Age and growth parameters of cachara Pseudoplastystoma reticulatum (Siluriformes, Pimelodidae) from the Cuiabá River, Brazil

Age and growth parameters of cachara Pseudoplatystoma reticulatum (Eigenmann & Eigenmann, 1889) (Siluriformes, Pimelodidae) (males and females) were estimated through the analysis of growth rings in spines of pectoral fins. Fish were collected from January to December 2007, in the area directly influenced by the Aproveitamento Múltiplo de Manso (APM Manso) and in the Cuiabá River (upper parts of the Pantanal). The maximum number of growth rings was seven for males, and eight, for females. The analysis of temporal variations in mean marginal increment showed that rings found in the spines were formed annually, in December. Growth rings were associated to spawning (in the study region from November to March) of the species. The growth curve in length was obtained by the von Bertalanffy model adjusted by the Ford-Walford transformation. The equations are: Ls = 72.7*[1-e-0.44(t+1.5974)] for males, and Ls = 84.5*[1-e-0.33(t+2.0943)] for females. The equations that describe the growth curve in weight are: Wt = 4991.61*[1-e-0.44 (t+1.5974] 2.70 for males and Wt = 7503.17*[1-e-0.33 (t+2.0943] 2.99 for females.

Neodrassex, a new genus of the Leptodrassex group (Araneae, Gnaphosidae) from South America

The new genus Neodrassex is proposed to include two new species of Gnaphosidae from Brazil. Neodrassex aureus sp. nov. is described from Amazonas, Paraná and Rio Grande do Sul states, and N. iguatemi sp. nov. is described from Paraná state. Neodrassex gen. nov. is characterized by small size, pale coloration, large anterior median eyes surrounded by black pigmentation, absence of a dorsal abdominal scutum in males and by the cheliceral dentition with 2-3 teeth on the promargin and 2-4 on the retromargin. The new genus is tentatively placed at the Leptodrassex group.

Effects of both ecdysone and the acclimation to low temperature, on growth and metabolic rate of juvenile freshwater crayfish Cherax quadricarinatus (Decapoda, Parastacidae)

Growth, metabolic rate, and energy reserves of Cherax quadricarinatus (von Martens, 1868) juveniles were evaluated in crayfish acclimated for 16 weeks to either 25ºC (temperature near optimum) or 20ºC (marginal for the species). Additionally, the modulating effect of ecdsyone on acclimation was studied. After 12 weeks of exposure, weight gain of both experimental groups acclimated to 25ºC (control: C25, and ecdysone treated: E25) was significantly higher than that of those groups acclimated to 20ºC (C20 and E20). A total compensation in metabolic rate was seen after acclimation from 25ºC to 20ºC; for both the control group and the group treated with ecdysone. A Q10value significantly higher was only observed in the group acclimated to 20ºC and treated with ecdysone. A reduction of glycogen reserves in both hepatopancreas and muscle, as well as a lower protein content in muscle, was seen in both groups acclimated to 20ºC. Correspondingly, glycemia was always higher in these groups. Increased lipid levels were seen in the hepatopancreas of animals acclimated to 20ºC, while a higher lipid level was also observed in muscle at 20ºC, but only in ecdysone-treated crayfish.

Aging and growth parameter from the Piaractus mesopotamicus (pacu) from the Cuiabá river, Mato Grosso, Brazil

This study has aims to determine the age and to estimate the growth parameters using scales of the species. Individuals of Piaractus mesopotamicus (Holmberg, 1887) used in this study were captured in the commercial fishery conducted in the region, along the year 2006. The model selected to express the growth of the species was the von Bertalanffy Sl= Sl∞*[1-exp-k(t-to)]. To determine if scales are suitable for studying the growth of pacu, we analyzed the relation between standard length (Sl) and the radius of the scales through linear regression. The period of annuli formation was determined analyzing the variations in the marginal increment and evaluating the consistency of the readings through the analysis of the coefficient of variations (CVs) for the average standard lengths of each age (number of rings) observed in the scales. The relationship between Ls of the fish and the radius of the scales showed that scales can be used to study the age and growth of P. mesopotamicus (R= 0.79). CVs were always below 20%, demonstrating the consistency of the readings. Annuli formation occurred in February, probably related to trophic migration that occurs in this month in the region. Equations that represents the growth in length obtained for P. mesopotamicus are Sl=50.00*[1-exp-0.18(t-(-3.00)] for males and Sl=59.23*[1-exp-0.14(t-(-3.36)] for females. The growth parameters obtained in this study were lower compared to other studies previously conducted for the same species and can related to overexploitation that species is submitted by fishing in the region. These values show also that females of pacu attain greater asymptotic length than males that growth faster.

