Intra-plant differences in seaweed nutritional quality and chemical defenses: Importance for the feeding behavior of the intertidal amphipod Orchestoidea tuberculata     

Cristian Duarte  Karin Acuña  Jorge M. Navarro  Iván Gómez 《Journal of Sea Research》2011,66(3):215-221

As a result of their morphological complexity, large macroalgae show intra-thallus variations in their nutritional composition and secondary metabolite content, which influences the trophic ecology of herbivorous invertebrates, and ultimately their fitness. In this study, we evaluated for the first time the variability in nutritional quality (protein content, carbohydrates, lipids, and total organic matter), secondary metabolites (phlorotannins), and structure (shape and toughness) between blades and stipes of the macroalgae Durvillaea Antarctica. Specifically, we looked at their effect on feeding preference, rate of consumption, absorption efficiency, and growth rate of the amphipod Orchestoidea tuberculata, one of the most abundant organisms on Chilean sandy beaches. Proteins, carbohydrates, total organic matter and phlorotannin contents were significantly higher in blades than in stipes. Preference experiments revealed that the amphipods preferred blades when fresh pieces of blades and stipes were offered at the same time. Similar results were found when artificial food (in which structures of both parts of the alga were standardized) was offered, suggesting that shape and toughness of the two different parts of the alga did not influence preference patterns of O. tuberculata. Absorption efficiency of O. tuberculata was higher on blades compared to stipes. When the amphipods were kept with each of the algal parts separately (i.e. no choice), they consumed a significantly higher amount of stipe, which suggests that O. tuberculata used food quantity to compensate for the lower nutritional quality of stipes. The higher nutritional values of blades compared to stipes appears to explain observed preference patterns by O. tuberculata. Phlorotannin content did not appear to inhibit blade consumption, suggesting that the nutritional quality of the food could be more important than chemical defense in determining food choice in O. tuberculata. Growth did not differ between the amphipods maintained with either blades or stipes (i.e. no choice), which is consistent with the hypothesis of compensatory feeding. To conclude, O. tuberculata can actively select specific parts of an alga and this selection appears to be based on nutritional quality. The capacity for using different feeding strategies allow O. tuberculata, in some cases, to successfully exploit food types with different nutritional qualities.  相似文献   

Growth forms,dispersal strategies and taxonomic spectrum in a semi-arid shrubland in SE Spain     

T. Navarro  V. Pascual  C.L. Alados  B. Cabezudo 《Journal of Arid Environments》2009,73(1):103-112

We have identified the dispersal strategies of major growth forms in a semi-arid Mediterranean shrubland of Cabo de Gata Natural Park (SE Spain), testing (1) whether dispersal strategies and antitelechoric mechanisms vary among growth forms and families, and (2) whether dispersal traits that identify dispersal strategies can be used to predict different ways of plant survival in response to seasonal changes in their habitat. In the survey, the data of 17 dispersal traits were collected of 140 species and analysed using cluster analysis and nonlinear principal components analysis. For shrubs and forbs, low diaspore release height, spheroidal diaspores with a low mass and small size and a low to high diaspore number were associated with restricted spatial dispersal. In contrast, medium to high release height, relatively large and heavy diaspores varying in shape and a high diaspore number were associated with developed spatial dispersal (telechory). Telechory is higher in shrubs than in forbs and grasses, where atelechory/antitelechory predominate. Dispersal was synchronized mainly with the drought period (July and August) and the beginning of the rainy season (October–December). 68% of shrubs and 61.6% of forbs were anemochores, whereas zoochory (6% of shrubs) and ballistic species (8% of shrubs and 6.9% of forbs) were less common. Ombrohydrochory was well represented among forbs (27.3%) but rare among shrubs (4%). The main antitelechoric mechanisms were: bradyspory (30.7%), myxospermy (15.7%) and trypanocarpy (29.4%, only for grasses). Species with restricted spatial dispersal and antitelechoric mechanisms are well adapted to survival in semi-arid climatic conditions, and should be taken into consideration in conservation planning.  相似文献   

