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Heliozoans are ambush protists that inhabit most limnetic systems. However, ecological information about planktonic heliozoans is still limited. In this study, we investigated seasonal changes in planktonic heliozoan abundance in the deep northern and shallow southern basins of Lake Biwa at pelagic stations between August 2020 and December 2021. We compared planktonic heliozoan abundance levels between the two basins and examined the relationship between heliozoan abundance and environmental variables. In both basins, high levels of planktonic heliozoan abundance were detected in autumn, winter and spring. In the south basin, there was a significant positive correlation between planktonic heliozoan abundance and chlorophyll a concentration as well as the abundance of the diatoms Aulacoseira granulata and Aulacoseira ambigua. These results suggest that planktonic heliozoans directly or indirectly consume diatoms and that heliozoan abundance is subjected to bottom-up control. Furthermore, planktonic heliozoan abundance in the south basin was higher than that in the north basin, possibly due to the presence of waterweeds, which can serve as habitat for heliozoans, and the redistribution of planktonic heliozoans through resuspension from lake bottom sediments. [ABSTRACT FROM AUTHOR]

In this paper we design efficient algorithms for enumerating (1) the rooted trees with exactly n vertices, (2) the maximal planar graphs with exactly n vertices and (3) the linear extensions of a given poset. Those algorithms are based on tree structures of objects, called the family trees. The first algorithm enumerates each ordered tree with exactly n vertices in O (1) time for each after O (n) time preprocessing. The second algorithm enumerates each maximal planar graph with exactly n vertices in O (n 3) time for each on average. The third algorithm enumerates each linear extension of a given poset in O (1) time for each after O (n 2) time preprocessing, where n is the number of the element in the set of the poset. [ABSTRACT FROM AUTHOR]

As interest in natural capital grows and society increasingly recognizes the value of biodiversity, we must discuss how ecosystem observations to detect changes in biodiversity can be sustained through collaboration across regions and sectors. However, there are many barriers to establishing and sustaining large-scale, fine-resolution ecosystem observations. First, comprehensive monitoring data on both biodiversity and possible anthropogenic factors are lacking. Second, some in situ ecosystem observations cannot be systematically established and maintained across locations. Third, equitable solutions across sectors and countries are needed to build a global network. Here, by examining individual cases and emerging frameworks, mainly from (but not limited to) Japan, we illustrate how ecological science relies on long-term data and how neglecting basic monitoring of our home planet further reduces our chances of overcoming the environmental crisis. We also discuss emerging techniques and opportunities, such as environmental DNA and citizen science as well as using the existing and forgotten sites of monitoring, that can help overcome some of the difficulties in establishing and sustaining ecosystem observations at a large scale with fine resolution. Overall, this paper presents a call to action for joint monitoring of biodiversity and anthropogenic factors, the systematic establishment and maintenance of in situ observations, and equitable solutions across sectors and countries to build a global network, beyond cultures, languages, and economic status. We hope that our proposed framework and the examples from Japan can serve as a starting point for further discussions and collaborations among stakeholders across multiple sectors of society. It is time to take the next step in detecting changes in socio-ecological systems, and if monitoring and observation can be made more equitable and feasible, they will play an even more important role in ensuring global sustainability for future generations. This article is part of the theme issue 'Detecting and attributing the causes of biodiversity change: needs, gaps and solutions'. [ABSTRACT FROM AUTHOR]

Given a set C of points and a horizontal line L in the plane and a set F of points on L , we want to find a set of disks such that (1) each disk has the center at a point in F (but with arbitrary radius), (2) each point in C is covered by at least one disk, and (3) the cost of the set of disks is minimized. Here the (transmission) cost of a disk with radius r is r α , where α is a positive constant depending on the power consumption model, and the cost of a set of disk is the sum of the cost of disks in the set. In this paper we first give an algorithm based on dynamic programming method to solve the problem in L 1 metric. A naive dynamic programming algorithm runs in O (| C | 3 | F | 2) time. We design an algorithm which runs in O (| C | | F | 2 + | C | log | C |) time. Then we design another algorithm to solve the problem in L 1 metric based on a reduction to a shortest path problem in a directed acyclic graph. The running time of the algorithm is O (| C | 2 + | C | | F |). [ABSTRACT FROM AUTHOR]

