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Human settlements within the Antarctic continent have caused significant coastal pollution by littering plastic. The present study assessed the potential presence of microplastics in the gastrointestinal tract of the Antarctic fish Harpagifer antarcticus, endemic to the polar region, and in the sub-Antarctic fish Harpagifer bispinis. H. antarcticus. A total of 358 microfibers of multiple colors were found in 89 % of H. antarcticus and 73 % of H. bispinis gastrointestinal track. A Micro-FTIR analysis characterized a sub-group (n = 42) of microfibers. It revealed that most of the fibers were cellulose (69 %). Manmade fibers such as microplastics polyethylene terephtalate, acrylics, and semisynthetic/natural cellulosic fibers were present in the fish samples. All the microfibers extracted were textile fibers of blue, black, red, green, and violet color. Our results suggest that laundry greywater discharges of human settlements near coastal waters in Antarctica are a major source of these pollutants in the Antarctic fish.

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Quantifying species trophic interaction strengths is crucial for understanding community dynamics and has significant implications for pest management and species conservation. DNA-based methods to identify species interactions have revolutionized these efforts, but a significant limitation is the poor ability to quantify the strength of trophic interactions, that is the biomass or number of prey consumed. We present an improved pipeline, called Lazaro, to map unassembled shotgun reads to a comprehensive arthropod mitogenome database and show that the number of prey reads detected is quantitatively predicted from the prey biomass consumed, even for indirect predation. Two feeding bioassays were performed: starved coccinellid larvae consuming different numbers of aphids (Prey Quantity bioassay), and starved coccinellid larvae consuming a chrysopid larvae that had consumed aphids (Direct and Indirect Predation bioassay). Prey taxonomic assignment against a mitochondrial genome database had high accuracy (99.8% positive predictive value) and the number of prey reads was directly related to the number of prey consumed and inversely related to the elapsed time since consumption with high significance (r2  = .932, p = 4.92E-6). Aphids were detected up to 6 h after direct predation plus 3 h after indirect predation (9 h in total) and detection was related to the predator-specific decay rates. Lazaro enabled quantitative predictions of prey consumption across multiple trophic levels with high taxonomic resolution while eliminating all false positives, except for a few confirmed contaminants, and may be valuable for characterizing prey consumed by field-sampled predators. Moreover, Lazaro is readily applicable for species diversity determination from any degraded environmental DNA.

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BACKGROUND: A central challenge of DNA gut content analysis is to identify prey in a highly degraded DNA community. In this study, we evaluated prey detection using metabarcoding and a method of mapping unassembled shotgun reads (Lazaro). RESULTS: In a mock prey community, metabarcoding did not detect any prey, probably owing to primer choice and/or preferential predator DNA amplification, while Lazaro detected prey with accuracy 43-71%. Gut content analysis of field-collected arthropod epigeal predators (3 ants, 1 dermapteran, and 1 carabid) from agricultural habitats in Brazil (27 samples, 46-273 individuals per sample) revealed that 64% of the prey species detections by either method were not confirmed by melting curve analysis and 87% of the true prey were detected in common. We hypothesized that Lazaro would detect fewer true- and false-positive and more false-negative prey with greater taxonomic resolution than metabarcoding but found that the methods were similar in sensitivity, specificity, false discovery rate, false omission rate, and accuracy. There was a positive correlation between the relative prey DNA concentration in the samples and the number of prey reads detected by Lazaro, while this was inconsistent for metabarcoding. CONCLUSIONS: Metabarcoding and Lazaro had similar, but partially complementary, detection of prey in arthropod predator guts. However, while Lazaro was almost 2× more expensive, the number of reads was related to the amount of prey DNA, suggesting that Lazaro may provide quantitative prey information while metabarcoding did not.

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This study investigated the occurrence of plastic particles in the digestive tracts of fish from headwater streams in a human-thinly populated region of the subtropical Sinos River basin in southern Brazil. In total, 258 individuals from 17 species were collected using electric fishing. Thirty-eight percent (38%) of the specimens contained plastic particles. All of them were fibers, with a maximum count of 43 per individual. Plastic fibers were the fourth most abundant food category. Results showed that the uptake of these plastic particles was proportional to the number of ingested food items. Fiber counts in the guts correlated with the uptake of Trichoptera, which are invertebrates using plastic particles to construct their protective cases. No significant difference in plastic uptake was detected between benthic and water column fish. No evidence of bioaccumulation of plastic particles was found in the intestines. The distance from urban areas was not related to the number of ingested plastic particles, concluding that plastics are ubiquitous and available to biota, even in remote locations. The most probable source of these particles is residences close to the streams which discharge the sewage of washing machines without any treatment.

