Modelling growth of Ruppia cirrhosa

The main objectives of this work were to synthesise information on the autoecology of Ruppia cirrhosa Petagna (Grande) in a mathematical model and to use the model to simulate its growth, production and harvest. Model parameters were allowed to vary as a result of acclimation, following experimental data reported in the literature. Biomass data from Santo André lagoon (SW Portugal) were used to calibrate the model. Validation was carried out with independent data sets from Santo André lagoon and from Tancada lagoon (NE Spain). Model simulations show a reasonable agreement with observed data with a similar biomass temporal dynamics and peaks. Self-shading appears to be an important self-regulating mechanism of biomass growth and production. The results obtained predict an annual net primary production of 361 gDWm−2well within the estimates based on harvesting techniques (295–589 gDWm−2). Model results suggest that controlled harvesting of macrophyte biomass may be carried out without affecting macrophyte real net production, through the reduction of light limitation under the plant canopy. © 2000 Elsevier Science B.V. All rights reserved

A new species of Calma Alder & Hancock, 1855 (Gastropoda: Nudibranchia) with a review of the genus

This paper presents the description of a new species of the genus Calma (Alder & Hancock, 1855). To date only one valid species, Calma glaucoides (Alder & Hancock, 1854), has been assigned to this genus, which feeds exclusively upon eggs of littoral teleost fishes. New morphological and ecological data, and review of the literature on the species attributed to this genus, lead us to conclude that there are two distinct species previously put together under the same specific name. Calma gobioophaga new species is described based upon consistent morphological differences, such as the diameter and position of the eyes, the size of the propodial tentacles, and the size of the metanefridium. Whereas Calma gobioophaga feeds on spawn of Gobius niger, Calma glaucoides feeds on eggs of Lepadogaster lepadogaster, Lepadogaster purpurea, Lepadogaster candollei, Parablennius gattorugine, and Parablennius pilicornis.Fundação para a Ciência e a Tecnologia - FCTinfo:eu-repo/semantics/publishedVersio

Does a shell matter for defence? Chemical deterrence in two cephalaspidean gastropodes with calcified shells

Opisthobranch molluscs show an evolutionary trend to reduce, internalize and lose the shell. Many of them base their defensive strategies on natural deterrent products and current evolutionary theory suggests that the acquisition of chemical defences preceded shell reduction and loss, which has characterized the evolution of this group. Here we show that basal, shelled opisthobranch molluscs are defended against sympatric predators even if their protective shell is removed. The cephalaspideans Bulla striata and Haminoea orbignyana, both with distinct shell calcification, significantly deterred feeding by sympatric crab and fish predators, both in laboratory and field assays. However, our results argue against a progressive increment of chemical defences associated with shell reduction, because the cephalaspidean with the more fully calcified shell, Bulla striata, was also the more deterrent. These findings suggest that effective chemical defences might have evolved independently from shell loss, at least in basal opisthobranchs such as cephalaspideans

O FMI e os memorandos Português e Irlandês no contexto da crise económica de 2008

A crise europeia das dívidas soberanas que assolou a Europa a partir de 2008 teve impactos profundos na economia mundial. A pertença de países como Portugal e Irlanda a uma zona monetária, a Zona Euro, teve implicações na natureza dos programas de resgate da Troika, criando a necessidade de implementar medidas alternativas à desvalorização cambial, um dos métodos-chave das intervenções anteriores do FMI. Nesta dissertação analisaremos os Memorandos de Entendimento produzidos pela Troika para Portugal e Irlanda, escrutinando as suas medidas e quais as teorias económicas nas quais elas se baseiam. Olharemos para os resultados macroeconómicos nos anos pós-Troika, comparando a implementação dos memorandos nos dois países, identificando quais as principais semelhanças e diferenças entre ambos. Este estudo permite concluir que o FMI implementou medidas de desvalorização interna nos países, através da contração dos custos do trabalho, de modo a simular os efeitos de uma desvalorização cambial, com o objetivo de aumentar a competitividade de preço e promover as exportações. Apesar dos memorandos serem bastante semelhantes relativamente às suas medidas fiscais, Portugal caracterizou-se pela implementação das medidas propostas pelo FMI no âmbito da desvalorização interna, ao passo que a Irlanda atribuiu maior centralidade a medidas fiscais com vista a incentivar o investimento externo. Estas medidas conjugadas com a menor taxa corporativa da União Europeia geraram um forte efeito positivo no investimento irlandês, capitalizando a economia, aumentando a sua competitividade e as suas exportações.The European crisis of the sovereign debts that devastated Europe from 2008 on had profound impacts in the global economy. The inclusion of countries like Portugal and Ireland in a monetary zone, the Eurozone, raised implications in the nature of Troika’s adjustment programs, creating the necessity of implementing alternative measures to currency devaluation, one of the key methods of the previous IMF interventions. In this dissertation we will analyze the Memorandums of Understanding designed by Troika for Portugal and Ireland, scrutinizing their measures and which economic theories they’re based off. We’ll look at the macroeconomic results in the years post-Troika, comparing the implementation of the memorandums in both countries, identifying the main similarities and differences between them. This study allows us to conclude that the IMF implemented internal devaluation measures in the countries, through the contraction of labor costs, in order to simulate the effects of a currency devaluation, in an effort to increase price competitivity and to promote exportations. Despite the memorandums being quite similar regarding their fiscal measures, Portugal characterized for the implementation of the measures proposed by the IMF in the scope of internal devaluation, while Ireland attributed more centrality to fiscal measures towards encouraging external investment. These measures conjugated with the lowest corporate tax of the European Union generated a strong positive effect on Irish investment, capitalizing the economy, increasing its competitivity and its exportations

Kleptoplast photoacclimation state modulates the photobehaviour of the solar-powered sea slug Elysia viridis.

