Species Differences Research Articles

Taxonomic difference in marine bloom-forming phytoplanktonic species affects the dynamics of both bloom-responding prokaryotes and prokaryotic viruses.

The production of dissolved organic matter during phytoplankton blooms and consumption by heterotrophic prokaryotes promote marine carbon biogeochemical cycling. Although prokaryotic viruses presumably affect this process, their dynamics during blooms are not fully understood. Here, we investigated the effects of taxonomic difference in bloom-forming phytoplankton on prokaryotes and their viruses. We analyzed the dynamics of coastal prokaryotic communities and viruses under the addition of dissolved intracellular fractions from taxonomically distinct phytoplankton, the diatom Chaetoceros sp. (CIF) and the raphidophycean alga Heterosigma akashiwo (HIF), using microcosm experiments. Ribosomal RNA gene amplicon and viral metagenomic analyses revealed that particular prokaryotes and prokaryotic viruses specifically increased in either CIF or HIF, indicating that taxonomic difference in bloom-forming phytoplankton promotes distinct dynamics of not only the prokaryotic community but also prokaryotic viruses. Furthermore, combining our microcosm experiments with publicly available environmental data mining, we identified both known and novel possible host-virus pairs. In particular, the growth of prokaryotes associating with phytoplanktonic organic matter, such as Bacteroidetes (Polaribacter and NS9 marine group), Vibrio spp., and Rhodobacteriales (Nereida and Planktomarina), was accompanied by an increase in viruses predicted to infect Bacteroidetes, Vibrio, and Rhodobacteriales, respectively. Collectively, our findings suggest that changes in bloom-forming species can be followed by an increase in a specific group of prokaryotes and their viruses and that elucidating these tripartite relationships among specific phytoplankton, prokaryotes, and prokaryotic viruses improves our understanding of coastal biogeochemical cycling in blooms.IMPORTANCEThe primary production during marine phytoplankton bloom and the consumption of the produced organic matter by heterotrophic prokaryotes significantly contribute to coastal biogeochemical cycles. While the activities of those heterotrophic prokaryotes are presumably affected by viral infection, the dynamics of their viruses during blooms are not fully understood. In this study, we experimentally demonstrated that intracellular fractions of taxonomically distinct bloom-forming phytoplankton species, the diatom Chaetoceros sp. and the raphidophycean alga Heterosigma akashiwo, promoted the growth of taxonomically different prokaryotes and prokaryotic viruses. Based on their dynamics and predicted hosts of those viruses, we succeeded in detecting already-known and novel possible host-virus pairs associating with either phytoplankton species. Altogether, we propose that the succession of bloom-forming phytoplankton would change the composition of the abundant prokaryotes, resulting in an increase in their viruses. These changes in viral composition, depending on bloom-forming species, would alter the dynamics and metabolism of prokaryotes, affecting biogeochemical cycling in blooms.

Analysis of 20 years of turtle exports from the US reveals mixed effects of CITES and a need for better monitoring

AbstractThe Convention on International Trade of Endangered Species (CITES) is the primary mechanism for controlling international wildlife trade and preventing overexploitation, but measuring its efficacy is difficult, which complicates management efforts. We examined the effects of CITES listings on the trade of freshwater turtles from the US and compared spatiotemporal trends and dynamics of trade across 16 genera using 20 years of export data, triangulated with mixed qualitative data. For each CITES‐listed genus, we analyzed the average changes, immediate changes, and changes in trends of export volumes and spatial diversity of trade. Boom‐and‐bust trends of exports for different taxa were driven by several factors, including CITES listings, but CITES had mixed effects on export volumes for both Appendix II and III species while the diversity of spatial trade networks consistently declined for CITES and non‐CITES listed genera. These results point to differences in demand and species' availability from captive breeders, farms, or wild harvest which are important to consider in future listing decisions. However, a lack of reliable data on the source of turtles limited our ability to understand these drivers as well as the efficacy of CITES listings in preventing overexploitation.