Biologia reprodutiva de Macrobrachium jelskii (Crustacea, Decapoda, Palaemonidae) no Rio São Francisco, Minas Gerais, Brasil

RESUMO O objetivo foi avaliar a biologia reprodutiva do camarão- sossego Macrobrachium jelskii (Miers, 1877) no Rio São Francisco, com ênfase na razão sexual, período reprodutivo, maturidade sexual e fecundidade. As coletas foram realizadas mensalmente entre março de 2005 e fevereiro de 2006 exceto nos meses de abril e outubro, nos dois pontos de coleta do Rio São Francisco, Represa de Três Marias (Estação Ecológica de Pirapitinga), a montante da barragem da usina hidroelétrica de Três Marias e a jusante da barragem, localizados no município de Três Marias, região central de Minas Gerais, Brasil. O puçá de 1 m² de boca e malha de 1,42 mm foi passado sob a vegetação marginal e na água à margem dos dois pontos de coleta, por um coletor em um período de até 30 minutos. Em laboratório, os espécimes foram identificados, mensurados e sexados. Um total de 2.945 espécimes foi analisado a montante, no qual correspondem a 1.064 machos e 1.857 fêmeas (1.653 não ovígeras e 204 ovígeras) e 1.973 a jusante, onde 1.120 machos e 841 fêmeas (643 não ovígeras e 198 ovígeras). A razão sexual diferiu significativamente a favor de fêmeas de M. jelskii a montante (0,57; χ2= 215,28; p < 0.01) e a favor dos machos a jusante (1,33; χ2= 39,69; p < 0.01). Ambas as populações possuem um período reprodutivo contínuo-sazonal com pico em janeiro e novembro para os camarões a montante e a jusante, respectivamente. A fecundidade média de M. jelskii foi de 37 ± 14 ovos (5 a 78 ovos) a montante da barragem e de 35 ± 14 ovos (5 a 69 ovos) a jusante. A razão sexual desviada para os machos de M. jelskii à jusante sugere que as fêmeas apresentaram o comportamento de se abrigarem entre as vegetações marginais. A razão sexual desviada para as fêmeas a montante demonstra a real proporção de machos e fêmeas, que pode ser considerada para a espécie no Rio São Francisco. O tamanho dos ovos carregados pelas fêmeas a jusante foi influenciado pelas baixas temperaturas da água proveniente da represa.

Lesões microscopicas do baço na purpura trombocitopenica idiopatica

Histopathological changes strikingly similar were found in the spleen of four cases (young female subjects) of idiopathic thrombocytopenic purpura hemorrhagica in which splenectomy was performed. The chief changes reported are enlargement of the marginal zone of the malpighian corpuscles, proliferation and mobilization of the reticulo-endothelial cells, myeloid metaplasia, local (tissue) eosinophilia, and stoppage of the circulation or stasis of platelets from which results a filling of the spelenic sinuses by such elements. The latter phenomenon will possibly present some bearing with thrombocytopenia which is such a characteristic feature in this disease and will perhaps account for the rapid increase in blood platelets which usually follows splenectomy and or the finding of increased megakaryocytes in the bone marrow.

The private and fiscal returns to schooling and the effect of public policies on private incentives to invest in education: a general framework and some results for the EU

This paper develops a comprehensive framework for the quantitative analysis of the private and fiscal returns to schooling and of the effect of public policies on private incentives to invest in education. This framework is applied to 14 member states of the European Union. For each of these countries, we construct estimates of the private return to an additional year of schooling for an individual of average attainment, taking into account the effects of education on wages and employment probabilities after allowing for academic failure rates, the direct and opportunity costs of schooling, and the impact of personal taxes, social security contributions and unemployment and pension benefits on net incomes. We also construct a set of effective tax and subsidy rates that measure the effects of different public policies on the private returns to education, and measures of the fiscal returns to schooling that capture the long-term effects of a marginal increase in attainment on public finances under c

An alternative way to model merit good arguments

Besley (1988) uses a scaling approach to model merit good arguments in commodity tax policy. In this paper, I question this approach on the grounds that it produces 'wrong' recommendations--taxation (subsidisation) of merit (demerit) goods--whenever the demand for the (de)merit good is inelastic. I propose an alternative approach that does not suffer from this deficiency, and derive the ensuing first and second best tax rules, as well as the marginal cost expressions to perform tax reform analysis.