Este estudo investigou a ocorrência de partículas plásticas no trato digestivo de peixes de riachos de cabeceira em uma região de baixa densidade humana da bacia subtropical do rio dos Sinos no sul do Brasil. No total, 258 indivíduos de 17 espécies foram coletados por meio da pesca elétrica. Trinta e oito por cento (38%) dos espécimes continham partículas de plástico. Todos eram fibras, com contagem máxima de 43 por indivíduo. As fibras plásticas foram a quarta categoria de alimentos mais abundante. Os resultados mostraram que a absorção dessas partículas plásticas foi proporcional ao número de itens alimentares ingeridos. A contagem de fibras nos intestinos se correlacionou com a absorção de Trichoptera, que são invertebrados que usam partículas de plástico para construir suas capas protetoras. Nenhuma diferença significativa na absorção de plástico foi detectada entre peixes bentônicos e de coluna d'água. Nenhuma evidência de bioacumulação de partículas plásticas foi encontrada nos intestinos. A distância das áreas urbanas não foi relacionada ao número de partículas plásticas ingeridas, concluindo que os plásticos são ubíquos e disponíveis para a biota, mesmo em locais remotos. A fonte mais provável dessas partículas são as residências próximas aos córregos que descarregam os esgotos das máquinas de lavar sem nenhum tratamento.

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As environmental change persists, understanding resource use patterns is of value to predict the consequences of shifting trophic structures. While many sharks are opportunistic predators, some exhibit prey selectivity, putting them at higher risk compared to species with greater trophic plasticity. In the Gulf of Mexico (GOM), Clupeids and Sciaenids comprise 69% of blacktip shark (Carcharhinus limbatus) diets, which is consequential considering potential responses of these prey groups to disturbance and over harvesting. We assessed if blacktips exhibit selectivity for Clupeids and Sciaenids in the western GOM based on stomach contents from sharks in coastal Texas. Clupeids comprised <2% of diets, while striped mullet (Mugil cephalus) and red drum (Sciaenops ocellatus) comprised >70% of identifiable prey. Ontogenetic shifts from smaller (Clupeids, small Sciaenids) to larger, higher trophic level (Ariidae, Elasmobranchii) prey fits our understanding of foraging among coastal sharks, and suggests our regional understanding of blacktip trophic ecology may be limited by the sizes of sampled sharks. Observed increases in blacktip densities coupled with declines in prey (Mugilids, Sciaenids) is concerning if blacktips have limited diet plasticity. Yet GOM blacktips may be more generalized than previously thought, which is promising for conservation and management.

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We developed species-specific primers of five microcrustacean preys, Ceriodaphnia richardi, Diaphanosoma cf. brevireme, Daphnia gessneri, Simocephalus serrulatus, Thermocyclops decipiens and Mesocyclops sp., to analyze food-web interactions involving their two insect predators Rheumatobates crassifemur and Martarega uruguayensis distributed in a tropical shallow lake. We designed internal primers of the COI gene (177-282 bp), and tested them, by means of PCR, for specificity and sensitivity. In our tests for specificity, all primers successfully amplified the DNA target but were species-specific failing to amplify the biomarker from any of the other species tested, even in a mixed DNA sample, including predators' DNA. In tests for sensitivity, primers successfully amplified zooplankton biomarkers from low concentration of DNA extractions and also from digestive tract of predators, even after many hours of ingestion. This technique provides a framework as an efficient tool for evaluation of food-web research in natural aquatic environments, where it is impossible to observe if predation occurs. Furthermore, this technique provides an effective solution for the identification of zooplankton species from the predator's digestive tract, where morphological identification alone is sometimes difficult because predators do not consume the prey but feeds using extra-oral digestion, such is the case of heteropterans.

