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1.
R Soc Open Sci ; 3(5): 150652, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-27293777

RESUMO

Body size has many ecological and evolutionary implications that extend across multiple levels of organization. Body size is often positively correlated with species traits such as metabolism, prey size and trophic position (TP) due to physiological and mechanical constraints. We used stable isotope analysis to quantify TP among minnows across multiple assemblages that differed in their species composition, diversity and food web structure. Body size significantly predicted TP across different lineages and assemblages, and indicated a significant negative relationship. The observed negative relationship between body size and TP is contrary to conventional knowledge, and is likely to have arisen owing to highly clade-specific patterns, such that clades consist of either large benthic species or small pelagic species. Cyprinids probably subvert the physiological and mechanical constraints that generally produce a positive relationship between body size and TP using anatomical modifications and by consuming small-bodied prey, respectively. The need for herbivorous cyprinids to digest cellulose-rich foods probably selected for larger bodies to accommodate longer intestinal tracts and thereby to facilitate digestion of nutrient-poor resources, such as algae. Therefore, body size and TP are likely to have coevolved in cyprinids in association with specialization along the benthic to pelagic resource axis.

2.
PLoS One ; 9(10): e110999, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25340614

RESUMO

Ontogenetic influences in patterns of niche breadth and feeding overlap were investigated in three species of Siluriformes (Heptapterus sp., Rhamdia quelen and Trichomycterus poikilos) aiming at understanding the species coexistence. Samplings were conducted bimonthly by electrofishing technique from June/2012 to June/2013 in ten streams of the northwestern state of Rio Grande do Sul, Brazil. The stomach contents of 1,948 individuals were analyzed by volumetric method, with 59 food items identified. In general Heptapterus sp. consumed a high proportion of Aegla sp., terrestrial plant remains and Megaloptera; R. quelen consumed fish, and Oligochaeta, followed by Aegla sp.; while the diet of T. poikilos was based on Simuliidae, Ephemeroptera and Trichoptera. Specie segregation was observed in the NMDS. Through PERMANOVA analysis feeding differences among species, and between a combination of species plus size classes were observed. IndVal showed which items were indicators of these differences. Niche breadth values were high for all species. The niche breadth values were low only for the larger size of R. quelen and Heptapterus sp. while T. poikilos values were more similar. Overall the species were a low feeding overlap values. The higher frequency of high feeding overlap was observed for interaction between Heptapterus sp. and T. poikilos. The null model confirmed the niche partitioning between the species. The higher frequency of high and intermediate feeding overlap values were reported to smaller size classes. The null model showed resource sharing between the species/size class. Therefore, overall species showed a resource partitioning because of the use of occasional items. However, these species share resources mainly in the early ontogenetic stages until the emphasized change of morphological characteristics leading to trophic niche expansion and the apparent segregation observed.


Assuntos
Peixes-Gato/fisiologia , Ecossistema , Comportamento Alimentar , Cadeia Alimentar , Animais , Brasil , Peixes-Gato/classificação , Dieta/veterinária , Peixes , Conteúdo Gastrointestinal , Rios , Estações do Ano , Especificidade da Espécie
3.
Neotrop. ichthyol ; 16(4): [e170167], out. 2018. mapas, ilus, graf, tab
Artigo em Inglês | LILACS, VETINDEX | ID: biblio-964046

RESUMO

Alterations in natural landscapes, mainly caused by anthropic pressures, have been threatening the world's biomes, including aquatic environments and its biota. This study describes the diet of Bryconamericus iheringii, and how its body shape relates to environmental variables in populations of 22 streams. A wide array of food items were found, mainly composed of allochthonous plants (50.5%) and autochthonous invertebrates (25.2%). Even though food items remained almost the same, the predominant food group significantly differed among streams, mainly in relation to environmental characteristics. There was variation in body shape primarily associated with body depth and length of the pre-dorsal region; however, these differences did not correspond with streams. PLS-CA analyses indicated that environmental characteristics, such as substrate type, percentage of marginal vegetation have some influence over food items availability but not on body shape. This may be because B. iheringii is a non-specialist species capable of prey switching based on availability due to an intermediate body shape suited for generalist feeding habits.(AU)


Alterações em paisagens naturais, principalmente as causadas por pressão antrópica, tem ameaçado os biomas mundiais, incluindo ambientes aquáticos e sua biota. Este estudo descreve a dieta de B. iheringii e como seu formato corporal se relaciona com variáveis ambientais, em populações de 22 riachos. Uma grande variedade de itens alimentares foi encontrada, principalmente compostos por plantas alóctones (50,5%) e invertebrados autóctones (25,2%). Ainda que os itens alimentares tenham permanecido quase os mesmos, o grupo alimentar predominante diferiu significativamente entre riachos, principalmente devido a características ambientais. Ocorreu variação no formato corporal principalmente associado com profundidade do corpo e comprimento da região pré-dorsal; entretanto, tais diferenças não corresponderam aos agrupamentos por riacho. A análise PLS-CA indicou que as características ambientais, tais como tipo de substrato, porcentagem de vegetação marginal exercem alguma influência sobre a disponibilidade dos itens alimentares, mas não sobre o formato corporal. Isso pode ocorrer por B. iheringii ser uma espécie não especialista com capacidade de mudar suas presas de acordo a com disponibilidade das mesmas, isto, devido ao seu formato corporal intermediário adequado a hábitos generalistas.(AU)


