An Efficient Solid-Phase Microextraction-Gas Chromatography-Mass Spectrometry Method for the Analysis of Methyl Farnesoate Released in Growth Medium by .

Methyl farnesoate (MF), a juvenile hormone, can influence phenotypic traits and stimulates male production in daphnids. MF is produced endogenously in response to stressful conditions, but it is not known whether this hormone can also be released into the environment to mediate stress signaling. In the present study, for the first time, a reliable solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) method was developed and validated for the ultra-trace analysis of MF released in growth medium by maintained in presence of crowding w/o MK801, a putative upstream inhibitor of MF endogenous production.

An integrated approach for chemical water quality assessment of an urban river stretch through Effect-Based Methods and emerging pollutants analysis with a focus on genotoxicity.

The impact of emerging chemical pollutants, on both status and functionality of aquatic ecosystems is worldwide recognized as a relevant issue of concern that should be assessed and managed by researchers, policymakers, and all relevant stakeholders. In Europe, the Reach Regulation has registered more than 100.000 chemical substances daily released in the environment.

DNA damage detection by Comet Assay on Daphnia magna: Application in freshwater biomonitoring.

Monitoring of water genotoxicity still remains underexploited in risk assessment. The present study aimed at standardizing and evaluating the sensitivity and applicability of the Comet Assay adapted for Daphnia magna in genotoxicological investigations in freshwater environments. Two sampling campaigns (2014-2015) were performed in the watercourses of a pilot basin located in the Parma district (Italy).

The relationship between sulfur metabolism and tolerance of hexavalent chromium in Scenedesmus acutus (Spheropleales): Role of ATP sulfurylase.

Sulfur availability and the end products of its metabolism, cysteine, glutathione and phytochelatins, play an important role in heavy metal tolerance, chromium included. Sulfate and chromate not only compete for the transporters but also for assimilation enzymes and chromium tolerance in various organisms has been associated to differences in this pathway. We investigated the mechanisms of Cr(VI)-tolerance increase induced by S-starvation focusing on the role of ATP sulfurylase (ATS) in two strains of Scenedesmus acutus with different chromium sensitivity.

Acartia tonsa eggs as a biomonitor to evaluate bioavailability/toxicity of persistent contaminants in anoxic/sulfidic conditions: The case of cadmium and nickel.

The evaluation of toxicity due to persistent pollutants in anoxic aquatic environments has met with various problems, as most test organisms can not withstand oxygen lack and exposure to free sulfide. We evaluated the suitability of the eggs of the brackish copepod Acartia tonsa for bioassays in anoxic/sulfidic conditions: when exposed to deep hypoxia and free sulfide, the eggs become quiescent and are able to resume hatching after restoring normoxic conditions. Tests with cadmium and nickel were performed in normoxic and deeply hypoxic conditions and in anoxic water containing H2S or H2S+FeSO4 on an equimolar basis.

Increase of chromium tolerance in Scenedesmus acutus after sulfur starvation: Chromium uptake and compartmentalization in two strains with different sensitivities to Cr(VI).

In photosynthetic organisms sulfate constitutes the main sulfur source for the biosynthesis of GSH and its precursor Cys. Hence, sulfur availability can modulate the capacity to cope with environmental stresses, a phenomenon known as SIR/SED (Sulfur Induced Resistance or Sulfur Enhanced Defence). Since chromate may compete for sulfate transport into the cells, in this study chromium accumulation and tolerance were investigated in relation to sulfur availability in two strains of the unicellular green alga Scenedesmus acutus with different Cr-sensitivities.

Comet Assay on Daphnia magna in eco-genotoxicity testing.

Detection of potentially hazardous compounds in water bodies is a priority in environmental risk assessment. For the evaluation and monitoring of water quality, a series of methodologies may be applied. Among them, the worldwide used toxicity tests with organisms of the genus Daphnia is one of the most powerful.

Standardized methods for acute and semichronic toxicity tests with the copepod Acartia tonsa.

The availability of standardized protocols for both organism culture and bioassay with ecologically relevant species is of great concern in ecotoxicology. Acartia tonsa represents an important, often dominant, member of zooplankton communities and meets all the practical criteria suggested for model species. New standardized procedures for laboratory culturing of the copepod A.

Identification of S2-T A63: a cDNA fragment corresponding to a gene differentially expressed in a Cr-tolerant strain of the unicellular green alga Scenedesmus acutus.

The gene expression of the wild type (S2-N) and a Cr-tolerant strain (S2-T) of the unicellular green alga Scenedesmus acutus has been compared in order to get more insight on their different chromium sensitivity. The RNA of the two strains was extracted after 4 days of culture in standard medium without chromium and analyzed by means of RNA differential display. The two strains showed differential gene transcription even in the absence of the heavy metal and six putatively differential amplicons were evidenced in the Cr-tolerant strain.

Sulfur starvation and chromium tolerance in Scenedesmus acutus: a possible link between metal tolerance and the regulation of sulfur uptake/assimilation processes.

