The effect of temperature and predation on performance in monoculture and in competition in three Daphniidae differing in body size

Zooplankton body size shows a strong association with temperature, competition, and predation. Global warming affects all three drivers of body size and is thus expected to lead to substantial changes in zooplankton community composition and body size distributions. To disentangle the isolated and joint effect of temperature, competition, and fish predation on species biomass and community composition in zooplankton, we monitored population biomasses of three Daphniidae species that differ in body size (Daphnia magna, Daphnia pulex, and Ceriodaphnia reticulata) for 20 days, manipulating competition (monoculture, pairwise trials, and three-species communities), temperature (20°C, 24°C, and 28°C) and presence or absence of fish predation. In the absence of predation, D. magna dominated in all competition experiments, even at high temperatures. D. magna went extinct, however, in the predation treatments at 24°C and 28°C. D. pulex outcompeted C. reticulata and was negatively affected by predation and high temperature. C. reticulata did not reduce biomass at high temperatures and was negatively affected by all competition trials, but was positively affected by predation. Our results indicate that the two larger-bodied species are more negatively affected by the combination of temperature and predation than the smallest species. While higher temperatures reduced the biomass of the larger-bodied species, it did not fundamentally change their ability to dominate over the smallest species in competition. The combined effect of warming and predation changed community composition more fundamentally, resulting in the dominance of small-bodied species. This can have important ecosystem-wide impacts, such as the transition to turbid, algae-dominated systems

Espécie exótica de zooplâncton na planície de inundação do Alto Rio Paraná, Daphnia lumholtzi Sars, 1885 (Crustacea: Branchiopoda)

The integrity of aquatic ecosystems is being challenged worldwide by invading species, which has been one of the frequent causes of biodiversity loss. The invader may cause extinctions of vulnerable native species through predation, grazing, competition and habitat alteration. Daphnia lumholtzi G. O. Sars, 1885, a native cladoceran from Australia, Southwestern Asia and North Africa, has recently been found in the Neotropical region. The D. lumholtzi records from the Upper Paraná River floodplain were restricted to the Pombas floodplain lake (22° 47' 55.92" S and 53° 21' 32.58" W) and Pau Véio Backwater (22° 44' 50.76" S and 53° 15' 11.16" W), in 2003 and 2008, respectively. This species can be distinguished from the other Daphnia species registered in Brazil by the conspicuous pointed fornix, the sizes of the tail spine and helmet, and a carapace ventral margin with strong spines. The high temperatures in the tropical region, as well as the increase in water transparency and the decrease in nutrient concentration observed in the environments of the Upper Paraná River floodplain due to the upstream retention by dams, may favor the development of D. lumholtzi populations. The development of populations of D. lumholtzi in natural environments of the Upper Paraná River floodplain may suggest that this species is establishing in the Neotropical region

Ocorrência de tecamebas (Protozoa, Amoebozoa, Rhizopoda) em águas continentais brasileiras. II. Famílias Centropyxidae, Trigonopyxidae e Plagipyxidae

The purpose of this study is to provide a checklist and a synthesis of the geographic distribution of the species within Centropyxidae, Trigonopyxidae and Plagiopyxidae (Protozoa, Amoebozoa, Rhizopoda). A total of 24 infra-generic taxa were listed, of which 15 belong to the genus Centropyxis, 5 to Cyclopyxis, 2 to Bullinularia, 1 to Hoogenraadia and 1 to Trigonopyxis. Some taxonomic information is also provided. Centropyxis aculeata, C. constricta and C. marsupiformis presented widespread distribution in the freshwater environments in BrazilO presente estudo tem por objetivo relacionar as espécies das famílias Centropyxidae, Trigonopyxidae e Plagiopyxidae (Protozoa, Amoebozoa Rhizopoda), e fornecer uma síntese sobre a distribuição geográfica das mesmas em nosso País. Um total de 24 táxons infra-genéricos é listado, sendo 15 taxa do gênero Centropyxis, 5 de Cyclopyxis, 2 de Bullinularia, 1 de Hoogenraadia and 1 de Trigonopyxis. Algumas informações taxonômicas são fornecidas. Centropyxis aculeata, C. constricta e C. marsupiformes foram as espécies que apresentaram uma maior freqüência de ocorrência e mais amplamente distribuidas nos sistemas de água doce no Brasi

