"In vitro" evaluation of the bacterivore potential of three Cladoceran species occurring in tropical and subtropical regions / Avaliação "in vitro" do potencial baterívoro de três espécies de Cladocera de ocorrência tropical e subtropical

Abstract Cladocerans occupy an important position among the bacterial consumers in freshwater food webs, being relatively non-selective filter feeders that can exert a strong impact on microbial populations. We evaluated the bacterivory potential of three cladocerans species of subtropical and tropical occurrence (Ceriodaphnia silvestrii, Daphnia gessneri and Ceriodaphnia cornuta) at different life stages, by scanning electron microscopy (SEM) and by the quantification of their bacterial consumption rates using fluorescently labeled bacteria (FLB). All species showed filter mesh sizes sufficiently narrow to retain bacteria. The largest distance between setules was found in primiparous C. cornuta, and the smallest in neonate D. gessneri. The lowest ingestion (IR) and removal (RR) rates were observed in primiparous C. silvestrii and the highest values were observed in adults of D. gessneri. We conclude that bacteria may be considered an important food supplement, particularly for neonates who presented smaller intersetular distances and higher filtration rates than the other life stages.

Resumo Dentre os diversos consumidores de bactérias nas teias alimentares de ambientes dulcícolas, os cladóceros ocupam uma posição relevante, sendo filtradores relativamente não seletivos que podem exercer forte impacto na redução populacional microbiana. Avaliamos o potencial bacterívoro de três espécies de cladóceros de ocorrência tropical e subtropical (Ceriodaphnia silvestrii, Ceriodaphnia cornuta e Daphnia gessneri) em diferentes fases de vida, através do estudo microscópico de suas estruturas filtradoras e da quantificação de suas taxas de ingestão em experimentos de bacterivoria utilizando-se bactérias marcadas fluorescentemente (FLB). As espécies estudadas mostraram ter uma rede de malhas filtradoras suficientemente estreitas para reter bactérias. A maior distância entre as sétulas foi encontrada em primíparas de C. cornuta, e a menor em neonatos de D. gessneri. As menores Taxas de Ingestão (TI) e Remoção (TR) foram observadas em primíparas de C. silvestrii e as maiores em adultas de D. gessneri. Concluímos que as bactérias podem ser consideradas um importante suplemento alimentar, principalmente para neonatos, que apresentaram pequenas distâncias intersetulares e altas taxas de ingestão comparadas aos outros estágios de vida.

Habitat architecture influencing microcrustaceans composition: a case study on freshwater Cladocera (Crustacea Branchiopoda) / Arquitetura do habitat influenciando a composição taxonômica de microcrustáceos: um estudo de caso sobre Cladocera de águas continentais (Crustacea Branchiopoda)

Abstract Environmental complexity is considered a key factor for diversity enhancement in aquatic ecosystems. Macrophyte stands are a major contributor for this complexity due to their differential architectures. Nevertheless, the influence of distinct aquatic habitat architectures (with different types of macrophytes or without them) on microcrustaceans’ taxa composition, usually found in macrophyte colonized water bodies, is underexplored in limnological studies. The main objective of this study was to analyze this influence by comparing the Cladocera composition among four habitat architectures: (1) fluctuant macrophytes, (2) rooted emergent macrophytes, (3) submerged macrophytes and (4) the limnetic zone of oxbow lakes associated to a large subtropical reservoir. Wide compositional variation was observed. Fluctuant macrophytes exhibited the richest Cladocera assemblage, dominated by Chydoridae. Submerged and rooted emergent macrophytes had the most similar assemblages between them. The most distinctive fauna was found in the limnetic zone, dominated by Bosminidae. Probable differences in resource availability in each sampled habitat architecture are considered as the driving factor for the Cladocera composition variation. We concluded that for a complete inventory of a given local fauna, it is imperative to take into account the aquatic habitat architecture, including macrophyte stands, in the data sampling design.

