Abstract
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 µm), 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 preferred habitats, marginal vegetation and sediment.
Highlights
The ecology of testate amoebae has been intensely focused in Brazil, from the 90’s decade in different aquatic environments, as rivers, reservoirs and lakes (DABÉS, 1995; VELHO et al, 1996, 2003, 2004; LANSAC-TÔHA et al, 2004, 2008, 2009; FULONE et al, 2005; ALVES et al, 2008, among others)
The most representative families of testate amoebae recorded in the present study, Difflugiidae, Arcellidae and Centropyxidae, have been highlighted for the great diversity in other studies performed in freshwater plankton (GREEN, 1975; DABÉS, 1995; LANDA; MOURGUÉSSCHURTER, 2000; LANSAC-TÔHA et al, 2008), as well as in other studies in this same floodplain (LANSAC-TÔHA et al, 2004, 2007, 2009; VELHO et al, 2000, 2001; ALVES et al, 2007)
This result may be related to the raise of hydrometric level and the increase in current flow observed during this period that allow the input of organisms coming from other habitats, mainly littoral vegetation, as verified in other studies accomplished in aquatic environments (GREEN, 1975; WALKER, 1982; VELHO et al, 1999, 2003; LANSAC-TÔHA et al, 2004, 2009)
Summary
The ecology of testate amoebae has been intensely focused in Brazil, from the 90’s decade in different aquatic environments, as rivers, reservoirs and lakes (DABÉS, 1995; VELHO et al, 1996, 2003, 2004; LANSAC-TÔHA et al, 2004, 2008, 2009; FULONE et al, 2005; ALVES et al, 2008, among others). Most of testate amoebae species (about 80% of the species) inhabit aquatic environments associated to marginal vegetation and sediment (BONNET, 1974) These organisms have been frequently recorded in samples of plankton from rivers and lakes, with high abundance (ARNDT, 1993; GREEN, 1975, 1994; VELHO et al, 1996, 2003; LANSAC-TÔHA et al, 2004, 2009). This significant representativeness of testate amoebae in plankton may be related to the presence of gas vacuoles for floating (STEPANÉK; JIRÍ, 1958), and shells with low density (SCHÖNBORN, 1962), which according to Velho et al (1999), may permit the access of these organisms to planktonic compartment
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