Responses of the zooplankton community to the formation of a small reservoir on the Caveiras River, southern Brazil

We investigated changes in the species richness, abundance, and composition of the zooplankton community in response to the formation of a small reservoir in the Caveiras River, southern Brazil. Zooplankton were collected using a motor-pump and aplankton net (68 μm mesh), with 600 L of water filtered per sample. Sampling occurred during the pre-(April, August, and December 2011) and post-impoundment (July and October 2013, and January 2014) phases of the Caveiras River. We identified 86 taxa in this study, and rotifers were the predominant group. The species richness and abundance of the zooplankton increased after the filling of the reservoir. Furthermore, the zooplankton community showed a clear change in the species composition between the phases before and after the formation of the reservoir, with the emergence of typical planktonic species. Changes in the structure of the zooplankton community were related to changes in limnological characteristics due to the impoundment of the river, mainlyin the availability of food and in the concentration of nutrients.

Review on the ecology and taxonomy of sessile rotifers (Rotifera) with special reference to Mexico

Aim: Review of the new research on medium- and large-sized rivers in China and its impact to develop more rational management strategies for medium- and large-sized rivers.Methodology: Papers on rivers-related research in China published over the past 15 years (2004–2018) were summarised through statistical analyses. The main topics, data sources and contributions were also summarised, and representative papers were presented to illustrate milestones and contributions. Results: The management strategies of medium- and large-sized rivers shifted remarkably from traditional agricultural utilisation of floods and water resources to ecological protection. Water resources and pollution, conservancy projects and flooding and droughts were the four most focused research areas. Interpretation: Chinese economy significantly contributed to the change in river management strategies over the last two decades.

Comunidades planctónicas y bacterianas asociadas al cultivo de bocachico Prochilodus magdalenae con tecnología biofloc / Describing the planktonic and bacterial communities associated with bocachico Prochilodus magdalenae fish culture with biofloc technology

RESUMEN Objetivo. Describir las comunidades planctónicas y bacterianas asociadas al cultivo de bocachico Prochilodus magdalenae con tecnología biofloc (BFT). Materiales y métodos. En nueve tanques rectangulares de concreto con volumen útil de 6.0 m3, se sembraron alevinos de bocachico con peso promedio de 1.6±0.2 g, a tres densidades 5 (T1), 10 (T2) y 20 (T3) peces/m3 con BFT, durante 120 días de cultivo. La identificación y cuantificación de los microorganismos se realizó cada ocho días, en una muestra de 250 ml de agua por tanque, mediante análisis de alícuotas en cámaras Sedgwick-Rafter y/o Neubauer bajo microscopio a 10x y 40x. Los días 15, 45 y 90 del cultivo se caracterizaron las comunidades bacterianas tomando una muestra de 2 g de floc en 90 ml de solución salina estéril y sometidas a pruebas microbiológicas convencionales. Resultados. Se identificarem cinco grupos planctónicos (microalgas, rotíferos, cladóceros, copépodos y protistas con predominancia de ciliados) con mayor cantidad de rotíferos y protistas en los cultivos con menor densidad (T1 y T2); y la mayor afluencia de microorganismos osciló entre 174.9±21.4 ind/ml (T1) y 125.6±16.1 ind/ml (T2). En el grupo de bacterias fue posible identificar 10 cepas: Escherichia coli, Enterobacter sp., Klebsiella sp., Salmonella sp. (Enterobacteriaceae) Bacillus subtilis, Bacillus sp, Lactobacillus sp, Pseduodomonas sp (Vibrionaceae), Micrococcus sp, Staphylococcus sp (Cocos gram+). Conclusiones. La composición del plancton fue similar en todos los tratamientos, con rotífero y protistas como los más abundantes; la mayor proporción de bacterias fueron Enterobacterias y Heterotróficas.

