Spider crab Hyas araneus larval dry weight, C/N ratio and developmental time during experiments from different latitudes (54° vs 79°N), 2010

The combined impacts of future scenarios of ocean acidification and global warming on the larvae of a cold-eurythermal spider crab, Hyas araneus L., were investigated in one of its southernmost populations (living around Helgoland, southern North Sea, 54°N) and one of the northernmost populations (Svalbard, North Atlantic, 79°N). Larvae were exposed at temperatures of 3, 9 and 15°C to present day normocapnia (380 ppm CO2) and to CO2 conditions expected for the near or medium-term future (710 ppm by 2100 and 3000 ppm CO2 by 2300 and beyond). Larval development time and biochemical composition were studied in the larval stages Zoea I, II, and Megalopa. Permanent differences in instar duration between both populations were detected in all stages, likely as a result of evolutionary temperature adaptation. With the exception of Zoea II at 3°C and under all CO2 conditions, development in all instars from Svalbard was delayed compared to those from Helgoland, under all conditions. Most prominently, development was much longer and fewer specimens morphosed to the first crab instar in the Megalopa from Svalbard than from Helgoland. Enhanced CO2 levels (710 and particularly 3000 ppm), caused extended duration of larval development and reduced larval growth (measured as dry mass) and fitness (decreasing C/N ratio, a proxy of the lipid content). Such effects were strongest in the zoeal stages in Svalbard larvae, and during the Megalopa instar in Helgoland larvae.

Effects of pre-hatching pCO2 on development and survival of zoea stages of Arctic spider crab Hyas araneus

Sensitivity of marine crustaceans to anthropogenic CO2 emissions and the associated acidification of the oceans may be less than that of other, especially lower, invertebrates. However, effects on critical transition phases or carry-over effects between life stages have not comprehensively been explored. Here we report the impact of elevated seawater PCO2 values (3100 µatm) on Hyas araneus during the last 2 weeks of their embryonic development (pre-hatching phase) and during development while in the consecutive zoea I and zoea II larval stages (post-hatching phase). We measured oxygen consumption, dry weight, developmental time and mortality in zoea I to assess changes in performance. Feeding rates and survival under starvation were investigated at different temperatures to detect differences in thermal sensitivities of zoea I and zoea II larvae depending on pre-hatch history. When embryos were pre-exposed to elevated PCO2 during maternal care, mortality increased about 60% under continued CO2 exposure during the zoea I phase. The larvae that moulted into zoea II, displayed a developmental delay by about 20 days compared to larvae exposed to control PCO2 during embryonic and zoeal phases. Elevated PCO2 caused a reduction in zoea I dry weight and feeding rates, while survival of the starved larvae was not affected by the seawater CO2 concentration. In conclusion, CO2 effects on egg masses under maternal care carried over to the first larval stages of crustaceans and reduced their survival and development to levels below those previously reported in studies exclusively focussing on acute PCO2 effects on the larval stages.

Understanding long-term hunting statistics: the case of Spain (1972-2007)

Hunting is assuming a growing role in the current European forestry and agroforestry landscape. However, consistent statistical sources that provide quantitative information for policy-making, planning and management of game resources are often lacking. In addition, in many instances statistical information can be used without sufficient evaluation or criticism. Recently, the European Commission has declared the importance of high quality hunting statistics and the need to set up a common scheme in Europe for their collection, interpretation and proper use. This work aims to contribute to this current debate on hunting statistics in Europe by exploring data from the last 35 years of Spanish hunting statistics. The analysis focuses on the three major pillars underpinning hunting activity: hunters, hunting grounds and game animals. First, the study aims to provide a better understanding of official hunting statistics for use by researchers, game managers and other potential users. Second, the study highlights the major strengths and weaknesses of the statistical information that was collected. The results of the analysis indicate that official hunting statistics can be incomplete, dispersed and not always homogeneous over a long period of time. This is an issue of which one should be aware when using official hunting data for scientific or technical work. To improve statistical deficiencies associated with hunting data in Spain, our main suggestion is the adoption of a common protocol on data collection to which different regions agree. This protocol should be in accordance with future European hunting statistics and based on robust and well-informed data collection methods. Also it should expand the range of biological, ecological and economic concepts currently included to take account of the profound transformations experienced by the hunting sector in recent years. As much as possible, any future changes in the selection of hunting statistics should allow for comparisons between new variables with the previous ones.

Sequential origin in the high performance properties of spider dragline silk

Major ampullate (MA) dragline silk supports spider orb webs, combining strength and extensibility in the toughest biomaterial. MA silk evolved ~376 MYA and identifying how evolutionary changes in proteins influenced silk mechanics is crucial for biomimetics, but is hindered by high spinning plasticity. We use supercontraction to remove that variation and characterize MA silk across the spider phylogeny. We show that mechanical performance is conserved within, but divergent among, major lineages, evolving in correlation with discrete changes in proteins. Early MA silk tensile strength improved rapidly with the origin of GGX amino acid motifs and increased repetitiveness. Tensile strength then maximized in basal entelegyne spiders, ~230 MYA. Toughness subsequently improved through increased extensibility within orb spiders, coupled with the origin of a novel protein (MaSp2). Key changes in MA silk proteins therefore correlate with the sequential evolution high performance orb spider silk and could aid design of biomimetic fibers.

