noncholangiocarcinoma group with DS. For diameter differences, the optimal cutoff value for the diagnosis of benign or malignant was 5.1 mm (area under the curve = 0.972). CONCLUSION: Transpapillary bile duct biopsy should be performed via localized DS with upstream dilation for the detection of cholangiocarcinoma in patients with PSC. Especially when the diameter differences are greater than 5 mm, the development of cholangiocarcinoma should be strongly suspected.

Linking mesohabitat selection and ecological traits of a fish assemblage in a small tropical stream (Tinggi River, Pahang Basin) of the Malay Peninsula.

Mesohabitat selection in fluvial fishes was studied in a small tropical stream of the Malay Peninsula. A total of 681 individuals representing 24 species were sampled at 45 stations within heterogeneous stream (ca. 1 km in length), in which water depth, water velocity, substrate size, and riparian canopy cover were measured as environmental variables. A canonical correspondence analysis (CCA) yielded a diagram that shows a specific mesohabitat selection of the fish assemblage, in which the species were plotted widely on the CCA1-CCA2 biplot. Generalized linear model also revealed a significant pattern of the mesohabitat selection of several species. Water velocity and substrate size mainly separated on CCA1, indicating variation of pool (deep, slow-flow section) and riffle (shallow, fast-flow section) structures is a primary factor of mesohabitat selection in the fluvial fish assemblage. The mean body weight of species significantly correlated with CCA1; larger species tended to inhabit pools, while small ones occupied riffles. The riparian canopy cover separated on CCA2. The trophic level of species significantly correlated with CCA2; herbivorous species (low trophic level) selected open sites without riparian cover, whereas omnivorous/carnivorous (middle-high trophic level) species preferred highly covered sites. In conclusion, our results suggest that mesohabitat selection is closely related to the species feeding habit, which is consistent with the results of previous studies.

Preliminary assessment of genetic variation in the Japanese endemic freshwater crab, Geothelphusadehaani, based on mitochondrial DNA sequences.

Geothelphusadehaani, a freshwater crab species endemic to Japan, has the largest distribution range amongst the 19 known species in the country. Due to its low dispersal capability and restricted habitat to freshwater, it serves as an excellent model for understanding gene flow between geographically isolated populations. In this study, we analysed the genetic relationships of 26 G.dehaani populations collected from different locations in the Japanese archipelago using two mitochondrial DNA regions - cytochrome oxidase subunit I (COI) and cytochrome b (cytB). Our results from the analysis of molecular variance (AMOVA) revealed high genetic variation amongst populations and the phylogenetic analysis identified four geographical groups: Clade I - Honshu and Shikoku, Clade II - north-eastern Kyushu, Clade III - southern Kyushu and Clade IV - north-western Kyushu. Notably, Clade IV exhibited the highest genetic distance amongst the observed groupings. These findings highlight the need for further examination of G.dehaani in Kyushu, including morphological and behavioural traits, to better understand the observed diversity within the species in the region.

Fish diversity of a spring field in Hopong Town, Taunggyi District, Shan State, Myanmar (the Salween River Basin), with genetic comparisons to some "species endemic to Inle Lake".

Hopong, a small town in the Salween (Thanlwin) River Basin, Myanmar, is located 35 km northeast of Inle Lake, a famous ancient lake with numerous endemic fish species. We surveyed the fish fauna of a spring pond in Hopong in 2016, 2019 and 2020 and identified 25 species. Of these, seven, including Inlecyprisauropurpureus and Sawbwaresplendens, had been considered endemic to Inle Lake and at least three species were genetically unique. Eight were suspected or definite introduced species, including Oreochromisniloticus and Gambusiaaffinis. We were unable to identify a nemacheilid species of the genus Petruichthys, which would need a taxonomic examination. The Hopong area is being developed rapidly and, hence, it is crucial to conserve its native fish species and the freshwater ecosystems.

Database of summer fish fauna sampled in river estuaries in the southern part of the Boso Peninsula, Japan.

BACKGROUND: River estuaries provide various ecosystem services, such as nutrient circulation, climate change mitigation, habitats and coastal defence. Information on the various taxonomic groups is collected from large-scale estuaries; however, few studies have focused on river estuaries of small and medium-sized rivers. In particular, information on river estuaries in peninsulas and islands with complex marine environments is lacking. NEW INFORMATION: This paper provides basic information on summer fish fauna in the southern part of the Boso Peninsula, Japan. The Boso Peninsula is located at the northernmost point of where the warm current (Kuroshio) reaches and is considered to have highly endemic fish fauna. In total, 28 families, 51 species and 2,908 individuals were collected from the 27 river estuaries. The data are all accessible from the document "database_fish_estuary_boso (http://ipt.pensoft.net/manage/resource.do?r=database_fish_estuary_boso)". Further, Sicyopterus japonicus and Microphis brachyurus, which appear in estuaries that are influenced by the Kuroshio, were confirmed. However, these species were confirmed in few of the rivers studied, highlighting the importance of habitat conservation.