Benthic microalgae (BMA) biomass and community structure in freshwater lotic systems are often limited by inorganic nutrient availability. We examined nutrient limitation of benthic algae biomass and community structure using nutrient diffusing substrates in four rivers along a land use gradient in the Lake Biwa basin, Japan. Ambient in-stream nutrient concentrations were correlated to catchment land use, with the highest nitrogen and phosphorus concentrations being found in rivers draining more forested catchments. Nutrient limitation of primary producer biomass and nutrient-driven changes in community structure were evident in all four rivers, regardless of in-stream nutrient concentrations and surrounding land use. BMA biomass (measured as chlorophyll log-response ratio) exhibited the greatest nutrient limitation in rivers with higher in-stream nutrient concentrations. The relationship to catchment land use was less clear, with the highest nutrient limitation being observed in the catchment with moderate amounts of agricultural and forested land use. Nutrient additions resulted in a shift from dominance by Bacillariophyceae (diatoms) to a mixed Bacillariophyceae-Chlorophyceae (chlorophyte) community in all rivers and this shift was most pronounced in the forested catchments. Changes within the diatom community with nutrient additions were also observed, although the shifts in diatom community within a river in response to nutrient additions were much smaller than the differences in diatom community composition among rivers. Diatom taxa classified as highly motile increased with nutrient additions in all rivers. Our results suggest that primary producer community in rivers may be sensitive to nutrient inputs even in areas with elevated nutrient concentrations and catchments dominated by agricultural land use. There is likely widespread nutrient limitation in rivers of Japan, across both in-stream nutrient and land use gradients and any increases in nutrient loading will likely stimulate benthic algal growth. Our findings highlight the importance of looking at both biomass and species composition to assess ecosystem-level impacts of elevated nutrient levels. [ABSTRACT FROM AUTHOR]

Few studies have explored changes in the sizes of diatom cells which can be due to sexual reproduction in lakes, as observations of natural populations have been limited. We measured seasonal changes in the cell sizes and densities of the diatom Fragilaria crotonensis Kitton in Lake Biwa from February 2012 to January 2017 and examined possible causal variables on sexual reproduction and cell density of F. crotonensis. Cell size tended to decrease with increase in cell density in spring and summer to autumn, though the pattern was not so clear in 2012 and 2013. The highest cell density (1.6 × 104 cells L-1) was recorded in May 2014, with the average cell size being 73.5 μm; the lowest density (7.1 cells L-1) was recorded in December 2016 (average cell size 86.5 μm), reflecting biannual cell size reduction and restoration which can be due to sexual reproduction. We used time series analysis to delineate the seasonality of cell size changes of the target diatom and Convergent Cross-Mapping (CCM) to explore the effects of possible causal variables on sexual reproduction and cell density of F. crotonensis and to evaluate the influences of environmental factors. We found that water temperature may influence the cell density (vegetative reproduction) of F. crotonensis, though we could not identify any possible causal variables for the algal sexual reproduction. In addition, time series decomposition analysis, together with the seasonal changes in cell size mentioned above, proved that the target diatom followed reduction in cell size twice a year. [ABSTRACT FROM AUTHOR]

Given a set P of n locations on which facilities can be placed and an integer k, we want to place k facilities on some locations so that a designated objective function is maximized. The problem is called the k-dispersion problem. For instance it is desirable to locate fire departments far away each other. In this paper we give a simple O ((2 k 2) k n) time algorithm to solve the max–min version of the k-dispersion problem if P is a set of points on a line. If k is a constant then this is an O(n) time algorithm. This is the first O(n) time algorithm to solve the max–min k-dispersion problem for the set of "unsorted" points on a line. If P is a set of sorted points on a line, and the input is given as an array in which the coordinates of the points are stored in the sorted order, then by slightly modifying the algorithm above one can solve the dispersion problem in O (log n) time. This is the first sublinear time algorithm to solve the max–min k-dispersion problem for the set of sorted points on a line. [ABSTRACT FROM AUTHOR]