Resumo A complexidade ambiental é considerada um fator chave para o aumento na diversidade de ambientes aquáticos. A presença de bancos de macrófitas é um dos principais contribuintes para tal complexidade devido às suas arquiteturas diferenciadas. Entretanto, a influência de diferentes arquiteturas de habitat (com diferentes macrófitas ou sem elas) sobre a composição taxonômica de microcrustáceos, comumente encontrados em ambientes colonizados por macrófitas, é pouco explorada em estudos limnológicos. O objetivo desse estudo foi avaliar esta influência através da comparação da composição das associações de Cladocera entre quatro arquiteturas de habitat: (1) macrófitas flutuantes, (2) macrófitas enraizadas emersas, (3) macrófitas submersas e (4) a zona limnética em lagoas laterais associadas a um grande reservatório subtropical. Ampla variação composicional foi observada. Macrófitas flutuantes apresentaram as mais ricas assembléias de Cladocera, dominadas por Chydoridae. Macrófitas submersas e emersas enraizadas apresentaram as associações mais similares. A fauna mais distinta foi a da zona limnética, dominada por Bosminidae. Prováveis diferenças na disponibilidade de recursos entre as arquiteturas de habitat amostradas foram consideradas o fator mais relevante levando à variação composicional dos microcrustáceos. Concluímos que para um inventário completo de uma determinada fauna local é imperativo que seja considerada a arquitetura dos habitats aquáticos, incluindo os bancos de macrófitas, no desenho amostral.

Growth and development time of subtropical Cladocera Diaphanosoma birgei Korinek, 1981 fed with different microalgal diets / Crescimento e tempo de desenvolvimento de uma espécie de Cladocera subtropical Diaphanosoma birgei Korinek, 1981 alimentada com dietas de microalgas.

The aim of this work was to investigate the growth performance of Diaphanosoma birgei fed with two Chlorophyceae algae, Ankistrodesmus gracilis and Haematococcus pluvialis using monoalgal diets and simpler mixed diets. D. birgei was daily fed on four treatments: 1) 100% Ankistrodesmus gracilis (Ag); 2) 100% Haematoccocus pluvialis (Hp); 3) 25% A. gracilis + 75% H. pluvialis (Ag-25+Hp-75) and 4) 75% A. gracilis + 25% H. pluvialis (Ag-75+Hp-25). The fecundity curve of D. birgei showed that the mixed feed Ag-25+Hp-75 and temperature 24±2°C triggered fast fecundity at approximately two days. The fecundity was low when based only on H. pluvialis (Hp), albeit with greater longevity (19 days) and a higher number of broods (8). D. birgei fed on Ag and Ag-75+Hp-25 diets in this experiment sustained higher growth rate and higher lipid content in these treatments. The present study showed that A. gracilis diet and mixed microalgae diets tested were able to support the egg production and development of D. birgei.

O objetivo deste estudo foi avaliar o crescimento de uma espécie de Cladocera Diaphanosoma birgei alimentada com dois tipos de microalgas Chlorophyceae, Ankistrodesmus gracilis e Haematococcus pluvialis cultivadas em monocultura e cultura mista. Quatro dietas foram utilizadas: 1) 100% Ankistrodesmus gracilis (Ag); 2) 100% Haematoccocus pluvialis (Hp); 3) cultura mista com 25% A. gracilis + 75% H. pluvialis (Ag-25+Hp-75) e 4) cultura mista com 75% A. gracilis + 25% H. pluvialis (Ag-75+Hp-25). A curva de fecundidade de D. birgei mostrou que a dieta mista Ag-25+Hp-75 e temperatura de 24±2°C promoveu rápida fecundidade em aproximadamente dois dias. A fecundidade foi baixa quando D. birgei foi alimentada somente com H. pluvialis (Hp), porém foi observada maior longevidade (19 dias) e consequentemente, maior número de descendentes (8). As dietas Ag and Ag-75+Hp-25 apresentaram efeito direto na taxa de crescimento de D. birgei com elevados teores de lipídios nestes tratamentos. O presente estudo mostrou que as dietas contendo somente A. gracilis e as dietas mistas de microalgas foram capazes de manter níveis adequados na produção de ovos e no desenvolvimento de D. birgei.

Demography of zooplankton (Anuraeopsis fissa, Brachionus rubens and Moina macrocopa) fed Chlorella vulgaris and Scenedesmus acutus cultured on different media

