Linking anatomical and histological traits of the digestive tract to resource consumption and assimilation of omnivorous tetra fishes.

This study explores the interplay between digestive tract traits, food intake, and assimilation in omnivorous tetra fishes (Psalidodon bifasciatus, P. aff. gymnodontus, and Bryconamericus ikaa) from the Iguaçu River basin, an ecologically significant region known for high endemism. We hypothesize that variations in digestive tracts across species would be associated with differences in diet, isotopic composition in fish tissues, and overall diet assimilation. To test this, we employed stereoscopic and light microscopy to characterize the gross anatomy, histomorphology, and histochemistry of fish digestive tracts. Additionally, we used stomach content and stable isotope analyses to trace fish diets. While these tetra fishes shared histological structures, disparities were noted in anatomical digestive traits and diet preferences. The smallest species, B. ikaa, with a shorter intestine, had fewer pyloric caeca and primarily consumed animal-based diets. Conversely, P. bifasciatus and P. aff. gymnodontus, with longer intestines, displayed numerous pyloric caeca and consumed a balanced mix of animal and plant items. Despite anatomical and dietary differences, all three species predominantly assimilated animal-origin food. The tetra fishes had histological variations among digestive tract segments, with the esophagus having the thickest muscular layer, gradually thinning towards the posterior intestine. The final portion of the intestine exhibited a significant expansion in the lumen perimeter, while the esophagus had the smallest lumen area. Goblet cells were most concentrated in the posterior intestine for all species. The gross anatomy of these tetra fishes aligns with their omnivorous habit, while diet assimilation was dominated by animal-origin food. These findings provide crucial insights into the structural and tissue characteristics of their digestive systems, laying the groundwork for deeper exploration into the physiological aspects of their digestive tracts and enhancing our understanding of their feeding strategies.

What are the global patterns of microplastic ingestion by fish? A scientometric review.

The billions of tons of plastic released into the environment mostly fragment into smaller particles that reach rivers and oceans, posing toxicity risks to aquatic organisms. As fish serve as excellent environmental indicator organisms, this study aims to comprehensively review and quantify published data regarding the abundance of microplastics (MPs) ingested by fish through scientometric analysis. Systematic analysis reveals that global aquatic ecosystems are contaminated by MPs, with the characteristics of these contaminants stemming from inadequate disposal management practices. The abundance of MPs was recorded in several fish species, notably Cyprinus carpio in natural environments and Danio rerio in controlled environments. According to the surveyed studies, laboratory experiments do not accurately represent the conditions found in natural environments. The results suggest that, in natural environments, the predominant colors of MPs are blue, black, and red. Fibers emerged as the most prevalent type, with polyethylene (PE) and polypropylene (PP) being the most frequently identified chemical compositions. On the other hand, laboratory studies showed that the spheres and fragments ingested were predominantly polystyrene (PS) green, followed by the colors blue and red. This discrepancy complicates drawing accurate conclusions regarding the actual effects of plastic particles on aquatic biota. Given the enduring presence of plastic in the environment, it is imperative to consider and implement environmental monitoring for effective, long-term management.

Metals in species of the Cambeva (Teleostei: Trichomycteridae) genus of the Iguaçu River basin (Brazil).

The population growth is connected to the demand for resources and waste disposal in water. Metals are among several pollutants affecting aquatic ecosystems, posing risks to biota when in high concentrations. Metals can present a great danger to the aquatic ecosystem because they are not degradable and can bioaccumulate. Many rivers are already considered highly polluted. Among them is the Iguaçu River, located in southern Brazil, which is recognized for the Iguaçu Falls and its rate of endemism. One species of the Cambeva genus is among the endemic species found in the Iguaçu River and is threatened with extinction due to anthropization. Thus, we aimed to evaluate and compare the concentrations of copper, zinc, iron, lead, manganese, and cadmium in Cambeva stawiarski and Cambeva sp. 1 in four different streams of the Iguaçu River (Brazil). We collected 20 fish in two municipalities along the Iguaçu River tributaries. The results showed a statistical difference in the metal concentrations in different species and locations, mainly manganese, iron, and copper, observed in both species and municipalities and cadmium, which showed a statistical difference only for C. sp1. Fish from agricultural regions generally had the highest concentrations of metals, some above the permitted limits. Cadmium was found at high concentrations, generating great ecological concern since it is one of the most toxic metals, even in small quantities. The lack of limits in Brazilian legislation makes it challenging to predict the long-term effects of iron.

Effects of human disturbance on habitat and fish diversity in Neotropical streams.

Human pressures have been intensely modifying freshwater ecosystems worldwide. We assessed the effects of human pressure on habitat diversity and primary productivity to understand the consequences on fish fauna in 25 tropical and subtropical streams of two globally important ecoregions: Iguassu and Upper Paraná. We hypothesized that the increased human pressure (urbanization and agriculture) on stream environments, both at the local and catchment scales, directly decreases habitat diversity. We also hypothesized that increased human pressure triggers changes in primary productivity and fish fauna composition and structure. We evaluated the human pressure intensity using the Integrated Disturbance Index and the Rapid Habitat Diversity Assessment protocol, which combines information about land use, land cover and environmental characteristics of the stream catchment and sampling sites. Streams with increased human disturbance had lower habitat diversity, higher primary productivity, and high non-native species abundance. Fish compositional turnover was associated with increased human disturbance. Native and degradation-sensitive fish species, especially endemic ones, were associated with streams with higher habitat diversity and forested cover. Degradation-resistant fishes, mostly non-native species, were associated with streams with higher human disturbance and urban land use. Although human pressure did not affect species richness, Shannon diversity, and Simpson dominance, there were significant effects on numerical abundance and fish species equitability. In this study, human pressure directly affected habitat structure, with indirect consequences for fish fauna, increasing the potential for local extirpation of rare species.