Let C be a set of n customers and F be a set of m facilities. An r -gather clustering of C is a partition of the customers in clusters such that each cluster contains at least r customers. The r -gather clustering problem asks to find an r -gather clustering which minimizes the maximum distance between a pair of customers in a cluster. An r -gathering of C to F is an assignment of each customer c ∈ C to a facility f ∈ F such that each facility has zero or at least r customers. The r -gathering problem asks to find an r -gathering that minimizes the maximum distance between a customer and his/her facility. In this work, we consider the r -gather clustering and r -gathering problems when the customers and the facilities are lying on a "star". We show that the r -gather clustering problem and the r -gathering problem with customers and facilities on a star with d rays can be solved in O (n + d d r d d r log d) and O (n + m + (d + log m) d 4 r 2 + d d r d 2 d d r log d) time, respectively. Furthermore, we prove the hardness of a variant of the r -gathering problem, called the min-max-sum r -gathering problem, even when the customers and the facilities are on a star. We also study the r -gathering problem when the customers and the facilities are on a line, and each customer location is uncertain. We show that the r -gathering problem can be solved in O (n k + m n log n + (m + n log k n + n r n r ) log m n) and O (m n log n + (n log n + m) log m n) time when the customers and the facilities are on a line, and the customer locations are given by piecewise uniform functions of at most k + 1 pieces and "well-separated" uniform distribution functions, respectively. [ABSTRACT FROM AUTHOR]

The objective of this study is to clarify the biogeochemical characteristics of the Hövsgöl–Ustilimsk water system in Mongolia and Russia. For this purpose, we measured dissolved major elements, minor elements, and nutrients in surface water throughout the system. Calcium ions and HCO3 + 2CO3 were the dominant cations and anions in Lake Hövsgöl, respectively. As the water flows down from Lake Hövsgöl to the Egiin Gol and Selenga Rivers in Mongolia, the water quality derived from carbonate rock was found to be influenced by river confluences. In the Selenga River in Russia, major elements were diluted with low-salinity waters from the tributaries. At the boundaries between the Angara River and Bratsk or Ustilimsk Reservoirs, the behaviors of nutrients were affected by the transition of the water area from a riverine zone to a lacustrine zone. Although the composition of cations and anions changes gradually as river water flows further downstream, the water type remains to be Ca–HCO3 throughout the system. Thus, it can be concluded that the fundamental water quality of this system was determined in northern Mongolia, the source area of this water system, and that the environmental factors such as the climate, geology and, geography in its basin from Hövsgöl to Ustilimsk regulated the dissolved chemical components. [ABSTRACT FROM AUTHOR]

Algal biomass has been utilized as a potential feedstock for bioenergy and a variety of other bioprocesses. At the core of this topic, there is a general demand for rapid, cost-effective, and accurate methods for algal biomass quantification. Here, we present a simple, low-cost, and non-destructive method to estimate algal biomass concentrations by image analysis based on the hue, saturation, intensity (HSI) color space. The applicability of the HSI-based quantitative method was verified using experimental data from both the present study and the literature. In addition, the HSI-based quantitative method showed better goodness of fit and a significantly higher detection range than related methods used in the literature. The results indicate that the HSI-based quantitative method can be used as an effective method for algal biomass monitoring and quantification. [ABSTRACT FROM AUTHOR]

Twenty water bodies in China were sampled, and 186 strains of different Microcystis species were isolated, from which eight morphospecies were identified and 43 stains containing the mcyB gene were detected. Phylogenetic analysis based on the mcyB gene indicated that the microcystin (MC)-producing Microcystis in China could be divided into two groups (I and II) and showed significant differences between the two groups. The maximum sequence similarity was 69.1%. Microcystins (MCs) were measured by high-performance liquid chromatography (HPLC) analysis, and no microcystin-RR (MC-RR) was detected in some strains belonging to Group II. Compared to other regions of the world, the proportion of Chinese MC-producing Microcystis was different, and the regional differences were more obvious. A whole-cell Polymerase Chain Reactio (PCR) assay was conducted to analyze the proportion of the mcyB gene in the laboratory cultured and field cultured Microcystis. The proportion of four morphospecies (M. vividis, M. ichthyoblabe, M. novacekii, and M. aeruginosa) that contained the mcyB gene exceeded 50% in the field cultured samples. Compared with former studies, M. aeruginosa was the most likely morphotype that can produce MCs in the world. This study provided new insight of Microcystis hazard assessment and field monitoring. [ABSTRACT FROM AUTHOR]

