Temporal effects and changes in the parasitic community of Prochilodus lineatus (Valenciennes, 1837) (Characiformes: Prochilodontidae) in a floodplain

The construction of dams causes several impacts on aquatic environments, altering the flow of rivers, environmental variables, and all biota present, including parasites. Little is known about how the parasitic community can be influenced in the long term by environmental changes. In this study, it was expected that the impacts caused by environmental disturbances will be directly reflected by the composition of the parasite populations. We evaluated the change in the structure of the Prochilodus lineatus endoparasite community between two periods sampled 15 years apart in the upper Paraná River floodplain. There was a significant difference in the weight–length relationship of P. lineatus between these periods and a total of 15 species of parasites were found: 11 species in Period 1 and nine species in Period 2 and five species occurred in both periods. The species richness and diversity were higher in Period 1, and we observed that the correlation of descriptors (richness, diversity and evenness) increased with fish length in this period. In both periods, digeneans numerically dominated the parasitic community, and we verified changes in the composition of parasites between periods. Both the host and the parasites were possibly affected by the environmental impacts resulting from the construction of dams over time, and it is noteworthy that complex life cycle parasites such as Digenea and Acanthocephala require intermediate hosts to complete their life cycle, and the population responds to fluctuations in the face of modified environments.

Reproduction and fecundity of invader of internal insemination Trachelyopterus galeatus in a Neotropical floodplain

After the formation of Itaipu Reservoir, the invader Trachelyopterus galeatus colonized the upper Paraná River. Light microscopy was used to describe gametogenesis and the reproductive phases of females and males. The following data were verified: diameter of the oocytes, spawning type, batch fecundity by ovary weight, standard length, and total weight of the fish, along with the regions where this species reproduced in the upper Paraná River floodplain. A total of 470 specimens were collected quarterly in 2016, 2018 and 2019, and bimonthly in 2017. The gonads were fixed in a Karnovsky solution, dehydrated, infiltrated, and embedded in historesin. The histological slides were stained using PAS + iron hematoxylin + metanil yellow, analyzed and photographed under an image-capturing microscope. As regards diameter of the oocytes and fecundity estimates, ovaries whose oocytes were measured under a stereomicroscope were sampled. In the oogenesis, undifferentiated and differentiated oogonia, early primary growth oocytes, secondary growth oocytes, full-grown oocytes and maturing oocytes were recorded. In the spermatogenesis, primary and secondary spermatogonia, primary and secondary spermatocytes, spermatids and spermatozoa were recorded. The reproductive phases found for females and males were: immature, early development, late development, spawning/sperm-releasing capable, regression, and regeneration. Trachelyopterus galeatus prefers to occupy and reproduce in the Ventura, Patos, Guaraná, Fechada, Garças, and Pau Véio lagoons. The diameter of the oocytes varied from 0.4 to 2.9 mm. Females spawn, on average, 113 oocytes per batch. Batch fecundity variation shows that the larger the ovary, standard length, and total weight, the larger the number of oocytes to be spawned. This invader possesses reproductive success in the upper Paraná River floodplain, especially in lagoons.

A new tribe, two new genera and three new species of Cypridopsinae (Crustacea, Ostracoda, Cyprididae) from Brazil

We describe one new tribe, two new genera and three new species of the subfamily Cypridopsinae Kaufmann, 1900 from Brazilian floodplains. Brasilodopsis gen. nov. belongs in the nominal tribe Cypridopsini, and both new species in this new genus were found in both sexual and asexual populations. Brasilodopsis baiabonita gen. et sp. nov. has a wide distribution and was found in three of the four major Brazilian floodplains. Brasilodopsis amazonica gen. et sp. nov. was recorded only from the Amazon floodplain. Brasilodopsis baiabonita gen. et sp. nov. has a subtriangular shape in lateral view, whereas Brasilodopsis amazonica gen. et sp. nov. is more elongated and has more rounded dorsal margins in both valves, as well as more pronounced external valve ornamentation, consisting of rimmed pores in shallow pits. Paranadopsis reducta gen. et sp. nov. was found in asexual populations in the Upper Paraná River floodplain only and differs from other Cypridopsinae in the more elongated carapace, an A1 with strongly reduced chaetotaxy (hence the specific name) and the total absence of caudal rami in females. Because of these strong reductions in valve and limb morphology, Paranadopsini trib. nov. is created within the Cypridopsinae for this intriguing new genus and species.

