Distribuição, abundância relativa e estrutura populacional de Isognomon bicolor (Adams, 1845) no litoral do Estado do Rio de Janeiro, Brasil

The exotic bivalve Jsognomon bicolor is found in large densities on the rocky shores of the Rio de Janeiro state and is apparently altering the native community. The aim of this study was to establish the geographic distribution of I. bicolor on the coast of Rio de Janeiro state, to compare population structure among three different areas and to verify the relationship of its relative abundance with the community structure in each area The temporal variation of relative abundance, vertical distribution and population structure of I. bicolor were also investigated. Samples were taken in winter (2002) and summer (2002-03) at Ilha do Brandão (Angra dos Reis), Ponta da Fortaleza (Arraial do Cabo) and Praia Vermelha (Rio de Janeiro). ln Praia Vermelha, samples were also taken in the following winter (2003). The individuals sampled at Praia Vermelha presented the highest maximum and medium sizes, whereas the individuals collected at Ilha do Brandão presented the lowest maximum and medium size. There was a lower number of recruits of L bicolor in these areas than in Ilha do Brandão, where a mode was found in the lower size classes. The most reasonable hypothesis to explain the highest number of recruits in Ilha do Brandão is that Petaloconchus sp. provides a substrate that enhances settlement of larvae and the attachment of individuals. Although Petaloconchus sp. acts as a trap. It enhances recruitment of more individuals but only a few can grow and develop within it.PETROBRÁSO bivalve invasor Isognomon bicolor vem ocupando uma ampla faixa em costões rochosos do litoral do estado do Rio de Janeiro e tem aparentemente causado alterações nas comunidades nativas. Este trabalho determina a distribuição geográfica de I. bicolor no litoral do estado do Rio de Janeiro, comparar a sua estrutura populacional entre três áreas e relacionar a sua abundância relativa à estrutura das comunidades em cada área. Também investiga a variação temporal da abundância relativa, da distribuição vertical e da estrutura populacional de I. bicolor. As coletas foram realizadas no inverno de 2002 e no verão de 2003 na Ilha do Brandão (Angra dos Reis), na Ponta da Fortaleza (Arraial do Cabo) e na Praia Vermelha (Rio de Janeiro). Nesta última, também foi realizada uma coleta no inverno de 2003. Os indivíduos coletados na Praia Vermelha são os que possuem o maior tamanho máximo e médio, sendo os indivíduos da Ilha do Brandão, os que possuem o menor tamanho máximo e médio. Nestas duas áreas, foram encontrados menos recrutas em comparação com a Ilha do Brandão, onde a moda ficou nas classes de tamanho menores. A hipótese mais provável para explicar o maior número de recrutas na Ilha do Brandão é que Petaloconchus sp fornece um substrato que favorece o assentamento de larvas e a fixação dos indivíduos impede que estes se desprendam. Entretanto, Petaloconchus sp. parece funcionar como uma armadilha, porque apesar de mais indivíduos de I. bicolor recrutarem, poucos conseguem crescer e se desenvolver

An immersed boundary level-set based approach for fluid-shell interaction with impact.

Fluid-shell interaction modeling is a challenging problem with application to\ud several engineering elds. In this research we develop a partitioned algorithm for large\ud displacements \ud uid-shell coupling with impact. The structure is modeled in a total La-\ud grangian description, using a novel shell nite element formulation to deal with geometric\ud nonlinear dynamics of thin or thick shells. This formulation is based on the principle of\ud minimum potential energy considering positions and generalized unconstrained vectors as\ud nodal parameters, instead of displacements and rotations. As a consequence, the formu-\ud lation eliminates the need for large rotation approximations and presents constant mass\ud matrix, allowing the use of Newmark time integrator for the nonlinear problem. The\ud Newton-Raphson method is employed to solve the resulting nonlinear system and contact\ud between structures is modeled by enforcing non-penetration conditions based on a signed\ud distance function. The \ud ow is assumed to be compressible and the \ud uid dynamics solver is\ud explicit with time integration based on characteristics. The \ud uid governing equations are\ud written in the Eulerian description generating a xed mesh method. The coupled prob-\ud lem is solved by using an embedded boundary technique where the \ud uid-shell interface\ud is tracked inside the unstructured \ud uid mesh by level sets of a signed distance to bound-\ud ary function. The versatility and e ciency of the proposed approach is demonstrated by\ud selected three- dimensional examples.CNPqFundação Araucari