<b>Flagellate protist abundance in phytotelmata of <i>Aechmea distichantha</i> Lem. (Bromeliaceae) in the upper Paraná river basin</b> - doi: 10.4025/actascibiolsci.v35i4.17134

In some Bromeliaceae species the leaf sheaths form a tank or phytotelma, accumulating water and organic detritus, conditions that allow the establishment of different communities. Thus, this study evaluated the relationship between diameter and volume of water in the tank of the bromeliad Aechmea distichantha Lem. and density of flagellates found in the phytotelmata, as well as the influence of the hydrological periods and proximity of sampled strata on the phytotelma patterns of abundance distribution. Samplings were conducted in two hydrological periods in 2010. In each sampling, four plants were collected from three different strata, classified according to the distance from the river level. A one-way ANOVA identified significant differences in flagellate density between hydrological periods. The influence of the water volume in the phytotelmata on the flagellate density was evidenced by regression analyses, as well as the lack of relationship between the density and perimeter of the tank. Moreover, the distance of the strata from the river level did not influence the pattern of flagellate abundance. Thus, our results suggested that the hydrological period and the volume of water in the tanks of Aechmea distichantha are determinant on the abundance of heterotrophic flagellate in the phytotelmata

Novas ocorrências de Lecane no plâncton de distintos ambientes da planície de inundação do alto rio Paraná = New occurrences of Lecane in plankton in different environments of the upper Paraná river floodplain

A planície de inundação do alto rio Paraná possui grande diversidade de rotíferos, com 288 táxons planctônicos registrados. Estudos realizados, nesse ecossistema, desde 1992, mostram que Lecanidae é a família mais especiosa, com 45 táxons registrados. Este trabalho teve como objetivo investigar a ocorrência dessa família em ambientes aindanão-estudados e consequentemente contribuir para a diversidade de rotíferos nessa planície de inundação. Foram registradas sete novas ocorrências de Lecane em amostras do plâncton: L. bifurca, L. rhytida, L. subtilis, L. crepida, L. bulla styrax, L. obtusa, e L.thienemanne. Embora os táxons descritos fossem encontrados no plâncton, essa família caracteriza-se por ser tipicamente não-planctônica. Dessa forma, visando ampliar o conhecimento sobre a diversidade dessa família na planície de inundação do alto rioParaná, estudos exclusivamente taxonômicos devem explorar a grande heterogeneidade de hábitats presente nessa planície, como, por exemplo, a região marginal e as extensas áreas colonizadas por macrófitas aquáticas.The upper Paraná river floodplain possesses a great diversity of rotifers, with 288 planktonic taxa recorded. Surveys performed in thisecosystem since 1992 have shown that Lecanidae is the most abundant family, with 45 registered taxa. The main goal of the present study was to investigate the occurrence of this family in environments that have not yet been studied. Seven new occurrences of Lecane were recorded in plankton samples: L. bifurca, L. rhytida, L. subtilis, L. crepida, L. bulla styrax, L. obtusa, and L. thienemanne. Although the described taxa were found in plankton, this family is characterized by being typically non-planktonic. As such, exclusively taxonomic studies must explore the great habitat heterogeneity in thisfloodplain, e.g., the littoral region and the extensive areas colonized by aquatic macrophytes, aiming to expand knowledge on the diversity of this family in the upper Paraná river floodplain

Novas ocorrências de Lecane no plâncton de distintos ambientes da planície de inundação do alto rio Paraná (Brasil) - DOI: 10.4025/actascibiolsci.v30i2.3636