Generally zooplankton growth is often limited by the quality of their algal diet. A cheaper common practice in aquaculture, is to culture algae with fertilizers; however, the demography of zooplankton when fed these algae has not yet been evaluated. We studied the population growth and life table demography of the rotifers Anuraeopsis fissa and Brachionus rubens, and the cladoceran Moina macrocopa. For this, the algae Scenedesmus acutus or Chlorella vulgaris were cultured on defined (Bold’s basal) medium or the commercial liquid fertilizer (Bayfolan). Experiments were conducted at one algal concentration 1.0x10(6)cells/mL of C. vulgaris or its equivalent dry weight of 0.5x10(6)cells/mL of S. acutus. The population dynamics were tested at 23±1ºC in 100mL transparent jars, each with 50mL of the test medium, with an initial density of 0.5indiv/mL, for a total of 48 test jars (3 zooplankton 2 algal species x 2 culture media x 4 replicates). For the life table experiments with M. macrocopa, we introduced 10 neonates (<24h old) into each test jar containing the specific algal type and concentration. For the rotifer experiments, we set 5mL tubes with one neonate each and 10 replicates for each algal species and culture medium. We found that the average rotifer life span was not influenced by the diet, but for M. macrocopa fed S. acutus cultured in Bold’s medium, the average lifespan was significantly lower than with the other diets. The gross and net reproductive rates of A. fissa (ranging from 18-36 offspring per female) were significantly higher for C. vulgaris cultured in Bold medium. Regardless of the culture medium, Chlorella resulted in significantly higher gross and net reproductive rates for B. rubens than S. acutus diets. The reproductive rates of M. macrocopa were significantly higher in all the tested diets except when fed with S. acutus in Bold medium. The population increase rate, derived from growth experiments of A. fissa and B. rubens, ranged from 0.1-0.25/d and were significantly higher on C. vulgaris cultured in liquid fertilizer as compared to the other diets. The growth rates of M. macrocopa ranged from 0.1 to 0.38/d, and were highest with diets of C. vulgaris cultured in Bold medium and S. acutus cultured in fertilizer. Thus, regardless of the culture medium used, the growth rates of the evaluated zooplankton species were higher with Chlorella than with Scenedesmus. The peak population density was highest (2 800ind/mL) for A. fissa fed Chlorella that was cultured on liquid fertilizers, while B. rubens and M. macrocopa had peak abundances of 480 and 12ind/mL, respectively under similar conditions.

Generalmente el crecimiento del zooplancton está a menudo limitado por la calidad de su dieta de algas. La demografía del zooplancton durante la alimentación con algas no ha sido estudiada, a pesar de que el cultivo de algas con fertilizantes es una práctica económica común en acuacultura. Se analizó la demografía de Anuraeopsis fissa y Brachionus rubens (rotíferos) y Moina macrocopa (cladóceros), alimentados con las algas verdes Scenedesmus acutus o Chlorella vulgaris cultivadas en medio Bold o fertilizante líquido comercial (Bayfolan, de Bayer). En los rotíferos no se observaron diferencias significativas en el promedio de vida, sin embargo, este parámetro en M. macrocopa con S. acutus cultivada en Medio Bold, fue significativamente menor que en otras dietas. Las tasas de reproducción bruta y neta de A. fissa fueron significativamente mayores con C. vulgaris cultivada en medio Bold, que con el fertilizante; estas tasas en B. rubens, independientemente del medio de cultivo, resultaron significativamente mayores con Chlorella que S. acutus. La tasa de reproducción de M. macrocopa fue significativamente mayor en todas, a excepción de S. acutus en Bold. En el crecimiento poblacional con A. fissa y B. rubens la tasa de crecimiento poblacional varió de 0.1 hasta 0.25/d, significativamente mayores en C. vulgaris cultivadas con fertilizante, en comparación con las otras dietas; en M. macrocopa la tasa de crecimiento varió desde 0.1 hasta 0.38/d, las más altas fueron: con C. vulgaris cultivadas en medio Bold y S. acutus cultivadas con fertilizante. Así, en todas las especies, la tasa de crecimiento fue más alta con Chlorella que con Scenedesmus.

Seasonal variations of species composition and abundance of zooplankton in Ehoma Lake, a floodplain lake in Nigeria

Ehoma Lake is among the important breeding sites of the major fishes in the Mid-Cross River, Nigeria. The juveniles of these fishes are solely dependent on zooplankton, which has not been studied previously. I studied monthly the lake’s physico-chemical variables and zooplankton composition in three stations (littoral, sub-littoral and pelagic) from March 2005 to August 2006. Sixty-seven zooplankton species (42 rotifers, 19 cladocerans and 6 copepods) were identified. Daphnia obtusa Kurz, Keratella valga Ehrenberg, Keratella ticinensis Callerrio, Keratella hiemalis Carlin, Brachionus dimidiatus Bryce and Lecane candida Hauer and Murray are new records for Nigeria. The dominant zooplankters were Diaphanosoma excisum Kurz and Moina micrura Kurz. There was an inverse relationship between species richness and abundance. Richness was highest in the dry season while peak zooplankton abundance was recorded in the rainy season. Zooplankton abundance and species richness decreased progressively from the littoral to the pelagic station while the Shannon-Weaver diversity index varied from 0.68 to 1.28 without a clear seasonal trend. There is a succession pattern: rotifers that are dominant in the dry season are replaced by cladocerans in the rainy season. This succession was greatly influenced by seasonal flooding of the lake. As no previous information on the zooplankton of the lake is available, this study provides baseline data on the lake`s zooplankton. Rev. Biol. Trop. 58 (1): 171-182. Epub 2010 March 01.