Abstract B013: In vitro stability and in vivo pharmacokinetic behavior of panobinostat in mouse models for the treatment of CNS tumors

Abstract Aberrant alterations of histone deacetylases (HDACs), an epigenetic regulator, are common in central nervous system (CNS) tumors and HDAC inhibitors have been found to have therapeutic potential for the treatment of CNS tumors. Panobinostat is a pan-HDAC inhibitor that has shown potency against multiple CNS tumors. Panobinostat has a hydroxamic acid side chain, a structural element reported to be susceptible to esterase activity in multiple compounds. Therefore, in vitro stability of panobinostat may allow the prediction of in vivo pharmacokinetic behavior. The objective of this study is to discover the mechanisms influencing the in vitro stability of panobinostat in multiple matrices and evaluate the in vivo pharmacokinetics in mouse models. In vitro stability studies in mouse plasma at different temperatures showed that panobinostat was unstable in mouse plasma and the decomposition rate was temperature-dependent. Meanwhile, panobinostat was stable in phosphate-buffered saline (PBS, pH7.4) tested at the same incubation conditions. Therefore, we propose that enzymatic activity is a contributor of the in vitro instability of panobinostat. Panobinonstat stability was also measured in plasma from different species. Data show that panobinostat was stable in human, monkey and dog plasma while unstable in mouse and rat plasma. The species difference observed was in line with the carboxylesterase 1c (Ces1c) expression among these species, where rodent plasma has abundant Ces1c expression while the other species have no Ces1c in plasma. With this in mind, we evaluated the impact of Ces1c removal from the matrices. We found that panobinostat was stable in plasma collected from Ces1c knockout mice (B6.Cg-Ces1ctm1.1Loc/J), indicating that Ces1c is contributing to the in vitro instability of panobinostat in plasma. To evaluate the influence of Ces1c on its pharmacokinetic behaviors, we studied the plasma and CNS distribution of panobinostat in wild-type C57BL6/J mice and Ces1c knockout mice following an intravenous bolus dose of 10 mg/kg via tail vein. Despite improved in vitro stability of panobinostat in plasma from Ces1c knockout mice compared with that in plasma from wild-type C57BL6/J, in vivo plasma concentration-time profiles were superimposable between these two genotypes. In addition, the CNS delivery of panobinostat was not influenced by the lack of Ces1c. Studies are ongoing to find potential in vivo mechanisms that are protecting the compound from robust in vitro degradation in the plasma. Citation Format: Wenqiu Zhang, Ju-Hee Oh, Wenjuan Zhang, Rachael W. Sirianni, William F. Elmquist. In vitro stability and in vivo pharmacokinetic behavior of panobinostat in mouse models for the treatment of CNS tumors [abstract]. In: Proceedings of the AACR Special Conference on Brain Cancer; 2023 Oct 19-22; Minneapolis, Minnesota. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_1):Abstract nr B013.

Dietary partitioning among three cryptobenthic reef fish mesopredators revealed by visual analysis, metabarcoding of gut content, and stable isotope analysis

AbstractUnderstanding how mesopredators partition their diet and the identity of consumed prey can assist in understanding the ecological role predators and prey play in ecosystem trophodynamics. Here, we assessed the diet of three common coral reef mesopredators; Pseudochromis flavivertex, Pseudochromis fridmani, and Pseudochromis olivaceus from the family Pseudochromidae, commonly known as dottybacks, using a combination of (i) visual stomach content analysis, (ii) stomach content DNA metabarcoding (18S, COI), and (iii) stable isotope analysis (δ15N, δ13C). In addition, P. flavivertex is found in two distinct color morphs in the Red Sea, providing an opportunity to analyze intra‐morph differences. These techniques revealed partitioning in the dietary composition and resource use among species. Arthropods comprised the main dietary component of P. flavivertex (18S > 60%; COI > 10%) and P. olivaceus (18S = 57.2%), while P. fridmani ingested predominantly mollusks (18S = 51.3%, COI = 24.6%). Despite being small predators, microplastics were found in the gut content of some of these fishes. Stable isotope analysis showed differences in species' isotopic niche breadth and trophic position. Pseudochromis olivaceus presented the largest isotopic niche (SEAC = 1.61‰2), while P. fridmani showed the smallest isotopic niche (SEAC = 0.45‰2) among species. Although the two techniques used for stomach content analysis did not show differences in the diet within color morphs of P. flavivertex, they differed in the isotopic niche and resource use. Despite our limited sampling, our findings provide evidence of species‐specific differences in the trophic ecology of dottybacks and demonstrate their important role as predators of cryptic invertebrates and small fishes. This study highlights the importance of combining several approaches (short‐term: visual analysis and DNA metabarcoding; and long‐term: isotope analysis) when assessing the feeding habits of coral reef fish, as they provide complementary information necessary to delimit their niches and understand the role that small mesopredators play in coral reef ecosystems.

