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The Nagoya Daruma pond frog Pelophylax porosus brevipodus (formerly Rana porosa brevipoda) requires a wet environment year-round, but such habitats have generally been lost due to improved rice paddy drainage such that the frog populations have been decreasing. There have been attempts to create permanent pools in rice paddy areas to help the populations recover, but the basic life history patterns and population dynamics in both environments have not been well studied. We captured frogs in rice paddies and adjacent biotopes. Using capture–mark–recapture data with 816 marked individuals, we compared frog demographics and population structure using a Jolly–Seber POPAN model. Constructed biotopes had conditions favoring long-term persistence. For example, biotopes had larger frogs of both sexes than rice paddies. The ratio of juveniles to adults was lower in biotopes than rice paddies. By contrast, rice paddies were an important habitat for breeding and producing new frogs. The two habitats complemented each other to support the local frog population. Because P. p. brevipodus is now exclusively distributed in rice paddy areas, the creation of permanent pools is a feasible way to improve habitat quality, especially in modernized rice paddy areas with few permanent lentic habitats. [ABSTRACT FROM AUTHOR]

The aggregated transfer factor (Tag) is commonly used to represent the actual transfer of radiocesium from soil to wild edible plants, but the values have shown substantial variation since the Fukushima nuclear accident. To elucidate the factors causing this variation, we investigated the effects of spatial scale and vertical 137Cs distribution in the soil on the variation of Tag-137Cs values for one of the most severely contaminated wild edible plants, Eleutherococcus sciadophylloides Franch. et Sav. (Koshiabura). The variation in Tag-137Cs values was not reduced by direct measurement of 137Cs deposition in soil samples from the Koshiabura habitat, as a substitute for using spatially averaged airborne survey data at the administrative district scale. The 137Cs activity concentration in Koshiabura buds showed a significant positive correlation with the 137Cs inventories only in the organic horizon of soil from the Koshiabura habitat. The ratio of 137Cs inventories in the organic horizon to the total 137Cs deposition in soil exhibited substantial variation, especially in broad-leaved deciduous forests that Koshiabura primarily inhabits. This variation may be the cause of the wide range of Tag-137Cs values observed in Koshiabura buds when calculated from the total 137Cs deposition in soil. [ABSTRACT FROM AUTHOR]

The measurements of photoexcited transport in mesoscopic regimes reveal the states and properties of mesoscopic systems. In this study, we focused on direct measurements of electromagnetic energy transports in the mesoscopic regions and constructed a scanning tunnelling microscope-assisted multi-probe scanning near-field optical microscope spectroscopy system. After producing an emission energy map through a single-probe measurement, two-probe measurement enables us to observe and analyse carrier transport characteristics. It suggests that exciton generation and transport in the mesoscopic region of semiconductors with quantum structure changes, such as the bias of dopant, affect the excited carrier emission recombination process. The measured probability density of the carrier transported with quantum effects can be used for applications in natural intelligence research by combining it with the analysis using tournament structures. Our developed measurement and analysis methods are expected to clarify the details of carrier's behaviour in the mesoscopic region in various materials and lead to applications for novel optoelectronic devices. [ABSTRACT FROM AUTHOR]

Understanding the migratory community dynamics of river networks is important for maintaining lotic system integrity. River animals migrate to their preferred habitats in spatiotemporally heterogeneous river environments. Spring-fed habitats are uniquely characterized by stable temperature and flow regimes, which create suitable spawning habitats for the chum salmon Oncorhynchus keta. O. keta exhibits "run up" to its birthplace for spawning, especially during floods. Because the eggs deposited by this anadromous fish are nutritious and actively consumed by freshwater animals, the location and timing of O. keta spawning events affect the spatiotemporal accumulation of mobile consumers. In this study, we examined changes in temporal population density in spawning O. keta and a mobile consumer (juvenile O. masou masou) in a lowland, spring-fed tributary in northern Japan during a 48.5-mm autumn rainfall event. In both species, population density increased, and then decreased, after the rainfall event. In O. keta, these changes were closely associated with rainfall intensity, whereas in O. masou masou the peak was delayed until 3 days after the rainfall event. A comparison of the gut contents of O. masou masou sampled from a spring-fed tributary and an adjacent non-spring-fed tributary indicated greater consumption of O. keta eggs in the spring-fed tributary. These results suggested that preferential migration of O. keta into spring-fed tributaries for spawning induces subsequent accumulation of juvenile O. masou masou, in turn increasing O. keta egg consumption. These findings improve our understanding of community dynamics during floods in a heterogeneous river network environment. [ABSTRACT FROM AUTHOR]

