Notes on some new or little known rotifera from Brazil

La présente contribution concerne la faune de rotifères de trois localités dans les environs de Boa Vista (Roraima, Brésil). Au total, 66 espèces ont été identifiées, dont 6 nouvelles pour la faune brésilienne. #Macrochaetus aspinus sp. n., #M. americanus sp. n. et #Trichocerca abilioi sp. n. sont décrites. #Lepadella latusinus striata Koste, #Dicranophorus halbachi Koste et #Trichocerca parvula Carlin sont reconnues comme synonymes de #L. costatoidesSegers, #D. kostei Pourriot et Zoppi de Roa et #T. rotundata$ Myers, respectivement. (Résumé d'auteur

Differences in population growth of rotifers and cladocerans raised on algal diets supplemented with yeast

AbstractWe studied the population growth of two rotifer (Brachionus calyciflorus and Brachionus rubens) and two cladoceran (Ceriodaphnia dubia and Moina macrocopa) species fed three diets (Chlorella vulgaris (Ch), Scenedesmus acutus (Sc) and yeast (Saccharomyces cerevisiae) (Y) in seven combinations (alone or mixed in equal proportions (on dry weight basis): Ch+Sc, Ch+Y, Sc+Y and Ch+Sc+Y). In general, the cladocerans were more adversely affected than the rotifers on the diet of yeast alone. The population growth curves of B. calyciflorus and B. rubens revealed that algal diets were superior to yeast. Regardless of diet, B. rubens had a longer lag phase and delayed peak density compared to B. calyciflorus. Both M. macrocopa and C. dubia had higher peak abundances when fed mixed algae than on either alga offered separately. B. rubens, C. dubia and M. macrocopa reached significantly lower maximal densities on diets containing yeast, S. acutus or both. When the data on the eggs/female (egg ratio) were plotted as function of population density, we found an inverse relation, which was curvilinear for B. calyciflorus and linear for B. rubens. In general, we found that yeast could effectively supplement algal diets in all the test species, thereby reducing costs in large scale production of zooplankton

Effect of algal food (Chlorella vulgaris) concentration and inoculation density on the competition among three planktonic Brachionidae (Rotifera: Monogononta)

Competitive outcomes among three rotifer species (Anuraeopsis fissa, Brachionus havanaensis and B. angularis) were quantified with different inoculation densities of two competing species at a time (0, 25, 50, 75 and100%) and using different algal (Chlorella vulgaris) densities (0.2 × 106 , 0.4 × 106 and 0.8 × 106 cells ml-1). In control cultures, when each species was grown alone, the population growth of rotifers increased with increasing food availability in the medium, but in mixed cultures, decreased with increasing proportion of the competing species. At low food level, compared to B. havanaensis, B. angularis had stronger negative impact on A. fissa. However, with increasing algal density, both species of Brachionus had similar but reduced impact on A. fissa. Population growth of B. havanaensis was more adversely affected by A. fissa than B. angularis at low and intermediate concentrations. At high food level, the impact of either A. fissa or B. angularis on the growth of B. havanaensis was similar. When grown alone, for a given food density, A. fissa was more numerically (4 to 6 times) abundant than the other two species. The rate of population increase (r) of rotifers increased with increasing food levels. Depending on the rotifer species and the test conditions, the r varied from -0.001 to 0.34 d-1. Results showed that the competitive outcome in the tested rotifers depended on the initial inoculation density of the competing species, the offered food concentration as well as the interaction of these two factors

Preface. Shallow lakes research: advances and perspectives

Preface to themed section relating to the 9th International Shallow Lakes Conference

Population dynamics of Brachionus calyciflorus and Brachionus havanaensis (Rotifera) on mixed diets with Microcystis aeruginosa and green algae