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Diaphorina citri Kuwayama is the vector of the pathogenic bacteria Candidatus Liberibacter spp., the causative agent of Huanglongbing (HLB), the most serious disease of citrus worldwide. Because predatory insects have been historically neglected in biological control programs for D. citri, the impact of generalist predators on D. citri population densities is little understood. A useful tool to evaluate the dynamics of predator-prey interactions is molecular analysis of predators' gut content. We constructed a specific molecular marker to detect D. citri DNA in the gut content of predator insects, for use in estimating the predation rate of field-collected predators in citrus orchards on D. citri. Bioassays of the DNA half-life detection time were carried out with two predatory species, the ladybird beetle Hippodamia convergens Guérin-Méneville and the lacewing Chrysoperla externa (Hagen). The D. citri DNA half-life detection time (DT50) was 6.11 h for H. convergens and 5.46 h for C. externa. One hundred and seven field-collected predators were used for gut-content analysis (52 larvae/adults of ladybirds and 55 larvae of lacewings). The assays showed that 17.3% of ladybirds but no lacewings tested positive for D. citri DNA. These results show that generalist predators can contribute to biological control of D. citri and should be considered for use in pest management programs in citrus orchards.

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The effects of ectoparasites on larvae of the clingfish Gobiesox marmoratus were evaluated at the dietary and morphometric levels. The larvae and ectoparasites were collected by nearshore plankton samplings during October, November and December 2013 off El Quisco Bay, central Chile. The standardized abundance of total larvae and those ectoparasitized larvae (PL) was positively related and high parasite prevalence was found throughout the sampling period (up to 38%). Geometric morphometrics analyses indicate main changes in the shape through early ontogeny and subtle but significant variations between PL and non-parasitized larvae (NPL). Prey composition varied between PL and NPL; small size (<6 mm standard length, LS ) parasitized larval G. marmoratus ate mostly gastropod larvae, whereas small non-parasitized specimens ate mainly cirripede nauplii. All larger (>8 mm LS ), pre-settlement stages parasitized by Trifur and, or Caligus copepods had content in their gut, suggesting that ectoparasites did not diminish prey capture in host with larger size. Morphometric and dietary changes occurring during larval development were decoupled, both for PL and NPL. The maintenance of a slender, more hydrodynamic body through pelagic development and the ingestion of less-mobile prey in PL suggests non-lethal effects of ectoparasitism on rocky-reef fish larvae.

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Resumen: La determinación de los hábitos alimentarios permite la comprensión de muchos procesos ecológicos que se dan en los ecosistemas lóticos. El objetivo de este trabajo es: 1) conocer los hábitos alimentarios de ninfas de Claudioperla tigrina en un amplio gradiente altitudinal y latitudinal en Argentina; 2) asignar el grupo funcional trófico (GFT) de C. tigrina; 3) evaluar diferencias entre dietas de los sitios estudiados. Las ninfas estudiadas fueron recolectadas a lo largo de un amplio rango espacial en el noroeste de Argentina e incluyen diferentes estados del desarrollo (cuatro clases de tamaño). El material ingerido fue extraído de la parte anterior del tubo digestivo mediante disección ventral del tórax. Los perfiles dietarios fueron analizados a través de la estimación de parámetros de la distribución multinomial de Dirichlet. Se efectuaron ANOVA's para cada rubro alimentario en función de los sitios. Se utilizó la técnica Multidimensional Scaling (MDS) para identificar los sitios con perfiles alimentarios promedios similares. Se realizó un análisis de amplitud de nicho trófico para evaluar la diversificación de los recursos consumidos en cada sitio. El aparato bucal no muestra variaciones a lo largo del desarrollo ninfal, excepto una mayor esclerotización con la edad. Poseen palpos mandibulares y maxilares relativamente cortos y mandíbulas y maxilas fuertes, esclerozadas y dentadas. Las ninfas ingirieron más de un ítem alimentario, sugiriendo que se trata de una especie flexible en su alimentación. El ítem dominante en la dieta fue la MOPG, los signos de haber sido masticado indican hábitos trituradores. Se encontraron diferencias entre sitios para los ítems MOPF, invertebrados, algas y sedimento, pero no para MOPG. Se obtuvieron las correlaciones para cada eje del análisis MDS. Con el eje 1 se correlacionaron negativamente los sitios AP, LT, LI, C y M (Selva de Yungas y Pastizal de neblina) asociados a un mayor consumo de MOPF, en el lado positivo del eje se encontró el sitio P (Altos Andes) asociado a los ítems invertebrados y sedimento. Para el eje 2 se relacionaron positivamente IN (Pastizal neblina) y LR (Monte de Sierras y Bolsones) con la presencia de algas. Los resultados del análisis de amplitud de nicho revelaron diferencias en el uso de los recursos secundarios de la dieta en los sitios estudiados que puede deberse a la oferta ambiental en las ecorregiones consideradas. El GFT de C. tigrina es triturador/ recolector en Selva de Yungas y Pastizales de Neblina y triturador/ depredador en Altos Andes. La definición del GFT de C. tigrina y el establecimiento de su rol como procesador primario de materia orgánica representa un paso importante para futuros estudios de redes tróficas y otras metodologías basadas en los grupos funcionales.