Mollusca, Bivalvia, Mytilidae, Myoforceps aristatus (Dillwyn, 1817): distribution and new record localities at Ilha Grande Bay, Brazil

In many intertidal rocky shores at Ilha Grande Bay, state of Rio de Janeiro, Brazil, the vermetid gastropod Petaloconchus varians is the dominant organism, forming a well-developed and complex structure, where different groups of organisms live, including the invasive bivalve Myoforceps aristatus. The present paper describes the distribution and new record localities of M. aristatus at Ilha Grande Bay

First records of the non-native bivalve Isognomon bicolor (C. B. Adams, 1845) rafting to the Uruguayan coast

In the southwestern Atlantic Ocean, Isognomon bicolor is an invasive bivalve on rocky shores along the coast of Brazil. We report here records of this species rafting on floating debris in Uruguay (ca. 34° S). Rafting may be an important mechanism for the dispersal of I. bicolor on the coast of Uruguay and elsewhere in the Southernmost Atlantic Ocean and the presence of this invasive species on rocky shores should be monitored

Flexible Multibody Dynamics Finite Element Formulation Applied to Structural Progressive Collapse Analysis

Abstract This paper presents a two-dimensional frame finite element methodology to deal with flexible multi-body dynamic systems and applies it to building progressive collapse analysis. The proposed methodology employs a frame element with Timoshenko kinematics and the dynamic governing equation is solved based on the stationary potential energy theorem written regarding nodal positions and generalized vectors components instead of displacements and rotations. The bodies are discretized by lose finite elements, which are assembled by Lagrange multipliers in order to make possible dynamical detachment. Due to the absence of rotation, the time integration is carried by classical Newmark algorithm, which reveals to be stable to the position based formulation. The accuracy of the proposed formulation is verified by simple examples and its capabilities regarding progressive collapse analysis is demonstrated in a more complete building analysis

Mollusca, Bivalvia, Mytilidae, Myoforceps aristatus (Dillwyn, 1817): distribution and new record localities at Ilha Grande Bay, Brazil

In many intertidal rocky shores at Ilha Grande Bay, state of Rio de Janeiro, Brazil, the vermetid gastropod Petaloconchus varians is the dominant organism, forming a well-developed and complex structure, where different groups of organisms live, including the invasive bivalve Myoforceps aristatus. The present paper describes the distribution and new record localities of M. aristatus at Ilha Grande Bay

The first finding of Ostrea cf. puelchana (Bivalvia) living as epibiont on Callinectes exasperates (Decapoda)

 This paper describes the epibiosis of Ostrea cf. puelchana on Callinectes exasperatus (Gerstaecker, 1856), both collected from the estuary of the Paraíba River, in the state of Paraíba, northeastern Brazil. The basibiont crab was captured using a trap installed in mangrove area at a depth of about 2 meters. The oyster was closely attached to the left side of dorsal carapace covering most of the epibranchial, mesobranchial and metabranchial regions. Possible advantages and disadvantages for both the epibiont and the basibiont are discussed. We believe that young O. cf. puelchana may avoid a variety of potential predators due to the considerable movement capacity of C. exasperatus and may also serve as a small protective shield for the basibiont. However, the oyster, which is a bivalve with an epifaunal lifestyle, is likely to be negatively affected, mainly due to burrowing activity of the crab. This is the first record of epibiosis between bivalves of the genus Ostrea Linnaeus, 1758 and crabs of the genus Callinectes Stimpson, 1860.