Parasites and diet of Serrasalmus maculatus in a hydroelectric reservoir in Brazil.

Serrasalmus maculatus is a species of piranha which, despite being abundant in a reservoir environment, has few studies related to its parasitological and diet aspects. Thus, we aimed to document the parasitic fauna and diet of the S. maculatus in a hydroelectric reservoir in Brazil. In addition, we perform two literature reviews for the Neotropical region, recording the parasitic fauna already associated with S. maculatus and the occurrence of parasite genera identified in this study parasitizing Characiformes from other aquatic systems. Thirty-one hosts were collected with gillnets, from August 2014 to September 2016. Serrasalmus maculatus had a piscivorous feeding habit and a low richness parasitic component community, including two taxa of monogeneans, Anacanthorus lepyrophallus and Mymarothecium sp.; no endohelminths were observed. Data from the literature review, together with the findings of the study, showed that S. maculatus in the Neotropical region harbors 25 helminth taxa, with the monogenean being the most prevalent parasitic group and Brazil is the country with the most reports of the parasitic genera. These findings provide information on the relationships between diet, social behavior, and parasitic fauna of S. maculatus and on the patterns of distribution and infection of the observed parasite rates.

Parasites and diet of Serrasalmus maculatus in a hydroelectric reservoir in Brazil / Parasitos e dieta de Serrasalmus maculatus em um reservatório no Brasil

Abstract Serrasalmus maculatus is a species of piranha which, despite being abundant in a reservoir environment, has few studies related to its parasitological and diet aspects. Thus, we aimed to document the parasitic fauna and diet of the S. maculatus in a hydroelectric reservoir in Brazil. In addition, we perform two literature reviews for the Neotropical region, recording the parasitic fauna already associated with S. maculatus and the occurrence of parasite genera identified in this study parasitizing Characiformes from other aquatic systems. Thirty-one hosts were collected with gillnets, from August 2014 to September 2016. Serrasalmus maculatus had a piscivorous feeding habit and a low richness parasitic component community, including two taxa of monogeneans, Anacanthorus lepyrophallus and Mymarothecium sp.; no endohelminths were observed. Data from the literature review, together with the findings of the study, showed that S. maculatus in the Neotropical region harbors 25 helminth taxa, with the monogenean being the most prevalent parasitic group and Brazil is the country with the most reports of the parasitic genera. These findings provide information on the relationships between diet, social behavior, and parasitic fauna of S. maculatus and on the patterns of distribution and infection of the observed parasite rates.

Resumo Serrasalmus maculatus é uma espécie de piranha que, a despeito de ser abundante em ambiente de reservatório, possui poucas informações sobre seus aspectos parasitológicos e dieta. Assim, o presente estudo objetivou documentar a fauna parasitária e a dieta de S. maculatus em um reservatório brasileiro. Além disso, foram realizadas duas revisões literárias para a região Neotropical, registrando a fauna parasitária, já associada a S. maculatus e a ocorrência dos gêneros parasitários identificados neste estudo, registrados em outros peixes Characiformes em outros sistemas aquáticos. Foram coletados 31 hospedeiros com redes de espera entre agosto de 2014 e setembro de 2016. Serrasalmus maculatus apresentou hábito alimentar piscívoro e comunidade componente parasitária com baixa riqueza, incluindo dois táxons de monogenéticos, Anacanthorus lepyrophallus e Mymarothecium sp.; não foram observados endohelmintos. Dados da revisão da literatura, juntamente com os achados deste estudo, mostraram que S. maculatus, na região Neotropical, abriga 25 táxons de helmintos, sendo monogenéticos o grupo de parasitos mais prevalente, e o Brasil o país com mais relatos de parasitos. Estes resultados fornecem informações sobre as relações entre dieta, o comportamento social e a fauna parasitária de S. maculatus e sobre os padrões de distribuição e infecção das taxas de parasitos observadas.

Morphological divergences as drivers of diet segregation between two sympatric species of Serrapinnus (Characidae: Cheirodontinae) in macrophyte stands in a neotropical floodplain lake

Diet and morphology of Serrapinnus notomelas and Serrapinnus sp.1 were investigated across ontogeny, as a way to elucidate the key elements linked to the resource partitioning (a main driver for species coexistence). Fish sampling was conducted monthly between October 2010 and March 2012. Individuals were captured, identified, and classified into juvenile or adult. Our results show ontogenetic and interspecific differences in feeding abilities and morphological traits. Differences in body shape (relative area of the dorsal fin, length of head, height of the caudal peduncle, the aspect ratio of the pectoral and pelvic fin) favored divergent swimming performances (more maneuverability in S. notomelas and continuous swimming to Serrapinnus sp.1). We also observed divergences in trophic apparatus traits and correlations with different diets. In this context, it is highlighted that understanding the relationship between morphology and diet can assist in elucidating the processes that permeate the coexistence between sympatric species, and between ontogenetic periods. Besides, the relevant contribution of the measures of the trophic apparatus (gill raker length, the number of teeth cuspids, and intestinal coefficient) in trophic segregation seems to be a strong evidence in favor of the proposed discriminatory and predictive capacities of these traits.(AU)