In Lake Biwa, picocyanobacteria blooms usually occur during the summer–autumn thermal stratification period. Intriguingly, a novel bloom was detected in winter 2015–2016, in which picocyanobacterial cell density increased by one order of magnitude despite lower water temperature, suggesting the possibility that "cold-water-preference" species dominate in the picocyanobacterial community. In the present study, we investigated the phylogenetic diversity of picocyanobacteria in Lake Biwa by analyzing the 16S rRNA gene. We found that the picocyanobacterial community were highly diverse in Lake Biwa, with eight Synechococcus-related operational taxonomic units (OTUs) detected in different seasons. These OTUs fell into distinct phylogenetic groups, and the majority were closely related to clusters reported previously. Notably, OTU04, detected during the winter bloom, was highly affiliated with sequences found in a variety of lakes, such as Tibetan lakes and Lake Superior, where the water bodies generally have a low trophic state and temperature, and different concentrations of total dissolved solids. Thus, we inferred that the group containing OTU04 may be a psychrotolerant lineage that is widely distributed in oligotrophic water systems with low–intermediate salinity. [ABSTRACT FROM AUTHOR]

The Asia‐Pacific Biodiversity Observation Network (APBON) was launched in 2009, in response to the establishment of the Biodiversity Observation Network under the Group on Earth Observations in 2008. APBON's mission is to increase exchange of knowledge and know‐how between institutions and researchers concerning biodiversity science research in the Asia‐Pacific (AP) region and thereby contribute to evidence‐based decision‐making and policy‐making. Here we summarize APBON activities and achievements in its first 10 years. We review how APBON has developed networks, facilitated communication for sharing knowledge, and built capacity of researchers and stakeholders through workshops and publications as well as discuss the network plan. Key findings by APBON members include descriptions of species new to science, mapping tropical forest cover change, evaluating impacts of hydropower dams and climate change on fish species diversity in the Mekong, and mapping "Ecologically and Biologically Significant Areas" in the oceans. APBON has also contributed to data collection, sharing, analysis, and synthesis for regional and global biodiversity assessment. A highlight was contributing to the "Intergovernmental Science‐Policy Platform on Biodiversity and Ecosystem Services" regional report. New strategic plans target the development of national‐level BONs and interdisciplinary research to address the data and knowledge gaps and increase data accessibility for users and for meeting societal demands. Strengthening networks in AP region and capacity building through APBON meetings will continue. By promoting monitoring and scientific research and facilitating the dialogue with scientists and policymakers, APBON will contribute to the implementation of conservation and sustainable use of biodiversity in the entire AP region. [ABSTRACT FROM AUTHOR]

Background: Freshwater ecosystems are inhabited by members of cosmopolitan bacterioplankton lineages despite the disconnected nature of these habitats. The lineages are delineated based on > 97% 16S rRNA gene sequence similarity, but their intra-lineage microdiversity and phylogeography, which are key to understanding the eco-evolutional processes behind their ubiquity, remain unresolved. Here, we applied long-read amplicon sequencing targeting nearly full-length 16S rRNA genes and the adjacent ribosomal internal transcribed spacer sequences to reveal the intra-lineage diversities of pelagic bacterioplankton assemblages in 11 deep freshwater lakes in Japan and Europe. Results: Our single nucleotide-resolved analysis, which was validated using shotgun metagenomic sequencing, uncovered 7–101 amplicon sequence variants for each of the 11 predominant bacterial lineages and demonstrated sympatric, allopatric, and temporal microdiversities that could not be resolved through conventional approaches. Clusters of samples with similar intra-lineage population compositions were identified, which consistently supported genetic isolation between Japan and Europe. At a regional scale (up to hundreds of kilometers), dispersal between lakes was unlikely to be a limiting factor, and environmental factors or genetic drift were potential determinants of population composition. The extent of microdiversification varied among lineages, suggesting that highly diversified lineages (e.g., Iluma-A2 and acI-A1) achieve their ubiquity by containing a consortium of genotypes specific to each habitat, while less diversified lineages (e.g., CL500-11) may be ubiquitous due to a small number of widespread genotypes. The lowest extent of intra-lineage diversification was observed among the dominant hypolimnion-specific lineage (CL500-11), suggesting that their dispersal among lakes is not limited despite the hypolimnion being a more isolated habitat than the epilimnion. Conclusions: Our novel approach complemented the limited resolution of short-read amplicon sequencing and limited sensitivity of the metagenome assembly-based approach, and highlighted the complex ecological processes underlying the ubiquity of freshwater bacterioplankton lineages. To fully exploit the performance of the method, its relatively low read throughput is the major bottleneck to be overcome in the future. CdoWEXw9NgzJzSXXN2MHFr Video abstract. [ABSTRACT FROM AUTHOR]