Photo images, 3D/CT data and mtDNA of the freshwater mussels (Bivalvia: Unionidae) in the Kyushu and Ryukyu Islands, Japan, with SEM/EDS analysis of the shell.

BACKGROUND: Freshwater mussels (Bivalvia: Unionidae), which are keystone species of freshwater ecosystems, are in global decline. In addition to ecological/genetic studies, morphological examinations are needed to help provide information for the development of additional freshwater mussel studies and eventually conservation efforts for freshwater ecosystems.The microscopic structure, which can be obtained by scanning electron microscopy (SEM) and elemental composition, which can be obtained with energy dispersive X-ray spectrometry (EDS), of mollusc shells are of interest to malacologists. However, information about freshwater mussels is still limited.Kyushu Island is the southernmost island of the four major islands of Japan. Kyushu Island is a hotspot of bitterling fishes in Japan, which simultaneously means that the island is a hotspot of freshwater mussels. The Ryukyu Islands stretch southwest from Kyushu Island to Taiwan; a freshwater mussel of unknown origin was reported from the Ryukyu Islands.Digital archiving for biology and ecology is a continuing challenge for open science. This data paper describes online published photo images, 3D/CT and mtDNA data and SEM/EDS analyses of the shell of freshwater mussels that inhabit the Kyushu and Ryukyu Islands, Japan. Our data will provide basic information regarding freshwater biology and be of public interest as open science. NEW INFORMATION: Photo images, 3D/CT data, mtDNA data, SEM images and EDS elemental analysis of freshwater mussels that inhabit the Kyushu and Ryukyu Islands (61 individuals, nine species/subspecies) were published online in a local database (http://ffish.asia/Unionidae3D), GBIF (http://ipt.pensoft.net/resource?r=unionidae3d) and DDBJ/EMBL/Genbank (LC431810-LC431840).

Photo images, 3D models and CT scanned data of loaches (Botiidae, Cobitidae and Nemacheilidae) of Japan.

BACKGROUND: Loach is one of the major cypriniform fishes in freshwater habitats of Japan; 35 taxa/clades have, until now, been recognised. Parallel to genetic studies, morphological examinations are needed for further development of loach study, eventually ichthyology and fish biology. Digital archiving, concerning taxonomy, ecology, ethology etc., is one of the progressive challenges for the open science of biology. This paper aimed to online publish photo images, 3D models and CT scanned data of all the known clades of loaches inhabiting Japan (103 individuals in total with several type specimens), contributing to ichthyology and public interest of biodiversity/biology. NEW INFORMATION: Photo images, 3D models and CT scanned data of all the known 35 taxa/clades of loaches inhabiting in Japan were online published at http://ffish.asia/loachesOfJapan and http://ffish.asia/loachesOfJapan3D.

Sympatric, simultaneous, and random mating between markless trout (iwame; Oncorhynchus iwame) and red-spotted masu salmon (amago; Oncorhynchus masou ishikawae).

The markless trout (iwame, Oncorhynchus iwame) has long been suspected not to be an independent species, but rather a markless mutant form of the red-spotted masu salmon (amago, O. masou ishikawae). Nevertheless, no field study has examined this issue. Here we report a field study on the reproductive ecology of iwame and amago coexisting in the upper stream of the Inabe River. We found that iwame and amago mate sympatrically, simultaneously, and randomly, and observed five cases of heterogeneous oviposition between the two. Our results suggest that no pre-mating reproductive isolation exists between iwame and amago. Because previous studies have shown the absence of post-mating isolation, we propose that iwame and amago are the same species. Iwame should be considered as a markless form of the red-spotted masu salmon, and O. iwame as a junior synonym of O. masou ishikawae.

A dataset of fishes in and around Inle Lake, an ancient lake of Myanmar, with DNA barcoding, photo images and CT/3D models.

