Flávio Henrique Ragonha

Chironomidae larvae (Diptera) of Neotropical floodplain: overlap niche in different habitats

The niche overlap between trophic groups of Chironomidae larvae in different habitats was observed between trophic groups and between different environments in Neotropical floodplain. For the evaluation we used the index of niche overlap (CXY) and analysis of trophic networks, both from the types and amount of food items identified in the larval alimentary canal. In all environments, the larvae fed on mainly organic matter such as plants fragments and algae, but there were many omnivore larvae. Species that have high values of food items occurred in diverse environments as generalists with great overlap niche and those with a low amount of food items with less overlap niche were classified as specialists. The largest number of trophic niche overlap was observed among collector-gatherers in connected floodplain lakes. The lower values of index niche overlap were predators. The similarity in the diet of different taxa in the same niche does not necessarily imply competition between them, but coexistence when the food resource is not scarce in the environment even in partially overlapping niches.

Limnoperna fortunei Dunker, 1857 larvae in different environments of a Neotropical floodplain: relationships of abiotic variables and phytoplankton with different stages of development

Limnoperna fortunei Dunker, 1857 is an Asian invasive freshwater bivalve. Although there need to contain their spread, studies about the biology of the larvae are scarce. We correlated the larval stages of L. fortunei with biotic factors such as phytoplankton and main abiotic variables in lotic environments of the Upper Paraná River floodplain. The four samples were taken quarterly during the year 2012. The Principal component analysis (PCA) showed only spatial differences, as did a Canonical Correspondence Analysis (CCA). High densities of larvae were recorded in all samples the Paraná River and Baía River only in December, especially those in their initial stage. In the biovolume of Class of algae, Bacillarophyceae showed the highest value, but Chlorophycea who was strongly correlated with the density of D-stage larvae. The large variety of phytoplankton, especially microplankton Chlorophyceae, high values of PO4, NH4 and temperature were positively correlated with high densities of D-stage larvae. We conclude that high temperature, and food availability, indicated by phytoplankton community, favored the reproduction of L. fortunei and enhance the ability of specie dispersion due to the increase in the emission of propagules. Therefore, studies that address the biology of golden mussel larvae should be performed in order to prevent its spread.

Chironomidae feeding habits in different habitats from a Neotropical floodplain: exploring patterns in aquatic food webs

Ecological studies on food webs have considerably increased in recent decades, especially in aquatic communities. Because Chironomidae family are highly specious, occurring in almost all aquatic habitats is considered organisms-key to initiate studies on ecological relationships and trophic webs. We tested the hypothesis that the diversity of the morphospecies diet reflects differences on both the food items available among habitats and the preferences of larval feeding. We analyzed the gut content of the seven most abundant Chironomidae morphospecies of the different habitats from the Upper Paraná River. We categorized the food items found into algae, fungal spores, fragments of plants, algae and animal fragments and sponge spicules. We observed the algae predominance in the gut content of morphospecies from lakes. Considering the different regions from each lake, we registered the highest food abundance in the littoral regions in relation to the central regions. From the variety of feeding habits (number of item kinds), we classified Chironomus strenzkei, Tanytarsus sp.1, Procladius sp.1 as generalist morphospecies. We found a nested pattern between food items and Chironomidae morphospecies, where some items were common to all taxa (e.g., Bacillariophyceae algae, especially), while others were found in specific morphospecies (e.g., animals fragments found in Procladius sp.1). The algae represented the most percentage of gut contents of Chironomidae larvae. This was especially true for the individuals from littoral regions, which is probably due to the major densities of algae associated to macrophytes, which are abundant in these regions. Therefore, the feeding behavior of these morphospecies was generalist and not selective, depending only of the available resources.