Dieta e morfologia de Serrapinnus notomelas e Serrapinnus sp.1 foram investigadas ao longo da ontogenia, como forma de elucidar os principais elementos ligados à partição de recursos (principal fator para a coexistência entre espécies). Foram realizadas coletas de peixes mensalmente entre outubro de 2010 e março de 2012. Os indivíduos foram capturados, identificados e classificados em juvenis ou adultos. Nossos resultados mostram diferenças ontogenéticas e interespecíficas na alimentação e características morfológicas. Diferenças na forma corporal (área da nadadeira dorsal, comprimento da cabeça, altura do pedúnculo caudal, proporção das nadadeiras peitorais e pélvicas) favoreceram desempenhos de natação divergentes (maior manobrabilidade para S. notomelas e natação contínua para Serrapinnus sp.1). Também observamos divergências nas características do aparato trófico e correlações com diferentes dietas. Nesse contexto, destaca-se que compreender a relação entre morfologia e dieta pode auxiliar na elucidação dos processos que permeiam a coexistência entre espécies simpátricas e entre períodos ontogenéticos. Além disso, a relevante contribuição das medidas do aparato trófico (número de cúspide nos dentes, rastros branquiais e coeficiente intestinal) na segregação trófica parece ser uma forte evidência a favor das propostas de capacidades discriminatórias e preditivas dessas características.(AU)

The biotic condition of dams run-of-the-river in sequence: adaptation of a multimetric index based on the Neotropical fish fauna.

The synergistic effects of run-of-the-river (ROR) on fish fauna, though still poorly understood, are amplified when dams form reservoir cascades. In an attempt to assist in this understanding, we used an adaptation of the Reservoir Fish Assemblage Index (RFAI) to evaluate the biotic conditions of the Rio das Antas Energy Complex, in the Neotropical Patos Lagoon ecoregion. We evaluated the attributes of the fish fauna from the point of view of the complex, for each reservoir and between different sections. Fish samplings were performed quarterly at nine sites for 2 years (2015-2017). We proposed 26 metrics, related to aspects of composition, reproduction, feeding, habitat, and tolerance, selected based on criteria of variability, responsiveness, and redundancy. The final RFAI score was distributed in four categories of biological status, based on the best-observed condition. Eight metrics composed the final index, among which, only the proportion of nektonic individuals + nektobenthic (PNNbI) correlated with all sections. The final RFAI was classified as poor in all sections of the reservoir cascade, showing no significant differences between the sampling sites. This scenario indicates that dams in sequence intensify and homogenize the amplitude of fragmentation impacts on fish fauna. The final RFAI proved to be representative of the transition sections, emphasizing the importance of these reaches in impounded environments. Although the disturbance scales presented here are applicable mainly to ROR systems with reduced discharge section, the index was developed so as to allow its replicability in any dammed water course.

Histopathological alterations in gills of a fish (Astyanax bifasciatus) in neotropical streams: negative effects of riparian forest reduction and presence of pesticides.

The reduction of riparian vegetation around aquatic environments causes several physicochemical alterations and favors the entry of pesticides via surface runoff. Such changes have negative effects on aquatic organisms. In this study, we evaluated histopathological alterations in gills of Astyanax bifasciatus to test the hypothesis that more severe histopathological alterations occur in gills of fish from streams with higher agricultural impact from the surrounding area. The specimens were collected by electrofishing in seven streams of the lower Iguaçu basin between August 2015 and February 2016. The gills were processed according to routine histological methods and examined by light microscopy. The histopathological alterations, mainly stage II (lamellar aneurysm and total fusion of lamellae), were observed in fish collected in streams with higher agricultural activity. In these streams, the histopathological index indicated slight to moderate organ lesions. In contrast, in streams with more vegetation cover, fish collected presented stage I histopathological alterations (lamellar edema and lamellar hyperplasia), and the HI indicated normal functioning of the gills. In addition, chloride and acid mucous cells were more abundant in the gills of fish collected in rural streams. Our findings demonstrate that more severe histopathological alterations were registered in fish collected from streams with intense agricultural activity in the surrounding area. Therefore, it highlights that vegetation cover around the streams is a positive force for the conservation and health of aquatic organisms.

Dolops carvalhoi as a vector of Epistylis sp. between cultivated and wild specimens of Oreochromis niloticus in Brazil.

Epistyliasis has been characterized as an emergent disease which has a great impact on fish farms, especially on Oreochromis niloticus production systems. Although epidemiological important, information about the dispersion of these parasites and their mechanical vectors is scarce. The present study reported the cooccurrence of Epistylis sp. as an epibiont of Dolops carvalhoi, a parasitic crustacean of cultivated/wild specimens (from accidental release) of O. niloticus from a cage fish farm area in the Ilha Solteira Reservoir, Grande River, SP, Brazil. The co-occurrence of Epistylis sp. and D. carvalhoi, and their epibiont relationship registered in this study suppose that the Epistylis may use the crustaceans for dispersion and as mechanical vectors for the dissemination of diseases in wild and cultivated hosts. Moreover, exchange of parasites between wild and cultivated hosts is possible, considering both organisms (protozoan and argulid). Furthermore, the results of the present study demonstrate the need to monitor the areas adjacent to cage fish farms as a preventive measure for the dispersion of pathogens. This is the first report of epibiosis between Epistylis sp. and argulid parasites of cultivated and wild O. niloticus, contributing to knowledge about host-parasite specificity, geographical distribution, dispersion of etiological agents and epidemiology in aquaculture.

