Search

An integral analysis of the acute and chronic toxicity, bioaccumulation, sites of entry, and distribution of four trace metals: copper, iron, lead, and nickel, and the non-trace metal mercury were performed in the ciliate Paramecium caudatum. Mercury was the fastest metal accumulated, and the most toxic. The sensitivity of Paramecium caudatum to the five metals tested (Cu, Fe, Hg, Ni, and Zn) falls in the range of other ciliate species. We observed similarities between the toxicity of the five metals to the ciliate P. caudatum with the rotifer Euchlanis dilatata: (a) Mercury was the most toxic metal in terms of acute and body burdens. (b) Acute values were very similar in both species, Hg as the most toxic and Fe as the less toxic, (c) the vacuole/ingestion chronic tests were more sensitive than growth inhibition chronic tests. These analyses would ideally help generate safer guidelines for protecting aquatic biota. [ABSTRACT FROM AUTHOR]

Metals are widely used in modern society harming the environment; their toxicity cause environmental adverse effects to many organisms including zooplankton. This contribution employed: (a) acute and chronic toxicity tests, (b) epifluorescence image analysis, and (c) atomic absorption techniques, to analyze toxicity of four trace (copper, iron, nickel, and zinc), and one non-trace metals (mercury) on the freshwater rotifer Euchlanis dilatata. This work integrated results of Bioconcentration Factors (BCF's), sites of entry and accumulation and to determine mechanisms of uptake and toxicity of these five metals of the freshwater rotifer Euchlanis dilatata. This integral analysis enhanced our understanding of knowledge on: (a) the toxicity mechanisms, (b) sites of metal entry and concentration inside the rotifer, (c) bioconcentration and body burdens. As expected, Hg the non-trace metal used here, was the most toxic. Our results suggest that the toxicity is ameliorated in the rotifer by selecting feeding avoiding the most toxic particles and reducing adverse effects on reproduction, until mortality per se reduces reproduction. The chronic effect on ingestion rate was quite sensitive for all metals whereas reproduction was slightly affected. The combination of acute and chronic tests and determination of BCF's for each metal allowed calculation of the acute and chronic body burdens. Body burdens again confirmed that mercury was the most toxic metal of the five employed here. [ABSTRACT FROM AUTHOR]

We conducted life table experiments on the freshwater rotifer Asplanchna brightwellii to analyze its demography when fed with prey items from several taxonomic groups (cladocerans, protozoans, and rotifers) and under two different temperature regimes (20 and 25°C); the aim of the study was to determine the preferred prey for A. brightwellii in terms of fitness (evaluated as reproductive success) among five cladoceran, protozoan, and rotifer preys, and to test which temperature (20 or 25°C) is better for life table parameters of Asplanchna. Our analysis identified Brachionus calyciflorus as the preferred prey for A. brightwellii based on life table statistics, ingestion rate and electivity indices. The greatest values for net reproductive rate and intrinsic growth rate were achieved when A. brightwellii was fed B. calyciflorus. Greater reproductive values ( R and r) were found at 25°C than at 20°C for A. brightwellii across the five prey species. We found significant differences in the ingestion rate and electivity index among zooplanktonic and benthic preys. The influence of temperature, the cost of predation, and how prey selection by A. brightwellii is influenced by: biomass, size, and swimming speed; they are discussed hoping to gain a better understanding of trophic transfers in zooplankton communities. [ABSTRACT FROM AUTHOR]