El lago Ehoma, situado en la mitad del río Cross, es uno de los lugares de reproducción de las principales especies de peces del río. Los juveniles de estos peces dependen exclusivamente del zooplancton, sin embargo poco se sabe sobre este recurso en el lago. En este estudio, las variables físico-químicas y del zooplancton del lago fueron estudiadas mensualmente en tres estaciones (litoral, sub-litoral y pelágica), de marzo de 2005 a agosto de 2006. Fueron identificadas 67 especies de zooplancton (42 rotíferos, 19 cladóceros y 6 copépodos). Daphnia obtusa Kurz, Keratella valga Ehrenberg, Keratella ticinensis Callerrio, Keratella hiemalis Carlin, Brachionus dimidiatus Bryce y Lecane candida Hauer y Murray son nuevos registros para Nigeria. Las especies dominantes fueron Diaphanosoma excisum Kurz y Moina micrura Kurz. Hubo una relación inversa entre la riqueza de especies y la abundancia. La riqueza de especies fue mayor en la estación seca, mientras que la abundancia de zooplancton registró su mayor valor en la estación lluviosa. La abundancia y riqueza de especies de zooplancton disminuyó progresivamente desde la estación del litoral a la pelágica, mientras que el índice de diversidad de Shannon-Weaver varió de 0.68 a 1.28, sin una clara tendencia estacional. Se encontró un patrón de sucesión: los rotíferos, dominantes en la estación seca, fueron reemplazados por cladóceros en la estación lluviosa. Esta sucesión estuvo fuertemente influenciada por las inundaciones estacionales del lago. Al no haber información disponible sobre el zooplancton de este lago, este estudio proporciona los primeros datos de referencia.

Experiments on the influence of Chaoborus brasiliensis Theobald, 1901 (Diptera: Chaoboridae) on the diel vertical migration of microcrustaceans from Lake Monte Alegre, Brazil / Experimentos sobre a influência de Chaoborus brasiliensis (Diptera: Chaoboridae) sobre a migração vertical de microcrustáceos do Lago Monte Alegre, Brasil

The aim of this work was to evaluate whether diel vertical migration of microcrustaceans from Lake Monte Alegre is related to invertebrate predators, namely larvae of Chaoborus brasiliensis. The hypothesis tested in the experiments was that the migratory behaviour of prey would depend on physical contact with Chaoborus brasiliensis larvae or with kairomones released by them. Two experiments were undertaken in the laboratory, with two treatments and three replicates each. Experiments were carried out in acrylic cylinders 1.5 m high and 0.20 m in diameter. Treatments in Experiment I were: A) predator and kairomones present and B) predator and kairomones present, but predator isolated in net tube inside the cylinder, having no physical contact with prey. Treatments in Experiment II were: A) predator and kairomones absent and B) the same as in experiment I. Physical and chemical factors (temperature, dissolved oxygen, pH, electrical conductivity) and food (algae) did not influence vertical distribution of prey, as they were almost homogeneously distributed in the water column in both experiments; food concentrations were not limiting. Adult copepods (Tropocyclops prasinus meridionalis and Thermocyclops decipiens) showed reverse migration in the treatment B of both experiments; the cladoceran Daphnia gessneri migrated nocturnally in the treatment A of the Experiment I; vertical migration was undetectable for copepodites, as well as for Chaoborus larvae. The experiments indicated that Daphnia responded to physical contact with Chaoborus larvae but not to kairomones alone. Adult copepods seemed to be more sensitive to kairomones.

