A game of russian roulette for a generalist dinoflagellate parasitoid: Host susceptibility is the key to success

© 2016 Alacid, Park, Turon, Petrou and Garcés. Marine microbial interactions involving eukaryotes and their parasites play an important role in shaping the structure of phytoplankton communities. These interactions may alter population densities of the main host, which in turn may have consequences for the other concurrent species. The effect generalist parasitoids exert on a community is strongly dependent on the degree of host specificity. Parvilucifera sinerae is a generalist parasitoid able to infect a wide range of dinoflagellates, including toxic-bloom-forming species. A density-dependent chemical cue has been identified as the trigger for the activation of the infective stage. Together these traits make Parvilucifera-dinoflagellate hosts a good model to investigate the degree of specificity of a generalist parasitoid, and the potential effects that it could have at the community level. Here, we present for the first time, the strategy by which a generalist dinoflagellate parasitoid seeks out its host and determine whether it exhibits host preferences, highlighting key factors in determining infection. Our results demonstrate that in its infective stage, P. sinerae is able to sense potential hosts, but does not actively select among them. Instead, the parasitoids contact the host at random, governed by the encounter probability rate and once encountered, the chance to penetrate inside the host cell and develop the infection strongly depends on the degree of host susceptibility. As such, their strategy for persistence is more of a game of Russian roulette, where the chance of survival is dependent on the susceptibility of the host. Our study identifies P. sinerae as a potential key player in community ecology, where in mixed dinoflagellate communities consisting of hosts that are highly susceptible to infection, parasitoid preferences may mediate coexistence between host species, reducing the dominance of the superior competitor. Alternatively, it may increase competition, leading to species exclusion. If, however, highly susceptible hosts are absent from the community, the parasitoid population could suffer a dilution effect maintaining a lower parasitoid density. Therefore, both host community structure and host susceptibility will determine infectivity in the field

Análisis cuantitativo de la técnica de paleo en kayakistas infantiles

Se analizó la evolución de la velocidad (V), la longitud de ciclo (LCL), la frecuencia de ciclo (FCL) y el índice de ciclo (ICL) sobre un test máximo de 500 metros realizado por 44 kayakistas de 13 y 14 años, 24 de ellos hombres y 20 mujeres. Los datos se obtuvieron tras digitalizar las filmaciones de cada uno de los test. La V, la FCL y el ICL disminuyeron a lo largo de la prueba, mientras que la LCL se mantuvo estable. La FCL fue similar en ambos sexos, mientras que para las demás variables la categoría masculina obtuvo valores superiores. Se encontró una alta correlación inversa entre la FCL y la LCL y directa entre el ICL con la V y la LCL.Evolution of speed (V), cycle length (LCL), cycle frequency (FCL) and cycle index (ICL) were analysed in 44 young kayakists (24 males and 20 females; 13 – 14 years old) who underwent a maximum-500 m test. Digitalized images from each test were obtained to measure the variables cited above. V, FCL and ICL decreased through the test, while LDL was kept stable. FCL was similar in both genders, although the values of remaining variables measured were significantly higher in males than in females. There was a significant inverse correlation between FCL and LCL and a significant direct correlation between ICL, V and LCL was found

Genetic and phenotypic diversity characterization of natural populations of the parasitoid Parvilucifera sinerae

Parasites exert important top-down control of their host populations. The host−parasite system formed by Alexandrium minutum (Dinophyceae) and Parvilucifera sinerae (Perkinsozoa) offers an opportunity to advance our knowledge of parasitism in planktonic communities. In this study, DNA extracted from 73 clonal strains of P. sinerae, from 10 different locations along the Atlantic and Mediterranean coasts, was used to genetically characterize this parasitoid at the species level. All strains showed identical sequences of the small and large subunits and internal transcribed spacer of the ribosomal RNA, as well as of the β-tubulin genes. However, the phenotypical characterization showed variability in terms of host invasion, zoospore success, maturation time, half-maximal infection, and infection rate. This characterization grouped the strains within 3 phenotypic types distinguished by virulence traits. A particular virulence pattern could not be ascribed to host-cell bloom appearance or to the location or year of parasite-strain isolation; rather, some parasitoid strains from the same bloom significantly differed in their virulence traits. Identical markers such as ITS and β-tubulin genes of P. sinerae strains from different geographic areas and from different years precludes their use in assessing intra-specific diversity and could indicate a recent dispersion of this species.Versión del editor2,393

TESELA: a new Virtual Observatory tool to determine blank fields for astronomical observations

The observation of blank fields, regions of the sky devoid of stars down to a given threshold magnitude, constitutes one of the typical important calibration procedures required for the proper reduction of astronomical data obtained in imaging mode. This work describes a method, based on the use of the Delaunay triangulation on the surface of a sphere, that allows the easy generation of blank fields catalogues. In addition to that, a new tool named TESELA, accessible through the WEB, has been created to facilitate the user to retrieve, and visualise using the VO-tool Aladin, the blank fields available near a given position in the sky.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical Society. 11 pages, 10 figures. Related Web tool accessible at http://sdc.cab.inta-csic.es/tesel