ABSTRACT Objective. To describe the planktonic communities and bacteria associated with the bocachico Prochilodus magdalenae fish culture with biofloc technology (BFT). Materials and methods. Bocachico fingerlings, with an average weight of 1.6±0.2 g, were stocked at three densities, i.e., 5 (T1), 10 (T2) and 20 (T3) fish/m3, with BFT in nine rectangular, 6.0 m3 concrete tanks for 120 days of culture. Identification and quantification of the microorganisms was performed every eight days in a sample of 250 ml of water per tank by analyzing aliquots on a Sedgwick-Rafter and/or in Neubauer chambers on a microscope at 10x and 40x magnification. On days 15, 45, and 90 of the fish culture, the bacterial communities were characterized by taking 2 g samples of floc and adding them to 90 ml of sterile saline solution, then subjecting them to conventional microbiological tests. Results. Five planktonic groups (microalgae, rotifers, cladocerans, copepods, and protists with ciliates predominating) with more rotifers and protists in the fish cultures at lower density (T1 and T2) were identified, and the largest amount of microorganisms oscillated between 174.9±21.4 ind/ml (T1) and 125.6±16.1 ind/ml (T2). It was possible to identify ten bacterial strains: Escherichia coli, Enterobacter sp., Klebsiella sp., Salmonella sp. (Enterobacteriaceae), Bacillus subtilis, Bacillus sp., Lactobacillus sp., Pseudomonas sp. (Vibrionaceae), Micrococcus sp., and Staphylococcus sp. (Coccus Gram+). Conclusions. The composition of plankton was similar in all treatments, with rotifers and protists being the most abundant; the bacteria showed a higher proportion of enterobacteria and heterotrophs.

Temperature-dependent demographic differences in sessile rotifers of the genus Limnias (Rotifera: Gnesiotrocha)

Aim: Rotifer research on sessile taxa has received less attention because they are not easy to identify in fixed samples. In the Lake Xochimilco, a Ramsar site in Mexico City, three morphotypes of L. ceratophylli and a single morphotype of L. cf. melicerta occur in different densities. The aim of this study was to test if temperature was responsible for the differences in the population densities of these morphotypes. Methodology: The present study was carried out using population growth method consisting of 4 treatments (3 morphotypes of L. ceratophylli and one of L. cf. melicerta) at 20 and 25°C. Experiments were carried out in 50 ml glass jars containing 25 ml synthetic medium with Chlorella vulgaris as food. The population growth rates (r) were derived. Analysis of variance (ANOVA) and post-hoc tests were used to quantify the intra-and interspecific differences in the population growth rates. Results: The temperature levels for optimal population growth rates differed among the morphotypes of same species. At 20°C, the morphotype 1 had the highest r (0.23 d-1) similar to that of L. cf. melicerta, while morphotype 3 had the lowest (0.15 d-1). For L. cf. melicerta, the r was higher at 25°C than at 20°C. Of three morphotypes of L. ceratophylli, morphotype 3 had the highest r at 25°C similar to that of L. cf. melicerta at same temperature. Interpretation: There were significant differences among growth patterns within the morphotypes of L. ceratophylli, depending on culture temperature. These trends highlight the relative importance of environmental variables in differentiating morphotypes of a sessile species complex which could explain their possible seasonal changes in the natural waterbodies.

Occurrence of concavities on the lorica of two species of Testudinella (Rotifera, Monogononta, Testudinellidae) / Ocorrência de concavidades na lórica de duas espécies de Testudinella (Rotifera, Monogononta, Testudinellidae)

Abstract: Testudinella is a taxon of Rotifera broadly distributed in Brazil. In a recent collection in marginal lakes connected to the Paranapanema River (São Paulo, Brazil), we found specimens of Testudinella mucronata and T. patina with concavities on their lorica. The objective of this study was to describe the concavities observed in individuals of both species and discuss their possible causes. Plankton samples were collected at two sampling stations, in the pelagic (PZ) and littoral (LZ) zones of the Panema and Coqueiral lakes; both of these lakes are ultra-oligotrophic and not polluted. For T. mucronata, 4% of individuals with concavities were found in the PZ of Coqueiral lake and 50% in the LZ of Panema lake. In T. patina, the proportion of specimens with concavities corresponded to 34% in the LZ of Panema lake and 17% in PZ of Coqueiral lake. In this study, we discussed that low water temperatures, predation events and/or recent hatching are factors that may justify the concavities in the lorica of specimens of our work.

