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Aim Fish diversity in two lentic environments: a lake connected (Barbosa lake) to a river and an artificial reservoir (Ninfeias reservoir) were determined in the dry and rainy periods in 2015. We expected to find more diversity in the connected lake and greater abundance in the reservoir. Methods Specimens were caught using gill nets. Moreover, environmental parameters such as temperature, electrical conductivity, pH, dissolved oxygen and water transparency were measured during the two periods. Results 546 specimens were collected from 9 families, 12 genera and 15 species of the orders Characiformes, Siluriformes, Cichliformes and Gymnotiformes. Pimelodus maculatus was the most abundant species in the connected lake. Two species were caught from the reservoir: Geophagus brasiliensis and Hoplias malabaricus, the former being predominant. The dominant species in the studied environments corresponded to 48.71% of the total number of specimens. The ichthyofaunal composition from the lake showed a high richness of the order Characiformes (66.7%). Siluriformes and Gymnotiformes represented 13.3% each and the order Cichliformes only 6.7% of the total number of species. In the artificial reservoir, there was an equivalent contribution of Cichliformes and Characiformes. The diversity was higher in the lake (H' = 2.05) and lower in the reservoir (H' = 0.34). Significant differences (p

Constituiu o objetivo deste estudo a taxonomia das algas perifíticas (exceto Bacillariophyceae) dominantes em três substratos naturais, Eichhornia azurea Kunth, Nymphaea amazonum Mart. & Zucc. e Oxycaryum cubense (Poepp. & Kunth) Lye, em um ambiente semilótico (Ressaco do Pau Véio), na planície de inundação do Alto Rio Paraná. Considerou-se apenas os táxons com freqüência de ocorrência acima de 75% das amostras, excetuando-se as diatomáceas. Trinta e um táxons foram descritos, ilustrados e medidos, distribuídos nas classes: Chlorophyceae (3), Cryptophyceae (1), Cyanobacteria (14 taxa), Zygnemaphyceae (7), Euglenophyceae (2) e Xanthophyceae (4). Vinte e três espécies consistiram em primeiros registros taxonômicos para a planície do Alto Rio Paraná: Chamaesiphon investiens Skuja, Geitleribactron subaequale (Geitler) Komárek, Chroococcus limneticus Lemmerm., C. minimus (Keissler) Lemmerm., C. minor (Kütz.) Nägeli, Aphanothece microscopica Nägeli, Phormidium molle (Kütz.) Gomont, Leptolyngbya angustissima (West & G.S. West) Anagn. & Komárek, L. foveolarum (Rabenhorst ex Gomont) Anagn. & Komárek e Pseudanabaena frigida (Fritsch) Anagn. (Cyanobacteria); Characium ensiforme Hermann, C. ornithocephalum A. Braun e Desmodesmus brasiliensis (Bohlin) E. Hegewald (Chlorophyceae); Cosmarium abbreviatum Racib., C. bireme Nordst., C. pseudopyramidatum Lundell, C. subadoxum Grönblad, C. trilobulatum Reinsch, Gonatozygon pilosum Wolle and Staurastrum forficulatum Lundell (Zygnemaphyceae); Trachelomonas hispida (Perty) Stein emend. Deflandre (Euglenophyceae); Cryptomonas tenuis Pascher (Cryptophyceae) e Characiopsis sphagnicola Pascher (Xanthophyceae). The purpose of this study was the taxonomy of dominant periphytic algae (except Bacillariophyceae) of three natural substrates, Eichhornia azurea Kunth, Nymphaea amazonum Mart. & Zucc. and Oxycaryum cubense (Poepp. & Kunth) Lye in a semi-lotic environment (the Pau Véio backwater) at the Paraná River floodplain. Only those taxa with a frequency of occurrence over 75% of all samples were considered, except diatoms. Thirty-one taxa were illustrated, measured and identified at species level, a total of 31 taxa were described, distributed in classes: Chlorophyceae (3), Cryptophyceae (1), Cyanobacteria (14 taxa), Zygnemaphyceae (7), Euglenophyceae (2) and Xanthophyceae (4). Twenty-three taxa are first taxonomic reports for the Upper Paraná River floodplain: Chamaesiphon investiens Skuja, Geitleribactron subaequale (Geitler) Komárek, Chroococcus limneticus Lemmerm., C. minimus (Keissler) Lemmerm., C. minor (Kütz.) Nägeli, Aphanothece microscopica Nägeli, Phormidium molle (Kütz.) Gomont, Leptolyngbya angustissima (West & G.S. West) Anagn. & Komárek, L. foveolarum (Rabenhorst ex Gomont) Anagn. & Komárek and Pseudanabaena frigida (Fritsch) Anagn. (Cyanobacteria); Characium ensiforme Hermann, C. ornithocephalum A. Braun and Desmodesmus brasiliensis (Bohlin) E. Hegewald (Chlorophyceae); Cosmarium abbreviatum Racib., C. bireme Nordst., C. pseudopyramidatum Lundell, C. subadoxum Grönblad, C. trilobulatum Reinsch, Gonatozygon pilosum Wolle and Staurastrum forficulatum Lundell (Zygnemaphyceae); Trachelomonas hispida (Perty) Stein emend. Deflandre (Euglenophyceae); Cryptomonas tenuis Pascher (Cryptophyceae) and Characiopsis sphagnicola Pascher (Xanthophyceae).