Coupling planktonic and benthic shifts during a bloom of Alexandrium catenella in southern Chile:Implications for bloom dynamics and recurrence

Cell abundances and distributions of Alexandrium catenella resting cysts in recent sediments were studied along time at two locations in the Chilean Inland Sea exposed to different oceanographic conditions: Low Bay, which is much more open to the ocean than the more interior and protected Ovalada Island. The bloom began in interior areas but maximum cyst concentrations were recorded in locations more open to the ocean, at the end of the Moraleda channel. Our results showed a time lapse of around 3 months from the bloom peak (planktonic population) until the number of resting cysts in the sediments reached a maximum. Three months later, less than 10% of the A. catenella cysts remained in the sediments. Maximum cyst numbers in the water column occurred one month after the planktonic peak, when no cells were present. The dinoflagellate assemblage at both study sites was dominated by heterotrophic cysts, except during the A. catenella bloom. CCA analyses of species composition and environmental factors indicated that the frequency of A. catenella blooms was associated with low temperatures, but not with salinity, chlorophyll a concentration, and predator presence (measured as clam biomass). However, resting cyst distribution was only related to cell abundance and location. The occurrence of A. catenella cysts was also associated with that of cysts from the toxic species Protoceratium reticulatum. By shedding light on the ecological requirements of A. catenella blooms, our observations support the relevance of encystment as a mechanism of bloom termination and show a very fast depletion of cysts from the sediments (<3 months), which suggest a small role for resting cyst deposits in the recurrence of A. catenella blooms in this area.Postprin

TEAD and YAP regulate the enhancer network of human embryonic pancreatic progenitors.

The genomic regulatory programmes that underlie human organogenesis are poorly understood. Pancreas development, in particular, has pivotal implications for pancreatic regeneration, cancer and diabetes. We have now characterized the regulatory landscape of embryonic multipotent progenitor cells that give rise to all pancreatic epithelial lineages. Using human embryonic pancreas and embryonic-stem-cell-derived progenitors we identify stage-specific transcripts and associated enhancers, many of which are co-occupied by transcription factors that are essential for pancreas development. We further show that TEAD1, a Hippo signalling effector, is an integral component of the transcription factor combinatorial code of pancreatic progenitor enhancers. TEAD and its coactivator YAP activate key pancreatic signalling mediators and transcription factors, and regulate the expansion of pancreatic progenitors. This work therefore uncovers a central role for TEAD and YAP as signal-responsive regulators of multipotent pancreatic progenitors, and provides a resource for the study of embryonic development of the human pancreas

The life history of the toxic marine dinoflagellate Protoceratium reticulatum (Gonyaulacales) in culture

Asexual and sexual life cycle events were studied in cultures of the toxic marine dinoflagellate Protoceratium reticulatum. Asexual division by desmoschisis was characterized morphologically and changes in DNA content were analyzed by flow cytometry. The results indicated that haploid cells with a C DNA content occurred only during the light period whereas a shift from a C to a 2C DNA content (indicative of S phase) took place only during darkness. The sexual life cycle was documented by examining the mating type as well as the morphology of the sexual stages and nuclei. Gamete fusion resulted in a planozygote with two longitudinal flagella, but longitudinally biflagellated cells arising from planozygote division were also observed, so one of the daughter cells retained two longitudinal flagella while the other daughter cell lacked them. Presumed planozygotes (identified by their longitudinally biflagellated form) followed two life-cycle routes: division and encystment (resting cyst formation). Both the division of longitudinally biflagellated cells and resting cyst formation are morphologically described herein. Resting cyst formation through sexual reproduction was observed in 6.1% of crosses and followed a complex heterothallic pattern. Clonal strains underwent sexuality (homothallism for planozygote formation and division) but without the production of resting cysts. Ornamental processes of resting cysts formed from the cyst wall under an outer balloon-shaped membrane and were fully developed in <1 h. Obligatory dormancy period was of ∼4 months. Excystment resulted in a large, rounded, pigmented, longitudinally biflagellated but motionless, thecate germling that divided by desmoschisis. Like the planozygote, the first division of the germling yielded one longitudinally biflagellated daughter cell and another without longitudinal flagella. The longitudinal biflagellation state of both sexual stages and of the first division products of these cells is discussed.Postprin

Psychometric Comparisons of Benevolent and Corrective Humor across 22 Countries: The Virtue Gap in Humor Goes International

