Abstract Among the Neotropical fish fauna, suckermouth armored catfishes (Hypostomus - Loricariidae) stands out as one of the most difficult groups to diagnose morphologically. So the use of different molecular markers, as is the case of cytogenetics, has been fundamental for a precise identification of some species. In the present study, we characterize the karyotypes of two allopatric Hypostomus spiniger populations, using classical and molecular cytogenetic methods. This species was described by Hensel (1870) but later synonymized with Hypostomus commersoni, and recently it was again recognized as a valid species. Taking to account this taxonomic problematic, the aim of this study is to determine chromosomal characters that may be useful to validate the taxonomic status of H. spiniger and to complement its diagnosis in relation to H. commersoni populations. The karyotype of H. spiniger is composed by 66 chromosomes (10m+16sm+14st+26a), few heterochromatin and a multiple nucleolar organizer regions (NORs) system. Despite, the currently geographic isolation among the samples collected in Forquetinha River (Patos Lagoon basin) and Quadros Lagoon (Tramandaí River basin), both shared the same karyotypic structure, this cytogenetic evidence, suggest that both populations belongs to the same species. Additionally, our results clearly distinguish H. spiniger from H. commersoni populations collected along the Paraná River basin, that exhibited 2n=68 chromosomes and several divergences in heterochromatin and NORs pattern. In sum, the present study reinforces the valid status of H. spiniger and demonstrated the importance of basic cytogenetic analysis to understand conflictuous taxonomic matters.

Resumo: Objetivo Este estudo investigou se variações sazonais induzem mudança na composição da dieta de Serrapinnus notomelas em uma lagoa marginal situada sob a área de influência do rio Tibagi, Bacia do Alto Paraná. Métodos As coletas foram realizadas mensalmente de fevereiro de 2017 a janeiro de 2018, e os exemplares foram capturados com duas peneiras (malha de 2 mm). O método volumétrico e de ocorrência foram usados para quantificar o conteúdo estomacal. Resultados Um total de 358 estômagos tiveram os seus conteúdos analisados. Os recursos autóctones foram dominantes na dieta de S. notomelas em todas as estações, com predominância de algas, detritos e Tecamebas. Vegetais foram os recursos alóctones mais abundante na dieta. A composição da dieta apresentou diferenças significativas entre todas as estações, e nas estações do outono e verão os indivíduos apresentaram maior amplitude de nicho trófico, respectivamente. Conclusões Nossos resultados mostram a grande importância dos recursos autóctones para a manutenção da população de S. notomelas, e que a sazonalidade pode influenciar a composição trófica na dieta da espécie. Observamos diferenças na dieta durante as estações, e que durante o outono e verão, os indivíduos apresentaram uma maior amplitude do nicho trófico. Assim, nossos resultados corroboram com informações para a preservação das espécies de pequeno porte, fundamentais para a rede trófica nos ecossistemas.

Abstract: Aim This study investigated whether seasonal variations have an effect on diet composition of Serrapinnus notomelas in a marginal lagoon located under the area of influence of the Tibagi River, Upper Paraná Basin. Methods Samples were carried out monthly between February 2017 and January 2018, and fish specimens were caught with two sieves (2 mm mesh). The volumetric and occurrence method were used to quantify stomach contents. Results A total of 358 stomachs had their contents analyzed. The autochthonous resources were dominant in the diet of S. notomelas in all seasons, with a predominance of algae, detritus and Tecamebas. Meanwhile, plant material was the most abundant allochthonous resource in the diet. Diet composition showed significant differences between all seasons, while in the autumn and summer seasons, individuals showed greater trophic niche breadth, respectively. Conclusions Our results show the great importance of autochthonous resources for the maintenance of the S. notomelas population, and that seasonality can influence the trophic composition in the species' diet. We observed difference in the diet during the seasons and that during autumn and summer, individuals presented a greater breadth of the trophic niche. Thus, our results corroborate with knowledge to the preservation of small fish species, which are fundamental for the trophic network in ecosystems.