Evaluating the Functional Properties of Spray-Dried Porcine Plasma in Gilthead Seabream (Sparus aurata) Fed Low Fish Meal Diets

Blood by-products are an untapped source of high-quality ingredients for aquafeeds, containing a broad variety of cytokines, hormones, growth factors, proteins, bioactive peptides, and amino acids. The effects of the spray-dried porcine plasma (SDPP), a type of processed animal protein on several immune parameters, were evaluated in sea bream using ex vivo and in vitro assays. In this study, fish were fed with two isoproteic, isolipidic, and isoenergetic diets: control diet (7% fish meal, FM) and SDPP diet (2% FM and 5% SDPP). At the end of the 92-days trial, those fed the SDPP diet were larger in body weight (p 0.05). The ex vivo immune stimulation of splenocytes indicated that SDPP had a beneficial effect in promoting systemic immunity, since the surface cell marker (cd4), pro- (il-1β), and anti-inflammatory (tgf-β1) cytokines, and genes involved in humoral immunity (IgM) were up-regulated. The co-culture assays of skin mucus corroborated that SDPP enhanced the antibacterial capacity of mucus against V. anguillarum. In addition, main mucus biomarkers did not show significant differences, except for cortisol levels which were lower in the SDPP diet. The present study indicated that SDPP may be considered a functional ingredient in aquafeeds formulated with low FM levels.info:eu-repo/semantics/publishedVersio

Energy balance and environmental impact analysis of marine microalgal biomass production for biodiesel generation in a photobioreactor pilot plant

A life cycle assessment (LCA) and an energy balance analysis of marine microalgal biomass production were conducted to determine the environmental impacts and the critical points of production for large scale planning. The artificial lighting and temperature conditions of an indoor bubble column photobioreactor (bcPBR) were compared to the natural conditions of an equivalent outdoor system. Marine microalgae, belonging to the dinoflagellate and raphidophyte groups, were cultured and the results were compared with published LCA data obtained from green microalgae (commonly freshwater algae). Among the species tested, Alexandrium minutum was chosen as the target marine microalgae for biomass production under outdoor conditions, although there were no substantial differences between any of the marine microalgae studied. Under indoor culture conditions, the total energy input for A. minutum was 923 MJ kg¯¹ vs. 139 MJ kg¯¹ for outdoor conditions. Therefore, a greater than 85% reduction in energy requirements was achieved using natural environmental conditions, demonstrating the feasibility of outdoor culture as an alternative method of bioenergy production from marine microalgae. The growth stage was identified as the principal source of energy consumption for all microalgae tested, due to the electricity requirements of the equipment, followed by the construction material of the bcPBR. The global warming category (GWP) was 6 times lower in outdoor than in indoor conditions. Although the energy balance was negative under both conditions, this study concludes with suggestions for improvements in the outdoor system that would allow upscaling of this biomass production technology for outdoor conditions in the Mediterranean

Carvacrol, thymol, and garlic essential oil promote skin innate immunity in gilthead seabream (Sparus aurata) through the multifactorial modulation of the secretory pathway and enhancement of mucus protective capacity

One of the main targets for the use of phytogenics in aquafeeds is the mucosal tissues as they constitute a physical and biochemical shield against environmental and pathogenic threats, comprising elements from both the innate and acquired immunity. In the present study, the modulation of the skin transcriptional immune response, the bacterial growth capacity in skin mucus, and the overall health condition of gilthead seabream (Sparus aurata) juveniles fed a dietary supplementation of garlic essential oil, carvacrol, and thymol were assessed. The enrichment analysis of the skin transcriptional profile of fish fed the phytogenic-supplemented diet revealed the regulation of genes associated to cellular components involved in the secretory pathway, suggesting the stimulation, and recruitment of phagocytic cells. Genes recognized by their involvement in non-specific immune response were also identified in the analysis. The promotion of the secretion of non-specific immune molecules into the skin mucus was proposed to be involved in the in vitro decreased growth capacity of pathogenic bacteria in the mucus of fish fed the phytogenic-supplemented diet. Although the mucus antioxidant capacity was not affected by the phytogenics supplementation, the regulation of genes coding for oxidative stress enzymes suggested the reduction of the skin oxidative stress. Additionally, the decreased levels of cortisol in mucus indicated a reduction in the fish allostatic load due to the properties of the tested additive. Altogether, the dietary garlic, carvacrol, and thymol appear to promote the gilthead seabream skin innate immunity and the mucus protective capacity, decreasing its susceptibility to be colonized by pathogenic bacteria

Porcine Protein Hydrolysates (PEPTEIVA®) Promote Growth and Enhance Systemic Immunity in Gilthead Sea Bream (Sparus aurata)

