Seasonal records of benthic macroinvertebrates in a stream on the eastern edge of the Iguaçu National Park, Brazil.

Background Iguaçu National Park (INP) is known worldwide due to Iguaçu Waterfalls, being considered a World Natural Heritage by UNESCO. The INP is one of the last large forested extensions of inland Brazil that provides protection to the Atlantic Forest, one of the world's biodiversity hotspots. However, its Natural Heritage status has been threatened by the construction and operation of the Baixo Iguaçu dam, agricultural and urban impacts on its boundaries and the increasing interest of the Brazilian government in re-opening of the "Colono road", an old illegal road that crossed the interior of the park. Indeed, since benthic macroinvertebrates have been widely used for the environmental assessment of streams, records and abundance of their taxa under different seasonal periods may provide an additional dataset for biomonitoring of hydrographic systems in the face of current anthropogenic impacts on the INP boundaries and other similar streams on forest edges. New information In this study, we improved the sampling design of benthic macroinvertebrates and provided seasonal records covering distinct precipitation/temperature periods between 2016 and 2017 of a stream on the eastern edge of the Iguaçu National Park, Brazil. The records total 2,840 individuals distributed in 88 different taxa. The most abundant taxa were the Diptera subfamilies, Chironominae (n = 1,487) and Tanypodinae (n = 256), besides the Heterelmis genus (n = 152, Elmidae; Coleoptera). Diptera was the richest order in number of families (n = 8), while Leptophlebiidae (Ephemeroptera) was the richest taxonomic family in number of genera (n = 11). Aegla (Crustacea) and the Insecta genera, Heterelmis, Hexacylloepus, Noelmis, Phylloicus and Thraulodes, were recorded through all samplings. Twenty-five genera of Ephemeroptera, Plecoptera, Trichoptera (EPT) and Odonata were recorded during intermediate precipitation/temperature periods. Twenty-one of them were recorded in May 2016, with five genera standing out in abundance (Hydrosmilodon, Anacroneuria, Argia, Coryphaeschna, Americabaetis) and four (Needhamella, Tikuna, Simothraulopsis, Neocordulia) in December 2016. Four general taxa were exclusive of the lower precipitation/temperature period (August 2016), standing out in abundance were the Oxystigma (Odonata) and Corydalus (Megaloptera) genera. In March 2017 (higher precipitation/temperature period), four exclusive taxa were recorded, amongst them, the Chimarra (Trichoptera) genus. Furthermore, seasonal records demonstrated higher occurrences and abundance of macroinvertebrates during the intermediate and lower precipitation/temperature periods, besides a varied taxa composition throughout the year, with the presence of both sensitive and tolerant groups to environmental impacts. Our findings suggest that the number and composition of the local-stream macrobenthic fauna were influenced by the seasonal climatic regime. These changes should be considered in the limnological monitoring developed on the hydrographic systems of INP eastern edges to improve the assessment of environmental quality under different local seasonal conditions.

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.

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.

Longitudinal use of feeding resources and distribution of fish trophic guilds in a coastal Atlantic stream, southern Brazil

This study described the use of food resources and the distribution of fish trophic guilds along the longitudinal gradient of a coastal Atlantic stream, southern Brazil. Allochthonous resources (terrestrial insects) predominated in the headwaters, whereas autochthonous food items (algae, fish) and detritus predominated in the mouth section. Detritivorous, aquaticinvertivorous, and terrestrial- and aquatic-insectivorous species occurred throughout the gradient, while omnivorous and piscivorous in the headwaters and middle stretches, respectively, and herbivorous in the middle and mouth. Detritivores and aquatic-insectivores were significantly more specialized than the other guilds, however, there was no evidence of a longitudinal increase in trophic specialization. Density and biomass of aquatic-invertivores and aquatic-insectivores decreased, whereas that of detritivores increased longitudinally. The distribution of trophic guilds was significantly associated with the stream section, where aquatic and terrestrial insectivorous were more frequent in rocky and flowed stretches from the headwater and detritivores in deeper environments with finer particles of substrate from the mouth. This suggests that fish assemblages in coastal streams with a steep longitudinal gradient may follow patterns in the use of food resources according with the food availability along the river, as predicted by the River Continuum Concept.

Este estudo descreve o uso dos recursos alimentares e a distribuição das guildas tróficas de peixes ao longo do gradiente longitudinal de um riacho da encosta Atlântica, Sul do Brasil. Recursos alóctones (insetos terrestres) foram consumidos com maior frequência na cabeceira, entretanto, recursos de origem autóctone (algas, peixes) e detritos foram mais frequentemente registrados na foz. Espécies detritívoras, invertívoras aquáticas, insetívoras terrestres e aquáticas ocorreram ao longo de todo gradiente, enquanto que as onívoras e piscívoras na cabeceira e meio, respectivamente, e herbívoras no meio e foz. Detritívoras e insetívoras aquáticas foram significativamente mais especializadas em relação às demais guildas; entretanto, não houve nenhuma evidência de aumento longitudinal da especialização trófica. A densidade e a biomassa de invertívoras e insetívoras aquáticas diminuíram, enquanto que das detritívoras aumentaram no sentido cabeceira-foz. A distribuição das guildas tróficas foi significativamente associada com a secção do riacho, onde insetívoras aquáticas e terrestres foram mais frequentes em trechos rochosos e de elevado fluxo da cabeceira, enquanto que detritívoras em ambientes mais profundos com partículas finas de substrato da foz. Tais resultados sugerem que assembleias de peixes de riachos tropicais de encosta, os quais apresentam acentuado gradiente longitudinal, podem seguir padrões de uso dos recursos alimentares de acordo com a disponibilidade alimentar ao longo do rio, como previstos no Conceito de Continuidade de Rios.