Summary: Diplonemids are considered marine protists and have been reported among the most abundant and diverse eukaryotes in the world oceans. Recently we detected the presence of freshwater diplonemids in Japanese deep freshwater lakes. However, their distribution and abundances in freshwater ecosystems remain unknown. We assessed abundance and diversity of diplonemids from several geographically distant deep freshwater lakes of the world by amplicon‐sequencing, shotgun metagenomics and catalysed reporter deposition‐fluorescent in situ hybridization (CARD‐FISH). We found diplonemids in all the studied lakes, albeit with low abundances and diversity. We assembled long 18S rRNA sequences from freshwater diplonemids and showed that they form a new lineage distinct from the diverse marine clades. Freshwater diplonemids are a sister‐group to a marine clade, which are mainly isolates from coastal and bay areas, suggesting a recent habitat transition from marine to freshwater habitats. Images of CARD‐FISH targeted freshwater diplonemids suggest they feed on bacteria. Our analyses of 18S rRNA sequences retrieved from single‐cell genomes of marine diplonemids show they encode multiple rRNA copies that may be very divergent from each other, suggesting that marine diplonemid abundance and diversity both have been overestimated. These results have wider implications on assessing eukaryotic abundances in natural habitats by using amplicon‐sequencing alone. [ABSTRACT FROM AUTHOR]

Alien species have invaded worldwide and altered native biodiversity and ecosystem functions. In Lake Biwa, Japan, Micrasterias hardyi—considered an endemic species in Australia—has become one of the major dominant species since 2016. To evaluate long-term and seasonal variations in M. hardyi, we analyzed 20 years of plankton samples from the northern basin of Lake Biwa. The presence of this species was first confirmed in February 2015, and increased for long periods from November 2015 (4.2 cells cm−2) to December 2016 (2.3 × 105 cells cm−2) and from September 2017 (2.0 × 102 cells cm−2) to January 2019 (5.7 × 104 cells cm−2). Particles similar to chytrid zoosporangia were observed and attached to M. hardyi cells. However, the infection rate was low (up to 22.5%), and the infection did not seem to be a major lethal factor. We estimated that M. hardyi was introduced in the early 2000s by simple linear regression of abundance. This result indicates the existence of long time lag from introduction to detection. Moreover, as the propagule pressure to nearby water systems has been high, it is highly probable that M. hardyi has spread to other lakes and ponds via Lake Biwa. [ABSTRACT FROM AUTHOR]

Summary: Metagenomics has dramatically expanded the known virosphere, but freshwater viral diversity and their ecological interaction with hosts remain poorly understood. Here, we conducted a metagenomic exploration of planktonic dsDNA prokaryotic viruses by sequencing both virion (<0.22 μm) and cellular (0.22–5.0 μm) fractions collected spatiotemporally from a deep freshwater lake (Lake Biwa, Japan). This simultaneously reconstructed 183 complete (i.e., circular) viral genomes and 57 bacterioplankton metagenome‐assembled genomes. Analysis of metagenomic read coverage revealed vertical partitioning of the viral community analogous to the vertically stratified bacterioplankton community. The hypolimnetic community was generally stable during stratification, but occasionally shifted abruptly, presumably due to lysogenic induction. Genes involved in assimilatory sulfate reduction were encoded in 20 (10.9%) viral genomes, including those of dominant viruses, and may aid viral propagation in sulfur‐limited freshwater systems. Hosts were predicted for 40 (21.9%) viral genomes, encompassing 10 phyla (or classes of Proteobacteria) including ubiquitous freshwater bacterioplankton lineages (e.g., Ca. Fonsibacter and Ca. Nitrosoarchaeum). Comparison with viral genomes derived from published metagenomes revealed viral phylogeographic connectivity in geographically isolated habitats. Notably, analogous to their hosts, actinobacterial viruses were among the most diverse, ubiquitous and abundant viral groups in freshwater systems, with potential high lytic activity in surface waters. [ABSTRACT FROM AUTHOR]