Dolops carvalhoi as a vector of Epistylis sp. between cultivated and wild specimens of Oreochromis niloticus in Brazil / Dolops carvalhoi como vetor de Epistylis sp. entre espécimes cultivados e silvestres de Oreochromis niloticus no Brasil

Abstract Epistyliasis has been characterized as an emergent disease which has a great impact on fish farms, especially on Oreochromis niloticus production systems. Although epidemiological important, information about the dispersion of these parasites and their mechanical vectors is scarce. The present study reported the cooccurrence of Epistylis sp. as an epibiont of Dolops carvalhoi, a parasitic crustacean of cultivated/wild specimens (from accidental release) of O. niloticus from a cage fish farm area in the Ilha Solteira Reservoir, Grande River, SP, Brazil. The co-occurrence of Epistylis sp. and D. carvalhoi, and their epibiont relationship registered in this study suppose that the Epistylis may use the crustaceans for dispersion and as mechanical vectors for the dissemination of diseases in wild and cultivated hosts. Moreover, exchange of parasites between wild and cultivated hosts is possible, considering both organisms (protozoan and argulid). Furthermore, the results of the present study demonstrate the need to monitor the areas adjacent to cage fish farms as a preventive measure for the dispersion of pathogens. This is the first report of epibiosis between Epistylis sp. and argulid parasites of cultivated and wild O. niloticus, contributing to knowledge about host-parasite specificity, geographical distribution, dispersion of etiological agents and epidemiology in aquaculture.

Resumo Epistilíase tem sido caracterizada como uma doença emergente de grande impacto nas pisciculturas, especialmente em sistemas de produção de Oreochromis niloticus. Embora seja importante epidemiologicamente, informações sobre a dispersão desses parasitas e seus vetores mecânicos são escassos. O presente estudo relata a coocorrência de Epistylis sp. como um epibionte de Dolops carvalhoi, um crustáceo parasita de espécimes cultivados e silvestres (de escapes acidentais) de O. niloticus em área de piscicultura de tanques-rede no reservatório de Ilha Solteira, Rio Grande, SP, Brasil. A coocorrência de Epistylis sp. e D. carvalhoi, e sua relação epibionte registrada neste estudo, supõem que Epistylis sp. possa utilizar os crustáceos para dispersão e como vetores mecânicos para a disseminação de doenças em hospedeiros silvestres e cultivados. Além disso, a troca de parasitas entre hospedeiros silvestres e cultivados é possível, considerando ambos os organismos (protozoários e argulídeos). Os resultados deste estudo, também demonstram a necessidade de monitorar as áreas adjacentes às pisciculturas como medida preventiva para a dispersão de patógenos. Este é o primeiro relato de epibiose entre Epistylis sp. e parasitas argulídeos de O. niloticus cultivados e silvestres, contribuindo para o conhecimento da especificidade parasitária do hospedeiro, distribuição geográfica, dispersão de agentes etiológicos e epidemiologia na aquicultura.

Fish fauna of the Pelotas River, Upper Uruguay River, southern Brazil / Fauna de peixes do rio Pelotas, Alto rio Uruguai, sul do Brasil

Abstract: The fish fauna of the Pelotas River, in the Upper Uruguay ecoregion of southern Brazil was inventoried. Samplings were performed quarterly between August 2013 and May 2014 at 14 sites in the Pelotas River and its tributaries, using gill nets of different mesh sizes, sein nets, cast nets and electrofishing. In total, 7,745 specimens were recorded, comprising 46 species, belonging to 13 families and five orders. Approximately 80% of the species belonged to the orders Characiformes and Siluriformes, as well as the families Characidae and Loricariidae, which included a greater number of species. Of the total species, 24% were endemic to the Upper Uruguay River, four were identified only at the genus level and none was considered non-native. Approximately, half of the 98 species previously recorded for the Upper Uruguay basin were also detected in this study. The tributaries of the Pelotas River exhibited different faunas with five exclusive species. Thirty species were present in both the tributaries and the main channel. In addition, higher species richness, as well as the presence of larger-sized species were observed in the main channel. Many of the species not restricted to the Upper Uruguay River have already been reported as part of the Taquari-Antas River fauna. However, the local biodiversity of this region is under several threats, such as land use and installation of small hydroelectric plants. These results highlight the importance of the conservation of plateau/upland rivers, especially in the Upper Uruguay ecoregion, which shows a peculiar fish fauna and endemism.