Self-similar shocked accretion of collisional gas with radiative cooling     

Mario G. Abadi  Richard G. Bower  Julio F. Navarro 《Monthly notices of the Royal Astronomical Society》2000,314(4):759-767

We describe similarity solutions that characterize the collapse of collisional gas on to scale-free perturbations in an Einstein–de Sitter universe. We consider the effects of radiative cooling and derive self-similar solutions under the assumption that the cooling function is a power law of density and temperature, Λ( T , ρ )∝ ρ ^3/2 T . We use these results to test the ability of smooth particle hydrodynamics (SPH) techniques to follow the collapse and accretion of shocked, rapidly cooling gas in a cosmological context. Our SPH code reproduces the analytical results very well in cases that include or exclude radiative cooling. No substantial deviations from the predicted central mass accretion rates or from the temperature, density and velocity profiles are observed in well-resolved regions inside the shock radius. This test problem lends support to the reliability of SPH techniques to model the complex process of galaxy formation.  相似文献   

Trace element geochemistry and Sr-Nd characteristics of Mesoproterozoic mafic intrusive rocks from Rondonia, Brazil, SW Amazonian Craton： Petrogenetic and tectonic inferences     

Girardi  V.A. V. Teixeira  W. Bettencourt  J.S. Andrade  S. Navarro  M.S. Sato  K. 《《幕》》2008,31(4):392-400

The Amazonian Craton comprises an Archean domain surrounded by four successively younger Proterozoic tectonic provinces. Within the Rio-Negro-Juruena province the Serra da Providencia Intrusive Suite （1.60 and 1.53 Ga） consists of A-type rapakivi gran- ites, charnockites and mangerites genetically associated with diabase dikes, gabbros and amphibolites. The original mafic melts were derived from a depleted mantle source （εN（T） ＋2.5 to ＋2.8;εSr（T） -12.1）. Underplated mafic magma induced melting of a short-lived felsic crust, thus originating coeval felsic-mafic magmatism in a conti- nental intraplate setting. The Colorado Complex, assigned to the Rondonian-San Ignacio province, comprises 1.35-1.36 Ga intrusive bimodal magmatism represented by monzonite gneisses associated with amphibolite, gabbro and metadiabase dikes intercalated with metasediments with detrital zircon that yield U- Pb ages of 1.35 to 1.42 Ga. Mafic samples dis- play juvenile signatures （εNd（T） 0.0 to ＋5.2; εSr（T） --5.0 to --30.7） and are less contaminated than the Serra da Previdencia and Nova Brasilandia ones. The generation of the basaltic magma is related to the subduction of an oceanic slab below the peridotite wedge （intraoceanic arc setting）. Fluids and/or small melts from the slab impregnated the mantle. The Nova Brasilandia Sequence （Sunsas-Aguapef province） comprises a metasedimentary sequence intruded by 1.10-1.02 Ga metadia- bases, gabbros, meta-gabbros, and amphibolites associated with granitic plutons （bimodal mag- matism）. The original tholeiitic magmas, derived from a depleted source （εNd（T） = ＋3.1 to ＋5.0）, in a proto-oceanic setting, underwent subsequent contamination by the host rocks, as indicated by the isotopic and trace element data.  相似文献   

Geochemical mobility of arsenic in the surficial waters from Argentina     

Alicia Daniela Robles  Paula Polizzi  María Belén Romero  Leila Natalia Chiodi Boudet  Sandra Medici  Agustín Costas  Marcela Gerpe 《Environmental Earth Sciences》2016,75(23):1479

The presence of arsenic (As) in surface water constitutes an important environmental risk, where mobility and adsorption processes are responsible for its behavior in the sediment–water interface. Therefore, the assessment of adsorption, mobility and water availability of arsenic in freshwater sediments, with agricultural, livestock and urban soil uses was performed. Arsenic concentrations in sediments ranged from 5.4 to 15.9 mg kg^?1 (total) and 2.8 to 6.5 mg kg^?1 (labile), and those of iron and manganese were 11,563–23,500 and 140.6–662.1 mg kg^?1, respectively. The As levels in water were significantly lower than those of sediments. Results would suggest that As co-precipitation and adsorption on Fe oxides are probably the major route of immobilization, determining its low lability. Manganese did not present an outstanding contribution to the retention, and cation-exchange capacity, pH and organic matter of sediments did not show an influence on the mobility of As.  相似文献   

