Hoplias malabaricus, the common trahira, extended its range into the Iguaçu River sometime in the last decades. To determine levels of genetic differentiation in neighboring basins of this nominal taxon, as well as to unveil the source of the invading population, we analyzed patterns of similarity of RAPD-PCR genomic markers of samples from Paraná, Iguaçu and Tibagi Rivers. The high genetic diversity of samples from the Paraná and Tibagi Rivers suggested strong population structuring or even the occurrence of undescribed species. All alleles of the sample from the headwaters of Tibagi River were present in the sample from the Iguaçu River, which suggests that the former population or another population with similar genetic makeup, may be the source of the trahiras of the Iguaçu River.

Foram avaliadas a composição, a dieta, as táticas alimentares e ocupação espacial da ictiofauna em um pequeno riacho dentro de um remanescente de Floresta com Araucária. Seis espécies de peixes foram coletadas, pertencentes a três ordens e quatro famílias, totalizando 110 exemplares. No ambiente de corredeira foram coletados e observados apenas Trichomycterus castroi Pinna, 1992 and Trichomycterus davisi Haseman, 1911, enquanto que no ambiente de remanso foram observados e capturados exemplares de Astyanax aff. scabripinnis (sensu Eigenmann, 1921), Astyanax totae Haluch & Abilhoa, 2005, Trichomycterus castroi Pinna, 1992, T. davisi, Phalloceros caudimaculatus (Hensel, 1868) e Jenynsia eigenmanni Haseman, 1911. Dezoito itens alimentares de origem autóctone, seis de alóctone e três de origem incerta foram identificados e tiveram sua freqüência de ocorrência calculada. Uma grande quantidade de itens exclusivos foi registrada, todavia os insetos constituíram a base alimentar mais importante, principalmente na forma de fragmentos e estágios imaturos (larvas e pupas), o que permitiu inferências a respeito de sobreposição alimentar. As espécies registradas no riacho foram classificadas em quatro guildas tróficas e quatro grupos funcionais. As espécies estudadas são capazes de utilizar diversos recursos alimentares e microambientes, o que é favorecido provavelmente pelo seu pequeno porte. O remanescente florestal estudado exerce grande importância no fornecimento de alimento, hábitats e refúgios, fatores importantes para manutenção da biota aquática.

Several hypotheses are used to explain species richness patterns. Some of them (e.g. species-area, species-energy, environment-energy, water-energy, terrestrial primary productivity, environmental spatial heterogeneity, and climatic heterogeneity) are known to explain species richness patterns of terrestrial organisms, especially when they are combined. For aquatic organisms, however, it is unclear if these hypotheses can be useful to explain for these purposes. Therefore, we used a selection model approach to assess the predictive capacity of such hypotheses, and to determine which of them (combined or not) would be the most appropriate to explain the fish species distribution in small Brazilian streams. We perform the Akaike’s information criteria for models selections and the eigenvector analysis to control the special autocorrelation. The spatial structure was equal to 0.453, Moran’s I, and require 11 spatial filters. All models were significant and had adjustments ranging from 0.370 to 0.416 with strong spatial component (ranging from 0.226 to 0.369) and low adjustments for environmental data (ranging from 0.001 to 0.119) We obtained two groups of hypothesis are able to explain the richness pattern (1) water-energy, temporal productivity-heterogeneity (AIC = 4498.800) and (2) water-energy, temporal productivity-heterogeneity and area (AIC = 4500.400). We conclude that the fish richness patterns in small Brazilian streams are better explained by a combination of Water-Energy + Productivity + Temporal Heterogeneity hypotheses and not by just one.

Astyanax eremus, a new species of geographically isolated characid fish, is described from a small tributary of the upper rio Iguaçu basin. The new species belongs to the Astyanax scabripinnis species complex and is easily distinguished from its congeners included in this group by its allometric growth of the mouth, which goes from terminal in young individuals to subterminal mouth in larger specimens. Additionally, the new species is distinguished by meristic and morphometric characters. Astyanax eremus presents an evident polymorphism on the traditional character "number of teeth in inner premaxillary row". Comments about that character are provided.Astyanax eremus, uma espécie nova de caracídeo geograficamente isolada, é descrita de um pequeno tributário da bacia do alto rio Iguaçu. A espécie nova pertence ao complexo de espécies Astyanax scabripinnis e é facilmente distinguível dos congêneres deste grupo por apresentar desenvolvimento alométrico da boca, a qual passa de terminal nos indivíduos jovens a subterminal nos maiores. Além disso, a espécie nova é diagnosticada por caracteres merísticos e morfométricos. Astyanax eremus apresenta um acentuado polimorfismo do tradicional caráter "número de dentes da série interna do pré-maxilar". Uma discussão a respeito deste caráter é apresentada.