The variability and interdependence of spider viscid line tensile properties

True stress-true strain curves of naturally spun viscid line fibers retrieved directly from the spiral of orb-webs built by Argiope trifasciata spiders were measured using a novel methodology. This new procedure combines a method for removing the aqueous coating of the fibers and a technique that allows the accurate measurement of their cross sectional area. Comparison of the tensile behaviour of different samples indicates that naturally spun viscid lines show a large variability, comparable to that of other silks, such as major ampullate gland silk and silkworm silk. Nevertheless, application of a statistical analysis allowed identifying two independent parameters that underlie the variability and characterize the observed range of true stress-true strain curves. Combination of this result with previous mechanical and microstructural data suggested the assignment of these two independent effects to the degree of alignment of the protein chains and to the local relative humidity which, in turn, depends on the composition of the viscous coating and on the external environmental conditions.

Estudio de validez del WAsP frente al WindSim en colinas Gaussinas

Este proyecto se basa en la comparación de un modelo de flujo lineal frente a un modelo de ecuaciones completas. Con esta motivación se empleará un programa de cada tipo. Los elegidos son el WAsP y el WindSim respectivamente. Tras una breve descripción de cada programa, estudiaremos los distintos elementos que los componen y su estructura. Entre todas las posibilidades que presentan ambos programas, el proyecto se centrará en la estimación del recurso eólico. En teoría, el programa que emplea un modelo lineal no será apto en terrenos complejos, por ello se tratará de estimar el error cometido por el modelo lineal tomando como referencia el modelo de ecuaciones completas. Con el objetivo de comparar ambos programas y poder distinguir sus diferencias, se plantea un caso común, en el cual se evaluarán distintas condiciones meteorológicas para colinas de forma gaussiana y distinta pendiente. Con ello se pretende medir la evolución de la precisión del WAsP conforme el terreno se va haciendo más complejo. Otras variables a tener en cuenta serán la variación de la velocidad del viento y la altura del punto de cálculo. Finalmente se analizan y explican los resultados obtenidos acompañados de elementos visuales proporcionados por los programas. 2. Abstract The main objective of this project is the comparison of two models, one based on the lineal flux and the other based on the complete equations. Thanks to two different computer programmes, WAsP and WindSim, the first one using a linear model and the second one using a complete equation model, we will be able to highlight the main differences between both models. Furthermore, a description of the structure and elements of each program will be outlined. This project will focus on the estimation of the wind resource. In theory, the program which uses a linear model will not be useful in complex terrains. Therefore, we will try to estimate the fault of the lineal model comparing it to the complete equation model. In order to be able to distinguish the differences between both programmes, the same exercise will be proposed to be solved by both of them. Here a range of meteorological conditions will be evaluated over a Gaussian hill with a slope that varies. Thereby, we will be able to measure the evolution of the precision of WAsP according to the increase of the slope. Finally, the results are analysed and explained with help of some visual characters.

Estudio y análisis para la elaboración de un modelo de certificado de calidad cinegética en España = Study and analysis for the development of a model of hunting quality certificate in Spain

Con esta tesis doctoral se pretende elaborar un modelo de Certificado de Calidad Cinegética independiente, de adhesión voluntaria y aplicable a todo tipo de espacios cinegéticos, de forma que posteriormente pueda convertirse en una metodología que sea empleada como instrumento válido de medición de la Calidad Cinegética y normalizada a través de una familia de Normas aprobadas por un organismo de normalización reconocido a nivel nacional o internacional. En primer lugar, se procedió a la realización de un riguroso y exhaustivo estudio de justificación siguiendo la metodología propuesta por la Norma UNE 66172:2003 IN, Directrices para la justificación y desarrollo de sistemas de gestión (equivalente a la Norma Internacional GUIA ISO/IEC 72:2001). A continuación, se procedió a la identificación y desarrollo de los parámetros de Ordenación Cinegética comunes a cualquier espacio cinegético en España y a la conceptualización de la Calidad Cinegética. Finalmente, se desarrolló un modelo estructurado en nueve Criterios y treinta y cuatro Indicadores de Calidad Cinegética, y un proyecto de familia de Normas para la Certificación de la Calidad Cinegética. ABSTRACT This doctoral thesis aims to produce a model of Hunting Quality Certificate independent, of voluntary adherence and applicable to all types of hunting areas, so that later it can become a methodology to be used as a valid instrument for measuring Hunting Quality and standardized through a family of standards approved by an organization of standardization recognized at a national or an international level. First, we proceeded to carry out a rigorous and comprehensive justification study following the methodology proposed by the UNE 66172: 2003 IN, Guidelines for the justification and development of management systems standards (equivalent to the International Standard GUIA ISO / IEC 72: 2001). Then, we proceeded to the identification and development of Hunting Management parameters common to any hunting area in Spain and the conceptualization of Hunting Quality. Finally, a model structured into nine Criteria and thirty-four Indicators of Hunting Quality and a draft of a family of standards for Hunting Quality Certification were developed.