The Instrumental voter goes to the news-agent: demand for information, election closeness, and the media

This paper studies the impact of instrumental voting on information demand and mass media behaviour during electoral campaigns. If voters act instrumentally then information demand should increase with the closeness of an election. Mass media are modeled as profit-maximizing firms that take into account information demand, the value of customers to advertisers and the marginal cost of customers. Information supply should be larger in electoral constituencies where the contest is expected to be closer, there is a higher population density, and customers are on average more profitable for advertisers. The impact of electorate size is theoretically undetermined. These conclusions are then tested with comfortable results on data from the 1997 general election in Britain.

Price competition under cost uncertainty: A laboratory analysis

We study the relation between the number of firms and price-cost margins under price competition with uncertainty about competitors' costs. We present results of an experiment in which two, three and four identical firms repeatedly interact in this environment. In line with the theoretical prediction, market prices decrease with the number of firms, but on average stay above marginal costs. Pricing is less aggressive in duopolies than in triopolies and tetrapolies. However, independently from the number of firms, pricing is more aggressive than in the theoretical equilibrium. Both the absolute and the relative surpluses increase with the number of firms. Total surplus is close to the equilibrium level, since enhanced consumer surplus through lower prices is counteracted by occasional displacements of the most efficient firm in production.

An Atkinson-Gini family of social evaluation functions

We investigate the properties of a family of social evaluation functions and inequality indices which merge the features of the family of Atkinson (1970) and S-Gini (Donaldson and Weymark (1980, 1983), Yitzhaki (1983) and Kakwani (1980)) indices. Income inequality aversion is captured by decreasing marginal utilities, and aversion to rank inequality is captured by rank-dependent ethical weights, thus providing an ethically-flexible dual basis for the assessment of inequality and equity. These ocial evaluation functions can be interpreted as average utility corrected for the illfare of relative deprivation. They can alternatively be understood as averages of altruistic well-being in a population. They moreover have a simple graphical interpretation.

Los principales elementos del nuevo IRPF: una valoración a partir de ESPASIM

El Impuesto sobre la Renta de las Personas Físicas (IRPF) es uno de los instrumentos claves del sistema tributario español. En este trabajo se estudia el impacto de los principales elementos del Nuevo IRPF, a partir de ESPASIM, el primer modelo integrado de microsimulación de impuestos y subsidios (tax-benefit) para España, que emplea micro datos procedentes de la Encuesta de Presupuestos Familiares (EPF) representativos de la población española. Tomando como sistema de base el impuesto sobre la renta anterior (IRPF 1998), se analiza cómo la introducción de la nueva figura impositiva afecta la tributación en términos de recaudación, número de contribuyentes y de declarantes, los tipos marginales efectivos de imposición y impacto distributivo, tanto para el conjunto de la población como por grupos de hogares. Las estimaciones que se presentan muestran que el Nuevo impuesto conlleva una reducción sustancial de la presión fiscal media por IRPF que va acompañada de una reducción del tipo marginal efectivo medio de 2,12 puntos de porcentaje. El importante coste que en términos recaudatorios suponen la introducción del mínimo vital personal y familiar, las nuevas escala de gravamen y deducción por rendimientos del trabajo por cuenta ajena, no contribuyen a reducir la desigualdad relativa, beneficiando sobretodo a la población situada en los tramos medios y altos de la escala de renta. La reforma no beneficia tampoco ni a los hogares con cargas familiares ni a los perceptores de rendimientos por cuenta ajena, que experimentan (ambos colectivos) una reducción impositiva muy similar a la del conjunto de la población. Igualmente, son los grupos relativamente más pobres -personas solas y hogares monoparentales- los que menos ganan con la reforma. La reducción del número de declarantes (en 2,1 millones) asociada al nuevo impuesto, va acompañada de más complejidad legislativa y de una pérdida de generalidad de este instrumento impositivo.

Demand elasticity and market power in the spanish electricity market

In this paper we check whether generator's bid behavior at the Spanish whosale electricity market is consistent with the hypothesis of profit maximization on their residual demands. Using OMEL data, we find the arc-elacticity of the residual demand around the system marginal price. The results suggest thet the larger firms are not actually profit-msximization. We argue how the regulatory environment may drive these results. Finally, we repeat the analysis for the first session of the intra-day market where presumably firms may not have the same incentives as in the day-ahead market.