Resumo: A fauna de peixes do rio Pelotas, bacia do Alto Uruguai foi inventariada. As amostragens foram realizadas trimestralmente entre agosto de 2013 e maio de 2014, em 14 pontos da bacia do rio Pelotas, utilizando-se redes de emalhar de diferentes tamanhos, redes de arrasto, tarrafas e pesca elétrica. No total, foram registrados 7.745 exemplares, compreendendo 46 espécies pertencentes a 13 famílias e cinco ordens. Aproximadamente 80% das espécies foram pertencentes as ordens Characiformes e Siluriformes, assim como as famílias Characidae e Loricariidae, que tiveram maior número de espécies. Do total de espécies amostradas, 24% são endêmicas do Alto rio Uruguai, quatro foram identificadas apenas em nível de gênero e nenhuma foi considerada não nativa. Aproximadamente metade das 98 espécies anteriormente registradas na bacia do Alto rio Uruguai foi registrada nesse estudo. Os tributários do rio Pelotas exibiram distinta fauna com cinco espécies exclusivas. Trinta espécies foram comuns aos afluentes e canal principal. Verificou-se maior riqueza, bem como a presença de espécies de maior porte no canal principal. Muitas das espécies não restritas ao alto rio Uruguai já foram relatadas como parte da fauna da bacia do rio Taquari-Antas. No entanto, a biodiversidade local da região de estudo está sob diversas ameaças, como o uso do solo e a instalação de pequenas centrais hidrelétricas. Esses resultados destacam a importância da preservação dos rios de planalto, especialmente na ecorregião do Alto rio Uruguai, que apresenta uma fauna de peixes peculiar e endemismos.

Influence of land use on the health of a detritivorous fish (Ancistrus mullerae) endemic to the Iguassu ecoregion: relationship between agricultural land use and severe histopathological alterations.

This study aimed to evaluate the histopathological biomarkers of the gills and liver of endemic catfish to test the hypothesis that, in environments under intense land use by agricultural activities, histopathological alterations occur more severely. Samples were collected by electrofishing in seven streams in the Lower Iguaçu basin quarterly from August 2015 to February 2016. The gills and livers were processed according to routine histological methods and examined by light microscopy. The histopathological alterations observed in fish from the streams with a higher percentage of natural vegetation cover were considered modest and indicated normal functioning of the organ (such as edema, hyperplasia, and leukocyte infiltration). As predicted, fish collected in streams with higher agricultural influence presented moderate to severe damage (aneurysm, vacuolization and cytoplasmic degeneration, and pyknotic nucleus). The abundance of chloride cells was significantly increased in the gills of Ancistrus mullerae collected in rural streams. In addition, in most streams, mucous cells were more abundant during the rainy period. Significant differences were observed in the histopathological index (HI) of the gills and livers, where severe histopathological alterations occurred in fish from streams with a higher agricultural influence. The observed alterations were more severe in the liver than in the gills, which are indeed related to the liver's key role in the detoxification of xenobiotics. We conclude that more severe histological alterations occurred in fish from streams with the highest land use by agricultural activities. Thus, our work provides important insight into the conservation and management of natural resources.

Fish fauna in forested and rural streams from an ecoregion of high endemism, lower Iguaçu River basin, Brazil / Fauna de peixe em riachos florestados e rurais de uma ecoregião de alto endemismo, bacia do baixo rio Iguaçu, Brasil

Abstract The fish fauna of eight streams with different land uses of their watersheds (forested and rural areas) in the lower Iguaçu River basin was inventoried, in order to evaluate the composition and species richness. The fishes were sampled quarterly from May 2015 to February 2016, using the electrofishing technique. In total, 4,239 individuals were captured, belonging to six orders, 11 families and 26 species. The orders Siluriformes and Characiformes, and the families Characidae and Trichomycteridae were the most specious. Of the total species sampled, 65% were endemic to the Iguaçu River basin, four are not described and four are non-native. As expected to the Iguaçu River basin, the inventoried fauna revealed low richness and high endemism, however was highly nested within the species composition reported for main channel of Iguaçu River and their larger tributaries. The species recorded here corresponded to a subset of 24.5% of the 106 species documented for the basin. The streams presented different faunas, with only two species (Astyanax bifasciatus and Trichomycterus stawiarski) common to both forested and rural streams. In addition, higher species richness was recorded in streams inserted in conservation units. The presence of non-native species was more frequent in rural streams. These results highlight the importance of the preservation of forested areas in the watersheds of lower Iguaçu, which presents a peculiar fish fauna, along with several threats to biodiversity such as habitat loss by intensive agriculture use.

Resumo A fauna de peixes foi inventariada em oito riachos com diferentes usos do entorno (áreas florestadas e rurais) na porção do baixo rio Iguaçu, em ordem para avaliar possíveis diferenças na composição e riqueza de espécies. Os peixes foram amostrados trimestralmente entre maio de 2015 e fevereiro de 2016, por meio da técnica de pesca elétrica. No total foram capturados 4239 indivíduos, pertencentes a seis ordens, 11 famílias e 26 espécies. As ordens Siluriformes e Characiformes foram as mais especiosas, assim como as famílias Characidae e Trichomycteridae. Do total de espécies amostradas, 65% foram endêmicas da bacia do rio Iguaçu, quatro foram não descritas e outras quatro foram não-nativas. Como esperado para a bacia do rio Iguaçu, a fauna inventariada revelou baixa riqueza e elevado endemismo, contudo, foi altamente aninhada dentro da composição de espécies relatada para o canal principal do rio Iguaçu e seus grandes tributários. As espécies aqui registradas corresponderam a um subconjunto de espécies de 24,5% das 106 documentadas para a bacia. Os riachos apresentaram faunas distintas, sendo que apenas duas espécies (Astyanax bifasciatus e Trichomycterus stawiarski) foram comuns a ambos os grupos de riachos florestados e rurais. Além disso, houve maior riqueza de espécies em riachos florestados. A presença de espécies não nativas foi maior em riachos rurais. Esses resultados ressaltam a importância da preservação de áreas florestadas nas bacias do baixo rio Iguaçu, as quais apresentam uma fauna de peixes peculiar, com várias ameaças para a biodiversidade tais como a perda de habitat por intensivo uso do solo pela agricultura.