The effect of the cyanobacterium Microcystis aeruginosa was evaluated as a diet, separately and together with one of the two edible algal species (Chlorella vulgaris or Scenedesmus acutus) at different proportions (0, 25, 50, 75 or 100% on the basis of biomass) on the population growth of two rotifers Brachionus calyciflorus and Brachionus havanaensis. Population growth curves of B. calyciflorus and B. havanaensis cultured on M. aeruginosa alone, or in combination with one of the two algal species decreased with increasing proportion of cyanobacteria in the diet. In treatments containing exclusive algal diets (either Chlorella or Scenedesmus) and those with low proportion of Microcystis, B. havanaensis was more abundant than B. calyciflorus. However, both rotifer species died in less than two weeks on an exclusive diet of M. aeruginosa. Peak population densities (mean ± standard error) of B. calyciflorus grown on an exclusive diet of Chlorella or Scenedesmus were 47 ± 6 and 15 ± 1 ind. ml-1, respectively. Corresponding values for B. havanaensis were much higher (203 ± 21 and 187 ± 2 ind. ml-1). Regardless of the rotifer species and the diet type and composition, the population growth rates (r) were inversely related to increasing proportion of M. aeruginosa in the diet

Effects of selected pharmaceuticals (ibuprofen and amoxicillin) on the demography of Brachionus calyciflorus and Brachionus havanaensis (Rotifera)

AbstractThe levels of emerging chemicals have increased dramatically during the last two decades posing problems for human and environmental health. Pain-killers such as ibuprofen and antibiotics such as amoxicillin are generally consumed together and hence are discharged into waterbodies as effluents. The lack of a rigorous control of pharmaceutical discharges into natural waterbodies is a concern for limnologists and ecotoxicologists because of their possible effects on non-target organisms. Rotifers, due to their sensitivity, short generation time and high reproductive rates, are widely used as bioassay organisms in testing the effects of different substances including pharmaceuticals. Here we quantified the demographic responses of Brachionus calyciflorus and Brachionus havanaensis exposed to three sublethal concentrations of ibuprofen (25, 12.5 and 6.25mgL−1) and amoxicillin (200, 100 and 50μgL−1). Our data showed that both survivorship- and reproduction-related variables were negatively affected with increasing concentrations of both pharmaceuticals. The rate of population increase of B. calyciflorus (0.63–0.72d−1) was not affected by amoxicillin or by ibuprofen but for B. havanaensis, it was decreased significantly (from 0.89 to 0.38d−1). Compared to ibuprofen, amoxicillin had more adverse effects on both the rotifer species

Population growth potential of rotifers from a high altitude eutrophic waterbody, Madín reservoir (State of Mexico, Mexico): The importance of seasonal sampling

To understand the population growth potential of different species of rotifers in nature, field collections through seasons are essential. We sampled zooplankton (and measured selected physicochemical variables) from the Madín reservoir, a high altitude eutrophic urban waterbody from Mexico, every month for a year. Qualitative analysis of zooplankton revealed 28 rotifer species and four cladoceran crustaceans plus one unidentified copepod. Cephalodella catellina (1400 ind L-1), Horaella thomassoni (550 ind L-1), Conochilus dossuarius (380 ind L-1) and Filinia longiseta (25 ind L-1) had higher peak density than other rotifers. Based on the concentrations of nitrates and phosphates, chlorophyll a levels or different diversity indices (e.g., Carlson, Shannon-Wiener, Pantle and Buck, Ejsmont-Karabin’s TSIRot), the waterbody is eutrophic to hypertrophic, depending on the season. In this waterbody we observed high densities of Aphanothece sp. which is a toxic picocyanobacterium. During the blooms of Aphanothece, we also recorded higher densities of H. thomassoni and C. catellina. Based on the gut contents we found that both these rotifer species feed on Aphanothece in this waterbody. This study thus suggests the potential growth of Horaella, Cephalodella, Conochilus and Filinia in this eutrophic reservoir containing blooms of Aphanothece

Bioensayo del efecto de fenoles producidos por Myriophylum aquaticum en cultivo sobre Lactuca sativa

