Mysterious bio-duck sound attributed to the Antarctic minke whale (Balaenoptera bonaerensis)

For decades, the bio-duck sound has been recorded in the Southern Ocean, but the animal producing it has remained a mystery. Heard mainly during austral winter in the Southern Ocean, this ubiquitous sound has been recorded in Antarctic waters and contemporaneously off the Australian west coast. Here, we present conclusive evidence that the bio-duck sound is produced by Antarctic minke whales (Balaenoptera bonaerensis). We analysed data from multi-sensor acoustic recording tags that included intense bio-duck sounds as well as singular downsweeps that have previously been attributed to this species. This finding allows the interpretation of a wealth of long-term acoustic recordings for this previously acoustically concealed species, which will improve our understanding of the distribution, abundance and behaviour of Antarctic minke whales. This is critical information for a species that inhabits a difficult to access sea-ice environment that is changing rapidly in some regions and has been the subject of contentious lethal sampling efforts and ongoing international legal action.     

Recurrent Pseudo-nitzschia calliantha (Bacillariophyceae) and Alexandrium insuetum (Dinophyceae) winter blooms induced by agricultural runoff

A winter bloom dominated by Pseudo-nitzschia calliantha Lundholm, Moestrup et Hasle (Bacillariophyceae), a potential domoic acid producer, is reported for the first time in the Aegean Sea, Greece, in a semi-enclosed embayment (Kalloni Gulf) surrounded by agricultural land and drained by intermittent rivers. Abundances of this species in the inner part of the Gulf during February were extremely high (max 1.1 × 10⁷ cells l⁻¹). The species Alexandrium insuetum Balech (Dinophyceae) was also found in considerable cell numbers (max 1.4 × 10⁵ cells l⁻¹) during the bloom and reached up to 40% of the total biovolume. This study demonstrates an evident cause and effect relationship between nutrient inflows originating from agricultural activities in the watershed and the development of a potential HAB. The massive bloom formation was observed soon after an episodic rainfall event during the fertilizer application period (December to February). A bloom was also observed the following year, but it was less pronounced due to the fact that rainfalls were more evenly spaced in time and were of moderate intensity.     

Quorum Sensing Peptides Selectively Penetrate the Blood-Brain Barrier

Bacteria communicate with each other by the use of signaling molecules, a process called ‘quorum sensing’. One group of quorum sensing molecules includes the oligopeptides, which are mainly produced by Gram-positive bacteria. Recently, these quorum sensing peptides were found to biologically influence mammalian cells, promoting i.a. metastasis of cancer cells. Moreover, it was found that bacteria can influence different central nervous system related disorders as well, e.g. anxiety, depression and autism. Research currently focuses on the role of bacterial metabolites in this bacteria-brain interaction, with the role of the quorum sensing peptides not yet known. Here, three chemically diverse quorum sensing peptides were investigated for their brain influx (multiple time regression technique) and efflux properties in an in vivo mouse model (ICR-CD-1) to determine blood-brain transfer properties: PhrCACET1 demonstrated comparatively a very high initial influx into the mouse brain (K_in = 20.87 μl/(g×min)), while brain penetrabilities of BIP-2 and PhrANTH2 were found to be low (K_in = 2.68 μl/(g×min)) and very low (K_in = 0.18 μl/(g×min)), respectively. All three quorum sensing peptides were metabolically stable in plasma (in vitro) during the experimental time frame and no significant brain efflux was observed. Initial tissue distribution data showed remarkably high liver accumulation of BIP-2 as well. Our results thus support the potential role of some quorum sensing peptides in different neurological disorders, thereby enlarging our knowledge about the microbiome-brain axis.     

Bivariate flow karyotyping of human chromosomes: evaluation of variation in Hoechst 33258 fluorescence, chromomycin A3 fluorescence, and relative chromosomal DNA content.

The total variation of chromosome peak positions, in bivariate distributions of Hoechst 33258 and chromomycin A3 fluorescence of 19 healthy individuals, was compared with the experimental variation, determined from 23 bivariate distributions of chromosomes prepared separately from a single cell lineage. The experimental variation in Hoechst and chromomycin fluorescence and the relative chromosomal DNA content were determined from experiments performed over several days. The additional variance contributed by time was the same as the daily variance. The accuracy by which the relative chromosomal DNA content can be calculated from bivariate peak positions was investigated. A least squares method was used to fit the distributions of relative DNA content, obtained, respectively, from mono- and bivariate flow analyses of chromosomes from the same cell lineage. In general the DNA contents match quite well, but for a few chromosomes a difference was found, statistically discernible at the 5% level. The average relative chromosomal DNA content of the chromosomes from the 19 normal individuals, calculated from bivariate peak positions, showed a linear relation with the estimates published by other investigators.     