Resumo: Testudinella é um táxon de Rotifera amplamente distribuído no Brasil. Em recentes coletas em lagos marginais conectados ao rio Paranapanema (São Paulo, Brasil), nós encontramos espécimes de Testudinella mucronata e T. patina com concavidades em suas lóricas. O objetivo do estudo foi descrever as concavidades observadas em indivíduos de ambas as espécies e discutir suas possíveis causas. Amostras de plâncton foram coletadas em duas estações de amostragem, na zona pelágica (PZ) e litorânea (LZ) dos lagos Panema e Coqueiral; ambos os lagos são ultra-oligotróficos e não poluídos. Para T. mucronata, 4% dos indivíduos com concavidades foram encontrados na PZ do lago Coqueiral e 50% na LZ do lago Panema. Em T. patina, a proporção de espécimes com concavidades correspondeu a 34% na LZ do lago Panema e 17% na PZ do lago Coqueiral. Nesse estudo, nós sugerimos que baixas temperaturas da água, eventos de predação e/ou recente eclosão são fatores que podem justificar as concavidades na lórica dos espécimes do nosso trabalho.

Dinámica de la dieta de Asplanchna girodi (De Guerne, 1888) en un embalse tropical, Colombia / The dynamics of the diet of Asplanchna girodi (De Guerne, 1888) inhabiting a tropical reservoir in Colombia / Dinâmica da dieta de Asplanchna girodi (De Guerne, 1888) em um reservatório tropical, Colômbia

Resumen Las interacciones bióticas como depredación, forrajeo y herbivoría han sido generalmente catalogadas como las fuerzas que determinan las variaciones espaciales y temporales de las poblaciones planctónicas, tanto de presas como de depredadores. Una especie del zooplancton, presente en aguas continentales, calificada como depredadora es el rotífero Asplanchna girodi. Sin embargo, se desconoce la composición real de su dieta, las preferencias alimentarias y la dinámica espacial y temporal en relación con sus presas o alimento. En esta investigación se determinaron las preferencias tróficas de A. girodi y su fluctuación espacio-temporal, basados en ítems verdaderamente consumidos en el medio natural, a través del análisis de los contenidos estomacales de individuos capturados en las aguas del embalse Riogrande II (Antioquia-Colombia), durante un año de muestreos realizados cada 10 días. Se observó que A. girodi presentó una preferencia trófica amplia que incluyó el forrajeo de, por lo menos, cinco taxones de algas y la depredación de ocho (8) especies de rotíferos y del cladócero Bosmina freyi. Se concluye que: 1. A. girodi es una especie omnívora, con mayor preferencia por el consumo de algas. 2. Este rotífero no fue factor de presión en la dinámica poblacional de las algas, pero posiblemente lo fue para Keratella americana. 3. No se observaron diferencias espaciales en la dieta de A. girodi, pero si existieron diferencias temporales en cuanto a la composición de la dieta, la cual estuvo determinada por la oferta de las algas, principalmente durante florecimientos de Ceratium. 4. Este tipo de dieta se enmarca dentro de los conceptos de forrajeo óptimo y oportunismo trófico, estrategias que conllevan el consumo de las especies con mayor disponibilidad (en este caso algas) y el máximo ahorro de energía, puesto que no se invierte en la búsqueda de presas específicas.

Abstract Biotic interactions such as predation, foraging and herbivory have been generally categorized as the forces that determine the spatial and temporal variations of planktonic populations, both preys and predators. A species of zooplankton, present in continental waters, classified as predator is the rotifer Asplanchna girodi. However, the true composition of its diet, dietary preferences and spatial and temporal dynamics in relation to its prey or food are unknown. In this research the trophic preferences of A. girodi and its spatio-temporal fluctuation were determined, based on items truly consumed in the natural environment, through analysis of stomach contents of individuals captured in the waters of Riogrande II reservoir (Antioquia-Colombia), during one year of sampling every 10 days. It was observed that A. girodi showed a broad trophic preference that included the foraging of, at least, five algae taxa and the predation of eight rotifer species and cladoceran Bosmina freyi. It is concluded that: 1. A. girodi is an omnivorous species, with a greater preference for the consumption of algae. 2. This rotifer was not a pressure factor in the population dynamics of the algae, but possibly it was for the Keratella americana. 3. No spatial differences were observed in the A. girodi diet, but there were temporal differences in the composition of the diet, which was determined by the algae supply, mainly during Ceratium blooms. 4. This type of diet is framed within the concepts of optimal foraging and trophic opportunism, strategies that involve the consumption of the most available species (in this case algae) and the maximum energy saving since it is not invested in the search for specific prey.