Background. Myriophyllum aquaticum has a high phenotypic plasticity and its plant dispersion is a function of its fast vegetative reproduction; its submerged leaves possess structural characteristics that allow the release of organic compounds, among them phenolic compounds. Goals. Under laboratory conditions, this study analyzed the development of Myriophyllum aquaticum (Vell.) Verdc. cultures associated with the release of phenolic compounds and evaluated the effect of these compounds on germination and root elongation of Lactuca sativa L. Methods. Under laboratory conditions, we cultivated emerging shoots of M. aquaticum to evaluate their growth and the production of phenolic compounds. We evaluated their effect using bioassays with L. sativa and applying phytotoxicity indices to the phenolic compounds released. Results. Our evaluation of the production of phenolic compounds found a direct relationship between this plant species and its behavior under cultivation; cultivation caused a quicker release of phenols during the first days of development. These compounds released by M. aquaticum on L. sativa, as measured by the IGN and IER index comparison, were found to have caused lower toxicity. Conclusions. The bioassay application with the evaluation of early development endpoints of L. sativa plantlets allowed us to confirm the effect of phenolic compounds released by the M. aquaticum submerged plants and characterize them as bioactive compounds.  Antecedentes. Myriophyllum aquaticum presenta una alta plasticidad fenotípica (heterofilia) y su dispersión está en función de su reproducción vegetativa; sus hojas sumergidas poseen características estructurales que permiten la liberación de compuestos orgánicos, dentro de los que se observan compuestos fenólicos. Objetivos. El presente estudio analizó el desarrollo de cultivos de Myriophyllum aquaticum (Vell) Verdc. bajo condiciones de laboratorio, su asociación con la liberación de compuestos fenólicos y evaluó el efecto que producen sobre la germinación y elongación radical de Lactuca sativa L. Métodos. Se establecieron cultivos de esquejes emergentes en condiciones de laboratorio para evaluar la producción de compuestos fenólicos liberados al medio de cultivo. Se evaluó su efecto usando bioensayos con L. sativa y mediante la aplicación de índices de fitotoxicidad de los compuestos fenólicos liberados. Resultados. La evaluación de la producción de compuestos fenólicos evidenció una relación directa entre esta especie y su comportamiento bajo cultivo, lo que produjo la aceleración en el proceso de liberación de fenoles durante los primeros días de desarrollo. El efecto de los compuestos fenólicos liberados por M. aquaticum sobre L. sativa, evaluado a través de la comparación de los índices IGN e IER, resultó en que éstos ocasionaron baja toxicidad. Conclusiones. La aplicación de bioensayos con la evaluación de endpoints de desarrollo temprano de plántulas de L. sativa permitieron mostrar el efecto manifiesto de los compuestos fenólicos liberados por las plantas sumergidas de M. aquaticum, por lo que se caracterizan como compuestos bioactivos

Getting into hot water: water quality in tropical lakes in relation to their utilisation

Over-exploitation of tropical lakes and reservoirs ('lakes') causes water quality problems that occur as a result of competing socio-economic demands and the presence of feedback loops within the system that exacerbate the situation. We review well documented case studies from Brazil, India, Indonesia, Kenya, Malaysia and Mexico to examine the effect that changes in water quality and quantity have had on the utilisation of these tropical lakes. By comparing the different approaches used to improve their sustainable management, we have found that nutrient enrichment is one of the most important and widespread water quality problems, causing adverse effects such as algal blooms, nuisance levels of aquatic plants, low oxygen levels and elevated greenhouse gas emissions. These effects restrict the use of these lakes for water supply, fisheries, recreation, tourism and wildlife. We conclude that tropical lakes require better management, urgently, to restore the ecosystem services that they deliver to man and nature. However, to be effective, the development of sustainable management programmes needs to be underpinned by reliable scientific evidence and the results of extensive stakeholder engagement activities. We note that, currently, there is little information available on how tropical lakes respond to management interventions that can be used to guide these activities. Further research is needed to address this knowledge gap. Presented at International Conference on the Ocean and Earth Sciences, 18-20 November 2020, Jakarta Selatan, Indonesia (held online)