Recently, two forms of virtue-related humor, benevolent and corrective, have been introduced. Benevolent humor treats human weaknesses and wrongdoings benevolently, while corrective humor aims at correcting and bettering them. Twelve marker items for benevolent and corrective humor (the BenCor) were developed, and it was demonstrated that they fill the gap between humor as temperament and virtue. The present study investigates responses to the BenCor from 25 samples in 22 countries (overall N = 7,226). The psychometric properties of the BenCor were found to be sufficient in most of the samples, including internal consistency, unidimensionality, and factorial validity. Importantly, benevolent and corrective humor were clearly established as two positively related, yet distinct dimensions of virtue-related humor. Metric measurement invariance was supported across the 25 samples, and scalar invariance was supported across six age groups (from 18 to 50+ years) and across gender. Comparisons of samples within and between four countries (Malaysia, Switzerland, Turkey, and the UK) showed that the item profiles were more similar within than between countries, though some evidence for regional differences was also found. This study thus supported, for the first time, the suitability of the 12 marker items of benevolent and corrective humor in different countries, enabling a cumulative cross-cultural research and eventually applications of humor aiming at the good

The Type Ia Supernova 1999aw: a Probable 1999aa-like Event In a Low-Luminosity Host Galaxy

SN 1999aw was discovered during the first campaign of the Nearby Galaxies Supernova Search (NGSS) project. This luminous, slow-declining (Delta m_{15} (B) = 0.81 \pm 0.03) Type Ia supernova was noteworthy in at least two respects. First, it occurred in an extremely low luminosity host galaxy that was not visible in the template images, nor in initial subsequent deep imaging. Secondly, the photometric and spectral properties of this supernova indicate that it very likely was similar to the subclass of Type Ia supernovae whose prototype is SN 1999aa. This paper presents the BVRI and J_{s} HK_{s} lightcurves of SN 1999aw (through 100 days past maximum light), as well as several epochs of optical spectra. From these data we calculate the bolometric light curve, and give estimates of the luminosity at maximum light and the initial ^{56}Ni mass. In addition, we present deep BVI images obtained recently with the Baade 6.5-meter telescope at Las Campanas Observatory which reveal the remarkably low-luminosity host galaxy.Comment: 18 pages, 10 figures, 8 tables, accepted for publication in A

Moving Forward in Fostering Humour: Towards Training Lighter Forms of Humour in Multicultural Contexts

The following theoretical position paper has the aim to outline two important future directions of humour intervention research. Firstly, existing humour trainings have not differentiated explicitly between different uses of humour or humour that may be virtuous or not. Within the realm of Positive Psychology, all virtuous forms of humour need to be identified and interventions developed that aim at fostering these benevolent/lighter forms. Secondly, most humour trainings have been adapted and conducted in one cultural context. Future trainings should consider cross-cultural perspectives to allow for comparative research and practice. Thus, the current paper first gives an overview on the extant literature on the distinction between lighter and darker forms of humour, as well as showing how humour can serve the virtues proposed by Peterson and Seligman (2004). Then, we elaborate on the findings on humour and well-being, as well as findings on existing humour interventions. The second section starts with open questions and hypotheses on how a new generation of trainings targeting lighter forms of humour could look like. Then, we discuss (potential) cultural differences in humour and how this may affect the design of interventions. When aiming for cross-cultural adaptations of the same humour program, several challenges have to be overcome, such as the term “humour” not having the same meaning in every culture, and cultural rules on what can be laughed at

Stressed out symbiotes:hypotheses for the influence of abiotic stress on arbuscular mycorrhizal fungi

Abiotic stress is a widespread threat to both plant and soil communities. Arbuscular mycorrhizal (AM) fungi can alleviate effects of abiotic stress by improving host plant stress tolerance, but the direct effects of abiotic stress on AM fungi are less well understood. We propose two hypotheses predicting how AM fungi will respond to abiotic stress. The stress exclusion hypothesis predicts that AM fungal abundance and diversity will decrease with persistent abiotic stress. The mycorrhizal stress adaptation hypothesis predicts that AM fungi will evolve in response to abiotic stress to maintain their fitness. We conclude that abiotic stress can have effects on AM fungi independent of the effects on the host plant. AM fungal communities will change in composition in response to abiotic stress, which may mean the loss of important individual species. This could alter feedbacks to the plant community and beyond. AM fungi will adapt to abiotic stress independent of their host plant. The adaptation of AM fungi to abiotic stress should allow the maintenance of the plant-AM fungal mutualism in the face of changing climates. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00442-016-3673-7) contains supplementary material, which is available to authorized users