Resumo Interações bióticas como predação, forrageamento e herbivoria têm sido geralmente classificadas como as forças que determinam as variações espaciais e temporais de populações planctônicas, tanto de presas quanto de predadores. Uma espécie de zooplâncton, presente em águas continentais, classificada como predador é o rotífero Asplanchna girodi. No entanto, a composição real de sua dieta, preferências alimentares e dinâmicas espaciais e temporais em relação a suas presas ou alimentos são desconhecidas. Nesta pesquisa, as preferências tróficas de A. girodi e sua flutuação espaço-temporal foram determinadas, com base em itens verdadeiramente consumidos no ambiente natural, através da análise do conteúdo estomacal de indivíduos capturados nas águas do reservatório Riogrande II (Antioquia-Colômbia), durante um ano de amostragem a cada 10 dias. Observou-se que A. girodi apresentou uma ampla preferência trófica que incluiu o forrageamento de pelo menos cinco taxa de algas e a predação de oito (8) espécies de rotíferos e o cladocero Bosmina freyi. Conclui-se que: 1. A. girodi é uma espécie onívora, com maior preferência pelo consumo de algas. 2. Este rotífero não foi um fator de pressão na dinâmica populacional das algas, mas possivelmente foi para Keratella americana. 3. Não foram observadas diferenças espaciais na dieta de A. girodi, mas houve diferenças temporárias na composição da dieta, que foi determinado pelo fornecimento de algas, principalmente durante a floração de Ceratium. Este tipo de dieta enquadra-se nos conceitos de forrageamento ótimo e oportunismo trófico; estratégias que envolvem o consumo de espécies com maior disponibilidade (neste caso algas) e a máxima economia de energia, uma vez que não é investido na busca por presas específicas.

TAXAS DE FILTRAÇÃO E INGESTÃO DE UMA MICROALGA POR Philodina roseola (Rotifera: Bdelloidea) / Rates of Filtration and Ingestion of a Microalga by Philodina roseola (Rotifera: Bdelloidea) / Tasas de filtración e ingestión de una microalga por Philodina roseola (Rotifera: Bdelloidea)

Rotíferos possuem um importante papel nos ciclos biogeoquímicos e na produtividade orgânica dos ecossistemas de água doce em decorrência de suas elevadas taxas metabólicas. Informações sobre a filtração, seu principal processo de aquisição de energia, são relevantes e ainda escassos para a região tropical. Os rotíferos da Subclasse Bdelloidea alimentam-se por filtração ou raspagem consumindo pequenos itens alimentares, como bactérias, algas, leveduras ou matéria orgânica particulada. Sabemos pouco sobre o papel que desempenham na dinâmica trófica dos habitats que ocupam e por isso o objetivo deste estudo foi quantificar em laboratório as taxas de filtração e ingestão do rotífero Philodina roseola, alimentado com Raphidocelis subcapitata. O delineamento experimental consistiu na exposição de 10 rotíferos adultos por tratamento, em cinco concentrações que variaram entre 10(4) e 10(7) cels mL-1, mantidos sob temperatura de 25 ± 1 °C. Os experimentos tiveram a duração de 1 hora e as concentrações iniciais e finais da suspensão algal foram quantificadas por contagem numérica das células em câmara de Neubauer. Não foram encontradas diferenças significativas entre as concentrações iniciais e finais de células nos controles indicando não ter ocorrido crescimento algal. As taxas de filtração de P. roseola variaram entre 0,09 e 0,25 mL ind-1 h-1. Tendo em vista que a filtração é o principal processo de aquisição de energia de Philodina roseola, assim como dos demais rotíferos, e que está relacionada a questões importantes da dinâmica trófica dos ecossistemas aquáticos, informações adicionais são desejáveis mas necessitam, no entanto, ser ampliadas para outros tipos de alimento e para diferentes combinações de condições experimentais.