Eunotia Ehrenberg (Eunotiaceae, Bacillariophyta) in a subtropical floodplain: a new species and taxonomic contributions

The Upper Paraná River floodplain is one of the few remaining non-dammed stretches in Brazil. It has a typical fluvial dynamics represented by the flood pulse and a highly complex habitat, which allows the existence and maintenance of a great biodiversity, including diatom species. As it happens in tropical lowland environments, also in this floodplain, the genus Eunotia is one of the most diverse and abundant diatom groups. Therefore, this study addresses morphologic and morphometric details of a new species and the most abundant Eunotia species in sediment cores from two wetland lakes. The morphological characteristics from each species were obtained through microscopy documentation of cell walls, and compared with other related species.

Staurosirella paranaensis sp. nov., a new epiphytic freshwater diatom (Bacillariophyceae) from the Paraná River floodplain, Brazil, South America

A new diatom species, Staurosirella paranaensis, is described only from epiphytic samples on the macrophyte Eichhornia azurea in a lake from the Upper Paraná River Floodplain in Brazil. Description of the new taxon is based on morphological characteristics observed using light and scanning electron microscopy. The new species is characterized by short elliptic valves with an axial area narrowly lanceolate, sometimes giving the impression of having a zig-zag form due the alternating nature of the striae. The lineolate striae, running uninterrupted from valve face to mantle. Spines are solid, thin, spatulate with two prominences at the top, located at the costae. Apical pore fields are inconspicuous, located at both apices and equally developed on both valves. Girdle elements variable in number, open, lacking pores, ligulated, and with valvocopula being much larger. The species previously identified in the region as the “catch-all” taxon “Staurosirella (Staurosira) pinnata” is placed in the genus Staurosirella based on the striae bearing well-developed internal vimines delimiting typically long areolae. Comparisons with similar species ascribed to the genus Staurosirella are provided to highlight the peculiar characteristics of S. paranaensis.

Upper Paraná River floodplain: synthesizing knowledge over time

Aim Considering the great environmental and social impact that floodplains have, several studies have been performed in the upper Paraná River floodplain. In this study, we applied a scientometric analysis to understand the evolution of scientific knowledge generated in the Upper Paraná River floodplain, based on studies published in this area. Methods We searched the literature published from 1995 to 2018 using the indexed database - Thomson ISI Web of Science. The following information was obtained for each scientific article: a) year of publication; b) place of research; c) research institution; d) study approach; e) environments; f) subject matter; g) theoretical approach; h) taxonomic groups. Results We found 435 published articles from different study areas (such as: exact and earth sciences, environmental sciences, social and human sciences, health sciences) that used this floodplain as a study area. The linear regression model showed an increase in the number of articles throughout the years. Studies with ecological themes were most prominent, ensuring research with various theoretical approaches and different biological communities used as proxies. Conclusions With this study, we conclude that long-term research was fundamental in generating data to address ecological issues and describe the dynamics of this plain. Studies such as these must have more political and financial support to develop basic scientific studies that can subsidize data for conservation programs and government policies, in order to maintain ecosystem services such as fishing and the availability of quality water.

Investigating the diversity of fish parasites in the floodplain of the upper Paraná River: a long-term ecological monitoring

Aim The aim of this study was to present the description of new species of fish parasites in native and non-native hosts and the parasite interaction / host, available in studies for 37 years in the upper Paraná River floodplain. Methods The sampling described in this study is part of a scientometric methodology, in which specific query expressions were used, together with the database available in the Nupelia Sector Library, through Theses and Dissertations. Results A total of 44 species of parasites belonging to different groups were described for 27 species of fish of different orders. In these 37 years of studies, an increase 68% was observed in the number of parasite species, presenting a richness of 201 species in the floodplain, being: Monogenea, Digenea, Nematoda and Cestoda are the groups that present the largest records of species. More than 80 hosts have their parasite fauna registered and most studies are carried out with species of native hosts in the floodplain, being Prochilodus lineatus the host with the highest number of records. Conclusions Parasitological studies are an important scientific tool for understanding the dynamics of ecological interactions in the natural environment, and knowledge of this diversity of organisms is continuous and necessary, and the results of the monitoring carried out in the floodplain during the last 37 years only reinforce this with a constant increase in the description of new species and new records of parasite-host interactions. In times of constant environmental loss and habitat fragmentation, it is of utmost importance to care for and preserve floodplains to maintain biodiversity.