Freshwater invasibility level depends on the population age structure of the invading mussel species

Environmental conditions may affect invasibility and potentially prevent successful invasions of the freshwater bivalve Limnoperna fortunei Dunker, 1857. However, even though the larval stage may be considered an important species’ characteristic, the invasion processes of L. fortunei are mainly evaluated using only the adult stage. Therefore, the aim of this study was to identify what, and how, environmental filters might predict the likelihood of occurrence of each of the L. fortunei larval stages. Logistic regressions were applied using the larval stages of L. fortunei as a surrogate of population age structure and the environmental variables as the main filters that potentially predicted the likelihood of the occurrence of each larval stage of L. fortunei. The turbidity predicted the occurrence of the D-shaped larvae and straight-hinged veliger stages, while the umbonated-veliger and pediveliger stages were predicted by the pH and conductivity. Finally, the phytoplankton density (diatoms) predicted the occurrence of the umbonated-veliger, pediveliger and mainly the plantigrade stages. Our findings suggested that, during larvae development, from younger to older stages, the main environmental predictor of larvae occurrence shifted from abiotic to biotic variables, indicating that larval stages are indeed an important factor that helps in the evaluation of freshwater invasibility. These findings are particularly important for floodplain systems, where flood pulse dynamics may increase propagule pressure, leading to a successful spread among habitats. Then, even though environmental filters were important to predict successful invasions, we highlight that a successful invasion might depend on the population age structure of the invading species arriving in the new habitat. Thus, successful L. fortunei invasions in floodplain systems may depend on the interaction between invasiveness, invasibility and propagule pressure.

Benthic invertebrates nestedness in flood and drought periods in a Neotropical floodplain: looking for the richest environments

Aim Floodplains are among the most biologically diverse systems in the world, where hydrological regime is recognized as crucial to structure aquatic communities. We predicted that i) structure of benthic metacommunity is nested in the drought and random in the flood season in a Neotropical floodplain. We expected to find ii) environmental homogenization during the flood season which may disrupt the nested pattern. Moreover, we identified habitats of high taxa richness of benthic invertebrates and characterized them by habitat type and fluvial systems. Methods We sampled benthic invertebrates from 36 habitats in the Upper Parana River floodplain. We tested nestedness using NODF index and evaluated the environmental variability using the multivariate homogeneity of group dispersions (PERMDISP), separately for flood and drought periods. Results The environmental variability was lower during the flood. We found a nested distribution among benthic invertebrates in both flood and drought periods. The highest species richness values were recorded in small and unconnected lakes from Parana fluvial system and some rivers and secondary channels, independent of the fluvial system. Chironomidae, Oligochaeta and Ostracoda were the most frequent taxa and were recorded in all habitats. Conclusion The nested distribution of benthic invertebrates is a consistent pattern for this metacommunity because its distribution was not disrupted by floods that homogenize limnological conditions and increase the connectivity among habitats. We also found that habitats with high taxa richness were both lotic and lentic in the three fluvial systems. Our findings emphasize that different habitats in different subsystems sustains the richness of the benthic invertebrates metacommunity in the Upper Parana River floodplain over time.

First records of Freshwater Bivalves of Ilha Grande National Park, Paraná, Brazil

The Ilha Grande National Park, Parana, Brazil, is located in the Upper Parana River and has characteristics typical of a floodplains. This protected area includes lagoons connected and disconnected to the Parana River, although the latter also connect during periods of high water level, thus composing a heterogeneous group of lacustrine environments. The enormous potential the flora and fauna diversities are still little known to the region, as can be seen through benthic invertebrates, inclunding bivalves mollusks. The granulometric composition of these floodplain lagoons was formed mainly by mud and very fine sand. Furthermore, organic matter composition was predominantly of fine particulate. The other abiotic factors differed from lagoons located within the island of the park to those located in the left margin of Parana River. The results demonstrated the importance of abiotic factors such as the physical composition of granulometric texture, organic matter and macrophyte banks, to the establishment of bivalves in these floodplain lagoons. We recorded bivalves of Pisidium (native), Diplodon (native), and Corbicula (invasive). The highest values of Diplodon sp. density were observed at Sao Joao/C lake, for Pisidium sterkianum (Pilsbry, 1897) at Sao Joao/M lake, and to Jatoba/C lagoon with high density of invasive species Corbicula fluminea (Muller, 1774). This study to obtain conduct the first records of freshwater bivalves in floodplains lagoon in the Ilha Grande National Park, and provides contributions to better understanding the ecology of these mollusks. The recording of native species in the region of Upper Parana River floodplain after a lomg period without new records, demonstrated the importance of protecting the lagoons of the Ilha Grande National Park as they can be a possible refuge to some species of native freshwater bivalves.