Distribution and abundance of early life stages of squid (Illex argentinus) in the south-west Atlantic   总被引：2，自引：0，他引：2  

Brunetti  Norma E.; Ivanovic  Marcela L. 《ICES Journal of Marine Science》1992,49(2):175-183

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The baryon fraction of ΛCDM haloes     

Robert A. Crain  Vincent R. Eke  Carlos S. Frenk  Adrian Jenkins  Ian G. McCarthy  Julio F. Navarro  Frazer R. Pearce 《Monthly notices of the Royal Astronomical Society》2007,377(1):41-49

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Effect of thickness variation on collapse pressure of seamless pipes     

Fuat Kara  Josef Navarro  Robert L. Allwood 《Ocean Engineering》2010,37(11-12):998-1006

The present paper is concerned with determining the effect of thickness variation on collapse pressure of seamless pipes. There exists extensive information on the effects external pressure has on pipelines. A substantial amount of literature deals with results of analysis, numerical modelling and testing of pipes those are gradually subject to external pressure. This knowledge has been incorporated into standards which are intended for designing linepipe operating in deepwater locations. One such example is the DNV-OS-101 (DNV, 2007) Submarine Pipeline Systems standard. This code only addresses pipes with a nominally uniform wall thickness making it inadequate for designing seamless pipe which is prone to thickness variation arising from the manufacturing process. The DNV (2007) code effectively ignores the problem as it simply provides a vague statement regarding a conservative value of wall thickness that should be used in the design calculations.The present paper uses finite element analysis (FAE) modelling to predict the external pressure acting on the pipes. The present paper explains the manner in which FEA models will be used to study the effect wall thickness variation will have on the pressure at which the pipe will collapse. An improvement to the DNV (2007) code is then suggested by interpreting the results of the FEA models. The case study that follows provides insight on the savings the improved method is projected to offer.  相似文献   

The RAVE survey: constraining the local Galactic escape speed     

Martin C. Smith  Gregory R. Ruchti  Amina Helmi  Rosemary F. G. Wyse  J. P. Fulbright  K. C. Freeman  J. F. Navarro  G. M. Seabroke  M. Steinmetz  M. Williams  O. Bienaymé  J. Binney  J. Bland-Hawthorn  W. Dehnen  B. K. Gibson  G. Gilmore  E. K. Grebel  U. Munari  Q. A. Parker  R.-D. Scholz  A. Siebert  F. G. Watson  T. Zwitter 《Monthly notices of the Royal Astronomical Society》2007,379(2):755-772

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Biogeography of the genusArtemia (Crustacea,Branchiopoda, Anostraca) in Spain     

F. Amat  C. Barata  F. Hontoria  J. C. Navarro  I. Varó 《International Journal of Salt Lake Research》1994,3(2):175-190

This is an updated study on the biogeographic distribution of the populations of the genusArtemia (Branchiopoda, Anostraca) in Spain, with special focus on populations inhabiting salt lagoons and inland salterns. The populations recorded (40) belong to the bisexual speciesA. tunisiana and to the asexual groupA. parthenogenetica (diploid and tetraploid strains). They usually appear in three different hypersaline ecosystems: solar salterns and lagoons filled with sea water, solar salterns and lagoons containing brines of diluted mineral salts, and lagoons filled with athalassic (endorheic) brines. The brines in salinas are chemically characterized by high Cl^– concentrations, especially in inland salinas, whose brine sources are geologically associated with evaporitic formations developed in the Triassic and Lower Liassic of eastern Spain. Brines in athalassic lagoons, geologically associated with Mesozoic and Cenozoic periods, show higher levels of sulfate (up to 40–50%) as well as Mg²⁺. From a geographical point of view, bisexual and diploid asexual populations are mainly found in coastal and inland salinas or lagoons below 40° N, while asexual tetraploid populations are found in inland salinas and athalassic lagoons above that latitude. These populations have been biologically characterized by the morphology of their adults through multivariate analysis.  相似文献