Histopathological alterations in Astyanax bifasciatus (Teleostei: Characidae) correlated with land uses of surroundings of streams

This study evaluated gills and liver of Astyanax bifasciatus as histological biomarkers for biomonitoring of streams along areas with different land uses. The fish were collected by electrofishing in six streams in the basin of the lower Iguaçu River. The objective was to correlate the presence and degree of histopathological alterations of gills and liver with the environmental variables among streams along different land uses. The low frequency of histopathological alterations found in fish from the forest streams suggested normal organ functioning. In fish from the rural and urban streams, the histopathological alterations occurred were in higher frequency, indicated light to moderate damage in gills and liver of fish from the rural streams, and moderate to severe damage in liver of fish from urban streams. The histopathological alterations in gills (lamellar aneurysm) and livers (vascular congestion) verified in impacted streams were significantly more frequent and severe. It was possible to distinguish streams along different land uses, suggesting that these histopathological alterations can be used as biomarkers for biomonitoring studies. The health integrity of fish from streams in forest areas further reinforces the importance of maintaining preservation areas in basins under intensive land use.(AU)

Esse estudo avaliou brânquias e fígado de Astyanax bifasciatus como biomarcadores histológicos para biomonitoramento de riachos em áreas com diferentes usos do solo. Os peixes foram coletados por pesca elétrica em seis riachos na bacia do baixo rio Iguaçu. O objetivo foi correlacionar a presença e o grau de alterações histopatológicas em brânquias e fígado com as variáveis ambientais entre riachos com diferentes usos do solo. A baixa frequência de alterações histopatológicas encontradas em peixes de riachos florestados indicou funcionamento normal do órgão. Em peixes de riachos rurais e urbanos, as alterações histopatológicas encontradas foram em maior frequência, indicando danos leves para moderados em brânquias e fígado de peixes dos riachos rurais, e danos moderados para severos em fígado de peixes de riachos urbanos. As alterações histopatológicas em brânquias (aneurisma lamelar) e fígados (congestão vascular) observadas nos riachos impactados foram significativamente mais frequentes e severas. Foi possível distinguir os riachos com diferente uso do solo, sugerindo que estas alterações histopatológicas podem ser usadas como biomarcadores para estudos de biomonitoramento. A integridade da saúde dos peixes dos riachos nas áreas florestadas reforça ainda mais a importância de manter áreas de preservação nas bacias com intenso uso do solo.(AU)

Use of Muscular Cholinesterase of Astyanax bifasciatus (Teleostei, Characidae) as a Biomarker in Biomonitoring of Rural Streams.

Cholinesterase (ChE) activity was measured in Astyanax bifasciatus maintained in controlled conditions. Muscle ChE activity of individuals collected in field conditions in two seasons was compared among specimens collected in seven streams (forest and rural) of the lower Iguaçu river basin in association with physical, chemical, pesticides and biological factors. Significant differences in muscle ChE activity between control fish and fish collected in streams in both seasons were found, with higher activity in natural conditions. This the first time that differences in muscle ChE activity have been found among fish collected from different streams, suggesting synergism among multiple factors (e.g. temperature, pH, animal weight) and ecological attributes (richness and abundance) as influencing the variation in biomarkers. It is necessary to evaluate the quality of aquatic environments for a more accurate biomonitoring approach.

Ichthyofauna of streams from the lower Iguaçu River basin, Paraná State, Brazil / Ictiofauna de riachos da bacia do baixo rio Iguaçu, estado do Paraná, Brasil

Abstract The drainages of the Iguaçu River basin, as well as the main channel of the river, have peculiar characteristics resulting from geomorphological processes in this area, including the formation of the Iguaçu River Falls. This slope in the lower portion of the basin is a biogeographical barrier to many organisms. In this study was inventoried the fish fauna of streams of the lower Iguaçu River basin, evaluating possible differences in the species composition upstream and downstream of this biogeographical barrier. Sampling were conducted between 2004 and 2013, in five streams, three upstream and two downstream of the Iguaçu River Falls, using electrofishing. The nMDS analysis was run to investigate possible groupings of similar fauna between the streams sampled. The scores of this test were tested as to the significance of groupings with the Hotelling T2 test. The indicator value method (IndVal) was used to detect the distribution of species among the groups of the streams upstream and downstream of the Iguaçu River Falls. We collected 18,908 individuals of six orders, 11 families, and 40 species. Siluriformes and Characiformes had the highest species richness; Cyprinodontiformes presented the highest abundance. Considering the species recorded, 21 are considered natives to the Iguaçu River basin, including 15 endemic, wich were found only in streams upstream of the falls. Additional 18 species were verified only in the streams downstream of such barrier. Four species were common to both stretches. The axis 1 of the nMDS separated two groups: streams upstream (S1, S2 and S3) and streams downstream of the Iguaçu River Falls (S4 and S5). The indicator species analysis also indicated a distinction between the groups of streams, that were significantly different (Hotelling's T2 = 234.36, p ˂ 0.0001). The number of endemic species in the streams upstream of the Falls (15 spp.) evidences a significant effect of isolation promoted by the Iguaçu River Falls, and confirms the role of this barrier in the vicariant processes and endemism typical of this basin. These results emphasize the importance of conserving these ecosystems, once the extinction of species in this region means the irreversible loss of them.