The epidermis of Ostariophysi fish is composed of 4 main cell types: epidermal cells (or filament containing cells), mucous cells, granular cells and club cells. The morphological analysis of the epidermis of the catfish Pimelodella lateristriga revealed the presence of only two types of cells: epidermal and club cells. The latter were evident in the middle layer of the epidermis, being the largest cells within the epithelium. Few organelles were located in the perinuclear region, while the rest of the cytoplasm was filled with a non-vesicular fibrillar substance. Club cells contained two irregular nuclei with evident nucleoli and high compacted peripheral chromatin. Histochemical analysis detected prevalence of protein within the cytoplasm other than carbohydrates, which were absent. These characteristics are similar to those described to most Ostariophysi studied so far. On the other hand, the epidermal cells differ from what is found in the literature. The present study described three distinct types, as follows: superficial, abundant and dense cells. Differences among them were restricted to their cytoplasm and nucleus morphology. Mucous cells were found in all Ostariophysi studied so far, although they were absent in P. lateristriga, along with granular cells, also typical of other catfish epidermis. The preset study corroborates the observations on club cells' morphology in Siluriformes specimens, and shows important differences in epidermis composition and cell structure of P. lateristriga regarding the literature data.

Rineloricaria langei and R. maacki, new species, are described from upper and middle regions of the rio Iguaçu basin, a left bank tributary of the rio Paraná basin, southern Brazil. Rineloricaria langei has narrow body and is similar to R. quadrensis, which is found in coastal rivers of Rio Grande do Sul State and is distinguishable by several morphometric characters. Rineloricaria maacki is distinguishable from all other congeners by the shape and extension of the naked area of the ventral region of pectoral girdle and other morphological characters. The presence of a naked region on the abdominal surface is shared with other species from the rio Paraná and rio Uruguay basins and coastal drainages from southeastern and southern Brazil. This may indicate a close phylogenetic relationship among these species. Similarities between the two new species and species from the aforementioned drainages also suggest close biogeographic relationship between the Paraná basin and other Brazilian coastal Atlantic drainages throughout the rio Iguaçu basin.Rineloricaria langei e R. maacki, espécies novas, são descritas para os cursos médio e alto da bacia do rio Iguaçu, tributário esquerdo do sistema do rio Paraná, sul do Brasil. Rineloricaria langei tem o corpo estreito e é semelhante a R. quadrensis, que ocorre nos rios costeiros do estado do Rio Grande do Sul, da qual distingui-se por características morfométricas. Rineloricaria maacki distingui-se de todas as suas congêneres pela forma e extensão da área nua da região ventral da cintura peitoral e outras características morfológicas. A presença de uma região nua na superfície ventral de R. maacki é compartilhada por outras espécies das bacias dos rios Paraná e Uruguai, e das drenagens costeiras do sudeste e sul do Brasil. Isto pode indicar uma proximidade filogenética entre estas espécies. Semelhanças entre as duas espécies novas e espécies das bacias supracitadas também sugerem um relacionamento biogeográfico próximo entre a bacia do Paraná e os rios costeiros brasileiros através da bacia do rio Iguaçu.

Astyanax varzeae, a new species of characid fish, is described from the rio da Várzea headwaters, a tributary of the upper portions of the rio Iguaçu in Paraná State, Brazil. The new species belongs to the Astyanax scabripinnis species complex and differs from its congeners by the presence of one or two humeral spots, maxilla with one to three (mostly two) teeth and 15 to 20 (usually 16 to 18) branched anal-fin rays.Astyanax varzeae, uma nova espécie de caracídeo, é descrita das cabeceiras do rio da Várzea, um tributário do trecho superior do rio Iguaçu no estado do Paraná, Brasil. A nova espécie pertence ao complexo de espécies Astyanax scabripinnis e difere das demais espécies do gênero Astyanax pela presença de uma ou duas manchas umerais, maxilar com um a três (freqüentemente dois) dentes e 15 a 20 (freqüentemente 16 a 18) raios bifurcados na nadadeira anal.

The Neotropical region hosts 4225 freshwater fish species, ranking first among the world's most diverse regions for freshwater fishes. Our NEOTROPICAL FRESHWATER FISHES data set is the first to produce a large‐scale Neotropical freshwater fish inventory, covering the entire Neotropical region from Mexico and the Caribbean in the north to the southern limits in Argentina, Paraguay, Chile, and Uruguay. We compiled 185,787 distribution records, with unique georeferenced coordinates, for the 4225 species, represented by occurrence and abundance data. The number of species for the most numerous orders are as follows: Characiformes (1289), Siluriformes (1384), Cichliformes (354), Cyprinodontiformes (245), and Gymnotiformes (135). The most recorded species was the characid Astyanax fasciatus (4696 records). We registered 116,802 distribution records for native species, compared to 1802 distribution records for nonnative species. The main aim of the NEOTROPICAL FRESHWATER FISHES data set was to make these occurrence and abundance data accessible for international researchers to develop ecological and macroecological studies, from local to regional scales, with focal fish species, families, or orders. We anticipate that the NEOTROPICAL FRESHWATER FISHES data set will be valuable for studies on a wide range of ecological processes, such as trophic cascades, fishery pressure, the effects of habitat loss and fragmentation, and the impacts of species invasion and climate change. There are no copyright restrictions on the data, and please cite this data paper when using the data in publications.