Kinetoplastid flagellates are generally abundant in the deep sea and recently they were even found to be dominant in the hypolimnion of a deep freshwater lake. Therefore, to understand the distribution of kinetoplastids in deep freshwater lakes, we have collected vertical samples from five lakes in Japan. The abundance of kinetoplastids was enumerated by Catalyzed Reporter Deposition-Fluorescence in situ Hybridization, and the diversity was determined by 18S amplicon sequencing using universal eukaryote and kinetoplastid-specific primers. Kinetoplastids were abundant in the deep waters of all the lakes, contributing up to 53.6% of total nanoeukaryotes. Despite this significant contribution, kinetoplastids remain undetected by amplicon sequencing using universal primers that are widely used in eukaryotic diversity studies. However, they were detected with specific primers, and the communities were characterized by both ubiquitous and lake-specific unique OTUs. Oligotyping of a ubiquitous and dominant OTU revealed the presence of lake-specific sequence types (oligotypes). Remarkably, we also detected diplonemids (a sister group of kinetoplastids and considered to be specific in the marine habitat) using kinetoplastid-specific primers, showing their presence in freshwaters. Underestimation of kinetoplastids and diplonemids using universal primers indicates that euglenozoan flagellates are overlooked in diversity studies worldwide. The present study highlighted the importance of kinetoplastids in the hypolimnion of deep lakes, thereby indicating their role in material cycling in deep waters. [ABSTRACT FROM AUTHOR]

We developed 10 novel simple sequence repeat markers from expressed sequence tags for the honey locust seed beetle, Megabruchidius dorsalis Fåhraeus 1839 (Coleoptera: Bruchidae, using de novo transcriptome analysis based on next-generation sequencing. In a M. dorsalis Harataima (Kanagawa-pref.) population, the number of alleles per locus ranged from 2 to 6, with an average of 4.0. Observed and expected heterozygosities ranged from 0.13 to 0.72 and 0.17 to 0.72, respectively. We initially developed 11 novel markers, but one was eliminated because it showed significant linkage disequilibrium with another locus after Bonferroni correction. To check the applicability of the remaining 10 markers, we used them to analyze two additional geographic populations (Yashima, Akita-pref., and Kameoka, Kyoto-pref.). Mean numbers of alleles per locus in the Yashima and Kameoka populations were 2.6 and 2.9, respectively, with corresponding mean observed heterozygosities of 0.36 and 0.52. These results based on the two additional populations confirm that our developed markers worked efficiently. The simple sequence repeat markers developed from expressed sequence tags in the present study should, therefore, be useful for explicating the population genetic structure of M. dorsalis and for future paternal analyses. [ABSTRACT FROM AUTHOR]

CL500-11 (phylum Chloroflexi) is one of the most ubiquitous and abundant bacterioplankton lineages in deep freshwater lakes inhabiting the oxygenated hypolimnion. While metagenomics predicted possible eco-physiological characteristics of this uncultured lineage, no consensus on their ecology has so far been reached, partly because their niche is not clearly understood due to a limited number of quantitative field observations. This study investigated the abundance and distribution of CL500-11 in seven deep perialpine lakes using catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH). Samples were taken vertically (5–12 depths in each lake) and temporally (in two lakes) at the deepest point of the lakes located in Switzerland, Italy, and Austria with varying depth, trophic state, mixing regime, and water retention time. The results showed a dominance of CL500-11 in all the lakes; their proportion to total prokaryotes ranged from 4.3% (Mondsee) to 24.3% (Lake Garda) and their abundance ranged from 0.65 × 105 (Mondsee) to 1.77 × 105 (Lake Garda) cells mL-1. By summarizing available information on CL500-11 occurrence to date, we demonstrated their broad habitat spectrum, ranging from ultra-oligotrophic to meso-eutrophic lakes, while low abundances or complete absence was observed in lakes with shallow depth, low pH, and/or short water retention time (<1 year). Together with available metagenomic and geochemical evidences from literatures, here we reviewed potential substrates supporting growth of CL500-11. Overall, the present study further endorsed ubiquity and quantitative significance of CL500-11 in deep freshwater systems and narrowed the focus on their physiological characteristics and ecological importance. [ABSTRACT FROM AUTHOR]