Some sacoglossan sea slugs incorporate intracellular functional algal chloroplasts (kleptoplasty) for periods ranging from a few days to several months. Whether this association modulates the photobehaviour of solar-powered sea slugs is unknown. In this study, the long-term retention species Elysia viridis showed avoidance of dark independently of light acclimation state. On the contrary, Placida dendritica, which shows non-functional retention of kleptoplasts, showed no preference over dark, low or high light. High light acclimated (HLac) E. viridis showed a higher preference for high light than low light acclimated (LLac) conspecifics. The position of the lateral folds (parapodia) was modulated by irradiance, with increasing light levels leading to a closure of parapodia and protection of kleptoplasts from high light exposure. Furthermore, closure of parapodia occurred at higher irradiances in HLac E. viridis. Our results strongly indicate that kleptoplasts photoacclimation state modulates the photobehaviour of the solar-powered sea slug E. viridis

Functional Histology and Ultrastructure of the Digestive Tract in Two Species of Chitons (Mollusca, Polyplacophora)

. Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland.To continue the investigation on the digestive system of polyplacophoran molluscs, a histological and ultrastructural study of the oesophagus, stomach and intestine of Chaetopleura angulata and Acanthochitona fascicularis was carried out. Stomach content examination revealed an omnivorous diet. In both species the epithelium of the whole digestive tract consisted mostly of elongated absorptive cells with an apical border of microvilli. Cilia were also frequently present. Mitochondria and electron-dense lysosomes were the prominent organelles in the region above the nucleus. The basal region was characterised by an association of mitochondria, peroxisomes and lipid droplets. In general, glycogen deposits were also abundant in absorptive cells. The ultrastructural features indicate that the absorptive cells of the digestive tract epithelium are involved in endocytosis, intracellular digestion and storage of reserves. Histochemical techniques showed that the secretory cells of the digestive tract contained proteins and polysaccharides in their secretory vesicles. The secretory cells with vesicles of low electron density were classified as mucous cells, and the ones with electron-dense vesicles were designated basophilic cells due to their staining by basic dyes in light microscopy. Additionally, basal cells that seem to correspond to enteroendocrine cells containing oval electron-dense vesicles were found along the digestive tract epithelium of both species. The thin outer layer of the digestive tract wall consisted of muscle cells and nerves embedded in connective tissue.publishersversionpublishe

Analysis of coastal lagoon metabolism as a basis for management

This work was carried out in a shallow eutrophic coastal lagoon (St. André lagoon, SW Portugal) which is artificially opened to the sea each year in early spring. Macrophytes, mainly Ruppia cirrhosa, are keystone species in this ecosystem covering up to 60% of its total area with peak biomasses over 500 g DWm−2. The main objectives were to study ecosystem metabolism, to evaluate the metabolic contribution to the community of the macrophyte stands and their influence in the development of thermal stratification and bottom oxygen depletion. The work combined an experimental and a modelling methodology. The experimental approach included open water, mesocosm and microcosm seasonal experiments. During these experiments several physical, chemical and biological parameters were monitored in the lagoon and in plastic enclosures (mesocosms) for periods of 24 hours. The microcosm experiments followed the light-dark bottle technique. The simultaneous use of these different methodologies allowed the analysis of the contribution of the planktonic and benthic compartments to the ecosystem’s oxygen budget. The modelling work was based on the mathematical simulation of heat and gas exchanges in a vertically resolved water column, under different macrophyte densities. Several simulations were carried out, in order to investigate the importance of the macrophytes in the development of water column stratification and anoxia. The simulation results suggest that macrophytes may greatly influence thermocline and oxycline development. This influence is proportional to their biomass and canopy height. It is suggested that controlled macrophyte biomass removal of up to 25% of available biomass in summer, may be useful in preventing bottom anoxia without compromising benthic net primary production

Analysis of coastal lagoon metabolism as a basis for management

This work was carried out in a shallow eutrophic coastal lagoon (St. André lagoon, SW Portugal) which is artificially opened to the sea each year in early spring. Macrophytes, mainly Ruppia cirrhosa, are keystone species in this ecosystem covering up to 60% of its total area with peak biomasses over 500 g DWm−2. The main objectives were to study ecosystem metabolism, to evaluate the metabolic contribution to the community of the macrophyte stands and their influence in the development of thermal stratification and bottom oxygen depletion. The work combined an experimental and a modelling methodology. The experimental approach included open water, mesocosm and microcosm seasonal experiments. During these experiments several physical, chemical and biological parameters were monitored in the lagoon and in plastic enclosures (mesocosms) for periods of 24 hours. The microcosm experiments followed the light-dark bottle technique. The simultaneous use of these different methodologies allowed the analysis of the contribution of the planktonic and benthic compartments to the ecosystem’s oxygen budget. The modelling work was based on the mathematical simulation of heat and gas exchanges in a vertically resolved water column, under different macrophyte densities. Several simulations were carried out, in order to investigate the importance of the macrophytes in the development of water column stratification and anoxia. The simulation results suggest that macrophytes may greatly influence thermocline and oxycline development. This influence is proportional to their biomass and canopy height. It is suggested that controlled macrophyte biomass removal of up to 25% of available biomass in summer, may be useful in preventing bottom anoxia without compromising benthic net primary production