Abstract: Dietary information gives insight into several ecological processes acting in lotic ecosystems. This work aimed: 1) to identify the dietary habits of Claudioperla tigrina immature stages along a wide altitudinal as well as latitudinal gradient in North Argentina; 2) to define the functional feeding group (FFG) of C. tigrina; 3) to evaluate differences in diet in the studied sites. Studied nymphs were collected from localities widely scattered in Northwestern Argentina and they fell into different developmental stages (four size classes). The ingested material was extracted from the foregut and midgut by using thorax ventral dissection. Dietary profiles were analyzed through the estimation of parameters associated with a Dirichletmultinomial distribution. ANOVA's were performed for each food item using sites as factor. Multidimensional Scaling was used to identify sites with similar dietary profiles. An analysis of food-niche breadth was also performed to evaluate the degree of dietary diversification for the resources consumed in each site. Mouthparts are similar across the different size classes, excepting the increasing sclerotization recorded with age. Mouthparts retained most of the typical chewing groundplan, showing relatively short labial and maxillar palps, and strong, sclerotized and denticulated mandibles and maxillae. Our results pointed out that the nymphs of C. tigrina always ingest two or more food items (CPOM, FPOM, invertebrates and algae), suggesting thus a flexible diet. The diet changed in relation to body size, while finer particles were consumed in the early stages, larger particles were ingested in final stages. Coarse particulate organic matter was the dominant food item, with signals of shredding during ingestion. Differences between sites for FPOM, invertebrates, algae and sediment were detected, but not for MOPG. Correlations were obtained for the first two axis of the MDS analysis. Sites AP, LT, LI, C and M (Yungas Rainforest and Humid Grassland) were negatively correlated with the axis 1 which was associated with increased consumption of FPOM. On the positive side of the axis the site P (High Andes) is associated with a greater proportion of invertebrates and sediment. The sites IN (Humid Grassland) and LR (Argentine Northwest Monte and Thistle of the Prepuna) were located at the positive domain of axis 2 which is in turn associated with a greater count of algae in the dietary contents. We found significant differences in the quantity of secondary items, and this is likely related with the resources environmental availability. The FFG of Claudioperla tigrina is primarily shredder/collector-gatherer in Yungas Rainforest and Humid Grassland shredder/predator in High Andes. FFG classification of C. tigrina and the definition of their role for organic matter processing is an important step for future studies based on functional groups such as analysis of food webs. Rev. Biol. Trop. 65 (3): 1174-1184. Epub 2017 September 01.

RESUMO

DNA methods are useful to identify ingested prey items from the gut of predators, but reliable detection is hampered by low amounts of degraded DNA. PCR-based methods can retrieve minute amounts of starting material but suffer from amplification biases and cross-reactions with the predator and related species genomes. Here, we use PCR-free direct shotgun sequencing of total DNA isolated from the gut of the harlequin ladybird Harmonia axyridis at five time points after feeding on a single pea aphid Acyrthosiphon pisum. Sequence reads were matched to three reference databases: Insecta mitogenomes of 587 species, including H. axyridis sequenced here; A. pisum nuclear genome scaffolds; and scaffolds and complete genomes of 13 potential bacterial symbionts. Immediately after feeding, multicopy mtDNA of A. pisum was detected in tens of reads, while hundreds of matches to nuclear scaffolds were detected. Aphid nuclear DNA and mtDNA decayed at similar rates (0.281 and 0.11 h(-1) respectively), and the detectability periods were 32.7 and 23.1 h. Metagenomic sequencing also revealed thousands of reads of the obligate Buchnera aphidicola and facultative Regiella insecticola aphid symbionts, which showed exponential decay rates significantly faster than aphid DNA (0.694 and 0.80 h(-1) , respectively). However, the facultative aphid symbionts Hamiltonella defensa, Arsenophonus spp. and Serratia symbiotica showed an unexpected temporary increase in population size by 1-2 orders of magnitude in the predator guts before declining. Metagenomics is a powerful tool that can reveal complex relationships and the dynamics of interactions among predators, prey and their symbionts.