Resumo: O rio Paranapanema é um importante tributário, amplamente explorado da bacia do Alto rio Paraná. A fauna de peixes do rio Paranapanema vem sendo investigada desde a década de 1990; no entanto, nenhum estudo caracterizou a riqueza de espécies de peixes em toda a bacia, incluindo o canal principal do rio, lagoas marginais, seus tributários e sub-tributários. Assim, realizamos uma revisão com 90 estudos independentes conduzidos nas regiões superior, média e inferior da bacia. Foram registradas 225 espécies, das quais 165 eram nativas e 60 eram não nativas. Verificamos que 77% das espécies dentro da bacia são compostas por Siluriformes e Characiformes. Cichliformes apresentou um número significativo de espécies não nativas estabelecidas em áreas de represamento da bacia. Estimadores de riqueza baseados em incidência (Bootstrap e Chao 2) demonstraram que a riqueza de espécies nativas ainda é subestimada. Algumas espécies nativas (e.g., Hypostomus ancistroides) e não nativas (e.g., Plagioscion squamosissimus) estão amplamente distribuídas na bacia, enquanto outras tem sua distribuição mais restrita. Entre as espécies registradas, a família Bryconidae obteve o maior número de representantes com status de conservação ameaçado. Além disso, observamos que o reservatório de Capivara e seus afluentes foram as regiões mais amostradas, sendo a maioria dos estudos realizados na bacia do baixo Paranapanema. A riqueza de espécies registrada em grandes afluentes, como os rios Tibagi, Cinzas, Congonhas e Pirapó, é fundamental para a manutenção da ictiofauna no rio Paranapanema. Nossa contribuição pode ser usada para apoiar ações de manejo e estratégias de conservação, bem como para indicar regiões na bacia que precisam ser melhor inventariadas.

Abstract: The Paranapanema River is an important, extensively explored tributary of the Upper Paraná River basin. The fish fauna of the Paranapanema River has been investigated since the 1990s; however, no study has characterized the richness of fish species throughout the basin, including the main channel of the river, marginal lagoons, its tributaries, and sub-tributaries. Thus, we performed a review with 90 independent studies conducted at the upper, middle, and lower sections of the basin. We recorded 225 species, of which 165 were native, and 60 were non-native. We found that 77% of the species within the basin are composed by Siluriformes and Characiformes. Cichliformes had a significant number of non-native species established in impoundment sections of the basin. Incidence-Based Estimators (Bootstrap and Chao 2) demonstrated that the richness of native species is still underestimated. Some native (e.g., Hypostomus ancistroides) and non-native species (e.g., Plagioscion squamosissimus) are widely distributed in the basin, while others had a more restricted distribution. Among the registered species, the family Bryconidae had the highest number of representatives with threatened conservation status. In addition, we observed that the Capivara Reservoir and its tributaries were the most sampled regions, with the majority of studies performed in the Lower Paranapanema basin. The species richness recorded in large tributaries, such as Tibagi, Cinzas, Congonhas, and Pirapó rivers is critical for maintaining the fish fauna in the Paranapanema River. Our contribution may be used to support management actions and conservation strategies, as well as to indicate regions in the basin that need to be better inventoried.

The monotypic genus Carlastyanax Géry was defined to include Astyanax aurocaudatus, a morphologically odd species having, among other features, four teeth in the posterior premaxillary row and eight branched dorsal-fin rays. Later on, the characters used to define Carlastyanax were considered as invalid and this genus was synonymized with Astyanax. In this paper, we include Astyanax aurocaudatus in a phylogeny of the Characidae and obtain a sister-group relationship between this species and Creagrutus, within the Stevardiinae. The resurrection of Carlastyanax as a valid genus is therefore proposed. The analysis presented is the largest phylogeny of the Stevardiinae so far published. Relationships of this subfamily are also discussed.

El género monotípico Carlastyanax Géry fue definido para incluir a Astyanax aurocaudatus, una especie morfológicamente extraña que tiene, entre otras cosas, cuatro dientes en la fila posterior del premaxilar y ocho radios ramificados en la aleta dorsal. Luego, los caracteres usados para definir Carlastyanax fueron considerados inválidos y este género fue sinonimizado con Astyanax. En este artículo incluimos Astyanax aurocaudatus en una filogenia de Characidae y obtenemos una relación de grupos hermanos entre esta especie y Creagrutus, dentro de Stevardiinae. La resurrección de Carlastyanax como un género válido es aquí propuesta. Este análisis es la filogenia más grande de Stevardiinae publicada hasta el momento. Se discuten también las relaciones de esta subfamilia.