Disentangling the determinants of symbiotic species richness in native and invasive gammarids (Crustacea, Amphipoda) of the Baltic region

Dispersal of alien species is a global problem threatening native biodiversity. Co-introduction of nonnative parasites and pathogens adds to the severity of this threat, but this indirect impact has received less attention. To shed light on the key factors determining the richness of microorganisms in native and invasive host species, we compared symbiotic (parasitic and epibiotic) communities of gammarids across different habitats and localities along the Baltic coast of Poland. Seven gammarid species, two native and five invasive, were sampled from 16 freshwater and brackish localities. Sixty symbiotic species of microorganisms of nine phyla were identified. This taxonomically diverse species assemblage of symbionts allowed us to assess the effect of host translocation and regional ecological determinants driving assembly richness in the gammarid hosts. Our results revealed that (i) the current assemblages of symbionts of gammarid hosts in the Baltic region are formed by native and co-introduced species; (ii) species richness of the symbiotic community was higher in the native Gammarus pulex than in the invasive hosts, probably reflecting a process of species loss by invasive gammarids in the new area and the distinct habitat conditions occupied by G. pulex and invasive hosts; (iii) both host species and locality were key drivers shaping assembly composition of symbionts, whereas habitat condition (freshwater versus brackish) was a stronger determinant of communities than geographic distance; (iv) the dispersion patterns of the individual species richness of symbiotic communities were best described by Poisson distributions; in the case of an invasive host, the dispersion of the rich species diversity may switch to a right-skewed negative binomial distribution, suggesting a host-mediated regulation process. We believe this is the first analysis of the symbiotic species richness in native and invasive gammarid hosts in European waters based on original field data and a broad range of taxonomic groups including Microsporidia, Choanozoa, Ciliophora, Apicomplexa, Platyhelminthes, Nematoda, Nematomorha, Acanthocephala and Rotifera, to document the patterns of species composition and distributio

Effect of cascade overlap and C15 clusters on the damage evolution in Fe : An OKMC study

In order to investigate the long-term evolution of radiation-induced defects in the fission- and fusion-relevant material iron, we introduce cascade overlap effects into Object Kinetic Monte Carlo simulations. In addition to cascade overlap, we study the effect of introducing discrete C15 Laves phase clusters into the simulations. By applying either, none, or both of these effects we identify how they influence the evolution of the system. We find that both cascade overlap and C15 clusters affect the evolution of the radiation damage in different ways and on different time scales. Cascade overlap is found to reduce the number of Frenkel pairs. On the other hand, the explicit consideration of C15 Laves phase clusters increases the accumulation of defects at low dose. The results are compared to Molecular Dynamics simulation results under similar conditions.Peer reviewe

Kudoa unicapsula n. sp. (Myxosporea: Kudoidae) a parasite of the Mediterranean mullets Liza ramada and L. aurata (Teleostei: Mugilidae)

A new multivalvulid myxozoan parasite, Kudoa unicapsula n. sp., is described from the intestinal mesentery, intestine and pyloric caeca of the thin-lipped grey mullet Liza ramada (Risso 1826) and the golden grey mullet L. aurata (Risso, 1810) from the Mediterranean coastal waters of Spain. It is characterized by the presence of elongated, rice corn-like white cysts of 0.47–0.56×0.18–0.38 mm, filled with tetracapsulate, slightly asymmetric spores, rectangular in apical view and tear-shaped in lateral view with four polar capsules of considerably different size and slightly unequal spore valves with rounded edges, overlapping each other on the apex of the spore. One large polar capsule includes a polar filament coiled in two to three turns, and the other three polar capsules, which are very small, posses only a rudimental filament. Both light and electron microscopy data showed that this species differs from all previously described Kudoa spp. with unequal polar capsules. The molecular analysis based on 18S and 28S ribosomal deoxyribonucleic acid DNA sequence data of K. unicapsula n. sp. indicates a close relationship and thus phylogenetic clustering together with K. trifolia, a myxozoan from the same host and the same geographical location