Reservoir longitudinal gradient promotes ordered losses on diversity and density of Ephemeroptera community

Reservoir operations alter, eliminate or restrain the natural hydrologic cycles. Biotic community has become subject to these non-cyclic events, responding by reducing the species diversity. Ephemeroptera species present distinct responses to environmental deterioration such that poses this assemblage between the most useful groups in biomonitoring programs. We hypothesized an alteration in beta diversity at the longitudinal species gradient, which will be influenced mainly by species losses between zones. Changes in temporal beta diversity is also expected, but the main drivers of such alterations will be the species turnover between the sampling period. Ephemeroptera community was monitored in nine sampling points from Itaipu Reservoir, where were installed three sets of substrates composed by a float and 2 wooden substrates. We took biological samples in triplicates monthly, from June-01 to August-02. Our initial hypothesis was partially supported and with significant variations only for spatial approach, between the Reservoir zones. The generated ordering from Non-Metric Dimensional Scale - NMDS - corroborated with spatial analyzes, with the formation of two groups along the gradient zonation of the reservoir. The temporal ordination showed no clear pattern. As expected, the contribution to beta diversity was different for our two approaches, such that the loss of species was more important along the spatial gradient and despite of no significant result, the species replacement was more important among months. The spatial results lead us to infer that differences in limnological characteristics between zones are important for determining differences in Ephemeroptera composition and can reflect the dependency degree of the species in relation to the lentic and sometimes-lotic conditions, mainly in the riverine zone of reservoirs. On the other hand, the absence of a temporal pattern can be result of chaotic variations in the physical and chemical attributes imposed by the reservoir operation, disrupting continuity of the biota and natural succession processes.

Effects of food availability and habitat features on the Ephemeroptera species composition at seasonal and spatial scales from neotropical floodplain rivers

Brazilian floodplains have suffered great changes in their natural characteristics in recent decades, mainly in the flood pulse. The Upper Paraná River floodplain is one of the few places where are found remained areas in which such peculiar characteristics keep reflecting on its high biodiversity. Ephemeroptera nymphs are one of the higher density groups among benthic community, occurring in many water bodies like large rivers and secondary channels. We sought to understand which factors are needed for the species establishment and how much important is the species colonization, especially in environments with anthropogenic changes. The marginal areas, which are more structured with presence of macrophytes, showed the highest density and richness even in the Paraná River that has great human impact. We verified dominance of Americabaetis alphus, Tricorythopsis araponga, Tricorythopsis artigas on the Parana River, correlated with transparency, depth and electric conductivity, while the dominance of Traverella sp. was correlated with water temperature, especially in marginal areas. Consequently, the increasing transparency and electric conductivity due to the Porto Primavera dam in Parana River can be favoring those Ephemeroptera species. We demonstrated the importance of preserving the wetlands of Ivinhema River State Park mainly for Guajirolus sp., which was only registered in this region. Therefore, our study provides support for understanding gaps from previously studies using artificial substrates in three large rivers which are of great importance to the upper Paraná River floodplain.

Oloigochaeta do Estado do Piauí

Neste trabalho foram realizados os primeiros registros de especies de Oligochaeta aquaticas para a regiao nordeste. O estudo foi realizado nos dois principais rios do Estado do Piaui. Verificou a importância de maiores esforcos de levantamento dessa fauna para a regiao Nordeste para ampliacao do conhecimento sobre a distribuicao de Oligochaeta.