Animals in Respiratory Research.

The respiratory barrier, a thin epithelial barrier that separates the interior of the human body from the environment, is easily damaged by toxicants, and chronic respiratory diseases are common. It also allows the permeation of drugs for topical treatment. Animal experimentation is used to train medical technicians, evaluate toxicants, and develop inhaled formulations. Species differences in the architecture of the respiratory tract explain why some species are better at predicting human toxicity than others. Some species are useful as disease models. This review describes the anatomical differences between the human and mammalian lungs and lists the characteristics of currently used mammalian models for the most relevant chronic respiratory diseases (asthma, chronic obstructive pulmonary disease, cystic fibrosis, pulmonary hypertension, pulmonary fibrosis, and tuberculosis). The generation of animal models is not easy because they do not develop these diseases spontaneously. Mouse models are common, but other species are more appropriate for some diseases. Zebrafish and fruit flies can help study immunological aspects. It is expected that combinations of in silico, in vitro, and in vivo (mammalian and invertebrate) models will be used in the future for drug development.

Novel RNA molecular bioengineering technology efficiently produces functional miRNA agents.

Genome-derived microRNAs (miRNA or miR) govern posttranscriptional gene regulation and play important roles in various cellular processes and disease progression. While chemo-engineered miRNA mimics or biosimilars made in vitro are widely available and used, miRNA agents produced in vivo are emerging to closely recapitulate natural miRNA species for research. Our recent works have demonstrated the success of high-yield, in vivo production of recombinant miRNAs by using human tRNA (htRNA) fused precursor miRNA (pre-miR) carriers. In this study, we aim to compare the production of bioengineered RNA (BioRNA) molecules with glycyl versus leucyl htRNA fused hsa-pre-miR-34a carriers, namely BioRNAGly and BioRNALeu, respectively, and perform initial functional assessment. We designed, cloned, overexpressed, and purified a total of 48 new BioRNA/miRNAs, and overall expression levels, final yields, and purities were revealed to be comparable between BioRNAGly and BioRNALeu molecules. Meanwhile, the two versions of BioRNA/miRNAs showed similar activities to inhibit non-small cell lung cancer cell viability. Interestingly, functional analyses using model BioRNA/miR-7-5p demonstrated that BioRNAGly/miR-7-5p exhibited greater efficiency to regulate a known target gene expression (EGFR) than BioRNALeu/miR-7-5p, consistent with miR-7-5p levels released in cells. Moreover, BioRNAGly/miR-7-5p showed comparable or slightly greater activities to modulate MRP1 and VDAC1 expression, compared with miRCURY LNA miR-7-5p mimic. Computational modeling illustrated overall comparable 3D structures for exemplary BioRNA/miRNAs with noticeable differences in htRNA species and payload miRNAs. These findings support the utility of hybrid htRNA/hsa-pre-miR-34a as reliable carriers for RNA molecular bioengineering, and the resultant BioRNAs serve as functional biologic RNAs for research and development.

Alternatives of Animal Models for Biomedical Research: a Comprehensive Review of Modern Approaches.