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In order to define the effect of nutrient enrichment on trophic webs in an Andean mountain stream we performed an experiment using stable isotope ratios (δ15N and δ13C) to analyze different trophic compartments: 1) basal level: CPOM and biofilm; 2) primary consumers - macroinvertebrates: collector-gatherers (Heterelmis sp., Thraulodes sp. and Trichorythodes sp.), and collectorfilterers (Simulium sp.); 3) predators - fish (Oncorhynchus mykiss and Trichomycterus bogotensis). The average fractionation of nitrogen among the primary consumers with respect to CPOM was 4.7 ‰, and 1.7 ‰ with respect to biofilm. Predators incremented their δ15N signal by 5.9 % with respect to primary consumers. A depletion of δ15N was observed in Impact with respect to Control reach after fertilization in different compartments (biofilm, Heterelmis, Simulium andTricorythodes), while depletion was not significant for top predators. In most cases, the δ13C signal of biofilm overlapped with that of primary consumers, but a clear enrichment was observed with respect to CPOM. Macroinvertebrate gut contents showed fine detritus to be their most abundant food, and that in general there were no changes in diet as a consequence of nutrient enrichment. The only exception was Heterelmis, who increased its consumption in the Impact reach.

Con el fin de determinar el efecto del incremento de nutrientes sobre la red trófica de un río de montaña andino, se realizó un experimento en donde se analizaron las proporciones de isotopos estables (δ15N y δ13C) para analizar los siguientes compartimientos tróficos: 1) Nivel basal: CPMO y Biofilm; 2) Consumidores primarios - macroinvertebrados: colectores - recolectores (Heterelmis sp., Thraulodes sp., yTrichorythodes sp.) y colectores - filtradores (Simulium sp.); 3) Depredadores - peces (Oncorhynchus mykiss y Trichomycterus bogotensis). La fracción promedio de nitrógeno entre los consumidores primarios con respecto a CPOM fue de 4.7 ‰, y de 1.7 ‰ con respecto al biofilm. Los depredadores incrementaron en un 5.9 % la señal δ15N con respecto a los consumidores primarios. Después de la fertilización, se observó en diferentes compartimientos (biofilm, Heterelmis, Simulium yTricorythodes) del tramo impacto un agotamiento de δ15N con respecto al control, mientras que el agotamiento no fue significativo para los depredadores superiores. En la mayoría de los casos la señal δ13C del biofilm se sobrepuso con la de los consumidores primarios pero un claro enriquecimiento fue observado con respecto a CPOM. Los macroinvertebrados referidos fueron seleccionados para analizar su contenido estomacal y los resultados nos mostraron que el detritus fino es el alimento más abundante para los invertebrados, y únicamente, Heterelmis mostró, después de la adición de nutrientes, diferencias significativas en el detritus fino y el material vegetal entre el tramo control y el impactado.

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This study aimed at analyzing the influence of different levels of environmental integrity of streams of the Ivinhema river basin (Mato Grosso do Sul State, Brazil) on the diet of A. altiparanae. Samplings were performed from July 2001 to November 2011 at 101 sites, using sieves, seining and gill nets, and electrofishing. Streams were classified into three levels of environmental integrity. We analyzed 664 stomachs with the methods of frequency of occurrence and volumetric analysis index, combined in the Importance Index (AI). The species was omnivorous, with predominance of allochthonous resources. At the least impacted sites, the most representative resource was allochthonous plant material; and in the altered sites in the rainy period the most consumed item was allochthonous arthropods. On the other hand, at the most impacted sites in the dry period there was a lower consumption of allochthonous plant material and allochthonous arthropods, compared with other levels of environmental integrity considered, with higher consumption of autochthonous arthropods. The results evidenced that in the least impacted sites there was greater contribution from allochthonous resources, probably because these environments show a more preserved riparian forest.