The stable flow and temperature regimes of spring-fed streams are distinct from the dynamic regimes of other streams. We investigated differences in habitat and macroinvertebrate assemblages among three stream types (spring-fed tributary, non-spring-fed tributary, and mainstream) in a clastic lowland of northern Japan. Current velocity was the slowest in the spring-fed reach, where the percent of fine sediment deposition was also 3.8–11.4 times higher than in the other stream types. The standing stock of detritus was also greater in the spring-fed reach. These results suggest that the stable flow regime in the spring-fed stream leads to the accumulation of fine sediment and detritus on the streambed. Oligochaeta and chironomids, which are burrower-gatherers, were remarkably abundant in the spring-fed reach. Total macroinvertebrate abundance was 3.8–12.2 times greater in the spring-fed reach than in the other stream types. Sprawler-grazer ephemeropterans were the most abundant in the mainstream reaches, likely due to higher primary productivity. Allomyia sp, which depend on cool spring-fed habitats, was found only in the spring-fed reach. The indicator species analysis also indicated multiple taxa of detritivores and Allomyia sp. for the spring-fed tributary. The macroinvertebrate assemblage in the spring-fed reach was characterized by numerous burrowers, collector-gatherers, and crenobiont taxa, highlighting the uniqueness and its contribution to enhance beta diversity in river networks. [ABSTRACT FROM AUTHOR]

A Correction to this paper has been published: https://doi.org/10.1038/s41427-021-00298-9 [ABSTRACT FROM AUTHOR]

Logging and human-induced conversion of natural forests into agricultural areas are major drivers of biodiversity loss in the tropics. Anuran larvae can be highly diverse, can reach high biomass and can play important roles in tropical streams; yet, compared to the adult frog communities, relatively little is known about how larval communities respond to disturbance. Information on larvae is highly relevant for amphibian conservation because larvae represent direct evidence of breeding and thus provide a good indicator of species persistence in disturbed habitats. We studied tadpole assemblages in Ranomafana, southeastern part of Madagascar, in streams in a disturbed forest (previously logged forest), at "forest edge" (streams embedded in matrix nearby forest blocks), and compared these to communities in a primary forest. We sampled tadpoles at the microhabitat level ("pools" and "riffles") in 9 streams. We recorded 27 species with a maximum of 17 species/stream recorded at edge. The three habitats harbored different assemblages, but, as could be expected, more similarities existed among forest habitats than between forest and non-forest habitats. The most and the least diverse communities were recorded at edge and in the disturbed forest, respectively. Assemblages were dominated by one generalist species, and changes in communities were mostly driven by changes in forest specialists, which either decreased in disturbed forest or were replaced by edge specialists outside forest. Although species richness varied, relative abundances were maintained among habitats, suggesting potential compensatory mechanisms in tadpole biomass. Community structure changed at the microhabitat level: pool environments usually harbored relatively higher species richness and abundance than riffles. Our study highlights the relevance of edge habitats for maintaining amphibian diversity and the pronounced negative effects of past logging activities on tadpole communities. Given the diverse roles of tadpoles in streams, changes in community structure potentially affect critical stream ecosystem processes. The study has strong implications for designing buffer zones around protected areas. [ABSTRACT FROM AUTHOR]

The total radioactive Cs concentration in final-instar Stenopsyche marmorata larvae from the Mano River, Fukushima Prefecture, in 2013 was found to be >1000 Bq kg−1 in dry weight. The concentration of radioactive Cs in the river water itself was on the order of 0.01 Bq kg−1, while its concentration in drifting fine particulate organic matter (FPOM) was on the order of 10,000 Bq kg−1 in dry weight. When excretion experiments were performed in the summer and winter, significant decreases in the Cs concentrations in the whole body of S. marmorata were observed in both seasons. The biological half-life of Cs-137 was 5.3 and 8.8 h for the nonwintering generation and the wintering generation, respectively. Another elimination test using a stable Cs solution was performed, and the Cs concentration was observed to decrease rapidly to 7.5% of its original level in the digestive tract of S. marmorata after 72 h, but stable Cs remained in muscle and extra-alimentary tissue of S. marmorata. As the total radioactive Cs in the water was quite low, its concentration in S. marmorata from the Mano River reflects the fact that it feeds on FPOM. The radioactive Cs concentration in the FPOM significantly declined in 2015, but a corresponding decline was not observed for S. marmorata. We therefore infer that ultrafine particulate matter such as suspended vermiculite clay is strongly contaminated with radioactive Cs, and that this radioactive Cs passes continuously through the digestive tract of S. marmorata. [ABSTRACT FROM AUTHOR]