Rotifers play an important role in biogeochemical cycles and organic productivity of freshwater ecosystems due to their high metabolic rates. Information on filter feeding, their main process of energy acquisition, are relevant and still scarce for tropical regions. The rotifers of the class Bdelloidea feed by filtration or scraping consuming small food items, such as bacteria, algae, yeasts or particulate organic matter. We know little of their role in the trophic dynamics in the habitats they occupy and so the aim of this study was to quantify laboratory filtration and ingestion rates of the rotifer Philodina roseola, fed with Raphidocelis subcapitata. The experiment consisted of 10 adult exposure treatment at five concentrations approximately in the range between 10(4) and 10(7) cells mL-1, at the temperature of 25 ± 1 °C. The experiments lasted one hour and initial and final concentrations of the algal suspensions were determined by counting the number of cells in a Neubauer chamber. There were no significant differences between the initial and final concentrations of cells in the control group indicating that algal growth did not occur. Philodina roseola filtration rates varied between 0.09 and 0.25 mL ind-1 h-1. Given that filtration is the main process of energy acquisition by Philodina roseola, as well as for most other rotifers, and that it comprises important issues related to trophic dynamics of aquatic ecosystems, additional experimental information is especially important and need to be extended to other types of food and combinations of experimental conditions.

Los rotíferos desempeñan un importante papel en los ciclos biogeoquímicos y en la productividad orgánica de los ecosistemas de agua dulce como consecuencia de sus elevadas tasas metabólicas. Es relevante la información sobre la filtración, su principal proceso de adquisición de energía, la cual es todavía escasa para la región tropical. Los rotíferos de la subclase Bdelloidea se alimentan por filtración o raspaje, consumiendo pequeños elementos alimentícios, como bacterias, algas, levaduras o materia orgánica particulada. Sabemos poco del papel que desempeñan en la dinámica trófica de los hábitats que ocupan, y por eso el objetivo de este estudio fue cuantificar en laboratorio las tasas de filtración e ingestión del rotífero Philodina roseola, alimentado con Raphidocelis subcapitata. El experimento consistió en la exposición de diez adultos por tratamiento en concentraciones entre 1x10(4) y 1x10(7) células mL-1 y bajo temperatura de 25±1 °C. Los experimentos tuvieron la duración de una hora y las concentraciones iniciales y finales de la suspensión algal fueron cuantificadas por conteo numérico de las células en cámara de Neubauer. No fueron encontradas diferencias significativas entre las concentraciones iniciales y finales de células en los controles, lo cual indica que no se presentó crecimiento algal. Las tasas de filtración de P. roseola variaron entre 0,09 y 0,25 mL ind-1 h-1. Teniendo en cuenta que la filtración es el principal proceso de adquisición de energía de la Philodina roseola, así como de los demás rotíferos, y que comprende cuestiones importantes relacionadas con la dinámica trófica de los ecosistemas acuáticos, es importante ampliar la información con experimentos usando otros tipos de alimento y diferentes combinaciones de las condiciones experimentales.

Efecto de los microorganismos acuáticos (rotífera y ciliata) sobre la emisión de cercarias de Schistosoma mansoni, por Biomphalaria glabrata en el laboratorio / Effect of aquatic organisms (rotifers and ciliate) on the issuance of Schistosoma mansoni larvae by Biomphalaria glabrata maintained in laboratory

Los rotíferos y ciliados son microorganismos que cohabitan con B. glabrata, y en el caracol infectado comparten espacio con el parásito S. mansoni, agente causal de la esquistosomosis. La experiencia con crías en cautiverio sugiere que la presencia de tales microorganismos puede afectar la evolución del parásito en el caracol, debido a competencia por espacio y nutrientes. En base a esto se evaluó el efecto de los rotíferos y ciliados, sobre la emisión de cercarias de S. mansoni por el molusco B. glabrata mantenida en cautiverio. En los experimentos se emplearon cinco grupos de 10 caracoles infectados con 10 miracidios de S. mansoni, los cuales, se colocaron en recipientes plásticos, con: (a) 87500 rotíferos y 25000 Paramecium sp, (b) 27000 rotíferos y 54000 Paramecium sp, (c) 800000 rotíferos, (d) 4500 Paramecium sp y rotíferos, respectivamente y (e) el grupo control de infección se mantuvo sin rotíferos y ciliados. Se demostró un efecto de inhibición en la emisión de las cercarias de S. mansoni en presencia de rotíferos y Paramecium sp, dependiente de la cantidad de organismos presentes. El porcentaje de inhibición en la emisión de las cercarias de S. mansoni se relacionó con la presencia de un gran número de rotíferos. El presente trabajo constituye el primer hallazgo que sugiere que organismos de los phyllum Rotifera y Ciliophora podrían ser empleados como control biológico de la infección por S. mansoni.