Este estudo teve como objetivo analisar se os diferentes níveis de integridade ambiental de riachos da bacia do rio Ivinhema (Mato Grosso do Sul, Brasil) influenciam a dieta da espécie A. altiparanae. As amostragens foram realizadas entre julho/2001 e novembro/2011, em 101 locais, utilizando peneiras, rede de arrasto, rede de espera e pesca elétrica. Os riachos foram categorizados em três níveis de integridade ambiental. Foram analisados 664 estômagos pelos métodos de frequências de ocorrência e índice de análise volumétrica, combinados no Índice de Importância Alimentar (AI). A espécie apresentou hábito alimentar onívoro, com predomínio de recursos alóctones. Nos locais menos impactados, o recurso mais representativo foi material vegetal alóctone; nos locais alterados, no período chuvoso, o item mais consumido foi artrópodes alóctones. Por outro lado, nos locais mais impactados, no período seco, houve menor consumo de material vegetal alóctone e artrópodes alóctones, em comparação aos outros níveis de integridade ambiental analisados, com maior consumo do item artrópodes autóctones. Os resultados evidenciaram que em locais menos impactados houve maior contribuição de recursos alimentares alóctones, provavelmente porque estes ambientes apresentam mata ciliar mais conservada.

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This study aimed at analyzing the influence of different levels of environmental integrity of streams of the Ivinhema river basin (Mato Grosso do Sul State, Brazil) on the diet of A. altiparanae. Samplings were performed from July 2001 to November 2011 at 101 sites, using sieves, seining and gill nets, and electrofishing. Streams were classified into three levels of environmental integrity. We analyzed 664 stomachs with the methods of frequency of occurrence and volumetric analysis index, combined in the Importance Index (AI). The species was omnivorous, with predominance of allochthonous resources. At the least impacted sites, the most representative resource was allochthonous plant material; and in the altered sites in the rainy period the most consumed item was allochthonous arthropods. On the other hand, at the most impacted sites in the dry period there was a lower consumption of allochthonous plant material and allochthonous arthropods, compared with other levels of environmental integrity considered, with higher consumption of autochthonous arthropods. The results evidenced that in the least impacted sites there was greater contribution from allochthonous resources, probably because these environments show a more preserved riparian forest.

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This study aimed at analyzing the influence of different levels of environmental integrity of streams of the Ivinhema river basin (Mato Grosso do Sul State, Brazil) on the diet of A. altiparanae. Samplings were performed from July 2001 to November 2011 at 101 sites, using sieves, seining and gill nets, and electrofishing. Streams were classified into three levels of environmental integrity. We analyzed 664 stomachs with the methods of frequency of occurrence and volumetric analysis index, combined in the Importance Index (AI). The species was omnivorous, with predominance of allochthonous resources. At the least impacted sites, the most representative resource was allochthonous plant material; and in the altered sites in the rainy period the most consumed item was allochthonous arthropods. On the other hand, at the most impacted sites in the dry period there was a lower consumption of allochthonous plant material and allochthonous arthropods, compared with other levels of environmental integrity considered, with higher consumption of autochthonous arthropods. The results evidenced that in the least impacted sites there was greater contribution from allochthonous resources, probably because these environments show a more preserved riparian forest. 

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Se analizó el contenido intestinal de nueve géneros de Chironominae y Tanypodinae bentónicos en ambientes de la llanura aluvial del río Paraná Medio (laguna y cauce secundario) para determinar su patrón alimentario y los grupos funcionales tróficos. En los contenidos intestinales se observaron detrito amorfo, material mineral (principalmente arena), tejidos vegetal y animal. El principal ítem alimentario encontrado en Polypedilum (Tripodura) sp., Chironomus gr. decorus sp., Endotribelos sp., Phaenopsectra sp., Cladopelma sp. y Pelomus sp. (Chironominae) fue detrito amorfo, mientras que en Ablabesmyia (Karelia) sp., Coelotanypus sp. y Procladius sp. (Tanypodinae) el ítem más importante fue tejido animal (principalmente restos de oligoquetos). Se calculó el solapamiento trófico entre todos los pares de géneros, obteniéndose el mayor solapamiento dentro de los depredadores entre Coelotanypus sp. y Ablabesmyia (Karelia) sp. y dentro de los detritívoros entre Endotribelos sp. y Phaenopsectra sp.

