Species richness of testate amoebae in different environments from the upper Paraná river floodplain (PR/MS) = Riqueza de amebas testáceas em diferentes ambientes da planície de inundação do alto rio Paraná (PR/MS)

This study evaluated the species richness of testate amoebae in the plankton from different environments of the upper Parana river floodplain. Samplings were performed at subsurface of pelagic region from twelve environments using motorized pump and plankton net (68 ƒÝm), during four hydrological periods. We identified 67 taxa, distributed in seven families and Arcellidae, Difflugiidae and Centropyxidae were the most representative families. Higher values of species richness were observed in the lakes (connected and isolated) during the flood pulses. Centropyxis aculeata, Difflugia gramem and D.pseudogramem were frequent throughout the study period. Seasonal variability of species in the channels and isolated lakes was evidenced by beta diversity. Besides that, in the rivers, extreme changes in species composition were verified during the high-water period. Our results highlight the importance of the present study to improve the knowledge about the diversity and geographic distribution of these organisms in Brazil and emphasize the importance of current flow in the displacement of testate amoebae from their preferredhabitats, marginal vegetation and sediment.<br><br>Este estudo objetivou avaliar a riqueza de taxons de amebas testaceas no plancton de diferentes ambientes da planicie de inundacao do alto rio Parana. Foram amostrados 12 pontos da regiao pelagica em diferentes ambientes (rios, canais e lagoas) e em quatro periodos hidrologicos. Foram identificados 67 taxons, distribuidos em sete familias. Arcellidae, Difflugiidae e Centropyxidae foram as familiasmais especiosas. Nas lagoas (abertas e fechadas), durante os pulsos de inundacao, foram observados os maiores valores para a riqueza de especies. Centropyxis aculeata, Difflugia gramem e D. pseudogramem foram frequentes durante todo o periodo estudado. Os dados obtidos pela diversidade beta evidenciaram a variabilidade sazonal das especies nos canais e lagoas fechadas. Nos rios, as alteracoes ocorreram com maior intensidade no periodo de cheia. Os resultados ressaltam a importancia desse estudo para o acrescimo do conhecimento sobre a diversidade e distribuicao geografica desses organismos no Brasil e ratifica a importancia do fluxo de corrente no carreamento de amebas testaceas de seus habitats preferenciais, vegetacao marginal e sedimento.