612 resultados para brachyura crabs


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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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The juvenile development of the freshwater crab Dilocarcinus pagei Stimpson, 1861 was studied under laboratory conditions, focusing on setae morphology. The ovigerous females were collected manually associated with water hyacinth at the Municipal Dam of Sao Jose do Rio Preto (Sao Paulo, Brazil). The specimens were raised in the laboratory under constant aeration, photoperiod (12: 12 h) and temperature (27 +/- 1 degrees C). Twelve juvenile stages were obtained with descriptions of the main morphological characters that allow their identification are presented. Fourteen types of setae were discovered: dentate, denticulate, serrulate, papposerrate, cuspidate, plumose, plumodenticulate, plumoserrulate, simple, pappose, brush, curved, nail and setules. The greatest diversity of setae was found on the mouth appendages, especially the maxillule. The gill ontogeny and sexual dimorphism becomes apparent from the second juvenile stage onwards. At the third juvenile stage, the carapace begins to exhibit a wider shape, becoming similar to that of the adults.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Callinectes ornatus tem sua distribuição geográfica no Atlântico ocidental: da Carolina do Norte até a Florida, golfo do México, Antilhas, Colômbia, Venezuela, Guiana e Brasil (Amapá ao Rio Grande ao Sul), ocorrendo em fundos de areia, lama e águas menos salinas podendo alcançar 75 metros de profundidade (Melo, 1996). Essa espécie tem um papel importante na teia trófica marinha, pois possui o habito carnívoro oportunista alimentando se também de detritos, assim controlando a estrutura de várias comunidades bentônicas (Haefner, 1990; Mantelatto & Christofoletti, 2001; Mantelatto et al., 2002). O presente estudo aborda as populações de C. ornatus que vivem no infralitoral não-consolidado das regiões das Ilhas do Mar Virado e das Couves, localizadas no litoral norte do Estado de São Paulo, e teve por objetivo a caracterização dos períodos de recrutamento e reprodutivos da espécie baseado na presença de jovens/adultos e fêmeas ovígeras respectivamente. Os dados utilizados nesse estudo foram coletados do Verão de 1998 á Primavera de 1999 no infralitoral não consolidado das Ilhas do Mar Virado e das Couves totalizando dois anos. As amostragens foram realizadas mensalmente, com auxilio de um barco de pesca equipado com duas redes do tipo “double-rig”. O total coletado durante os dois anos foi de 1164 animais. Os menores indivíduos machos e fêmeas encontrados na Ilha do Mar Virado apresentam os seguintes tamanhos respectivamente 22,2 mm e 17,7 mm, já na Ilha das Couves foram de 20,2 mm e de 32,3 mm. Foi obtido um total de 12 classes de tamanho, com 5,0 mm de amplitude. As duas primeiras classes foram ocupadas apenas por indivíduos jovens já as cinco ultimas principalmente por indivíduos adultos e fêmeas ovígeras. Para os indivíduos machos adultos foi possível observar o deslocamento de modas da Primavera de 1998 à Primavera de 1999... (Resumo completo, clicar acesso eletrônico abaixo)