The gut contents of nine genera of benthic Chironominae and Tanypodinae from the Middle Paraná River floodplain habitats (a lake and a secondary channel) were analyzed to determine their feeding patterns and functional feeding groups. Amorphous detritus, animal and vegetal tissues, and mineral materials (predominantly sand) were observed in the larval guts. Amorphous detritus were the main food item found for Polypedilum (Tripodura) sp., Chironomus gr. decorus sp., Endotribelos sp., Phaenopsectra sp., Cladopelma sp., and Pelomus sp. (Chironominae), while animal tissues (mainly oligochaetes) were the most important food item found for Ablabesmyia (Karelia) sp., Coelotanypus sp., and Procladius sp. (Tanypodinae). Dietary overlap was calculated for all pairs of genera. Within predators, the highest overlap was obtained between Coelotanypus sp. and Ablabesmyia (Karelia) sp., while within detritivores the highest niche overlap was obtained between Endotribelos sp. and Phaenopsectra sp.

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Se analizó el contenido intestinal de nueve géneros de Chironominae y Tanypodinae bentónicos en ambientes de la llanura aluvial del río Paraná Medio (laguna y cauce secundario) para determinar su patrón alimentario y los grupos funcionales tróficos. En los contenidos intestinales se observaron detrito amorfo, material mineral (principalmente arena), tejidos vegetal y animal. El principal ítem alimentario encontrado en Polypedilum (Tripodura) sp., Chironomus gr. decorus sp., Endotribelos sp., Phaenopsectra sp., Cladopelma sp. y Pelomus sp. (Chironominae) fue detrito amorfo, mientras que en Ablabesmyia (Karelia) sp., Coelotanypus sp. y Procladius sp. (Tanypodinae) el ítem más importante fue tejido animal (principalmente restos de oligoquetos). Se calculó el solapamiento trófico entre todos los pares de géneros, obteniéndose el mayor solapamiento dentro de los depredadores entre Coelotanypus sp. y Ablabesmyia (Karelia) sp. y dentro de los detritívoros entre Endotribelos sp. y Phaenopsectra sp.

The gut contents of nine genera of benthic Chironominae and Tanypodinae from the Middle Paraná River floodplain habitats (a lake and a secondary channel) were analyzed to determine their feeding patterns and functional feeding groups. Amorphous detritus, animal and vegetal tissues, and mineral materials (predominantly sand) were observed in the larval guts. Amorphous detritus were the main food item found for Polypedilum (Tripodura) sp., Chironomus gr. decorus sp., Endotribelos sp., Phaenopsectra sp., Cladopelma sp., and Pelomus sp. (Chironominae), while animal tissues (mainly oligochaetes) were the most important food item found for Ablabesmyia (Karelia) sp., Coelotanypus sp., and Procladius sp. (Tanypodinae). Dietary overlap was calculated for all pairs of genera. Within predators, the highest overlap was obtained between Coelotanypus sp. and Ablabesmyia (Karelia) sp., while within detritivores the highest niche overlap was obtained between Endotribelos sp. and Phaenopsectra sp.

RESUMO

The diet of macroinvertebrates sampled in leaf-bags incubated in a tropical stream was analyzed on a spatial scale (one forested and one deforested area) and on a temporal scale (dry and rainy seasons). The macroinvertebrates were mostly represented by detritivores specialized in fine detritus (69%), followed by generalist detritivores (10% with a diet based on fine and coarse detritus), carnivores (10%), omnivores (8%), and one detritivore genera specialized on coarse detritus (3%). The detritivores exhibited a broad spatial and temporal distribution and were represented mainly by Ephemeroptera, Trichoptera and Diptera. Phylloicus sp. (Trichoptera) consumed mostly coarse detritus (CPOM) and can be classified as the unique specialist shredder in this stream. Carnivores were represented by Anacroneuria sp. (Plecoptera), Hetaerina sp. and Heteragrion sp. (two Odonata). Omnivory was observed for Anacroneuria sp. and Smicridea sp. (Trichoptera), which evidently varied spatially and temporally in the proportion of the food consumed. The high diversity and the wide distribution of the taxa that used organic matter as food resource demonstrated the great importance of this food item to the macroinvertebrates community in this tropical stream.