The effects of porcine plasma protein hydrolysate (PPH) on growth, feed efficiency, and immune responses was evaluated in Sparus aurata. Fish were fed two isoproteic (48% protein), isolipidic (17% fat), and isoenergetic diets (21.7 MJ/kg) diets, one of them containing 5% PPH at the expense of fishmeal. Both diets were tested for 92 days. A significant increase in growth was observed in fish fed the PPH diet in comparison to the control group (182.2 ± 4.4 vs. 173.8 ± 4.1 g), as well as an increase in feed intake without worsening FCR values. An ex vivo assay, with splenocytes incubated with lipopolysaccharide, was conducted to evaluate the cellular immune competence of fish. Genes involved in humoral immunity (lys, IgM), pro- (tnf-α, il-1β), and anti-inflammatory (tgf-β1, il10) cytokines were upregulated in the PPH group in comparison to the control group. The inclusion of PPH in diets enhanced the antibacterial capacity of skin mucus, as the co-culture of selected bacteria (E. coli, V. anguillarum, and P. anguilliseptica) with skin mucus indicated. The present results showed that the PPH in low fishmeal diets (2%) promoted growth and feed efficiency, as well as enhancing the immune response, which indicates that this is a safe and functional ingredient for aquafeeds.info:eu-repo/semantics/publishedVersio

Dietary Debaryomyces hansenii promotes skin and skin mucus defensive capacities in a marine fish model

The present study explores the effects of two supplementation levels of Debaryomyces hansenii (1.1% and 2.2%) as a probiotic in a reference low fish meal-based diet on the skin mucosal tissue in Sparus aurata. This study includes the evaluation of fish performance coupled with a holistic study of the skin mucosa: i) a transcriptomic study of the skin tissue, and ii) the evaluation of its secreted mucus both in terms of skin mucosal-associated biomarkers and its defensive capacity by means of co-culture analysis with two pathogenic bacteria. Results showed that after 70 days of diet administration, fish fed the diet supplemented with D. hansenii at 1.1% presented increased somatic growth and a better feed conversion ratio, compared to fish fed the control diet. In contrast, fish fed the diet including 2.2% of the probiotic presented intermediate values. Regarding gene regulation, the probiotic administration at 1.1% resulted in 712 differentially expressed genes (DEGs), among which 53.4% and 46.6% were up- and down-regulated, respectively. In particular, D. hansenii modulated some skin biological processes related to immunity and metabolism. Specifically, D. hansenii administration induced a strong modulation of some immune biological-related processes (61 DEGs), mainly involved in B- and T-cell regulatory pathways. Furthermore, dietary D. hansenii promoted the skin barrier function by the upregulation of anchoring junction genes (23 DEGs), which reinforces the physical defense against potential skin damage. In contrast, the skin showed modulated genes related to extracellular exosome and membrane organization (50 DEGs). This modulated functioning is of great interest, particularly in relation to the increased skin mucus defensive capacity observed in the bacterial co-culture in vitro trials, which could be related to the increased modulation and exudation of the innate immune components from the skin cells into the mucus. In summary, the modulation of innate immune parameters coupled with increased skin barrier function and cell trafficking potentiates the skin's physical barrier and mucus defensive capacity, while maintaining the skin mucosa's homeostatic immune and metabolic status. These findings confirmed the advantages of D. hansenii supplementation in low fish meal-based diets, demonstrating the probiotic benefits on cultured marine species

Porcine Protein Hydrolysates (PEPTEIVA ) Promote Growth and Enhance Systemic Immunity in Gilthead Sea Bream (Sparus aurata)

The effects of porcine plasma protein hydrolysate (PPH) on growth, feed efficiency, and immune responses was evaluated in Sparus aurata. Fish were fed two isoproteic (48% protein), isolipidic (17% fat), and isoenergetic diets (21.7 MJ/kg) diets, one of them containing 5% PPH at the expense of fishmeal. Both diets were tested for 92 days. A significant increase in growth was observed in fish fed the PPH diet in comparison to the control group (182.2 ± 4.4 vs. 173.8 ± 4.1 g), as well as an increase in feed intake without worsening FCR values. An ex vivo assay, with splenocytes incubated with lipopolysaccharide, was conducted to evaluate the cellular immune competence of fish. Genes involved in humoral immunity (lys, IgM), pro- (tnf-α, il-1β), and anti-inflammatory (tgf-β1, il10) cytokines were upregulated in the PPH group in comparison to the control group. The inclusion of PPH in diets enhanced the antibacterial capacity of skin mucus, as the co-culture of selected bacteria (E. coli, V. anguillarum, and P. anguilliseptica) with skin mucus indicated. The present results showed that the PPH in low fishmeal diets (2%) promoted growth and feed efficiency, as well as enhancing the immune response, which indicates that this is a safe and functional ingredient for aquafeeds