Following food clouds: Feeding association between a minute loricariid and a characidiin species in an Atlantic Forest stream, Southeastern Brazil

Following behavior is a widespread feeding tactic among marine fishes, but remains poorly documented for freshwater fishes. The present study describes such association between two freshwater species: the minute armored catfish Parotocinclus maculicauda and the South American darter Characidium sp. During underwater observations in an Atlantic Forest stream, we recorded Characidium sp. closely following P. maculicauda (<5cm), catching the particles dislodged by this catfish's grazing activity. The following behavior displayed by the darter is considered opportunistic and possibly favors the capture of preys associated to the periphyton. This study is one of the few records of nuclear-follower feeding association between freshwater fishes and the first one in Atlantic Forest streams. Copyright © 2007 Sociedade Brasileira de Ictiologia

ECOLOGIA DE PEIXES DE RIACHO

Editorial do volume especial ECOLOGIA DE PEIXES DE RIACH

Distance to large rivers affects fish diversity patterns in highly dynamic streams of Central Amazonia

Longitudinal-zonation hypotheses generally predict gradual changes in fish composition from upstream to downstream due to changes in habitat conditions, but largely disregard downstream effects on upstream segments. Floodplains of large rivers represent areas of high connectivity during flood periods and can act as stable refuges in dry seasons, which may attenuate deterministic constraints imposed by local conditions on fish assemblages in surrounding habitats. In this study, we investigated the effects of proximity to large rivers on taxonomic- and functional-diversity patterns of stream-fish assemblages in an extensive region of Central Amazonia. We sampled 31 headwater-stream reaches in nine catchments in the Purus and Madeira Rivers interfluve between December 2014 and March 2015. Ninety seven fish species from seven orders and 19 families were captured. The results indicate that distance to large rivers is more important than distance among sites and local conditions in explaining functional and taxonomic diversity of stream-fish assemblages at large spatial scales. We also found a decrease in taxonomic and functional richness towards headwaters, mainly related to the loss of benthic and sedentary species along the distance gradient. These species may be favored by the proximity to refuge areas and high resource availability near the floodplain. In contrast, upstream assemblages were mainly occupied by small-sized, nektonic species with higher dispersal capacity, highly dependent of allochthonous resources. Downstream effects could be detected for many kilometers upstream in hydrographic catchments and this reinforces the crucial role of connectivity between fluvial habitats in maintenance of stream-fish diversity patterns in the region. © 2019 Stegmann et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

A new Centromochlus Kner, 1858 (Siluriformes: Auchenipteridae: Centromochlinae) from the transition between Amazon floodplain and Guiana shield, Brazil

ABSTRACT Species of Centromochlus are widely distributed in South America, with records for major basins such as the Amazon and Orinoco, rivers draining the Guiana Shield such as the Essequibo, Courantyne (Corantijn), Coppename, Maroni, and Oyapock, and Brazilian Shield drainages as upper Paraná and São Francisco. In the last four years, three species of Centromochlus have been described, raising the total number of valid species to sixteen. The new species of Centromochlus described herein is diagnosed by having black ground color sharply delimited from a white underside by conspicuous wavy border. The new species is recorded from the Nhamundá, left bank tributary to the lower Amazon that drain from the Brazilian portion of the Guiana Shield. Although apparently similar to some Tatia species (e.g. Tatia musaica , T. carolae and T. melanoleuca ), the new species possess two conditions of the Weberian apparatus otherwise observed only in Centromochlus heckelii and C. existimatus among centromochlin catfishes. The new Centromochlus comprises small catfishes with adults ranging from 48 to 57 mm SL.</jats:p

Dieta de duas espécies sintópicas de crenuchidae (Ostariophysi: Characiformes) em um riacho rochoso Amazônico

This study assessed the diet of two poorly known syntopic fish species of the family Crenuchidae, Characidium aff. declivirostre and Leptocharacidium omospilus, in a Presidente Figueiredo’ rocky stream, Amazonas, Brazil. The stomach contents were analyzed and their Frequency of Occurrence (FO %) and Relative Volume (Vol %) were combined in a Feeding Index (IAi). We examined 20 individuals of C. aff. declivirostre and 23 of L. omospilus. The Morisita-Horn Index was used to estimate the overlap between the diets of these species. Immature insects were the most valuable items consumed by both fish species. The diet of C. aff. declivirostre was mainly composed of larvae and pupae of Chironomidae, while L. omospilus predominantly consumed larvae of Hydroptilidae, Hydropyschidae and Pyralidae. Thus, both species were classified as autochthonous insectivorous. Characidium aff. declivirostre was considered a more specialized species, probably reflecting lower feeding plasticity or the use of more restricted microhabitats compared to L. omospilus. When the food items were analyzed at the family taxonomic level, the diet overlap between these species was considered moderate (Morisita-Horn Index = 0.4). However, a more thorough analysis, at the genus level, indicates a very low diet overlap. Therefore, we conclude that the feeding segregation between C. aff. declivirostre and L. omospilus may favor their co-existence, despite their high phylogenetic closeness. © 2017, Universidade Estadual de Campinas UNICAMP. All rights reserved