This study examined 137Cs detachment from needle litter of Japanese cedar (Cryptomeria japonica) through leaching and decomposition in a headwater stream located 45 km from Fukushima Daiichi Nuclear Power Plant. We placed litter bags in pools and riffles and removed them after 4, 15, 75, 150, and 240 days. The 137Cs activity concentration in litter collected after 4 and 15 days was 48–72 % of the initial 137Cs activity concentration in litter. The 137Cs activity concentration in litter after 240 days in the pools decreased by 26 %, while that in litter of riffles decreased by 9 % compared with the initial 137Cs activity concentration. The dry weight of litter became 71 and 86 % of initial weight after 75 days, and from 32 to 51 % after 150 days. The decay coefficient of litter (k = 0.0060) in the riffles was 1.6-fold higher than that in the pools (k = 0.0037). The greater decrease in litter weight with longer submergence time was possibly associated with a combination of leaching and decomposition, in particular in litter that was submerged for 100 days in the water column. The difference in the rate of decomposition and 137Cs detachment from litter between the riffles and pools was due to the substrate and flow conditions at the litter bag sites. Examining the different patterns of 137Cs detachment from litter among channel morphologies is necessary for comprehending the mechanisms of 137Cs accumulation in aquatic biota. The findings of this study suggest that elucidating leaching and decomposition processes in litter of stream channels is important for understanding 137Cs dynamics in forested headwater ecosystems. [ABSTRACT FROM AUTHOR]

We investigated the diets of stream detritivores in a coniferous plantation and a deciduous-coniferous mixed forest using stable isotope (δC and δN) mixing models. In summer, collector-gatherers ( Ephemera japonica, McLachlan, and Paralichas sp.) and a shredder ( Lepidostoma crassicorne, Ulmer) utilized coniferous needle litter but not broad-leaved deciduous litter as their food resource because coniferous litter was persistent and remained on the streambed in both the forests even in summer. In early spring, L. crassicorne in the mixed forest utilized both coniferous needle litter and broad-leaved deciduous litter because both were abundant and available. However, coniferous needle litter was the only dominant food source available for the shredder species in the plantation where deciduous trees were less abundant. E. japonica and a collector-filterer ( Hydropsyche sp.) in the forest possibly utilized fine materials derived from coniferous needle litter but not those derived from broad-leaved deciduous litter as their food resource. Although previous studies have indicated that coniferous needle litter is less nutritious than broad-leaved deciduous litter, persistence of the coniferous needle litter provides a stable basal food resource for shredders, collector-gatherers, and collector-filterers in forested streams that receive litter inputs from neighboring conifers. [ABSTRACT FROM AUTHOR]

Advances in fabrication of mesoscopic membrane sensors with unique structures and morphologies inside anodic alumina membrane (AAM) nanochannels have led to the development of various methods for detecting, visualizing, adsorbing, filtering, and recovering ultra-trace concentrations of toxic metal ions, such as Hg and Pb, in water and blood. These often 'one-pot' screening methods offer advantages over conventional methods in that they do not require sophisticated instruments or laborious sample preparation. In the present study, we fabricated two mesoscopic membrane sensors for naked-eye detection, recognition, filtration, and recovery of Hg and Pb in biological and environmental samples. These sensors were characterized by the dense immobilization of organic colorants on the mesopore surfaces of silica nanotubes that were constructed using the nanochannels of an AAM as a scaffold. We confirmed that the nanotubes were oriented along the long axis of the AAM nanochannels, open at both ends, and completely and uniformly filled with organic colorants; also, the dense immobilization of the organic colorants did not affect the speed of ion-to-ligand binding events. We used simple, desk-top, flow-through assays to assess the suitability of the developed membrane sensors for detection, removal, and filtration of Hg and Pb with respect to recyclability and continuous monitoring. Removal of the target ions from biological fluids was assessed by means of flow cytometric analysis. Our results demonstrate the potential of our membrane sensors to be used for preventing the health risks associated with exposure to toxic metal ions in the environment and blood. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

In this contribution, high photocatalytic activity under visible-light irradiation realized by means of the fine control of the nitrogen content in doped titania photocatalysts is reported. The photocatalyst samples were prepared from a layered titania/isostearate nanocomposite as precursor, and the fine control of nitrogen content was achieved by the adjustment of the amount of hybridized isostearate in the nanocomposite, preserving the crystallinity and specific surface area of the final samples. Photocatalytic activity under the UV-light irradiation (290 and 350 nm) decreases with nitrogen content. Under visible-light irradiation (470 nm), a maximum value of photocatalytic activity was observed at [N]/[Ti] = 0.0145, whereas the absorbance in the visible-light region increases with nitrogen content. Fine control of the doped-nitrogen content provides a possible route to achieving high visible-light photocatalytic activity where the maximum value of the apparent quantum yield under 470 nm light irradiation exceeds 2%. [ABSTRACT FROM AUTHOR]

The article discusses the high-contrast imaging of nano-channels using reflection near-field scanning optical microscope (NSOM) enhanced by optical interference. The researchers of the study have demonstrated a contrast enhancement in a near-field scanning optical microscope by optical interference with an aperture probe in reflection mode operation. The reflection NSOM was a promising instrument for high-resolution optical detection and estimation of low-contrast nanostructures.