The rotifers and ciliates are microorganisms that coexist with B. glabrata, Inside tissues normally infected by S. mansoni in the snails. the causative agent of schistosomiasis. The captive breeding experience suggests that the presence of such microorganisms can affect the evolution of the parasite in the snail, because competition for space and nutrients. The effect of rotifers and ciliates in the release of cercariae of S. mansoni by the mollusc B. glabrata maintained in captivity. The experimental setting was constituted by five groups of snails (n=10) infected with 10 miracidia from S. mansoni, which were placed in plastic containers with (a) 87500 25000 rotifers and Paramecium sp, (b) 27000 54000 rotifers and Paramecium sp, (c) 800000 rotifers, (d) Paramecium sp 4500 and the same number of rotifers and (e) infection control group remained rotifers and ciliates. It was possible to observe an number-dependent inverse correlation between the release of cercaria from S. mansoni and the number of rotifers and Paramecium sp. Used in this study. Particularly, the percentage of inhibition was strongly associated with the presence of large numbers of rotifers. To date, these are the first findings suggesting that microorganisms from the genus ciliata, subphylum Crustacea, are capable of regulating S. mansoni lyfe cycle progression in the snail stage, therefore could be potentially used as biological controls for the infection caused by S. mansoni.

Monoculture of the ciliate protozoan Euplotes sp. (Ciliophora; Hypotrichia) fed with different diets / Monocultivo do protozoário ciliado Euplotes sp. (Ciliophora; Hypotrichia) com diferentes dietas

Ciliate protozoa of the genus Euplotes commonly appears contaminating mass cultures of rotifers but also with potential to be used as live food in the larviculture of marine fish. To obtain a monoculture of Euplotes sp., three diets were tested: 1) microalgae Nannochloropsis oculata, 2) commercial diet for rotifers Culture Selco 3000, and 3) baker's yeast (Saccharomyces cerevisiae). The ciliates were inoculated at 10 ind. mL -¹. On day 5, protozoa densities in the groups fed the commercial diet (1,911.0 ± 248.7 ind. mL-¹) and the baker's yeast (2,600.0 ± 195.3 ind. mL-1) did not differ, but were higher than the group fed microalgae (2.0 ± 1.4 ind. mL-1) (p < 0.05). On day 6, the density in the group fed baker's yeast was higher (15,484.0 ± 1,164.9 ind. mL-¹) than in the groups fed microalgae (3.0 ± 1.4 ind. mL-¹) or commercial diet (11,287.0 ± 1,468.0 ind. mL-¹). An exponential growth curve was observed for the protozoa fed baker's yeast (R² = 0.992; p < 0.05) and commercial diet (R² = 0.979; p < 0.05). The microalgae diet did not result in satisfactory growth of the protozoan. Feeding baker's yeast or commercial rotifer's diet to a monoculture of Euplotes sp. can result in very high densities of this protozoan.

Protozoários ciliados do gênero Euplotes comumente aparecem como contaminante em culturas massivas de rotíferos, apresentando potencial para ser utilizado na larvicultura de peixes marinhos. Para obter um monocultivo de Euplotes sp., foram testados três tipos de alimento: 1) microalga Nannochloropsis oculata, 2) dieta comercial para rotíferos Culture Selco 3000, e 3) fermento biológico (Saccharomyces cerevisiae). Os ciliados foram inoculados na concentração de 10 indivíduos mL-¹. No quinto dia, a densidade de protozoários nos tratamentos com dieta comercial para rotíferos (1.911,0 ± 248,7 ind. mL-¹; média ± desvio padrão) e fermento biológico (2. 600,0 ± 195,3) não diferiram entre si, mas foram superiores ao tratamento com microalga (2,0 ± 1,4) (p < 0,05). Ao sexto dia de cultivo, a densidade no tratamento com fermento (15.484,0 ± 1.164,9 ind. mL-¹) foi superior aos tratamentos com microalga (3,0 ± 1,4 ind. mL-¹) e dieta comercial (11.287,0 ± 1.468,0 ind. mL-¹). O cultivo destes ciliados apresentou uma curva de crescimento exponencial para o fermento (R² = 0,992; p < 0,05) e a dieta comercial (R² = 0,979; p < 0,05). O uso da microalga N. oculata não resultou em crescimento satisfatório destes organismos. O uso de fermento biológico e dieta comercial para rotíferos no monocultivo de Euplotes sp., pode resultar em altas densidades do protozoário.