ANÁLISE DE DIFUSÃO TÉRMICA EM UMA PLACA PLANA POR MEIO DA APLICAÇÃO DO MÉTODO DE VOLUMES FINITOS

In the exact sciences and engineering, it is common to encounter a variety of physical and mathematical problems for which it is necessary to find a solution. Ideally, an exact solution should be obtained. However, largely because of the difficulties encountered, there are often no exact solutions to the mathematical equations that model many problems. Therefore, as an alternative to analytical methods, numerical methods have emerged to solve the equations governing a given physical phenomenon, making them mathematically simpler. The finite volume method (FVM) is the most widely used method for solving engineering problems in the area of thermofluid dynamics for a number of reasons, such as the possibility of applying it to non-linear problems and the observance of conservation principles at all levels, global and discrete. This work aims to apply the MVF under an explicit approach to the solution of a two-dimensional problem of transient heat diffusion in a flat carbon steel plate subjected to convection with a fluid, by implementing a computational routine in the free software Octave. The temperature profiles were obtained for different time instants of 50, 100 and 200 minutes of exposure to the imposed boundary conditions, so that it was possible to visualize, through the results obtained, that the temperature gradients initially arise due to a reduction in temperature on the external faces, due to the temperature difference with the fluid, so that the heat transfer begins by convection and, later, due to the temperature gradient created between the internal and external regions of the plate, the heat transfer begins by diffusion from the inside of the plate to the external surfaces.En las ciencias exactas y la ingeniería, es frecuente encontrarse con diversos problemas físicos y matemáticos para los que es necesario hallar una solución. Lo ideal sería, por tanto, obtener una solución exacta. Sin embargo, debido en gran parte a las dificultades encontradas, a menudo no existen soluciones exactas para las ecuaciones matemáticas que modelizan muchos problemas. Por ello, como alternativa a los métodos analíticos, han surgido métodos numéricos para resolver las ecuaciones que rigen un determinado fenómeno físico, haciéndolas matemáticamente más sencillas. El método de los volúmenes finitos (MVF) es el más utilizado para resolver problemas de ingeniería relacionados con la dinámica de termofluidos por varias razones, como la posibilidad de aplicarlo a problemas no lineales y la observación de los principios de conservación a todos los niveles, global y discreto. Este trabajo tiene como objetivo aplicar el MVF bajo un enfoque explícito a la solución de un problema bidimensional de difusión transitoria de calor en una placa plana de acero al carbono sometida a convección con un fluido, mediante la implementación de una rutina computacional en el software libre Octave. Los perfiles de temperatura se obtuvieron para diferentes instantes de tiempo de 50, 100 y 200 minutos de exposición a las condiciones de contorno impuestas, de manera que fue posible visualizar a partir de los resultados obtenidos que los gradientes de temperatura surgen inicialmente como consecuencia de una reducción de temperatura en las caras externas, debido a la diferencia de temperatura de las mismas.Nas ciências exatas e na engenharia, é comum encontrar uma variedade de problemas físicos e matemáticos para os quais é necessário encontrar uma solução. Assim, o ideal seria obter uma solução exata. No entanto, em grande parte devido às dificuldades encontradas, muitas vezes não existem soluções exatas para as equações matemáticas que modelam muitos problemas. Dessa forma, como alternativa aos métodos analíticos, surgiram os métodos numéricos para resolver as equações que regem um determinado fenômeno físico, tornando-as matematicamente mais simples. O método de volumes finitos (MVF) é o método mais empregado na solução de problemas de engenharia envolvendo a área de termofluidodinâmica por algumas razões, como a possibilidade de aplicações em problemas não lineares e a observância dos princípios de conservação em todos os níveis, global e discreto. Este trabalho tem como objetivo aplicar o MVF sob abordagem explícita na solução de um problema bidimensional de difusão de calor transiente em uma placa plana de aço carbono, submetida à convecção com um fluido, por meio da implementação de uma rotina computacional no software livre Octave. Os perfis de temperatura foram obtidos para diferentes instantes de tempo de 50, 100 e 200 minutos de exposição às condições de contorno impostas, de modo que foi possível visualizar, por meio dos resultados obtidos, que os gradientes de temperatura surgem inicialmente em função de uma redução de temperatura nas faces externas, devido à diferença de temperatura com o fluido, de modo que a transferência de calor se inicia por convecção e, posteriormente, devido ao gradiente de temperatura criado entre as regiões interna e externa da placa, a transferência de calor se inicia por difusão do interior da placa para as superfícies externas