Biomedical research has long relied on animal models to unravel the intricacies of human physiology and pathology. However, concerns surrounding ethics, expenses, and inherent species differences have catalyzed the exploration of alternative avenues. The contemporary alternatives to traditional animal models in biomedical research delve into three main categories of alternative approaches: in vitro models, in vertebrate models, and in silico models. This unique approach to artificial intelligence and machine learning has been a keen interest to be used in different biomedical research. The main goal of this review is to serve as a guide to researchers seeking novel avenues for their investigations and underscores the importance of considering alternative models in the pursuit of scientific knowledge and medical breakthroughs, including showcasing the broad spectrum of modern approaches that are revolutionizing biomedical research and leading the way toward a more ethical, efficient, and innovative future. Models can insight into cellular processes, developmental biology, drug interaction, assessing toxicology, and understanding molecular mechanisms.

Evaluating scientific confidence in the concordance of in vitro and in vivo protective points of departure

To fulfil the promise of reducing reliance on mammalian in vivo laboratory animal studies, new approach methods (NAMs) need to provide a confident basis for regulatory decision-making. However, previous attempts to develop in vitro NAMs-based points of departure (PODs) have yielded mixed results, with PODs from U.S. EPA's ToxCast, for instance, appearing more conservative (protective) but poorly correlated with traditional in vivo studies. Here, we aimed to address this discordance by reducing the heterogeneity of in vivo PODs, accounting for species differences, and enhancing the biological relevance of in vitro PODs. However, we only found improved in vitro-to-in vivo concordance when combining the use of Bayesian model averaging-based benchmark dose modeling for in vivo PODs, allometric scaling for interspecies adjustments, and human-relevant in vitro assays with multiple induced pluripotent stem cell-derived models. Moreover, the available sample size was only 15 chemicals, and the resulting level of concordance was only fair, with correlation coefficients <0.5 and prediction intervals spanning several orders of magnitude. Overall, while this study suggests several ways to enhance concordance and thereby increase scientific confidence in vitro NAMs-based PODs, it also highlights challenges in their predictive accuracy and precision for use in regulatory decision making.

Distribution and influencing factors of macrobenthos on three seagrass beds in the intertidal zone of Shandong province, China

IntroductionThe macrobenthos plays a vital role within the ecosystem of seagrass beds, with its characteristics and spatial distribution serving as indicators of the well-being of the seagrass beds.MethodsIn August 2018, three seagrass beds located in the Yellow River Estuary of Dongying, the west coast of Yantai, and Swan Lake of Weihai, were investigated to compare the ecological influences of seagrass habitat on the benthic environment and macrobenthic community. Within each seagrass bed, porewater, sediment, and macrobenthos were sampled from three separate stations (center of seagrass bed, edge of seagrass bed and bare area).Results and discussionOne-way ANOVA showed significant differences (p &amp;lt; 0.05) in environmental factors and macrobenthos species, abundance, biomass and diversity indices among the three seagrass beds. The present data did not show significant impacts on habitat and macrobenthos in the different coverage areas of seagrass beds at the investigated spatial scales, though crustacea and some carnivores were relatively more inclined to inhabit areas with higher seagrass densities. Aquaculture and eutrophication may trigger the loss of seagrass bed habitats, that affects macrobenthic biodiversity, and conservation measures are needed to protect seagrass bed habitats.

Some like it burnt: species differences in small mammal assemblage in a Mediterranean basin nearly 3 years after a major fire