O objetivo deste trabalho foi avaliar se a migração vertical dos microcrustáceos do Lago Monte Alegre é relacionada aos predadores invertebrados, nomeadamente larvas de Chaoborus brasiliensis. A hipótese testada no experimento foi a de que o comportamento migratório da presa seria dependente do contato físico com as larvas de Chaoborus ou dos "kairomones" liberados por elas. Dois experimentos foram realizados no laboratório, com dois tratamentos e três réplicas cada. Os experimentos foram feitos dentro de cilindros de acrílico de 1,5 m de altura e 0,20 m de diâmetro. Os tratamentos do Experimento I foram: A) predador e "kairomones" presentes e B) predador e "kairomones" presentes, mas o predador isolado em tubos de rede dentro do cilindro, não tendo contato físico com a presa. Os tratamentos do Experimento II foram: A) predador e "kairomones" ausentes e B) igual ao Experimento I. Fatores físicos e químicos (temperatura, oxigênio dissolvido, pH, condutividade elétrica) e alimento (algas) não influenciaram a distribuição vertical das presas, pois eles estavam quase homogeneamente distribuídos na coluna d'água em ambos os experimentos; as concentrações de alimento não foram limitantes. Copépodos adultos (Tropocyclops prasinus meridionalis e Thermocyclops decipiens) realizaram migração reversa no tratamento B dos dois experimentos; o cladócero Daphnia gessneri migrou de modo noturno no tratamento A do Experimento I; migração vertical não foi detectada para copepoditos, bem como para larvas de Chaoborus. Os experimentos indicaram que Daphnia respondeu ao contato físico com as larvas de Chaoborus e não aos "kairomones". Copépodos adultos foram aparentemente mais sensíveis aos "kairomones".

Composition, diversity and short-term temporal fluctuations of zooplankton communities in fish culture ponds (Pindamonhangaba), SP / Composição, diversidade e flutuações temporais de curto prazo da comunidade zooplanctônica de viveiros de piscicultura (Pindamonhangaba), SP

The present study aimed at evaluating the composition, diversity and short-term temporal fluctuations of zooplankton communities in fish ponds. The study was carried out in two fish ponds, with 180 m² of water surface (6 × 30 m) each, located in the Aquiculture Centre of the Pindamonhangaba Fisheries Institute - São Paulo. The study was developed over eight weeks, from February 16 to April 6, 1998. The physical and chemical conditions of the water in the fish ponds were adequate for zooplankton development. The zooplanktonic community was characterised by high richness of species and a greater diversity was observed in the first fish pond, with a superior density of Rotifera. Temporal changes in zooplankton composition occurred in both ponds with Cladocera appearing in abundance later, in the fourth week, whereas copepods and rotifers were well represented since the beginning. Many species found are typical of fish ponds and are considered to constitute an excellent food source, showing high nutritional value for fish larvae, a good example being individuals from the Rotifera group and the micro-crustacean species Moina minuta and Thermocyclops decipiens.

O presente estudo visou avaliar a composição, a diversidade e a flutuação do zooplâncton em dois viveiros escavados na terra com 180 m² de espelho d'água (6 × 30 m) cada um, no Núcleo de Aquicultura do Instituto de Pesca de Pindamonhangaba-SP. O estudo foi realizado durante oito semanas, no período de 16 de fevereiro a 6 de abril de 1998. As condições observadas, em relação às características físicas e químicas da água dos viveiros, foram adequadas ao desenvolvimento dos organismos zooplanctônicos. A comunidade zooplanctônica foi caracterizada por elevada riqueza de espécies, com maiores densidades de organismos pertencentes ao grupo Rotifera. Mudanças temporais na composição do zooplâncton ocorreram em ambos os tanques, com Cladocera aparecendo em maior abundância mais tarde, na quarta semana, enquanto que copepodos e rotíferos foram bem representados desde o início. Muitas espécies encontradas são típicas de viveiros de piscicultura e constituem excelente fonte alimentar, apresentando alto valor nutritivo para larvas de peixes, como por exemplo os indivíduos do grupo Rotifera e as espécies Moina minuta e Thermocyclops decipiens.

Life table demography of Ceriodaphnia dubia (Cladocera) exposed to copper at different levels and periods.

We studied the demographic responses of Ceriodaphnia dubia exposed to copper at 3 different levels (0.1, 0.2 and 0.4 mg l(-1)) and at 4 exposure periods (3, 6, 12 and 24 hr) in addition to controls (without the heavy metal). The tested levels of Cu concentration and the chosen periods of exposure affected some demographic variables (average lifespan, gross and net reproductive rates and generation time). Depending on the heavy metal concentration and the period of exposure, the average lifespan of C. dubia varied from 18 to 24 day Net reproductive rates (NRR) ranged from 50 to 80 offspring per female per lifespan, while the rate of population increase (r) varied from 0.30 to 0.34 per day Though gross reproductive rates (especially at low and intermediate copper levels and shorter duration of exposure) showed significantly higher values than controls, both NRR and r were either unaffected or decreased. It is therefore necessary to regulate the release of untreated industrial effluents containing copper into freshwater ecosystems. Our study thus highlights the importance of including, not only toxicant concentrations but also exposure time, in ecotoxicological evaluations.