Resumo As drenagens da bacia do rio Iguaçu, bem como o canal principal do rio, possuem características peculiares resultantes de processos geomorfológicos dessa área, incluindo a formação das Cataratas do rio Iguaçu. Esse desnível na porção inferior da bacia constitui uma barreira biogeográfica para muitos organismos. Neste trabalho inventariamos a fauna de peixes de riachos na porção do baixo rio Iguaçu, avaliando possíveis diferenças na composição de espécies acima e abaixo dessa barreira biogeográfica. Entre 2004 e 2013, foram amostrados cinco riachos, sendo três localizados acima das Cataratas do Iguaçu e dois abaixo, por meio de pesca elétrica. Para investigar possíveis padrões de agrupamentos de fauna similares entre os riachos amostrados foi realizada uma análise nMDS, cujos escores foram testados quanto à significância dos agrupamentos utilizando o teste de T2 de Hotelling. O valor indicador (IndVal) foi usado para detectar a distribuição das espécies entre os grupos de riachos. Foram amostrados 18.908 indivíduos, pertencentes a seis ordens, 11 famílias e 40 espécies. As ordens Siluriformes e Characiformes destacaram-se em riqueza de espécies; Cyprinodontiformes apresentou maior abundância. Do total de espécies amostradas, 21 são consideradas nativas da bacia do rio Iguaçu, sendo 15 delas endêmicas e registradas somente nos riachos acima das Cataratas do rio Iguaçu. Outras 18 espécies foram registradas somente nos riachos que desembocam abaixo das cataratas. Quatro espécies foram comuns em ambos os ambientes. A dimensão do eixo 1 da análise nMDS resultou na separação de dois grupos: riachos acima (S1, S2 e S3) e riachos abaixo das cataratas (S4 e S5). A análise de espécies indicadoras também indicou a distinção entre os grupos de riachos, sendo que esses agrupamentos foram significativamente diferentes (Hotelling's T2 = 234.36, p ˂ 0.0001). O número de espécies endêmicas registrado nos riachos acima das cataratas (15 spp.), demonstra um significativo efeito de isolamento da fauna proporcionado pelas Cataratas do rio Iguaçu e confirmam o papel dessa barreira nos processos vicariantes e endemismos característicos dessa bacia. Esses resultados ressaltam a importância da preservação desses ecossistemas, pois a extinção de espécies nessa região significa a perda global dessas entidades biológicas.

Carnivory during Ontogeny of the Plagioscion squamosissimus: A Successful Non-Native Fish in a Lentic Environment of the Upper Paraná River Basin.

This study evaluated feeding patterns and ontogenetic variations in a non-native fish species (Plagioscion squamosissimus) in an isolated lake in the Upper Paraná River floodplain. Quarterly samplings were performed from April 2005 to February 2006 using plankton nets to capture larvae, seining nets for juveniles, and gill nets and trammel for adults. Stomach contents (n = 378) were examined according to the volumetric method in which the volume of each food item was estimated using graduated test tubes or a glass counting plate. During early development (larval stage), P. squamosissimus consumed mainly Cladocera and Copepoda. Juveniles showed a more diverse diet, including shrimp (Macrobrachium amazonicum), fish, aquatic insects (Trichoptera, Ephemeroptera, Chironomidae and pupae of Diptera) and plants. It was notable the high proportion of cannibalism (23.3%) in this stage. Adults consumed predominantly shrimp and fish. The use of food resources varied significantly between development stages (ANOSIM; r = 0.458; p<0.005), showing changes in food preferences during ontogeny. The Similarity Percentage Analysis (SIMPER) indicated that Cladocera and Copepoda were responsible for the differences observed between the larval stages of pre-flexion, flexion and post-flexion. M. amazonicum and Chironomidae were responsible for the differences between juvenile and larval stages, while M. amazonicum and other fishes caused the differences between adults and other ontogenetic stages. These results are confirmed by the relationship between standard length and developmental periods (ANCOVA; r2 = 0.94; p<0.0001). In general, there were low values of trophic niche breadth. The essentially carnivorous habit from the early stages of P. squamosissimus and the predominant use of M. amazonicum by adults have important roles in feeding patterns of the species, suggesting a major contribution to its success and establishment, especially in lentic environments.

Diet and ecomorphological relationships of an endemic, species-poor fish assemblage in a stream in the Iguaçu National Park

This study investigated the morphological and dietary relationships of the fish assemblage in a stream with an endemic fauna and low species richness. The ichthyofauna was sampled quarterly from September 2011 to July 2012, through the electrofishing technique. The stomach contents of 419 individuals belonging to seven species were analyzed by the volumetric method, and the ecomorphological traits of 30 specimens of each species were estimated. The main food items consumed were detritus, aquatic and terrestrial insects, and other aquatic invertebrates. We observed low levels of trophic niche breadth and diet overlap between most species. The PCA scores indicated the occurrence of three ecomorphotypes. PCA axis 1 segregated at one extreme, species with dorsoventrally depressed bodies, longer caudal peduncles, and well-developed swimming fins; and at the other extreme, species with compressed bodies and peduncles, and relatively larger eyes and anal fins. PCA axis 2 segregated species with elongated bodies and ventrally oblique mouths. The partial Mantel test revealed a significant correlation between diet and morphology, indicating independence from the phylogeny. The patterns observed suggest that the low richness did not result in a broadening of the species' trophic niches, or in the absence of some of the main ecomorphotypes expected.