New scope on the relationship between rotifers and Biomphalaria alexandrina snails

Objective: To investigate the effect of rotifer internalization into snail tissue on the development of schistosomes. Methods:Susceptible laboratory-bred Biomphalaria alexandrina (B. alexandrina) snails were exposed to lab-maintained rotifers; Philodina spp., two weeks before and after being infected with Schistosoma mansoni (S. mansoni) miracidia. The consequent histopathological impact on snail tissues and cercarial biology were investigated before and after emergence from snails. Results:Contamination of B. alexandrina snails with philodina, two weeks before miracidial exposure, was found to hinder the preliminary development of S. mansoni cercariae inside the snail tissues. Furthermore, when snails were contaminated with rotifers two weeks post miracidial exposure; growth of already established cercariae was found to be retarded. The consequent influence of internalized rotifers within the snail tissue was clearly reflected on cercarial emergence, activity and infectivity along the four weeks duration of shedding. In the present study, comparison of snail histopathological findings and altered cercarial biology observed between the experimental and control groups indicated that the rotifers may have affected the levels of snail's energy reservoirs, which eventually was found to have had an adverse impact on reproduction, growth and survival of the parasite within the snail host, coupled with its performance outside the snail. Conclusions:In future biological control strategies of schistosomiasis, ritifers should be considered as a parasitic scourge of humanity.

Vermicompost: Quality organic manure for zooplankton production in aquaculture.

Purpose of the present study was to evaluate the effect of vermicompost on water quality parameters of fish pond and zooplankton production. No significant effect on the physico-chemical properties of pond water were observed though the zooplankton population was better with significant difference in rotifers population (68.38%) comparing with cow dung treated pond. Application of vermicompost as an organic manure in fish pond is not only better but also safe than the raw cow dung. This is excellent manure for nursery and rearing pond as it has a potential to produce good rotifers population.

Pastas de Rhodomonas salina (Cryptophyta) como alimento para Brachionus plicatilis (Rotifera)

Rhodomonas salina (Cryptophyta) pastes as feed for Brachionus plicatilis (Rotifera). Rotifers are an important live feed for first feeding larvae of many fish species. The use of concentrated algae cells in the mass culture of the rotifer Brachionus plicatilis (Brachionidae) has opened new horizons for research on this organism. Pastes of Rhodomonas salina (Pyrenomonadaceae) obtained either by centrifugation or flocculation with chitosan were preserved, with or without vitamin C, at -20°C for four weeks and were evaluated biochemically (proteins, lipids, pigments and fatty acids contents) and subsequently, were used to feed the rotifer Brachionus plicatilis at a ratio of 25mg/L/day. Four different microalgae pastes were prepared: (1) centrifuged and preserved with vitamin C (CV), (2) centrifuged and preserved without vitamin C (C), (3) flocculated and with vitamin C (FV) and (4) flocculated without vitamin C (F). All treatments showed similar contents of proteins and total lipids with respect to control culture (a fresh culture of R. salina), with mean values of 40.0±2.32% and 12.0±1.45%, respectively. The pheophytin a/chlorophyll a ratio, a general indicator of the chemical status of microalgal concentrates, was similar (0.09-0.11) between centrifuged pastes and control culture, but was found to be higher in flocculated pastes (1.28-1.48). The fatty acid profile varied with respect to the control culture, mainly in the proportion of the essential polyunsaturated fatty acids (PUFAs): eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Total PUFAs, EPA and DHA contents were statistically similar between centrifuged pastes and control culture (PUFAs: 47%, EPA: 4% and DHA: 4.7%), whereas values obtained for flocculated pastes were significantly lower. The rotifers grew equally well when fed with centrifuged pastes or control culture (maximum density: 320rotifers/mL; instantaneous growth rate: 0.23rotifers/day, fecundity: 1.49eggs/female and productivity: 43x103rotifers/L/day. No significant effect of vitamin C was found when used as a paste preservative. We concluded that centrifugation is an effective harvesting method, and that freezing to -20ºC for four weeks (no vitamin added), may help maintain the nutritional quality of R. salina paste, similar to fresh microalgae and can be offered to Brachionus plicatilis. Rev. Biol. Trop. 59 (4): 1503-1515. Epub 2011 December 01.