In aquatic ecosystems, tributaries play an important role in maintaining the populations and diversity of aquatic organisms throughout the drainage basin, but because of their small catchments, these ecosystems are often more susceptible to the effect of land-use changes and flow-regime alterations. Here, we examined anthropogenic effects on benthic macroinvertebrate diversity in the tributary lagoons, collectively called “Naiko,” surrounding Lake Biwa. We sampled macroinvertebrates and determined the environmental characteristics of 20 tributary lagoons. We identified the environmental factors determining the diversity of macroinvertebrates and found that turbidity significantly diminished species diversity. We assessed the anthropogenic stressors that contributed to the increase in turbidity and found that human population density and the proportion of paddy fields in the watershed area were positively correlated with turbidity, most likely caused by erosion of terrigenous organic matter from the paddy fields and urban areas. In addition, the presence of sluice gates and the lengths of channels connecting to the main lake were positively correlated with turbidity, suggesting that these factors lowered hydrologic connectivity and retained organic matter. We concluded that changes to the landscape and decreased hydrologic connectivity caused by human activity increased turbidity, which in turn decreased macroinvertebrate diversity. The identification of these factors in tributaries is vital for developing a strategy for habitat restoration to conserve the entire ecosystem of the Lake Biwa basin. [ABSTRACT FROM AUTHOR]

Intramuscular adipose tissue ( IMAT) formation is a hallmark of marbling in cattle. IMAT is considered to originate from skeletal muscle progenitor cells with adipogenic potential. However, the mechanism involved in IMAT formation from these progenitor cells in vivo remains unclear. In the present study, among the growth factors tested, which were known to be expressed in skeletal muscle, we found only basic fibroblast growth factor ( bFGF) has a pro-adipogenic effect on skeletal muscle derived adipogenic progenitor clone, 2G11 cells. Pre-exposure of 2G11 cells to bFGF did not affect initial gene expressions of CCAAT/enhancer-binding protein ( C/ EBP)β and C/ EBPδ, while resulting in an enhancement of subsequent expressions of C/ EBPα and proliferator-activated receptor gamma ( PPARγ) during adipogenesis, indicating that bFGF is acting on the transcriptional regulation of C/ EBPα and PPARγ. In addition, the effect of bFGF is mediated via two types of FGF receptor ( FGFR) isoforms: FGFR1 and FGFR2 IIIc, and both receptors are prerequisite for bFGF to express its pro-adipogenic effect. These results suggest that bFGF plays an important role as a key trigger of IMAT formation in vivo. [ABSTRACT FROM AUTHOR]

Single-cell PCR and gene sequencing were conducted to evaluate species and genotypic compositions of Cryptomonas in the eutrophic Lake Hira, Japan. We determined the sequences of nuclear internal transcribed spacer 2 region from single Cryptomonas cells with a high success rate (83.3-97.9 %), excluding one case (56.3 %). A total of 325 sequences were obtained over eight sampling days from May 28, 2012, to October 3, 2012, and phylogenetic analysis indicated that all sequences were divided into six groups. Four groups were clustered together with known sequences of C. curvata, C. marssonii, C. pyrenoidifera or C. tetrapyrenoidosa, although the sequences of the other two groups did not show high similarity to known Cryptomonas species. Cryptomonas curvata dominated during the study period (45-98 %), and unidentified Cryptomonas species (group 2) became dominant at high water temperatures. The genotypic composition of C. curvata also varied temporarily, suggesting that the genotypic composition of Cryptomonas was susceptible to environmental changes. These results indicated that single-cell PCR can be used to analyze the species composition and ecology of Cryptomonas. [ABSTRACT FROM AUTHOR]