In a laboratory-selected Cr-tolerant strain of the unicellular green alga Scenedesmus acutus, the capacity to synthesize higher amounts of cysteine (Cys) and reduced glutathione (GSH) than the wild-type was demonstrated to underlie tolerance to Cd and Cr(VI). In photosynthetic organisms sulfate constitutes the main sulfur source for the biosynthesis of GSH and its precursor Cys, hence it was hypothesized that the sensitivity of the two strains to Cr(VI) could be modified after culturing in sulfate-deprived medium. Both strains were grown in the presence of different concentrations or in the absence of sulfate (sulfur-starved) and then assayed for Cr(VI) tolerance in standard medium.

Bioavailability, bioaccumulation and tolerance of chromium: consequences in the food chain of freshwater ecosystems.

Many abiotic and biotic factors can influence the partitioning equilibrium of heavy metals, thus influencing metal impact on aquatic environments. Unicellular algal species release soluble organic substances able to complex metals. In our laboratory a Cr-tolerant strain was selected and isolated from a wild type strain of Scenedesmus acutus.

Cadmium tolerance, cysteine and thiol peptide levels in wild type and chromium-tolerant strains of Scenedesmus acutus (Chlorophyceae).

Two strains of the unicellular green alga Scenedesmus acutus with different sensitivity to hexavalent chromium were compared for their tolerance of cadmium, by means of growth and recovery tests, and determination of cysteine, reduced glutathione and phytochelatin content, after short-term exposure to various cadmium concentrations (from 1.125 to 27 microM). Growth experiments showed that, after 7-day treatments with cadmium, the chromium-tolerant strain reached a significantly higher cell density and, after 24-h exposure to Cd, was able to resume growth significantly better than the wild type.

Is Cr(VI) toxicity to Daphnia magna modified by food availability or algal exudates? The hypothesis of a specific chromium/algae/exudates interaction.

The long-term effects of Cr(VI) on life history traits of Daphnia magna Straus were studied in relation to different feeding conditions or to the presence of Scenedesmus acutus exudates, which had proved to reduce chromium toxicity to the alga. In high feeding conditions the concentration of 14 microg Cr(VI)/L had negative effects on survival, growth and fecundity. In low feeding conditions the effects on growth were not evident, but daphnids changed the reproductive strategy normally adopted in case of food shortage and showed a daily rate of newborn production higher than control; however, newborn were of a smaller size and less resistant to starvation.

Light intensity influences chromium bioaccumulation and toxicity in Scenedesmus acutus (Chlorophyceae).

The influence of light intensity on chromium uptake was studied in two strains of the freshwater unicellular alga Scenedesmus acutus (Chlorophyceae) having different sensitivity to Cr poisoning and light intensity. The two strains were subjected to different Cr treatments at 3000 and 80 lux. Cr toxicity was assessed by algal growth rate, recovery test, methylene blue staining, and determination of photosynthetic activity.

Comparison between a normal and a Cr-tolerant strain of Scenedesmus acutus as a food source to Daphnia magna.

A normal (S2-N) and a Cr-tolerant (S2-T) strain of Scenedesmus acutus, grown in Cr-free medium or in the presence of 1, 5, or 10 mg/liter Cr(VI), were fed to Daphnia magna. An increase of growth and fecundity was observed in the daphnids when the algae had undergone an increase of dry mass following Cr treatment, which happened in S2-N in the presence of 1 mg/liter and in S2-T in the presence of 5 mg/liter. When the algae were pretreated with 10 mg/liter, growth and fecundity were reduced in the daphnids fed on S2-N, but remained normal in the daphnids fed on S2-T.

Chromium-induced sexual reproduction gives rise to a Cr-tolerant progeny in Scenedesmus acutus.

A clonal population of Scenedesmus acutus was treated for 3 months with 1 mg/liter Cr(VI) and then returned to Cr-free medium. After several months, the cells were treated with different Cr concentrations and then subjected to a series of morphological observations and metabolic tests. The results, compared with those obtained with a normal cell population treated in the same way, demonstrate that the progeny of algae subjected to the prolonged Cr treatment has acquired tolerance to the metal, as it can survive and grow in the presence of Cr concentrations that are lethal to normal cells.

Hexavalent chromium induces gametogenesis in the freshwater alga Scenedesmus acutus.

The aggregates formed by Scenedesmus acutus cultivated in the presence of 1 mg/liter Cr(VI) persist even after 7 days of treatment. They were examined by fluorescence and electron microscopy and were found to be an early stage of sexual reproduction. They consist of four small cells deprived of a true cell wall and enclosed in a common envelope.

Chromium toxicity on two linked trophic levels. II. Morphophysiological effects on Scenedesmus acutus.

The morphophysiological effects of Cr(VI) on Scenedesmus acutus were studied by light and fluorescence microscopy. Axenic cultures of S. acutus were grown in the presence of 1, 5, and 10 mg/liter of Cr(VI) supplied as K2Cr2O7.

Chromium toxicity on two linked trophic levels. I. Effects of contaminated algae on Daphnia magna.

The effects of feeding Daphnia magna on algae (Scenedesmus acutus) pretreated with different concentrations of Cr(VI) were studied. A positive effect on growth and newborn production rate was observed in the daphnids fed on algae exposed to 1 mg/liter Cr(VI). Fecundity and growth were drastically reduced in daphnids fed on algae exposed to 10 mg/liter Cr(VI).