Assuntos
Animais , Composição Corporal/genética , Characidae/anatomia & histologia , Ecossistema
4.
Neotrop. ichthyol ; 10(2): 389-399, 2012. graf, mapas, tab
Artigo em Inglês | LILACS | ID: lil-640799

RESUMO

This study addressed the feeding ecology of fish fauna from a first-order stream located in a rural area. The purposes were to evaluate the influence of interspecific, seasonal and spatial factors on the diet, examine the dietary overlap, and determine the predominant food sources. Sampling was conducted in December 2007, September 2008, and March 2009, in three 50-m stretches of Itiz stream (upstream, intermediate, and downstream), through electrofishing. A total of 1,102 stomach contents were analyzed from 14 species, by the volumetric method. In general, allochthonous resources were predominant in the diets. Astyanax aff. fasciatus, Astyanax aff. paranae, Astyanax bockmanni, and Bryconamericus aff. iheringi consumed a higher proportion of plant remains, and Bryconamericus stramineus consumed predominantly Hymenoptera. The diets of Cetopsorhamdia iheringi, Characidium aff. zebra, Imparfinis schubarti, and Trichomycterus sp. consisted of aquatic insects, especially immature forms of Trichoptera, Ephemeroptera, Plecoptera, and Diptera. Hypostomus ancistroides, Hisonotus sp., Poecilia reticulata, and Rineloricaria aff. pentamaculata exploited mainly detritus, while Rhamdia quelen used a variety of items, predominantly terrestrial insects. Detrended Correspondence Analysis (DCA) showed a clear distinction among the species, with different morphology and feeding tactics. The Multi-Response Permutation Procedure (MRPP) supported this differentiation, and also indicated significant spatial and temporal variations in the dietary composition; the Indicator Value Method (IndVal) indicated the main items that contributed to these differences. The diet overlap among species was low (< 0.4) to around 78% of pairs, and the mean value did not vary significantly among the sites or between hydrological periods within each site. According to the null model of Pianka’s index, the values for dietary overlap were significantly higher than expected at random, showing evidence of resource sharing. This was related to the availability of allochthonous resources, highlighting the importance of riparian vegetation as a source of these resources for maintaining the fish fauna of the stream.


Este estudo abordou a ecologia alimentar da ictiofauna de um riacho de primeira ordem situado em área rural. Os objetivos foram verificar a influência dos fatores interespecíficos, sazonais e espaciais sobre a dieta, avaliar a sobreposição alimentar, além de determinar os recursos alimentares predominantes. As amostragens foram realizadas em dezembro/2007, setembro/ 2008 e março/2009, em três pontos do riacho Itiz (montante, intermediário e foz) com extensões de 50 m, através de pesca elétrica. Foram analisados 1102 conteúdos estomacais referentes a 14 espécies de acordo com o método volumétrico. De forma geral observou-se que a maior contribuição na dieta das espécies foi de recursos alóctones. Astyanax aff. fasciatus, Astyanax aff. paranae, Astyanax bockmanni, Bryconamericus aff. iheringi, consumiram maior proporção de vegetal e Bryconamericus stramineus predominantemente Hymenoptera. Cetopsorhamdia iheringi, Characidium aff. zebra, Imparfinis schubarti e Trichomycterus sp. tiveram sua dieta baseada em insetos aquáticos, especialmente formas imaturas de Trichoptera, Ephemeroptera, Plecoptera e Diptera. Hypostomus ancistroides, Hisonotus sp., Poecilia reticulata e Rineloricaria aff. pentamaculata exploraram principalmente detrito, enquanto Rhamdia quelen usou uma variedade de itens, com predomínio de insetos terrestres. A análise de Correspondência com Remoção do Efeito do Arco (DCA) demonstrou uma segregação evidente entre as espécies com morfologia e táticas alimentares distintas. O Procedimento Permutacional de Multiresposta (MRPP) além de corroborar essa diferenciação, também mostrou variações espaciais e temporais significativas na composição da dieta das espécies, e o Método de Valor Indicador (IndVal) apontou os principais itens que contribuíram para essas diferenças. A sobreposição alimentar entre as espécies foi baixa (< 0.4) para cerca de 78% dos pares e a média não variou significativamente entre os locais, assim como entre os períodos hidrológicos dentro de cada ponto. De acordo com o modelo nulo do índice de Pianka, os valores de sobreposição alimentar foram significativamente maiores do que o esperado ao acaso, apresentando evidência de partição de recursos. Isto se deve à disponibilidade de itens alóctones, evidenciando a importância da mata ciliar como fonte desses recursos para a manutenção da ictiofauna do riacho estudado.


Assuntos
Animais , Comportamento Alimentar/etnologia , Peixes/crescimento & desenvolvimento , Preferências Alimentares/etnologia , Ração Animal/análise , Comportamento Alimentar/etnologia , Estações do Ano/efeitos adversos
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