The habitat accommodation model (HAM) is a theoretical framework that predicts wildlife community recovery based on their habitat requirements. While post-fire habitat-related research is well documented in the Mediterranean basin, studies specifically focusing on HAM are scarce. Here, we described the small mammal assemblage in a Mediterranean area ~3 years after a fire, specifically examining three functional small mammalian categories: ground-foraging insectivorous, ground-foraging herbivorous/granivorous, and arboreal-foraging species. The study was conducted in Monte Pisano (Italy), where fire burnt ~12 km2 in September 2018. A stratified random sampling was adopted, basing on burnt status and forest type. In each of the 50 sites, during late spring-summer 2021, 12 hair-tubes were deployed, and collected hairs were taxa-attributed based on morphology. A presence/absence dataset was built, and db-RDA was used to explore assemblage composition, and single-species occupancy models to test specific hypotheses. The relative abundance of ground-foraging herbivorous/granivorous was higher in the burnt area, characterised by a dense undergrowth, which could be related to anti-predatory strategies and food opportunities. Insectivorous could be in a recolonisation phase, masking their earlier absence, which could explain why their abundance was not associated with any factor tested. Arboreal-foraging species were associated with forest type, indicating a primary role for tree cover and other factors such as rocky cover and likely in situ survival. The HAM was overall confirmed also in Mediterranean basin ecosystems. This may facilitate predictions about post-fire animal successions, which in turn may provide valuable insights into post-fire management practices and biodiversity conservation strategies.

In vitro biocompatibility of polycaprolactone/hydroxyapatite nanocomposite membranes modified by oleic acid for bone regeneration

The bone defect is common in the orthopedic clinic, possibly due to trauma, tumor, or congenital diseases. Also, some patients with alveolar bone defects in the dental clinic result from the different proliferation speeds between soft and hard tissue. Biomaterials made of polymers and bioceramics have been developed to deal with these problems but mixing them directly can result in a low-mechanical strength complex. To solve this, we used oleic acid (C18) as a surfactant to improve the dispersity of hydroxyapatite (HA) in the polycaprolactone (PCL) matrix, and then immerse the material in a simulated biomineralization process. The results showed that the low crystallinity PCL formed an evenly distributed mineralized layer that had phosphate ions signal and a hydroxyapatite peak. The biocompatibility of the material was assessed using MC3T3 cells, and found that the PCL-HA membrane and PCL-C18-HA membranes had significant cell filopodia and lamellipodia. Additionally, the polycaprolactone/oleic acid/hydroxyapatite (PCL-C18-HA) membrane had the highest cell viability among all groups. The addition of C18 also decreased the platelets activation degree but had a significant difference in the reactive oxygen species (ROS) amount compared to the control, which requires further investigation. Overall, this study successfully fabricated a safe and promising polycaprolactone/hydroxyapatite/oleic acid nanocomposite membrane as a potential solution for bone biomaterials.

Water loss after stomatal closure: Quantifying leaf minimum conductance and minimal water use in 9 temperate European tree species during a severe drought.

Residual canopy transpiration (Emin_canop) is a key physiological trait that determines trees' survival time under drought after stomatal closure and after trees have limited access to soil water. Emin_canop mainly depends on leaf minimum conductance (gmin) and vapor pressure deficit (VPD). Here we determined the seasonal variation of gmin and how gmin is related to interspecies variation in leaf cuticular and stomatal traits for nine European tree species in a mature forest. In addition, we determined the species-specific temperature responses of gmin. With this newly obtained insight, we calculated Emin_canop for the nine species for one day at our research site during the 2022 central European hot drought. Our results show that at ambient temperatures gmin ranged from 0.8 to 4.8mmolm-2s-1 across the nine species and was stable in most species throughout the growing season. The interspecies variation of gmin was associated with leaf cuticular and stomatal traits. Additionally, gmin exhibited strong temperature responses and increased, depending on species, by a factor of two to four in the range of 25 to 50°C. For the studied species at the site, during a single hot drought day, Emin_canop standardized by tree size (stem basal area) ranged from 2.0 to 36.7Lm-2, and non-standardized Emin_canop for adult trees ranged from 0.3 to 5.3L. Emin_canop also exhibited species-specific rapid increases under hotter temperatures. Our results suggest that trees, depending on species, need reasonable amounts of water during a drought, even when stomates are fully closed. Species differences in gmin and ultimately Emin_canop can affect, together with other traits, the ability of a tree to keep its tissue hydrated during a drought and is likely to contribute to species-specific differences in drought vulnerability.