A utilização do treinamento de força na prevenção de quedas em idosos

A síndrome do idoso frágil se origina&nbsp; a&nbsp; partir&nbsp; do&nbsp; declínio&nbsp; das&nbsp; funções&nbsp; fisiológicas&nbsp; dos idosos. Observa-se entre estes pacientes a diminuição de atividades físicas, perda de peso, queda da velocidade de mobilidade e redução das funções cognitivas, sendo estas situações avaliadas a partir dos critérios de fragilidade de Fried, especialmente em idosos com&nbsp; doenças&nbsp; crônicas.&nbsp; Nesse&nbsp; sentido,&nbsp; este estudo teve como objetivo evidenciar&nbsp; estudos&nbsp; que&nbsp; verificaram&nbsp; sobre a utilização do treinamento de força na prevenção de quedas em idosos e sua influência&nbsp; na&nbsp; qualidade&nbsp; de vida&nbsp; de&nbsp; idosos&nbsp; com&nbsp; fragilidade.&nbsp; Identificou-se que a sarcopenia aumenta&nbsp; com&nbsp; a&nbsp; idade, sendo&nbsp;&nbsp;&nbsp; mais&nbsp;&nbsp;&nbsp; comum&nbsp;&nbsp;&nbsp; em&nbsp;&nbsp;&nbsp; mulheres,&nbsp;&nbsp;&nbsp; idosos institucionalizados e idosos hospitalizados. Sendo assim, identificou-se que a prática de exercícios&nbsp; físicos,&nbsp; é&nbsp; capaz&nbsp; de&nbsp; impedir&nbsp; que&nbsp; idosos&nbsp; se tornem frágeis. Com relação à queda, ela é a variável clínica mais presente,&nbsp; sendo&nbsp; um&nbsp; histórico&nbsp; comum&nbsp; em&nbsp; boa&nbsp; parte&nbsp; deles. Os maus-tratos foram objeto de poucos estudos, porém conclui-se que idosos homens e depressivos são as maiores vítimas de violência física e verbal. O envelhecimento natural traz consigo diversas alterações fisiológicas, como a perda de massa muscular e a diminuição da força, que podem comprometer a autonomia e a independência dos indivíduos. Essas mudanças são conhecidas como sarcopenia e estão associadas a um maior risco de quedas, fraturas e outras complicações. O treinamento de força surge como uma estratégia eficaz para reverter esses efeitos do envelhecimento fortalecendo os músculos, melhorando o equilíbrio, coordenação, prevenindo quedas, mantendo a autonomia e a qualidade de vida dos idosos

Aberturas del cordón de arena de la laguna costera imboassica (estado de Rio de Janeiro, Brazil) no alteran la abundancia de los peces comerciales

The coastal lagoon Imboassica (Rio de Janeiro State) had from 1993 to 2004 four openings of the sand bar that separates it from the ocean. During this period, 28 samples of fish fauna occurred; 55.6% with commercial value classified in functional guilds as: residents of coastal lagoons (RLC), marine dependent (MD), marine visitors (VM) and from freshwater (D). The catch per unit effort CPUE from the fish species with commercial value during the periods before and after the openings was availed according to exposure time and area of the gill nets. It was observed a growing trend of the individuals VM, RCL and MD with commercial interest during the periods after the openings of the sand bar. When the sand bar remained closed for at least three years, it was observed an increase on the abundance of freshwater fish, as a reduction on other guilds (VM, RCL and MD). The fish production in Imboassica lagoon is considered low and varies in function of the opening and closing of the sand bar. © 2016, Instytut Technologii Drewna. All rights reserved

Mercury distribution in different tissues and trophic levels of fish from a tropical reservoir, Brazil

Concentrations of organic (OrgHg) and inorganic mercury (InorgHg) were assessed in different fish tissues (liver, muscle, kidney, gut and gonads) and trophic levels collected in an impacted tropical reservoir in southeastern Brazil. Organic mercury concentrations in muscle were remarkably higher in the carnivorous species Hoplias malabaricus and Oligosarcus hepsetus. The ratios of OrgHg in relation to total mercury (%OrgHg) in muscle also varied according to the species trophic level: 93% for carnivores, 84% for omnivores, 73% for algivores/planktivores and 58% for detritivores. The %OrgHg in the gut tissue of carnivores (78%) was much higher than that found in omnivores (30%), possibly reflecting a process of trophic biomagnification in the reservoir. On the other hand, the InorgHg concentrations in muscle decreased with the trophic level increase, suggesting that this form of mercury did not biomagnify through the food web. Gonads contained the least total mercury, and approximately all of this mercury was represented by the organic form (83 to 98%). The kidney and the liver of all fish species contained less than 50% OrgHg. We suggest that the low %OrgHg in the liver is related to different capacities or strategies of OrgHg detoxification by the fish. © 2009 Sociedade Brasileira de Ictiologia