oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Competencia en Cladocera: implicancias de la sobreposición en el uso de los recursos tróficos
MARTINEZ,GINGER; MONTECINO,VIVIAN;
Revista chilena de historia natural , 2000, DOI: 10.4067/S0716-078X2000000400020
Abstract: although numerous evidence reveals the use of different feeding strategies among cladocerans, the impact of trophic niche overlap on their patterns of coexistence has been underestimated due to the classical description of passive feeding behavior. under microcosm conditions, paired experiments of population dynamics were conducted for the cladocerans moina micrura (moinidae) and ceriodaphnia dubia (daphnidae), specialists on the resources chlorella sp. and oocystis sp. (chlorococcales) respectively, and for the generalist species daphnia ambigua (daphnidae), during 35 - 45 days. while, the specialists m. micrura and c. dubia did not show evidences of competition, their presence lead to a significant decrease in the density of the generalist d. ambigua and in some cases even led to extinction. although the generalist qualitatively affected the dynamics of each specialist, it did not affect their density, thus resulting in an asymmetrical interaction among each specialist with the generalist species. these results demonstrate that the feeding behavior and resource use overlap should be determinant conditions in the composition of cladoceran assemblages
Competencia en Cladocera: implicancias de la sobreposición en el uso de los recursos tróficos Competition in Cladocera: implications of the trophic resources use overlap  [cached]
GINGER MARTINEZ,VIVIAN MONTECINO
Revista chilena de historia natural , 2000,
Abstract: A pesar que numerosa evidencia demuestra el uso de diferentes estrategias de alimentación entre cladóceros, la clásica descripción de una conducta alimentaria pasiva ha conducido a una subestimación de la sobreposición de nicho trófico sobre sus patrones de coexistencia. En condiciones de microcosmos, se mantuvieron experimentos pareados de dinámica poblacional de los cladóceros Moina micrura (Moinidae) y Ceriodaphnia dubia (Daphnidae), especializados en los recursos Chlorella sp. y Oocystis sp. (Chlorococcales) respectivamente y del generalista Daphnia ambigua (Daphnidae), durante 35 - 45 días. Mientras que los especialistas M. micrura y C. dubia no dieron evidencias de competencia, la presencia de cada uno produjo un significativo decrecimiento de la densidad del generalista D. ambigua, ocasionando en algunos casos su extinción. A pesar que las dinámicas poblacionales de cada especialista fueron afectadas cualitativamente por la presencia del generalista, no hubo efecto de esta especie sobre las densidades, resultando una interacción asimétrica entre cada especialista con el generalista. Estos resultados demuestran que la conducta alimentaria y la sobreposición en el uso de los recursos serían condiciones determinantes en la composición de ensambles de cladóceros Although numerous evidence reveals the use of different feeding strategies among cladocerans, the impact of trophic niche overlap on their patterns of coexistence has been underestimated due to the classical description of passive feeding behavior. Under microcosm conditions, paired experiments of population dynamics were conducted for the cladocerans Moina micrura (Moinidae) and Ceriodaphnia dubia (Daphnidae), specialists on the resources Chlorella sp. and Oocystis sp. (Chlorococcales) respectively, and for the generalist species Daphnia ambigua (Daphnidae), during 35 - 45 days. While, the specialists M. micrura and C. dubia did not show evidences of competition, their presence lead to a significant decrease in the density of the generalist D. ambigua and in some cases even led to extinction. Although the generalist qualitatively affected the dynamics of each specialist, it did not affect their density, thus resulting in an asymmetrical interaction among each specialist with the generalist species. These results demonstrate that the feeding behavior and resource use overlap should be determinant conditions in the composition of cladoceran assemblages
The effect of abiotic factors on the hatching of Moina micrura Kurz, 1874 (Crustacea: Cladocera) ephippial eggs
ROJAS, N. E. T.;MARINS, M. A.;ROCHA, O.;
Brazilian Journal of Biology , 2001, DOI: 10.1590/S1519-69842001000300005
Abstract: the roles of some abiotic factors in controlling the hatching rates of moina micrura ephippial eggs were investigated. determination of optimum hatching conditions would be important in developing the use of this species as a food for fish larvae in aquaculture. ephippia were exposed to different treatments in the laboratory, and monitored for hatching over a period of seven days. optimum hatching conditions were: ph 5-9, temperature 25oc, photoperiod eight or more hours light per day and light intensity equal to or greater than 850 lux. differences in water ionic concentrations (from deionized water to 880 mg.l-1 of selected salts) had no effect.
The effect of abiotic factors on the hatching of Moina micrura Kurz, 1874 (Crustacea: Cladocera) ephippial eggs  [cached]
ROJAS N. E. T.,MARINS M. A.,ROCHA O.