Transformation of passionfruit (Passiflora edulis fv flavicarpa Degener.) using Agrobacterium tumefaciens

Leaf and stem explants of passionfruit (Passiflora eadulis fv flavicarpa) were co-cultivated with a disarmed strain of Agrobacterium tunefaciens harbouring the co-integrate vector pMON200. Four plants of passionfruit were regenerated from leaf explants on agar-solidified Murashige and Skoog (1962) based medium containing 4.43 M 6-benzyl-aminopurine and supplemented with 86 M kanamycin sulphate. The four plants were rooted by transfer to MS based medium with 14.7 M 3-indolebutyric acid and 2.68 M -naphthyleneacetic acid for 7 d, followed by MS based medium lacking growth regulators. Both media used for rooting contained 172 M kanamycin sulphate. Rooted plants were potted and grown to maturity. Three of the plants synthesised nopaline and expressed neomycin phosphotransferase activity; DNA dot blot and polymerase chain reaction analyses confirmed the presence of the neomycin phosphotransferase gene in three plants.Abbreviations BAP 6-benzylaminopurine - CTAB hexadecy-Itrimethylammonium bromide - EDTA ethylenediaminetetraacetic acid - IBA 3-indolebutyric acid - MS Murashige and Skoog (1962) - NAA -naphthyleneacetic acid - NPTII neomycin phosphotransferase II - nptII neomycin phosphotransferase II gene - PCR polymerase chain reaction - SDS sodium dodecyl sulphate - Tris tris(hydroxymethyl)aminomethane     

Century‐long apparent decrease in intrinsic water‐use efficiency with no evidence of progressive nutrient limitation in African tropical forests

Forests exhibit leaf‐ and ecosystem‐level responses to environmental changes. Specifically, rising carbon dioxide (CO₂) levels over the past century are expected to have increased the intrinsic water‐use efficiency (iWUE) of tropical trees while the ecosystem is gradually pushed into progressive nutrient limitation. Due to the long‐term character of these changes, however, observational datasets to validate both paradigms are limited in space and time. In this study, we used a unique herbarium record to go back nearly a century and show that despite the rise in CO₂ concentrations, iWUE has decreased in central African tropical trees in the Congo Basin. Although we find evidence that points to leaf‐level adaptation to increasing CO₂—that is, increasing photosynthesis‐related nutrients and decreasing maximum stomatal conductance, a decrease in leaf δ¹³C clearly indicates a decreasing iWUE over time. Additionally, the stoichiometric carbon to nitrogen and nitrogen to phosphorus ratios in the leaves show no sign of progressive nutrient limitation as they have remained constant since 1938, which suggests that nutrients have not increasingly limited productivity in this biome. Altogether, the data suggest that other environmental factors, such as increasing temperature, might have negatively affected net photosynthesis and consequently downregulated the iWUE. Results from this study reveal that the second largest tropical forest on Earth has responded differently to recent environmental changes than expected, highlighting the need for further on‐ground monitoring in the Congo Basin.     

Projected climate and land use change alter western blacklegged tick phenology,seasonal host‐seeking suitability and human encounter risk in California

Global environmental change is having profound effects on the ecology of infectious disease systems, which are widely anticipated to become more pronounced under future climate and land use change. Arthropod vectors of disease are particularly sensitive to changes in abiotic conditions such as temperature and moisture availability. Recent research has focused on shifting environmental suitability for, and geographic distribution of, vector species under projected climate change scenarios. However, shifts in seasonal activity patterns, or phenology, may also have dramatic consequences for human exposure risk, local vector abundance and pathogen transmission dynamics. Moreover, changes in land use are likely to alter human–vector contact rates in ways that models of changing climate suitability are unlikely to capture. Here we used climate and land use projections for California coupled with seasonal species distribution models to explore the response of the western blacklegged tick (Ixodes pacificus), the primary Lyme disease vector in western North America, to projected climate and land use change. Specifically, we investigated how environmental suitability for tick host‐seeking changes seasonally, how the magnitude and direction of changing seasonal suitability differs regionally across California, and how land use change shifts human tick‐encounter risk across the state. We found vector responses to changing climate and land use vary regionally within California under different future scenarios. Under a hotter, drier scenario and more extreme land use change, the duration and extent of seasonal host‐seeking activity increases in northern California, but declines in the south. In contrast, under a hotter, wetter scenario seasonal host‐seeking declines in northern California, but increases in the south. Notably, regardless of future scenario, projected increases in developed land adjacent to current human population centers substantially increase potential human–vector encounter risk across the state. These results highlight regional variability and potential nonlinearity in the response of disease vectors to environmental change.