The upper Paraná river floodplain possesses a great diversity of rotifers, with 288 planktonic taxa recorded. Surveys performed in this ecosystem since 1992 have shown that Lecanidae is the most abundant family, with 45 registered taxa. The main goal of the present study was to investigate the occurrence of this family in environments that have not yet been studied. Seven new occurrences of Lecane were recorded in plankton samples: L. bifurca, L. rhytida, L. subtilis, L. crepida, L. bulla styrax, L. obtusa, and L. thienemanne. Although the described taxa were found in plankton, this family is characterized by being typically non-planktonic. As such, exclusively taxonomic studies must explore the great habitat heterogeneity in this floodplain, e.g., the littoral region and the extensive areas colonized by aquatic macrophytes, aiming to expand knowledge on the diversity of this family in the upper Paraná river floodplain.planície de inundação do alto rio Paraná possui grande diversidade de rotíferos, com 288 táxons planctônicos registrados. Estudos realizados, nesse ecossistema, desde 1992, mostram que Lecanidae é a família mais especiosa, com 45 táxons registrados. Este trabalho teve como objetivo investigar a ocorrência dessa família em ambientes ainda não-estudados e consequentemente contribuir para a diversidade de rotíferos nessa planície de inundação. Foram registradas sete novas ocorrências de Lecane em amostras do plâncton: L. bifurca, L. rhytida, L. subtilis, L. crepida, L. bulla styrax, L. obtusa, e L. thienemanne. Embora os táxons descritos fossem encontrados no plâncton, essa família caracteriza-se por ser tipicamente não-planctônica. Dessa forma, visando ampliar o conhecimento sobre a diversidade dessa família na planície de inundação do alto rio Paraná, estudos exclusivamente taxonômicos devem explorar a grande heterogeneidade de hábitats presente nessa planície, como, por exemplo, a região marginal e as extensas áreas colonizadas por macrófitas aquáticas

Abundância de nanoflagelados heterotróficos no plâncton de reservatórios com distintos graus de trofia - DOI: 10.4025/actascibiolsci.v27i1.1358

The aim of this study was to investigate the influence of the trophic state on the planktonic heterotrophic nanoflagellates abundance from three reservoirs of the State of Paraná: Iraí (eutrophic), Rosana (mesotrophic) and Chavantes (oligotrophic). The samples were collected during dry (July) and rainy (November) periods in 2001 and were taken at the sub-surface and mixing layers of the lacustrine zone of the reservoirs. Heterotrophic nanoflagellates abundance was determined by epifluorescence microscopy, after staining with Dapi, and cells volumes were calculated aiming to estimate biomass, using a cell volume-to-carbon conversion factor. Higher values of density and biomass were observed in Iraí Reservoir, the most eutrophic environment, whereas the lower ones were registred in Chavantes Reservoir, in both studied periods. In all reservoirs, a clear vertical pattern was observed, with higher values in the sub-surface layer. The results suggested that the trophic state influenced strongly the abundance patterns of planktonic heterotrophic nanoflagellates, indicating that the resources available determined the patterns. In other words, although there certainly is a predation pressure on the heterotrophic nanoflagellates community, it is not enough to prevent that the increase of resources determine a significant enlargement in these organisms abundanceO objetivo deste trabalho foi investigar a influência do grau de trofia sobre a abundância dos nanoflagelados heterotróficos no plâncton de três reservatórios do Estado do Paraná: Iraí (eutrófico), Rosana (mesotrófico) e Chavantes (oligotrófico). As coletas foram realizadas durante os períodos de estiagem (julho) e chuva (novembro) de 2001, à subsuperfície e camada de mistura da região lacustre desses reservatórios. A abundância dos nanoflagelados heterotróficos foi determinada sob microscópio de epifluorescência, utilizando o Dapi como corante, e os volumes celulares calculados objetivando estimar a biomassa, usando um fator de conversão volume celular-carbono. Maiores valores de densidade e biomassa foram observados no reservatório Irai, enquanto que os menores foram registrados em Chavantes, em ambos os períodos estudados. Em relação à distribuição vertical, maiores valores de densidade e biomassa foram encontrados, em geral, à subsuperfície. Os resultados sugerem que o grau de trofia influenciou fortemente os padrões de variação da abundância (densidade e biomassa) dos nanoflagelados heterotróficos planctônicos, indicando que a disponibilidade de recursos alimentares prevaleceu na determinação de tais padrões. Em outras palavras, embora uma pressão de predação sobre a comunidade de nanoflagelados heterotróficos esteja certamente ocorrendo, não é suficiente para evitar que o aumento desses recursos determine um incremento significativo na abundância desses organismo