RESUMO

The diet of macroinvertebrates sampled in leaf-bags incubated in a tropical stream was analyzed on a spatial scale (one forested and one deforested area) and on a temporal scale (dry and rainy seasons). The macroinvertebrates were mostly represented by detritivores specialized in fine detritus (69%), followed by generalist detritivores (10% with a diet based on fine and coarse detritus), carnivores (10%), omnivores (8%), and one detritivore genera specialized on coarse detritus (3%). The detritivores exhibited a broad spatial and temporal distribution and were represented mainly by Ephemeroptera, Trichoptera and Diptera. Phylloicus sp. (Trichoptera) consumed mostly coarse detritus (CPOM) and can be classified as the unique specialist shredder in this stream. Carnivores were represented by Anacroneuria sp. (Plecoptera), Hetaerina sp. and Heteragrion sp. (two Odonata). Omnivory was observed for Anacroneuria sp. and Smicridea sp. (Trichoptera), which evidently varied spatially and temporally in the proportion of the food consumed. The high diversity and the wide distribution of the taxa that used organic matter as food resource demonstrated the great importance of this food item to the macroinvertebrates community in this tropical stream.

RESUMO

The diet of macroinvertebrates sampled in leaf-bags incubated in a tropical stream was analyzed on a spatial scale (one forested and one deforested area) and on a temporal scale (dry and rainy seasons). The macroinvertebrates were mostly represented by detritivores specialized in fine detritus (69%), followed by generalist detritivores (10% with a diet based on fine and coarse detritus), carnivores (10%), omnivores (8%), and one detritivore genera specialized on coarse detritus (3%). The detritivores exhibited a broad spatial and temporal distribution and were represented mainly by Ephemeroptera, Trichoptera and Diptera. Phylloicus sp. (Trichoptera) consumed mostly coarse detritus (CPOM) and can be classified as the unique specialist shredder in this stream. Carnivores were represented by Anacroneuria sp. (Plecoptera), Hetaerina sp. and Heteragrion sp. (two Odonata). Omnivory was observed for Anacroneuria sp. and Smicridea sp. (Trichoptera), which evidently varied spatially and temporally in the proportion of the food consumed. The high diversity and the wide distribution of the taxa that used organic matter as food resource demonstrated the great importance of this food item to the macroinvertebrates community in this tropical stream.

RESUMO

The catfish, Eremophilus mutisii, was cultured under different densities in artificial rainfall reservoirs at Caldas, Boyacá, Colombia. At capture, the average total length of the animals was 10 cm and the weight ranged between 9 and 10 g. These fish were in initial stages of sexual development. After a year in the reservoirs, they had increased in length and weight as follows (densities in parentheses): 5.22 cm and 27.23 g (0.5 individuals/m2); 1.98 cm and 8.79 g (1 individual/m2), and 2.45 cm and 0.82 g (2 individuals/m2). They were at the early stages of sexual maturity, and their condition factor fluctuated between 0.61 and 0.96. They preferably ingested insect larvae that were found in benthic and littoral communities of the reservoirs. The benthos was dominated by ephippia of Daphnia, lumbriculids, and chironomid larvae. The biomass of benthic organisms ranged between 0.1126 and 1.3847 g/m2. In the littoral community aquatic insects were the most important component, especially the hemipterans. The biomass of the littoral fauna ranged between 0.14 and 4.05 g/m2.

El “capitán de la sabana”, Eremophilus mutisii (Humboldt, 1805), fue cultivado en diferentes densidades en pequeños lagos artificiales localizados en Caldas, Boyacá, Colombia. Al inicio, el promedio de la longitud corporal fue 10 cm y el peso osciló entre 9 y 10 gr. Los peces se encontraban en estados iniciales de desarrollo sexual. Luego de un año de experimentación, los peces cultivados a una densidad de 0.5 ind/m2 incrementaron 5.22 cm en longitud y 27.23 gr en promedio (1 ind/m2: 1.98 cm y 8.79 gr; 2 ind/m2: 2.45 cm y 0.82 gr). Los peces se encontraban iniciando su madurez sexual, y su factor de condición fluctuó entre 0.61 y 0.96 y consumían principalmente larvas de insectos. El bentos estaba dominado por efipios de Daphnia, lumbricúlidos y larvas de quironómidos. La biomasa de organismos benticos osciló entre 0.1126 y 1.3847 gr/m2. En la comunidad litoral, los insectos acuáticos fueron los componentes mas importantes, especialmente los hemípteros. La biomasa de la fauna litoral osciló entre 0.14 y 4.05 gr/m2.

Assuntos