Brazilian Journal of Biology , 2001,
Abstract: The roles of some abiotic factors in controlling the hatching rates of Moina micrura ephippial eggs were investigated. Determination of optimum hatching conditions would be important in developing the use of this species as a food for fish larvae in aquaculture. Ephippia were exposed to different treatments in the laboratory, and monitored for hatching over a period of seven days. Optimum hatching conditions were: pH 5-9, temperature 25oC, photoperiod eight or more hours light per day and light intensity equal to or greater than 850 lux. Differences in water ionic concentrations (from deionized water to 880 mg.L-1 of selected salts) had no effect.
Population growth and development of two species of Cladocera, Moina micrura and Diaphanosoma birgei, in laboratory
SIPAúBA-TAVARES, L. H.;BACHION, M. A.;
Brazilian Journal of Biology , 2002, DOI: 10.1590/S1519-69842002000400018
Abstract: the objective of the present work was to investigate the influence of four diets on population growth, development, total length, dry weight, and nutritional value of two zooplanktonic species, moina micrura and diaphanosoma birgei. the four dietary treatments were: algae alone (a); algae + vitamins (av); algae + ration (ar); and algae + ration + vitamins (arv). growth rate peak for both species occurred faster with av treatment. in general, av treatment for m. micrura showed better results for intrinsic rate, fecundity, and embryonic and post-embryonic development. on the other hand, longevity and total spawning number were better with ar treatment (p < 0.05). vitamin and ration treatments produced the best results in d. birgei species (p < 0.05). the highest percentage of protein and lipids for both cladocerans was verified for ration treatments. carbohydrate was higher for the treatment containing algae alone (p < 0.05). generally, diets containing ration and vitamin showed better results in cladocerans development, with water quality adequate for culture systems. ration and vitamin diets may also be used in high-density cultures in the laboratory.
Population growth and development of two species of Cladocera, Moina micrura and Diaphanosoma birgei, in laboratory  [cached]
SIPAúBA-TAVARES L. H.,BACHION M. A.
Brazilian Journal of Biology , 2002,
Abstract: The objective of the present work was to investigate the influence of four diets on population growth, development, total length, dry weight, and nutritional value of two zooplanktonic species, Moina micrura and Diaphanosoma birgei. The four dietary treatments were: algae alone (A); algae + vitamins (AV); algae + ration (AR); and algae + ration + vitamins (ARV). Growth rate peak for both species occurred faster with AV treatment. In general, AV treatment for M. micrura showed better results for intrinsic rate, fecundity, and embryonic and post-embryonic development. On the other hand, longevity and total spawning number were better with AR treatment (p < 0.05). Vitamin and ration treatments produced the best results in D. birgei species (p < 0.05). The highest percentage of protein and lipids for both cladocerans was verified for ration treatments. Carbohydrate was higher for the treatment containing algae alone (p < 0.05). Generally, diets containing ration and vitamin showed better results in cladocerans development, with water quality adequate for culture systems. Ration and vitamin diets may also be used in high-density cultures in the laboratory.
Influence of seston quantity and quality on growth of tropical cladocerans
Fer?o-Filho, A. S;Arcifa, M. S.;Fileto, C.;
Brazilian Journal of Biology , 2005, DOI: 10.1590/S1519-69842005000100011
Abstract: the seston of the small, shallow, and tropical lake monte alegre was tested for quantity and quality for cladocerans by growth bioassays, which were carried out in spring (daphnia gessneri and moina micrura), summer (d. gessneri, m. micrura, ceriodaphnia cornuta, and simocephalus mixtus), and winter (d. gessneri and d. ambigua). cohorts of newborns originating from ovigerous females collected in the lake or from laboratory cultures were submitted, at a room temperature of 23oc to the following treatments: (1) the chlorophytes ankistrodesmus falcatus and/or scenedesmus spinosus; (2) lake seston; and (3) lake seston + chlorophytes. growth rate, clutch size, and fecundity were evaluated. seston alone was not the best food for promoting cladoceran growth. there were seasonal differences in food quantity and quality with spring and summer seston being better for growth than that of the winter. adding chlorophytes to the seston increased clutch size and fecundity for most species in summer and winter, but not in spring. energy limitation seems to be the most important factor influencing cladoceran growth in summer and especially in winter.