Field evaluation of rigid and flexible scarifier shanks

Se llevaron a cabo ensayos en campo con el objeto de evaluar parámetros de prestación de arcos de escarificador rígidos y flexibles. Se empleó un tractor de diseño convencional de 73 kW de potencia y un bastidor de tracción libre, registrándose los esfuerzos traccionales mediante una celda de carga interpuesta entre ambos, determinándose el área removida mediante un perfilómetro y obteniéndose los valores de resistencia específica. Los arcos rígidos produjeron un frente de labor significativamente mayor que los arcos flexibles. Los arcos rígidos son energéticamente más eficientes que los arcos flexiblesField tests were carried out with the aim to evaluate both rigid and flexible scarifier shanks performance parameters. A 2WD, 73 kW tractor and a pull type implement were used. The draft force was measured with a force transducer with strain gauges. The loosening area was recorded through a profilometer and, from this data, the specific resistance was calculated. The rigid shanks produced a significantly greather working area than the flexible shanks. The rigid shanks shows higher efficiency than the flexible shanksFacultad de Ciencias Agrarias y Forestale

On the complexity of computing the kk-restricted edge-connectivity of a graph

The \emph{$k$-restricted edge-connectivity} of a graph $G$, denoted by $\lambda_k(G)$, is defined as the minimum size of an edge set whose removal leaves exactly two connected components each containing at least $k$ vertices. This graph invariant, which can be seen as a generalization of a minimum edge-cut, has been extensively studied from a combinatorial point of view. However, very little is known about the complexity of computing $\lambda_k(G)$. Very recently, in the parameterized complexity community the notion of \emph{good edge separation} of a graph has been defined, which happens to be essentially the same as the $k$-restricted edge-connectivity. Motivated by the relevance of this invariant from both combinatorial and algorithmic points of view, in this article we initiate a systematic study of its computational complexity, with special emphasis on its parameterized complexity for several choices of the parameters. We provide a number of NP-hardness and W[1]-hardness results, as well as FPT-algorithms.Comment: 16 pages, 4 figure

Field evaluation of rigid and flexible scarifier shanks

Se llevaron a cabo ensayos en campo con el objeto de evaluar parámetros de prestación de arcos de escarificador rígidos y flexibles. Se empleó un tractor de diseño convencional de 73 kW de potencia y un bastidor de tracción libre, registrándose los esfuerzos traccionales mediante una celda de carga interpuesta entre ambos, determinándose el área removida mediante un perfilómetro y obteniéndose los valores de resistencia específica. Los arcos rígidos produjeron un frente de labor significativamente mayor que los arcos flexibles. Los arcos rígidos son energéticamente más eficientes que los arcos flexiblesField tests were carried out with the aim to evaluate both rigid and flexible scarifier shanks performance parameters. A 2WD, 73 kW tractor and a pull type implement were used. The draft force was measured with a force transducer with strain gauges. The loosening area was recorded through a profilometer and, from this data, the specific resistance was calculated. The rigid shanks produced a significantly greather working area than the flexible shanks. The rigid shanks shows higher efficiency than the flexible shanksFacultad de Ciencias Agrarias y Forestale

Magnetic characterization of Fe, Ni, Co nanoparticles dispersed in phyllosilicate type silicon oxide

International audienceWe present the magnetic properties of silica-supported metal (Fe,catalyst) nanoparticles synthesized by precipitation of metal nitrate in ammonia-based medium. Our goal is the study of possible metal-support interactions in the nanoporous catalyst. The temperature dependence of the magnetization for all samples display spin-glass like behavior below c.a. 11-12 K, with clear Curie-Weiss dependence in the high-temperature regime. Spin-glass-like behavior was inferred from dynamic AC susceptibility data after analyzing the frequency-dependence of the in-phase component χ'(f) by the expression W = ΔTf/[Tf Δlog(f)] = 3.0 × 10−3. We found that the magnetic behavior of the catalyst is drastically affected by the existence of interactions between the metal and the support

Bloom’s taxonomy and the application of knowledge: problem-based learning in the subject ‘Zoology’ at the University of Valencia