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This study evaluated the effect of environmental stimuli and selective pressures in different geographical areas along a latitudinal gradient, on the juvenile recruitment, population structure, and sex ratio of the speckled swimming crab Arenaeus cribrarius. Samples were collected monthly during 1 year in three locations along the Brazilian coast: Macaé, state of Rio de Janeiro (MAC, 22°47′ S, 41°45′ W); Ubatuba, São Paulo (UBA, 23°27′ S, 44°58′ W); and São Francisco do Sul, Santa Catarina (SFS, 26°08′ S, 48°34′ W). The specimens of A. cribrarius were identified, counted, sexed, and measured for maximum carapace width (CW). The largest juvenile found was in UBA (47.7 ± 1.36 mm); and the largest adult females and males in MAC (74.26 ± 0.93 and 77.04 ± 0.79 mm, respectively). Recruitment in MAC was continuous, whereas in UBA and SFS, recruitment showed seasonal characteristics. The sex ratio was skewed toward females only in UBA; in MAC and SFS, males and females were present in equal proportions. These results indicate that geographical variations can cause differences in the recruitment and population structure of A. cribrarius. These regional differences call attention to the necessity for improved management plans and control of shrimp fishing, which can affect population patterns such as juvenile recruitment, population structure and life history of the target species and species that are caught in bycatch from shrimping, such as the swimming crab A. cribrarius.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Mithrax hispidus (Herbst, 1790) is a mithracid majoid crab occurring on sand, corals and rocks in waters of the western Atlantic. Larval development consists of two zoeal stages and a megalopa. All larval stages are described in detail based on multiple cultures. Prior to this study, larvae of M hispidus were considered to be different and grouped separately from most other larvae of Mithrax, primarily based on setation. A detailed morphological examination, based on the same specimens used for the first description, revealed that the inclusion of M hispidus in a separate group is not valid as zoeae now fully agree with the morphological characteristics defined for the other group of five Mithrax species, including M. pleuracanthus, M. verrucosus, M. caribbaeus, M. coryphe, and M. forceps. This illustrates the importance of precisely recording morphological details such as setation, which may otherwise lead to incorrect interpretations with regard to perceived taxonomic affinities. A comparison of larvae of the Mithrax -Mithraculus species complex does not support separation into two genera. Larval evidence supports the recently suggested adult-based synonymization of M caribbaeus with M. hispidus.

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Experimental analyses of hermit crabs and their preferences for shells are essential to understand the intrinsic relationship of the crabs` dependence on shells, and may be useful to explain their shell use pattern in nature. The aim of this study was to evaluate the effect of crab species and site on the pattern of shell use, selection, and preference in the south-western Atlantic hermit crabs Pagurus brevidactylus and Pagurus criniticornis, comparing sympatric and allopatric populations. Differently from the traditional approach to evaluate shell preference by simply determining the shell selection pattern (i.e., the number of shells of each type selected), preference was defined (according to [Liszka, D., Underwood, AJ., 1990. An experimental design to determine preferences for gastropod shells by a hermit-crab. J. Exp. Mar. Biol. Ecol., 137(1), 47-62]) by the comparison of the number of crabs changing for a particular shell type when three options were given (Cerithium atratum, Morula nodulosa, and Tegula viridula) with the number of crabs changing for this same type when only this type was offered. The effect of crab species was tested at Cabelo Gordo Beach, where P. brevidacrylus was found occupying shells of C. atratum, M. nodulosa, and T viridula in similar frequencies, whereas P. criniticornis occupied predominantly shells of C atratum. In laboratory experiments the selection patterns of the two hermit-crab species for these three gastropods were different, with P criniticornis selecting mainly shells of C atratum, and R brevidactylus selecting more shells of M. nodulosa. The shell preference was also dependent on crab species, with P. criniticornis showing a clear preference for shells of C atratum, whereas P. brevidactylus did not show a preference for any of the tested shells. The effect of site was tested for the two species comparing data from Cabelo Gordo to Preta (P brevidactylus) and Araca beaches (P. criniticornis). The pattern of shell use, selection, and preference was demonstrated to be dependent on site only for P. brevidactylus. The results also showed that the shell use pattern of P criniticornis can be explained by its preference at both sites, whereas for P. brevidactylus it occurred only at Cabelo Gordo, where the absence of preference was correlated with the similar use of the three gastropod species studied. Finally, the results showed that the shell selection pattern cannot be considered as a measure of shell preference, since it overestimates crab selectivity. (C) 2009 Elsevier B.V. All rights reserved.

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Podochela meloi Sankarankutty, Ferreira & Cunha, 2001, originally described in the Inachidae MacLeay, 1838, was recently transferred to the Inachoididae genus Inachoides H. Milne Edwards & Lucas, 1842, based upon overall similarities. Placement of P. meloi in both Inachoididae and Inachoides is found to be supported by a number of synapomorphies as shown herein. Podochela meloi is shown to be a junior synonym of Inachoides forceps A. Milne-Edwards, 1879.