Scar, a WASp-related protein, activates nucleation of actin filaments by the Arp2/3 complex

The Arp2/3 complex, a stable assembly of two actin-related proteins (Arp2 and Arp3) with five other subunits, caps the pointed end of actin filaments and nucleates actin polymerization with low efficiency. WASp and Scar are two similar proteins that bind the p21 subunit of the Arp2/3 complex, but their effect on the nucleation activity of the complex was not known. We report that full-length, recombinant human Scar protein, as well as N-terminally truncated Scar proteins, enhance nucleation by the Arp2/3 complex. By themselves, these proteins either have no effect or inhibit actin polymerization. The actin monomer-binding W domain and the p21-binding A domain from the C terminus of Scar are both required to activate Arp2/3 complex. A proline-rich domain in the middle of Scar enhances the activity of the W and A domains. Preincubating Scar and Arp2/3 complex with actin filaments overcomes the initial lag in polymerization, suggesting that efficient nucleation by the Arp2/3 complex requires assembly on the side of a preexisting filament—a dendritic nucleation mechanism. The Arp2/3 complex with full-length Scar, Scar containing P, W, and A domains, or Scar containing W and A domains overcomes inhibition of nucleation by the actin monomer-binding protein profilin, giving active nucleation over a low background of spontaneous nucleation. These results show that Scar and, likely, related proteins, such as the Cdc42 targets WASp and N-WASp, are endogenous activators of actin polymerization by the Arp2/3 complex.

A conserved mode of head segmentation in arthropods revealed by the expression pattern of Hox genes in a spider

Chelicerates constitute a basic arthropod group with fossil representatives from as early as the Cambrian period. Embryonic development and the subdivision of the segmented body region into a prosoma and an opisthosoma are very similar in all extant chelicerates. The mode of head segmentation, however, has long been controversial. Although all other arthropod groups show a subdivision of the head region into six segments, the chelicerates are thought to have the first antennal segment missing. To examine this problem on a molecular level, we have compared the expression pattern of Hox genes in the spider Cupiennius salei with the pattern known from insects. Surprisingly, we find that the anterior expression borders of the Hox genes are in the same register and the same relative segmental position as in Drosophila. This contradicts the view that the homologue of the first antennal segment is absent in the spider. Instead, our data suggest that the cheliceral segment is homologous to the first antennal segment and the pedipalpal segment is homologous to the second antennal (or intercalary) segment in arthropods. Our finding implies that chelicerates, myriapods, crustaceans, and insects share a single mode of head segmentation, reinforcing the argument for a monophyletic origin of the arthropods.

Removing symbiotic Wolbachia bacteria specifically inhibits oogenesis in a parasitic wasp

Wolbachia are bacteria that live in the cells of various invertebrate species to which they cause a wide range of effects on physiology and reproduction. We investigated the effect of Wolbachia infection in the parasitic wasp, Asobara tabida Nees (Hymenoptera, Braconidae). In the 13 populations tested, all individuals proved to be infected by Wolbachia. The removal of Wolbachia by antibiotic treatment had a totally unexpected effect—aposymbiotic female wasps were completely incapable of producing mature oocytes and therefore could not reproduce. In contrast, oogenesis was not affected in treated Asobara citri, a closely related species that does not harbor Wolbachia. No difference between natural symbiotic and cured individuals was found for other adult traits including male fertility, locomotor activity, and size, indicating that the effect on oogenesis is highly specific. We argue that indirect effects of the treatments used in our study (antibiotic toxicity or production of toxic agents) are very unlikely to explain the sterility of females, and we present results showing a direct relationship between oocyte production and Wolbachia density in females. We conclude that Wolbachia is necessary for oogenesis in these A. tabida strains, and this association would seem to be the first example of a transition from facultative to obligatory symbiosis in arthropod–Wolbachia associations.

Extraordinarily high spider densities on islands: flow of energy from the marine to terrestrial food webs and the absence of predation.

Some islands in the Gulf of California support very high densities of spiders. Spider density is negatively correlated with island size; many small islands support 50-200 spiders per m3 of cactus. Energy for these spiders comes primarily from the ocean and not from in situ productivity by land plants. We explicitly connect the marine and terrestrial systems to show that insular food webs represent one endpoint of the marine web. We describe two conduits for marine energy entering these islands: shore drift and seabird colonies. Both conduits are related to island area, having a much stronger effect on smaller islands. This asymmetric effect helps to explain the exceptionally high spider densities on small islands. Although productivity sets the maximal potential densities, predation (by scorpions) limits realized spider abundance. Thus, prey availability and predation act in concert to set insular spider abundance.