Impact of non-diffusive interactions on Turing instability

Observational studies of the chemical reactions have shown that the uniform state, driven by the diffusion differences of activator and inhibitor species, can seed the spontaneous emergence of spatially organized patterns—also known as Turing instability. The presence of diffusive interaction between the species in discrete media can naturally form the structure of the network Laplacian, thereby resulting in that the Turing instability can be better understood via the eigenvectors and eigenvalues of the graph Laplacian. However, it is still unclear whether and under which conditions the Turing instability can be induced in the absence of diffusive transport. In this work, to overcome the limitation of network Laplacian matrix that only has non-positive eigenvalues, we investigate the effects of non-diffusive (or no-local) coupling between the species on the Turing instability for the directed and undirected networks, respectively, where the interaction matrix may produce the positive and negative eigenvalues. In particular, we first derive the critical conditions that the Turing instability occurs by employing the linear stability analysis. Then we apply them to the networked systems governed by the FitzHugh–Nagumo dynamics and obtain the critical range of eigenvalues of the interaction matrix. Finally, we use the Girko’s circular law to predict the eigenvalues’ distribution, and show, via extensive numerical simulations, the transition process of the Turing instability depending on network size, network connectivity and connection weights (intraspecific interaction strength). Our results reveal that in the absence of diffusive transport, the Turing instability still can arise, offering a new perspective on the generation mechanism of the Turing instability.

Raman spectrum combined with deep learning for precise recognition of Carbapenem-resistant Enterobacteriaceae.

Carbapenem-resistant Enterobacteriaceae (CRE) is a major pathogen that poses a serious threat to human health. Unfortunately, currently, there are no effective measures to curb its rapid development. To address this, an in-depth study on the surface-enhanced Raman spectroscopy (SERS) of 22 strains of 7 categories of CRE using a gold silver composite SERS substrate was conducted. The residual networks with an attention mechanism to classify the SERS spectrum from three perspectives (pathogenic bacteria type, enzyme-producing subtype, and sensitive antibiotic type) were performed. The results show that the SERS spectrum measured by the composite SERS substrate was repeatable and consistent. The SERS spectrum of CRE showed varying degrees of species differences, and the strain difference in theSERS spectrum of CRE was closely related to the type of enzyme-producingsubtype. The introduced attention mechanism improved the classification accuracy of the residual network (ResNet) model. The accuracy of CRE classification for different strains and enzyme-producing subtypes reached 94.0% and 96.13%, respectively. The accuracy of CRE classification by pathogen sensitive antibiotic combination reached 93.9%. This study is significant for guiding antibiotic use in CRE infection, as the sensitive antibiotic used in treatment can be predicted directly by measuring CRE spectra. Our study demonstrates the potential of combining SERS with deep learning algorithms to identify CRE without culture labels and classify its sensitive antibiotics. This approach provides a new idea for rapid and accurate clinical detection of CRE and has important significance for alleviating the rapid development of resistance to CRE.

Impaired T3 uptake and action in MCT8-deficient cerebral organoids underlie Allan-Herndon-Dudley syndrome.

Patients with mutations in the thyroid hormone (TH) cell transporter monocarboxylate transporter 8 (MCT8) gene develop severe neuropsychomotor retardation known as Allan-Herndon-Dudley syndrome (AHDS). It is assumed that this is caused by a reduction in TH signaling in the developing brain during both intrauterine and postnatal developmental stages, and treatment remains understandably challenging. Given species differences in brain TH transporters and the limitations of studies in mice, we generated cerebral organoids (COs) using human induced pluripotent stem cells (iPSCs) from MCT8-deficient patients. MCT8-deficient COs exhibited (i) altered early neurodevelopment, resulting in smaller neural rosettes with thinner cortical units, (ii) impaired triiodothyronine (T3) transport in developing neural cells, as assessed through deiodinase-3-mediated T3 catabolism, (iii) reduced expression of genes involved in cerebral cortex development, and (iv) reduced T3 inducibility of TH-regulated genes. In contrast, the TH analogs 3,5-diiodothyropropionic acid and 3,3',5-triiodothyroacetic acid triggered normal responses (induction/repression of T3-responsive genes) in MCT8-deficient COs, constituting proof of concept that lack of T3 transport underlies the pathophysiology of AHDS and demonstrating the clinical potential for TH analogs to be used in treating patients with AHDS. MCT8-deficient COs represent a species-specific relevant preclinical model that can be utilized to screen drugs with potential benefits as personalized therapeutics for patients with AHDS.