Este estudo teve como objetivos investigar as relações morfológicas e alimentares de uma assembleia de peixes com fauna endêmica e de baixa riqueza de espécies. Os peixes foram amostrados trimestralmente entre setembro de 2011 a julho de 2012, através da técnica da pesca elétrica. Foram obtidas as medidas morfométricas que possibilitaram os cálculos dos índices ecomorfológicos e analisados os conteúdos estomacais de 419 indivíduos, pertencentes a sete espécies, através do método volumétrico. Os principais itens alimentares consumidos pela assembleia de peixes foram detrito, insetos aquáticos e terrestres e outros invertebrados aquáticos. Observou-se baixos valores de amplitude de nicho trófico e de sobreposição alimentar entre a maioria das espécies. Os escores da PCA, indicaram a ocorrência de três ecomorfotipos. O eixo CP1 segregou em um extremo espécies com corpo deprimido dorso-ventralmente, pedúnculo caudal longo e as nadadeiras desenvolvidas, enquanto no outro extremo, espécies com corpos e pedúnculos comprimidos, área dos olhos e das nadadeiras anais relativamente maiores. Por outro lado, o eixo CP2 segregou espécies com corpos mais alongados, bocas ventralmente oblíquas. Através do Teste de Mantel verificou-se relação significativa entre a dieta e a morfologia. Assim, os principais padrões tróficos e ecomorfológicos verificados sugerem que a baixa riqueza, não repercutiu no alargamento do nicho trófico das espécies ou na inexistência de algum dos principais grupos ecomorfológicos.

Diet and trophic structure of the fish fauna in a subtropical ecosystem: impoundment effects

This study examined the diet and trophic structure of the fish fauna, over temporal and spatial scales, as affected by the impoundment of the Iguaçu River in the region of Salto Caxias, Paraná State, Brazil. Sampling was conducted before (March 1997 - February 1998) and after the impoundment (March 1999 - February 2000), at four sampling sites. The stomach contents were analyzed by the volumetric method. The species could be organized in 10 trophic guilds: algivores, carcinophages, detritivores, herbivores, aquatic insectivores, terrestrial insectivores, invertivores, omnivores, piscivores, and planktivores; the first and last guilds were represented only in the post-impoundment period. Similarity patterns and feeding changes were summarized by a non-metric Multi-dimensional Scaling (nMDS) analysis and statistically tested by a Permutational multivariate analysis of variance (PERMANOVA). Most species showed feeding changes, except for the piscivores and detritivores. These changes were related to the temporal factor (impoundment phases), such as reduced intake of benthic organisms and allochthonous food, which were usually replaced by resources from the reservoir itself (algae, microcrustaceans, and fish), simplifying the food spectrum of the fish fauna. A different indicator of food resources (IndVal) corroborated these changes in the feeding of the species. The proportions of the trophic guilds evaluated based on the catch per unit of effort (CPUE) and tested by ANOSIM were significantly different before and after the impoundment. Herbivores and piscivores were the guilds that contributed (SIMPER) to these differences, especially the high increase in biomass of the piscivore guild after the impoundment. Variations in the abundance of trophic guilds were more directly related to changes in the feeding habits of the fish fauna than to increases in the number and biomass of the species that constitute these guilds.

Neste estudo foram avaliadas a dieta e a estrutura trófica da ictiofauna em escala temporal e espacial, sob efeito do represamento do rio Iguaçu, na região de Salto Caxias, Paraná, Brasil. Para tanto, foram realizadas amostragens nas fases pré (março/97 a fevereiro/98) e pós represamento (março/99 a fevereiro/00) em quatro pontos de coleta. Os conteúdos estomacais foram avaliados pelo método volumétrico. As espécies foram organizadas em 10 guildas tróficas: algívora, carcinófaga, detritívora, herbívora, insetívora aquática, insetívora terrestre, invertívora, omnívora, piscívora e planctívora, sendo a primeira e a última representadas apenas após o represamento. Os padrões de similaridade e alterações na dieta foram sintetizados através da ordenação multidimensional não paramétrica (nMDS) e estatisticamente testados pela análise de variância permutacional (PERMANOVA). Foram constatadas alterações na dieta da maioria das espécies, com exceção das piscívoras e detritívoras. Essas alterações foram relacionadas ao fator temporal (fases do represamento), configuradas como redução no consumo de organismos bentônicos e alimentos alóctones, os quais foram geralmente substituídos por recursos provenientes do próprio ambiente (algas, microcrustáceos e peixes), simplificando o espectro alimentar. Diferentes recursos alimentares indicadores (IndVal) corroboram essas alterações na composição alimentar das espécies antes e após o represamento. As proporções na abundância (número e biomassa) das guildas tróficas avaliadas com base na captura por unidade de esforço (CPUE) e testadas pela ANOSIM foram significativamente diferentes antes e após o represamento. As guildas herbívora e piscívora foram as que mais contribuíram (SIMPER) para essas diferenças, especialmente o elevado incremento em biomassa da guilda piscívora após o represamento. As variações na abundância das guildas tróficas foram mais relacionadas às alterações no hábito alimentar da fauna de peixes, do que propriamente aos incrementos em número e em biomassa das espécies que anteriormente compunham tais guildas.