Population dynamics of Moina minuta Hansen (1899), Ceriodaphnia cornuta Sars (1886), and Diaphanosoma spinulosum Herbst (1967) (Crustacea: Branchiopoda) in different nutrients (N and P) concentration ranges
Vieira, Ana Carolina Brito;Medeiros, Ana Maria Alves;Ribeiro, Leonardo Le?ncio;Crispim, Maria Cristina;
Acta Limnologica Brasiliensia , 2011, DOI: 10.4322/actalb.2011.018
Abstract: aim: aquatic environments of semi-arid regions are subject to changes in water quality and volume due to short and irregular rain seasons. consequently, zooplankton composition changes in association to fluctuations in the trophic degree. to comprehend these processes, this study analyzed the influence of nutrient concentrations (n and p) on the population dynamics of three species of cladocera - moina minuta, ceriodaphnia cornuta, and diapahnosoma spinulosum - from the taperoá ii dam, paraíba, brazil; methods: animals were experimentally submitted to different nutrient concentrations as a means to reproduce specific trophic conditions from natural environments. zooplankton densities were evaluated once every three days, with food (i.e. algal cultures) being supplied in alternate days. to compare population growth, an anova was performed, followed by tukey's hsd post-hoc test; results: the population growth of the three species differed significantly both among species and among treatments. moina minuta populations showed higher growth rates under higher nutrient concentrations, whereas ceriodaphnia cornuta growed more efficiently in intermediate concentrations, and diaphanosoma spinulosum showed a better development in low nutrient concentrations; conclusions: the results from the experimental approach, presented here, are similar to what is observed in the field, based on previous studies carried out in the taperoá ii dam. therefore, these results suggest that the hydrological cycle seems to be the major determinant of zooplankton population dynamics in aquatic semi-arid environments
The use of PCR-RFLP to genetically distinguish the morphologically close species: Ceriodaphnia dubia Richard, 1894 and Ceriodaphnia silvestrii Daday, 1902 (Crustacea Cladocera)
Abreu, MJ.;Santos-Wisniewski, MJ.;Rocha, O.;Orlando, TC.;
Brazilian Journal of Biology , 2010, DOI: 10.1590/S1519-69842010000100016
Abstract: the cladocerans are important components of planktonic and benthic freshwater and good indicators of the trophic state of water bodies. the morphological taxonomy of many species of cladocera is considered complex with minor differences separating some species. nowadays, molecular techniques provide a powerful tool to identify and classify different taxonomical levels, using mainly ribosomal rna genes (rrna) as molecular markers. in the present work we performed pcr-rflp to separate ceriodaphnia dubia, an exotic species in brazil and the native species ceriodaphnia silvestrii, widely distributed in brazilian freshwater. the rflp analysis of the its1-5.8s-its2 region of rrna genes showed to be different between c. dubia and c. silvestrii when using enzymes ecori, apai and sali. thus, the its1-5.8s-its2 region proved to be a useful molecular marker to differentiate the studied ceriodaphnia species, which makes the task easier of telling apart species that are morphologically very similar. also, this methodology might be interesting in determining the distribution of the exotic species c. dubia in brazilian freshwaters, particularly in cases when c. dubia occurs in the absence of c. silvestrii, a particularly difficult task for ecologists who are not taxonomy specialists.
Morphological and Molecular Identification of Three Ceriodaphnia Species (Cladocera: Daphniidae) from Australia  [PDF]
Pranay Sharma
Advances in Zoology , 2014, DOI: 10.1155/2014/258134
Abstract: Australian Ceriodaphnia (Cladocera: Daphniidae) are examined using morphological attributes and two mitochondrial DNA (COI and 16s) and one nuclear DNA (28s) gene fragments to differentiate the species. The sequence data supports the existence of three species, that is, C. dubia, one reinstated species C. spinata Henry, 1919, and one new species C. sp. 1. Morphological characteristics were also able to accurately separate the three species. Furthermore, genetic analysis of COI sequences from Ceriodaphnia supported three clades. The high degree of correlation between morphological and molecular identification in this study indicates that mitochondrial markers, COI and 16s, are appropriate molecular markers for species discrimination and identification of Ceriodaphnia. 1. Introduction Ceriodaphnia Dana, 1853 (Cladocera: Daphniidae), displays little diversification in terms of species richness and morphological disparity, with the genus currently comprising 14 “valid” species worldwide, predominantly based on morphology [1]. In addition, there are 21 species inquirenda and 24 species that are probably junior synonyms of previously described species [1]. There is limited morphological and genetic evidence to support this proliferation of the large number of proposed names. According to Smirnov and Timms (1983) [2], there are only five Ceriodaphnia species from Australia which includes one beaked species (‘beak’ = a rostral projection) i.e. C. cornuta Sars, 1885, and four non-beaked species C. dubia Richard, 1894, C. laticaudata Müller, 1867, C. quadrangula (Müller, 1785) and C. rotunda Sars, 1862. One further, non-beaked species, C. pulchella Sars, 1862, has been recorded since [3]. In addition to these, two more non-beaked species, C. planifrons Smith, 1909 and C. spinata Henry, 1919 were re-instated by Berner [4], thereby increasing the total number of recorded species from Australia to eight. The literature on Ceriodaphnia sp. generally points towards the absence of divergent morphological characters for this group. Additionally, the historical taxonomic descriptions are incomplete and primarily focused on the head, antennule, antennae, postabdomen, carapace, reticulation, and rarely trunk appendages of Ceriodaphnia. Where morphological evidence is unclear, molecular techniques can be used to improve our understanding of taxonomic divergence and speciation. Barnett et al. [5] emphasised that genetics has become an increasingly important parameter in the classification and identification of organisms in comparison to more traditional morphological
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.