Oscar Akio Shibatta

Diversidade da ictiofauna do Alto Rio Paraná: composição atual e perspectivas futuras

Langeani, F., Castro, R.M.C., Oyakawa, O.T., Shibatta, O.A., Pavanelli, C.S. & Casatti, L. Ichthyofauna diversity of the upper rio Parana: present composition and future perspectives. Biota Neotrop. Sep/Dez 2007 vol. 7, no. 3 http://www.biotaneotropica.org.br/v7n3/pt/abstract?article+bn03407032007. ISSN 1676-0603. A synthesis concerning fishes from Upper Parana River basin is presented, based on data from fish-collections, literature, and new field samples. Three hundred and ten species, pertaining to 11 orders and 38 families, are referred to the drainage, elevating anterior estimates. Concerning total species, 236 (76.1%) are autochthonous, 67 (21.6%) are allochthonous, and seven (2.3%) are exotic. Principal causes of occurrence of non-native species are: a) dispersal from the Lower Parana, after the construction of Itaipu dam, and b) escapes from aquaculture farms. Most species (65%) are small-sized, having less than 21 cm of length, and the great majority occurs only in headwaters and small streams. One of the best known and most studied in Brazil, Upper Parana ichthyofauna richness is far from reaching actual numbers, considering the exponential elevation of species presented herein. Indeed, in the last years various new species have been described and around 50 other species, already recognized as new, are now under description. The improvement on the knowledge about Upper Parana ichthyofauna is proportional to the number of researchers involved with studies in the area and, unequivocally, reflects recent initiatives stimulating and incrementing taxonomic research, and also improving access to fish collections and to poor or never-sampled areas. However, if we are going to maintain the number of species descriptions per year of last decade, the 50 new species already recognized, will be described only in the next ten years, a period too long. In consequence it is very important that scientific community and grant agencies find and offer initiatives in order to elevate the number of new taxa descriptions per year.

Astyanax aff. fasciatus Cuvier, 1819 (Teleostei; Characidae): evidences of a species complex in the upper rio Tibagi basin (Paraná, Brazil)

Four populations of Astyanax aff. fasciatus of the upper rio Tibagi (municipal district of Ponta Grossa, Parana State, Brazil), had their karyotypes and morphometry analyzed. The cytogenetic data show the occurrence of distinct karyotypes (cytotypes), here named cytotype A, with 2n=48 chromosomes (6m+18sm+14st+10a), cytotype B, with 2n=50 chromosomes (8m+18sm+14st+10a) and cytotype C, with 2n=50 chromosomes (8m+18sm+14st+10a). The distribution pattern of the constitutive heterochromatin was very similar between cytotypes A and B, but diverged in relation to cytotype C. Distinct cytotypes may occur in sympatry in the upper rio Tibagi region, with the exception of the Furna 2 sample, which presents cytotype A exclusively. In addition, a specimen with 2n=49 chromosomes (7m+18sm+14st+10a) was also found and, by the characteristics presented, may be a consequence of a rare hybridization event between cytotypes A and B. The morphometric analyses of canonical variates indicate a consistent isolation of the Furna 2 sample, while the other samples seem to be superimposed, indicating a possible gene flow or even a recent isolation event. This model points to a probable complex of cryptic species in the studied region.

Diversidade de peixes do reservatório da UHE Escola Engenharia Mackenzie (Capivara), Rio Paranapanema, bacia do alto rio Paraná, Brasil, e a importância dos grandes tributários na sua manutenção

As especies foram coletadas em quatro trechos ao longo de um gradiente formado pelo reservatorio UHE Escola Engenharia Mackenzie (Capivara). A diversidade de especies foi analisada pela constância, indice de Shannon-Wiener e similaridade da composicao entre trechos atraves do coeficiente de Jaccard. O reservatorio tem uma riqueza de peixes composta por 67 especies incluidas em 5 ordens; 47% das especies sao constantes, 15 % sao acessorias e 28% sao acidentais. Os maiores indices de diversidade de Shannon-Wiener e similaridade de Jaccard foram obtidos em Cinzas e Tibagi, que sao os trechos mais distantes da barragem e que apresentam grandes tributarios. Os menores indices foram encontrados em Cruzalia e Porecatu, os quais correspondem aos trechos com caracteristicas, respectivamente, de ambientes lotico e semi-lotico. Este trabalho demonstra a extrema importância da presenca dos tributarios para a manutencao da diversidade das especies em um reservatorio, em funcao da preservacao das caracteristicas originais do sistema lotico naqueles trechos e consequente reducao do impacto do represamento.

Peixes como indicadores da qualidade ambiental do ribeirão Esperança, município de Londrina, Paraná, Brasil

To evaluate the environmental quality and patterns of diversity of fish species from an altered urban stream, we analyzed habitat quality, water velocity and fish species distribution. In order to include a larger amount of environments and considering the distinct physical characteristics and human influence, five stream sites were seasonally sampled. A total of 5,426 individuals, being 12 species and 6 orders, were collected. The degree of environmental alteration at each sampling site was determined through the analysis of habitat diversity and water velocity. The intermediate sites showed higher species richness as the upper sites were the most altered ones. The lower sites showed adverse physical characteristics to the permanence of some species. These results indicated that hydrological and geomorphological characteristics should influence the aquatic biota richness. Nonetheless, it was found that native species still find favorable places to their development, even with exotic species that have became abundant and are potential competitors in environmental and resources exploration.