Spatial, seasonal and ontogenetic variation in the diet of Astyanax aff. fasciatus (Ostariophysi: Characidae) in an Atlantic Forest river, Southern Brazil

This study described the feeding habits of the characin Astyanax aff. fasciatus. The diet compositions of specimens from two sites (A and B) on a river in Southern Brazil were compared according to the size of individuals and seasonal period. The collections were performed monthly from March 2005 to February 2006, where the stomach contents of 290 specimens were assessed. Food items for A. aff. fasciatus were basically composed of plants and insects, especially leaf fragments, seeds, fruits, filamentous algae, aquatic and terrestrial insects and insect fragments. At site A, the most common items were insect and plant fragments. Conversely at site B, plant fragments were more representative. In general, all items of animal origin showed the highest feeding index values at site A, whereas at site B detritus and grass items were more abundant. The composition of items varied seasonally, with higher diversity of items being recorded during the spring at both sites. Smaller individuals preferred items of animal origin, while the larger ones consumed mainly items of plant origin. According to its size, A. aff. fasciatus in this study may be considered a species with insectivorous tendencies when immature or herbivorous tendencies when adult. Nevertheless, its feeding habits may be flexible according to resource availability, showing wide ontogenetic, besides spatial and temporal variation.

Este estudo descreveu os hábitos alimentares do lambari Astyanax aff. fasciatus. Foram comparadas as composições alimentares de espécimes de dois sítios (A e B) de um rio no sul do Brasil de acordo com o tamanho dos indivíduos e do período sazonal. As coletas foram realizadas mensalmente de março de 2005 a fevereiro de 2006, sendo o conteúdo estomacal de 290 exemplares analisado. A dieta de A. aff. fasciatus foi composta basicamente por plantas e insetos, especialmente fragmentos de folhas, sementes, frutos, algas filamentosas, insetos aquáticos e terrestres e fragmentos de insetos. No sítio A, os itens de maior importância foram fragmentos de insetos e plantas. Ao contrário no sítio B, fragmentos de plantas foram mais representativos. Em geral, todos os itens de origem animal apresentaram os maiores valores do índice alimentar no sítio A, enquanto que no sítio B detritos e gramíneas foram mais abundantes. A composição dos itens ingeridos variou sazonalmente, sendo a maior diversidade registrada durante o período da primavera para ambos os sítios. Indivíduos pequenos preferiram itens de origem animal enquanto que os maiores consumiram principalmente itens de origem vegetal. De acordo com seu tamanho A. aff. fasciatus neste estudo pode ser considerada uma espécie com tendências à insetivoria quando imaturo, ou à herbivoria quando adulto. No entanto, seu hábito alimentar pode ser flexível de acordo com a disponibilidade de recursos, mostrando ampla variação tanto ontogenética quanto espacial e temporal.

Population structure of Phalloceros caudimaculatus (Hensel, 1868) (Cyprinodontiformes, Poeciliidae) collected in a brook in Guarapuava, PR

The population structure of Phalloceros caudimaculatus was studied in a brook (sites A and B) existing in the CEDETEG - Guarapuava/PR. Fourteen length classes of 3 mm amplitude were defined for P. caudimaculatus. The widest length amplitude and the average and maximum sizes were observed in females. Females were significantly more predominant in the whole sample and more frequent in all length classes. The sexual proportion data, showed that the number of females was superior to that of males throughout most of the year. Young occurrence peaks were registered in November and March. Pregnant females were present from March to April, from July to August and in January, characterizing the reproductive season. At sampling site A, a higher occurrence of pregnant females and young was observed.

A estrutura populacional de Phalloceros caudimaculatus foi estudada em um riacho (pontos A e B) existente no CEDETEG - Guarapuava/PR. Para P. caudimaculatus foram encontradas 14 classes de comprimento com amplitude de 3,0mm. A maior amplitude de comprimento e os maiores tamanhos médios e máximos foram observados nas fêmeas. As fêmeas foram significativamente predominantes na amostra total e mais abundantes em todas as classes de comprimento. Pela proporção sexual pode-se detectar que o número de fêmeas é superior ao de machos a maior parte do ano. Os picos de ocorrência de jovens foram registrados nos meses de novembro e março. As fêmeas grávidas estiveram presentes nos bimestres de março-abril, julho-agosto e no mês de janeiro, caracterizando a época reprodutiva. No ponto de coleta A foi observado uma maior ocorrência de fêmeas grávidas e de jovens.