Water quality and habitat drive phytoplankton taxonomic and functional group patterns in the Yangtze River

BackgroundAlthough phytoplankton are important primary producers in food webs, they are relatively less studied in large rivers compared to other types of systems. To fill this research gap, we studied phytoplankton taxonomic and functional composition and their relationships with water quality, habitat, climate, and land use across 30 river sections in the middle and lower reaches of the Yangtze River during 2017–2018.ResultsMajor observed phytoplankton groups were cyanobacteria, bacillariophyta, and chlorophyta. Phytoplankton total abundance, total biomass, and species richness significantly decreased in the dry season compared to the wet season, with the species and functional composition differing significantly between seasons. Phytoplankton species differences between seasons were mainly contributed by Oscillatoria sp., Pseudanabaena sp., and Melosira granulata. The dfferences in phytoplankton functional groups between seasons were mainly contributed by P (including Closterium sp., Melosira sp.), Lo (including Merismopedia sp., Peridinium sp., Ceratium sp., and Gymnodinium sp.), and J (including Pediastrum sp., Tetraedron sp., Crucigenia sp., Scenedesmus sp., and Coelastrum sp.). The variance partitioning showed that water quality (NO3-N, total suspended solids, turbidity) and habitat (water flow, river bank and river channel conditions) were critical factors in shaping phytoplankton patterns, followed by climate and land use.ConclusionsResults indicated that there was significant seasonal variation of phytoplankton in the Yangtze River, with water quality and habitat primarily driving phytoplankton patterns. Our study contributes to the understanding of natural and anthropogenic factors that drive seasonal successional processes of phytoplankton in the Yangtze River. These findings have important implications for environmental management as well as towards the ecological restoration of large rivers.

Assimilate Remobilization in Five Spring Grain Legumes Under Mediterranean Conditions

A comparative evaluation of grain legumes is essential for the effective planning of legume-based agricultural systems in a given environment. The goal of this work was to contrast the growth, translocation of assimilates, and grain yield of spring-planted common vetch (Vicia sativa L.), red pea (Lathyrus cicera L.), lentil (Lens culinaris Medik.), chickpea (Cicer arietinum L.), and field pea (Pisum sativa L.) under rainfed Mediterranean conditions. Two cultivars of each species were cultivated on a silty clay soil in northeastern Greece for 2 years (2014 and 2015) with contrasting rainfall patterns. Chickpea and field pea exhibited better early crop growth rate than any other legume. Species differences in assimilates availability prior to grain filling affected the remobilization of assimilates to seed, which increased by 45% for every kg ha−1 rise in early dry matter accumulation. Dry matter translocation efficiency varied from 9 to 51% depending on species and year. Red pea was the best option in terms of seed yield, regardless of the seasonal rainfall. Chickpea in the drier year (2015) and field pea in the wetter year (2014) produced seed yields that were comparable to that of red pea. Lentil and common vetch were generally less productive species in terms of seed yield. Species seed yield was associated with their ability to accumulate biomass either before podding (r = 0.52, P < 0.05) or at maturity (r = 0.51, P < 0.05), but not with harvest index or translocation of dry matter. Findings provide new knowledge regarding growth attributes and reallocation of assimilate in five legume species grown simultaneously in the same environment, which has never been studied before. In addition, results highlight that selecting species with enhanced early or final biomass potential as well as adopting cultural practices that promote biomass accumulation in the growing season appear to be effective management strategies for improving seed yield of the tested grain legumes under Mediterranean conditions.

Glycine is a transmitter in the human and chimpanzee cochlear nuclei.