BACKGROUND: Inle (Inlay) Lake, an ancient lake of Southeast Asia, is located at the eastern part of Myanmar, surrounded by the Shan Mountains. Detailed information on fish fauna in and around the lake has long been unknown, although its outstanding endemism was reported a century ago. NEW INFORMATION: Based on the fish specimens collected from markets, rivers, swamps, ponds and ditches around Inle Lake as well as from the lake itself from 2014 to 2016, we recorded a total of 948 occurrence data (2120 individuals), belonging to 10 orders, 19 families, 39 genera and 49 species. Amongst them, 13 species of 12 genera are endemic or nearly endemic to the lake system and 17 species of 16 genera are suggested as non-native. The data are all accessible from the document "A dataset of Inle Lake fish fauna and its distribution (http://ipt.pensoft.net/resource.do?r=inle_fish_2014-16)", as well as DNA barcoding data (mitochondrial COI) for all species being available from the DDBJ/EMBL/GenBank (Accession numbers: LC189568-LC190411). Live photographs of almost all the individuals and CT/3D model data of several specimens are also available at the graphical fish biodiversity database (http://ffish.asia/INLE2016; http://ffish.asia/INLE2016-3D). The information can benefit the clarification, public concern and conservation of the fish biodiversity in the region.

Impacts of Dams and Global Warming on Fish Biodiversity in the Indo-Burma Hotspot.

Both hydropower dams and global warming pose threats to freshwater fish diversity. While the extent of global warming may be reduced by a shift towards energy generation by large dams in order to reduce fossil-fuel use, such dams profoundly modify riverine habitats. Furthermore, the threats posed by dams and global warming will interact: for example, dams constrain range adjustments by fishes that might compensate for warming temperatures. Evaluation of their combined or synergistic effects is thus essential for adequate assessment of the consequences of planned water-resource developments. We made projections of the responses of 363 fish species within the Indo-Burma global biodiversity hotspot to the separate and joint impacts of dams and global warming. The hotspot encompasses the Lower Mekong Basin, which is the world's largest freshwater capture fishery. Projections for 81 dam-building scenarios revealed progressive impacts upon projected species richness, habitable area, and the proportion of threatened species as generating capacity increased. Projections from 126 global-warming scenarios included a rise in species richness, a reduction in habitable area, and an increase in the proportion of threatened species; however, there was substantial variation in the extent of these changes among warming projections. Projections from scenarios that combined the effects of dams and global warming were derived either by simply adding the two threats, or by combining them in a synergistic manner that took account of the likelihood that habitat shifts under global warming would be constrained by river fragmentation. Impacts on fish diversity under the synergistic projections were 10-20% higher than those attributable to additive scenarios, and were exacerbated as generating capacity increased-particularly if CO2 emissions remained high. The impacts of dams, especially those on river mainstreams, are likely to be greater, more predictable and more immediately pressing for fishes than the consequences of global warming. Limits upon dam construction should therefore be a priority action for conserving fish biodiversity in the Indo-Burma hotspot. This would minimize synergistic impacts attributable to dams plus global warming, and help ensure the continued provision of ecosystem services represented by the Lower Mekong fishery.

Waterfalls drive parallel evolution in a freshwater goby.

Waterfalls may affect fish distribution and genetic structure within drainage networks even to the extent of leading evolutionary events. Here, parallel evolution was studied by focusing on waterfall and the landlocked freshwater goby Rhinogobius sp. YB (YB), which evolved from amphidromous R. brunneus (BR). The fish fauna was surveyed at 30 sites in 11 rivers on Iriomote Island, Japan, the geography of which was characterized by terraces/tablelands with many waterfalls. We found that all YB individuals were distributed only above waterfalls (height 6.8-58.7 m), whereas BR, and other fishes, were mostly distributed below waterfalls. Mitochondrial DNA analysis showed that every YB local population above the waterfall was independently evolved from BR. In contrast, cluster analysis of nine morphological characters, such as fin color and body pattern, showed that the morphology of YB individuals held a similarity beyond the genetic divergence, suggesting parallel evolution has occurred relating to their morphology. Genetic distance between each YB local population and BR was significantly correlated with waterfall height (r(2) = 0.94), suggesting that the waterfalls have been heightened due to the constant geological erosion and that their height represents the isolation period of YB local populations from BR (ca. 11,000-88,000 years). Each local population of BR was once landlocked in upstream by waterfall formation, consequently evolving to YB in each site. Although the morphology of YB had a high degree of similarity among local populations, finer scale analysis showed that the morphology of YB was significantly correlated with the genetic distance from BR. Consequently, there could be simultaneous multiple phases of allopatric/parallel evolution of the goby due to variations in waterfall height on this small island.