Atividade alimentar de espécies de peixe do rio Tibagi, relacionada com o desenvolvimento de gordura e das gônadas

The fish assemblage in a stretch of Tibagi river was studied during the period of one year, throught monthly sampling. It was observed that four fish species (Schizodon intermedius Garavello & Britski, 1990, Acestrorhynchus lacustris Reinhardt, 1874, Pimelodus maculatus Lacepede, 1803 and Steindachnerina insculpta Fernandez-Yepez, 1948) were very frequent and they represent all the main trophic groups. In order to characterize feeding activity, fat storage and reproduction the means degree of repletion, fat and maturation, obtained for each species in each month were compared among the four fish species. Steindachnerina insculpta, a detritivovous species was the one with the highest feeding activity while A. lacustris, a piscivorous fish, showed the lowest feeding activity. For these two species it was clearly observed a sequence of events: higher feeding activity followed by higher fat storage followed by reproduction, that was not observed for P. maculatus and S. intermedius. The variations in feeding activity and fat storage showed by P. maculatus and S. intermedius might be related to their diets.

Composição em tamanho dos peixes (Actinopterygii, Teleostei) de ribeirões da bacia do rio Tibagi, Paraná, Brasil

The standard length of 7610 specimens of 43 species from eight streams of rio Tibagi basin was obtained in order to analyze the means of fish sizes. The higher mean size was observed in Gymnotus carapo Linnaeus, 1758 (165,5 mm) and the smaller, in Phalloceros caudimaculatus (Hensel, 1868) (16,25 mm). Some fish like Acestrorhynchus lacustris (Reinhardt, 1874), Leporinus obtusidens (Valenciennes, 1836), Gymnotus carapo Linneus, 1758 and Synbranchus marmoratus Bloch, 1795 can reach big or medium size when adults but were collected only young, evidencing they use some streams in beginning of life. The mean size of total species was 49,81mm, what shows the small size composition of fishes in the streams. The Kolmogov-Smirnov test comparing the mean size of all streams showed significant similar size both in upstream and downstream regions, independent to the different environmental conditions.

Plasticidade alimentar em Rivulus pictus Costa (Osteichthtyes, Cyprinodontiformes, Rivulidae) de uma pequena lagoa em Brasília, Distrito Federal, Brasil

Rivulus pictus has a wide distribution in Distrito Federal and lives in different environments, including small lakes. The analysis of gastric and intestinal contents showed that most of the 21 ingested food items were from autochthonous origin and characterized the diet of an omnivorous fish with a trend to planktivory. Five feeding items were important in the composition of the alimentary spectrum and revealed that food resources are explored near water surface (Acari), in the water column (Copepoda, Cladocera and Closterium sp.) and also in the bottom (Chironomidae). The varied diet and the capacity to explore all levels of the environment evidenced that feeding flexibility is one of the factors that facilitates the survival of this species in different environments.

Diversity of the Astyanax scabripinnis species complex (Teleostei: Characidae) in the Atlantic Forest, Brazil: species limits and evolutionary inferences

The Astyanax scabripinnis species complex with its wide geographical distribution is an excellent model for evolutionary studies. Populations are usually geographically isolated but also, in some cases, occur in sympatry. In this study, five allopatric and/or sympatric populations of A. scabripinnis were analysed using geometric morphometry, cytogenetic markers, assays for induced breeding and phylogenetic inferences to draw conclusions on species limits and speciation processes in a natural setting. The morphometry of individuals indicated that the populations were well differentiated from each other. Cytogenetic evidence revealed a more conserved karyotypic macrostructure; however, molecular cytogenetic results obtained by in situ hybridization indicated 5S and 18S rDNA gene probe locations specific to each population. The reproduction tests for three locations suggest isolation between populations and the phylogenetic analyses suggest that the fish evaluated cluster in a monophyletic group. The combined data indicate that individuals are adapted to different environments in a complex evolutionary scenario, with linkage of populations during a recent geological period. However, due to reproductive isolation, the populations are evolving independently, reinforcing the existence of distinct cryptic species.

A new species of Hypostomus Lacépède, 1803 (Siluriformes: Loricariidae) from the upper rio Paraná basin, Southern Brazil

A new species of Hypostomus with large and spaced light roundish spots is described from the upper rio Parana basin. Hypostomus multidens new species is distinguished from all remaining congeners with light spots on a darker background by two independent characters: the presence of teeth with two symmetrical cusps, and a high tooth number in each dentary (122267, mean 196.8) and premaxilla (115-260, mean 190.8).

Abundância e aspectos reprodutivos de Loricariichthys platymetopon (Siluriformes, Loricariidae) em quatro trechos da represa Capivara, médio rio Paranapanema

The armored catfish Loricariichthys platymetopon was recently caught by the first time in the middle region of river Paranapanema. It has quickly become one of the most abundant species. This study evaluated reproductive aspects of 1,044 specimens collected in the Capivara reservoir. Abundance, sex ratio, RGS, IAR and oocyte diameter were evaluated. Sites far away from the dam showed higher abundances than the one next to it. Breeding occurred when temperature was higher, with moderate intensity. Mean absolute fecundity and mean relative fecundity were 663.95 ± 141.99 oocytes and 4.9 ± 1.24 oocytes.gr-1 respectively. Spawning occurred in batches. Mean diameter of mature oocytes was 3.67 mm.