Auditory information is relayed from the cochlea via the eighth cranial nerve to the dorsal and ventral cochlear nuclei (DCN, VCN). The organization, neurochemistry and circuitry of the cochlear nuclei (CN) have been studied in many species. It is well-established that glycine is an inhibitory transmitter in the CN of rodents and cats, with glycinergic cells in the DCN and VCN. There are, however, major differences in the laminar and cellular organization of the DCN between humans (and other primates) and rodents and cats. We therefore asked whether there might also be differences in glycinergic neurotransmission in the CN. We studied brainstem sections from humans, chimpanzees, and cats. We used antibodies to glycine receptors (GLYR) to identify neurons receiving glycinergic input, and antibodies to the neuronal glycine transporter (GLYT2) to immunolabel glycinergic axons and terminals. We also examined archival sections immunostained for calretinin (CR) and nonphosphorylated neurofilament protein (NPNFP) to try to locate the octopus cell area (OCA), a region in the VCN that rodents has minimal glycinergic input. In humans and chimpanzees we found widespread immunolabel for glycine receptors in DCN and in the posterior (PVCN) and anterior (AVCN) divisions of the VCN. We found a parallel distribution of GLYT2-immunolabeled fibers and puncta. The data also suggest that, as in rodents, a region containing octopus cells in cats, humans and chimpanzees has little glycinergic input. Our results show that glycine is a major transmitter in the human and chimpanzee CN, despite the species differences in DCN organization. The sources of the glycinergic input to the CN in humans and chimpanzees are not known.

Deep N acquisition in cultivated grasslands: Uptake of slow-release 15N-labeled ammonium in hemiboreal monospecific leys

Abstract Aims To develop a methodology to study uptake and redistribution by plants of NH4+ from deep soil, applying it to investigate deep root N uptake by cultivated grassland species. Methods A slow-release 15NH4+ label adsorbed to clinoptilolite was placed into soil (depth 42 cm) well below the densest root zone in well-established monospecific stands of five grass and two clover species. Species showing a variety of deep rooting patterns, N acquisition strategy, forage qualities, and persistence in hemiboreal conditions were chosen. The label was placed in early spring and tracked throughout one or two growing seasons in two repeated experiments. Results After two growing seasons ~ 90% of the label was tracked in the soil and harvested herbage of grasses, less in clovers. Deep N uptake was limited in spring, increased during mid-season, and was strongest in autumn in all species, despite lower herbage yield in autumn. Species differed in ability to recover and maintain 15N in the soil–plant system. In one growing season, Lolium perenne L., Phleum pratense L., Schedonorus pratensis (Huds.) P.Beauv. and Schedonorus arundinaceus (Schreb.) Dumort herbage recovered ~ 65% of the label, Poa pratensis L. 54%, and Trifolium pratense L. and Trifolium repens L. 36–48%. Label transport to topsoil was observed, mainly attributable to plant nutrient redistribution rather than physical diffusion. Conclusions The innovative slow-release 15N label enabled tracing species differences and seasonal changes in uptake of NH4+ from deep soil. Among the tall-growing grasses, growth vigor appeared as important for deep N uptake as expected root depth.

A Spatial Signal of Niche Differentiation in Tropical Forests.

AbstractExplaining diversity in tropical forests remains a challenge in community ecology. Theory tells us that species differences can stabilize communities by reducing competition, while species similarities can promote diversity by reducing fitness differences and thus prolonging the time to competitive exclusion. Combined, these processes may lead to clustering of species such that species are niche differentiated across clusters and share a niche within each cluster. Here, we characterize this partial niche differentiation in a tropical forest in Panama by measuring spatial clustering of woody plants and relating these clusters to local soil conditions. We find that species were spatially clustered and the clusters were associated with specific concentrations of soil nutrients, reflecting the existence of nutrient niches. Species were almost twice as likely to recruit in their own nutrient niche. A decision tree algorithm showed that local soil conditions correctly predicted the niche of the trees with up to 85% accuracy. Iron, zinc, phosphorus, manganese, and soil pH were among the best predictors of species clusters.