Terceira contribuicäo ao conhecimento do gênero Archytas Jaennicke, 1867: (Diptera, Tachinidae)

Twelve species of the genus Archytas Jennicke, 1867, eight of which described as new are studied and figured in detail. Definitions of the species are based mainly on characters of male genitalia. The male genital characters are the most significant for separation of the species and most demonstrative of their affinities. By examining a long series of species of this genus we came to the conclusion that the presence of one pair of median marginal bristles on the third abdominal tergite seems to be characteristic of the genus. This caracter apparently so important, is not however considered fundamental. The most significant example is found in Archytas lenkoi sp. n. and Archytas vexor Curran, 1928. In A. lenkoi we can find one or two pairs or thay may, less frquently, be absent. In A. vexor these bristles are lacking. The shape of the male copulatory apparatus of Jurinia nitidiventris Curran, 1928 refered to by CURRAN in his "Revision of Archytas", is not characteristic of any species of the group and so, is not considered in this paper. To help in the identification, the species studied here are divided into groups. The analis group" includes: A. apicifer (Walker, 1894), A. californiae (Walker, 1856), A. nivalis Curran, 1928, a. giacomellii (Blanchard, 1941), A. basifulvus (Walker, 1849), A. incasanus Townsend, 1912 and A. cirphis Curran, 1927. The identification of members of these group is extremely difficult owing both to their similarity in colour pattern and to their variability. They all have black testaceous or dark brown abdomen, the last segment pale or brownish pollinose; second segment without bristles; third with a pair of strong marginals, fourth and fifth with two rows of discals on apical third. The final determination often rests upon the structure of the male copulatory apparatus. Fortunately in this group, many of the forcipes superiores and palpi genitalium are strikingly different from one another. The "zikani group" includes: A. zikani sp. n., A seabrai sp. n., A. duckei sp. n. and A. vernalis Curran, 1928. This group may be characterized as follows: forcipes interiores absent; forcipes superiores strongly chitinized an dilated at anex. Within this group, the forcipes of. A. seabrai sp. n. do not present an aberrant form. The "dissimilis group" will be studied in forthcoming papers. The limits of the genus Archyta Jaen. are not as yet sharply difined, the evaluation of the significance of each character used in the definition remaining as most difficult problem. The distinction between Archytas and other related genera is very difficult, chiefly because it is based on variable characters. In this paper we place the genera Parafabricia Towsend, 1931, Itachytas Blanchard, 1940, Archynemochaeta Blanchard, 1941, Proarchytoides Blanchard, 1941 and Archytodejeania Blanchard, 1941 in the synonymy of Archytas Jaen. The detailed examination of the characters used in their definition, proved them to be fundamentally proposed on basis of chaetotasy, these characters alone being precarious, because of the considerabel intraspecifical variation. The type of the new species are in the Oswaldo Cruz Institute collection. Rio de Janeiro, Brazil, and paratypes in the collections of the followings institutions: Departamento de Zoologia da Secretaria de Agricultura do Estado de São Paulo; Instituto de Ecologia e Experimemtação Agrícolas; Departamento de Defesa Sanitária Vegetal; Campos Seabra collection; and Barbiellini collection.

Notas sôbre o gênero Colobogaster Solier, 1833, com a descrição de duas novas espécies da Região Amazônica: (Coleoptera, Buprestidae)

The study of materials belonging to several brazilian collections led us discover 2 new species of the genus Colobogaster which are here described. C. seabrai sp. n. seems to be related to C. puncticollis Waterhouse, 1882, from which it can be distinguished by: a) apical alitral tooth placed suturally, b) pronotum with 3 pairs of depressions, the 1st. pair transversal and conigous to the 2nd one, c) elitral suture brilliantgreen coloured but not the marginal edge, d) front without a horse-shoe shaped structure, e) pronotum with the discal region concolor. The structures of pronotum, the elitral and pronotal colour paterns and the genial morphology separate this one from other species of the genus. C. paraensis sp. n. is closely related to C. cupricollis Kerremans, 1897, but it is distinguished by the absence of depressions on the pronotum, by the elitral tooth placed suturally, by the abscence of humeral rip and by the general colour. Eleven other species were studied and their apical segment of the abdomen and scutellum were illustrated. It was also established the synonymy of C. ecuadoricus Obengerger, 1926.