Pastas de Rhodomonas salina, obtenidas mediante centrifugación y floculación con quitosano y preservadas con o sin vitamina C, a -20°C fueron evaluadas bioquímicamente y proporcionadas como alimento al rotífero Brachionus plicatilis. Las pastas microalgales: (1) centrifugada y con vitamina C (CV), (2) centrifugada y sin vitamina C (C), (3) floculada y con vitamina C (FV) y (4) floculada y sin adición de vitamina C (F); mantuvieron sus contenidos de proteínas y lípidos totales similares al cultivo control, con valores de 40.0±2.32% y 12.0±1.45%, respectivamente. La relación feofitina a/clorofila a fue similar (0.09-0.11) entre las pastas centrifugadas y el cultivo control, pero mayor en las pastas floculadas (1.28-1.48). Las pastas centrifugadas presentaron porcentajes de PUFAs totales, EPA y DHA similares al cultivo control (PUFAs: 47%, EPA: 4% y DHA: 4.7%) y superiores al de las pastas floculadas. Las pastas obtenidas por centrifugación indujeron un crecimiento del rotífero igual al obtenido con el alimento control (densidad máxima: 320rotíferos/mL; tasa instantánea de crecimiento: 0.23rotíferos/día, fecundidad: 1.49huevos/ hembra y productividad: 43x103rotíferos/L/día). Se concluye que la pasta de R. salina centrifugada y congelada a -20°C, durante cuatro semanas, sin adición de vitamina C, mantiene su calidad nutricional similar a la del alga fresca y puede ser usada como alimento de Brachionus plicatilis.

Influencia de las macrófitas sobre la estructura poblacional de rotíferos y microscrustáceos en un plano de inundación tropical

The influence of macrophytes on rotifer and microcrustacean assemblage in a tropical floodplain. Most studies on zooplankton ecology have been conducted in open waters. However, it has been considered of great importance to extend such studies to other habitats, such as those generated of macrophytes. We studied the spatial and temporal variation of the microcrustacean and rotifer assemblage structures associated with macrophytes, and compare them with the variation exhibited in open waters. Integrated samples were collected for zooplankton and phytoplankton biomass using a Schindler bottle, in four open water sites and four other sites covered by macrophytes in the floodplain complex of Ayapel (Córdoba, Colombia) during different limnimetric levels. The significant differences in the structure were evaluated using Kruskal & Wallis and discriminant analyses, and the similarity among sampling sites was evaluated using Bray & Curtis analysis. Zooplanktonic richness was favored by macrophytes. However, we did not find a constant spatial pattern for density, and only particular trends apparently conditionated by flood pulses. The presence of Eichhornia azurea (Pontederiaceae) contributed in a significant way with an increase in the diversity and density of benthic taxa. The density of some zooplanktonic groups was related with environmental conditions and phytoplanktonic biomass. Rev. Biol. Trop. 59 (2): 853-870. Epub 2011 June 01.

La mayoría de estudios ecológicos del zooplancton se han realizado en aguas abiertas. No obstante, es importante ampliar la exploración hacia hábitats como el de las macrófitas. En este estudio se evaluó la variación espacio-temporal de la estructura del ensamble de rotíferos y microcrustáceos asociados a macrófitas y se comparó con la variación de su estructura en aguas abiertas, para lo cual se tomaron muestras integradas de zooplancton y biomasa de fitoplancton usando una botella Schindler de 5L en cuatro sitios de aguas abiertas y en cuatro sitios cubiertos por macrófitas durante diferentes niveles limnimétricos en el complejo cenagoso de Ayapel (Córdoba, Colombia). Las diferencias significativas de la estructura se evaluaron mediante Kruskal & Wallis y discriminantes; y la similitud entre sitios de muestreo mediante Bray & Curtis. Las macrófitas favorecieron la riqueza zooplanctónica; sin embargo, no hubo un patrón espacial constante en la densidad, pero sí tendencias particulares condicionadas por el pulso de inundación. La presencia de Eichhornia azurea (Pontederiaceae) contribuyó significativamente a la mayor diversidad y densidad de taxones bentónicos y sólo la densidad de algunos taxones y grupos del zooplancton se relacionó con las condiciones ambientales y la biomasa de fitoplancton.