De acuerdo con la taxonomía de Bloom, en el contexto de la enseñanza los procesos cognitivos se encuentran jerarquizados en seis niveles de complejidad creciente e inclusiva. Así, una materia puede perseguir que los studiantes (1) memoricen información, (2) la comprendan, (3) la apliquen para resolver problemas nuevos, (4) la analicen, (5) la evalúen o (6) incluso creen nuevo conocimiento a partir de ella. Tradicionalmente, en las universidades españolas la asignatura de Zoología ha promovido primordialmente la memorización y la comprensión. Sin embargo, parece hoy recomendable trabajar también procesos cognitivos superiores, haciendo hincapié en la aplicación del conocimiento zoológico. Esto proporciona herramientas a los estudiantes para abordar una gran variedad de preguntas, ayudando a forjar un estilo de pensamiento; permite adaptar los contenidos a una menor presencialidad, generando autonomía en la forma de trabajar, y desplaza el énfasis epistemológico desde una ciencia de sujetos hacia una ciencia de principios. En este trabajo presentamos un diseño realista de clases de problemas de zoología para grupos numerosos, tal y como se plantea en la Universidad de Valencia. El elemento clave de nuestra iniciativa es una selección muy cuidadosa de los problemas: no se trata de memorizar o comprender debates clásicos o recientes en zoología, ni de meros ejercicios de corroboración. Los problemas de aplicación que planteamos obligan al estudiante a buscar relaciones o consecuencias no inmediatas de los conocimientos que van adquiriendo sobre filogenia, diversidad, planes corporales, morfología funcional y estrategias vitales; intentamos además que incluyan filos que no se tratan en el temario. En este trabajo ilustramos diversos problemas tipo y describimos qué temporalización, carga docente y metodología pueden resultar más adecuadas dentro de un programa “clásico” de Zoología. El criterio fundamental de evaluación es que las respuestas sean plausibles, aunque no necesariamente correctas.According to Bloom’s taxonomy, the cognitive processes that are involved in any learning context can be organized into six inclusive levels of increasing complexity. The aim(s) of any academic subject can be (1) to memorize information, (2) to understand it, (3) to apply it to solve new problems, (4) to analyze it, (5) to evaluate it, and even (6) to create new knowledge based on it. Traditionally, in Spanish universities the subject ‘Zoology’ has primarily addressed memorization and understanding. However, it would seem advisable to also deal with upper cognitive processes, particularly the application of knowledge. This would allow students to tackle a great diversity of zoology questions, help creating a thinking style, and to reduce the number of lectures since students could deal with several contents by themselves. Also, the application of knowledge would shift emphasis from subjects (animals) to principles. In this presentation we describe a realistic design for problem-based lectures on zoology that are devised for large classes at the University of Valencia. The key element for a successful implementation is a careful selection of problems. Applying knowledge has nothing to do with memorizing / understanding classical or current zoological debates, or with making corroborative exercises. A genuine problem invites students to seek relationships and non-trivial consequences of the knowledge they acquire about phylogeny, diversity, body plans, functional morphology, and life history strategies, particularly when they are applied to animal phyla that are not included in the subject programme. In this presentation we include type problems and describe the schedule, teaching load and methodology that could best fit within a “classical” Zoology programme. The fundamental criterion to evaluate problems is that answers are plausible, though not necessarily correc

Crop residue grazing and tillage systems effects on soil physical properties and corn (Zea Mays L.) performance

Crop-livestock systems under no till (NT) could negatively affect soil physical properties and crop performance, due to the additive effects of reduced soil cover and cattle trampling due to livestock grazing, and the absence of tillage. We evaluated the effects of four grazing strategies and of a shallow tillage (ST) on soil physical properties and corn (Zea mays L.) performance for a mollisol after 15 years under crop-livestock systems under NT in Argentina. Grazing strategies evaluated were: closure (C), one grazing (OG), high stocking rate (HR) and farmer's management (FM), and the tillage systems were: NT and ST. Bulk density (BD), penetration resistance (PR), hydraulic conductivity (ks), plant population, surface root distribution, aboveground dry matter accumulation, aboveground total N (TN) accumulation and corn yield were evaluated. High stocking rate and FM increased RP. On the other hand, ST decreased PR and BD and increased ks. Corn yield was higher under ST than under NT, and under HR than under the other grazing strategies. Total N accumulation was higher under HR than under the rest of grazing strategies. Rational grazing management and use of tillage systems on resilient soils could have prevented soil physical properties be affected beyond critical thresholds.Facultad de Ciencias Agrarias y Forestale