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At least 109 records · Page 6Linked to original sources
PubMed2003

Morphological response of a bdelloid rotifer to desiccation.

We desiccated bdelloid rotifers (Macrotrachela quadricornifera), submitting the animals to four desiccation procedures (protocols A, B, C, D) that differed in the rate of water evaporation, in the time of desiccation, and in the substrates provided. We observed external morphological changes of the rotifer bodies during drying with scanning electron microscopy and, in parallel, assessed rates of recovery after a 7-day period of dormancy. Two protocols produced disorganized morphologies of the anhydrobiotic animals, with no (A) or very poor (B) recovery. Protocols C and D gave rather high rates of recovery and dry rotifers appeared unaltered and well organized. The different protocols affected rotifer morphology during the 7-day anhydrobiosis and rates of recovery after the 7-day anhydrobiosis; high recovery rates corresponded to well-organized morphologies of anhydrobiotic bdelloids, suggesting that a proper contraction of the body into a tun shape and probably a rigorous packing of internal structures are necessary for survival after anhydrobiosis. These features are affected by the time between water shortage and full desiccation, but also by the surrounding relative humidity and by the nature of the substrate. Possible adaptations of anhydrobiotic rotifers are discussed.

Acclimatization↗
PubMed2004

Application of Toxkit microbiotests for toxicity assessment in soil and compost.

The potential of Toxkit microbiotests to detect and analyze pollution in agricultural soil and the quality of compost was studied. The toxicity tests used included seed germination biotests using cress salad (Lepidum sativum L.), tomato (Lycopersicum esculentum L.), and cucumber (Cucumis sativus L.), and the Toxkit microbiotests included those with microalgae (Selenastrum capricornutum), protozoa (Tetrahymena thermophila), crustaceans (Daphnia magna, Thamnocephalus platyurus, and Heterocypris incongruens), and rotifers (Brachionus calyciflorus). Experiments on compost were undertaken in a modified solid-state fermentation system (SSF) and under field conditions (in a windrow). To promote the composting process, two strains of Trichoderma (Trichoderma lignorum and Trichoderma viride), as well as a nitrification association that regulated the nitrogen-ammonification and nitrification processes were applied.

Animals↗
PubMed2005

Acute toxicity to freshwater organisms of antiparasitic drugs for veterinary use.

The acute toxicity of five antiparasitic drugs used in the veterinary field-amprolium hydrochloride (APH), bithionol (BT), levamisole hydrochloride (LVH), pyrimethamine (PYM) and trichlorfon (TRC)-to the aquatic organisms Oryzias latipes, Daphnia magna, and Brachionus calyciflorus was examined. The toxicity test with O. latipes was conducted in accordance with the OECD Guidelines for the Testing of Chemicals (1993) to determine the 24-, 48-, 72-, and 96-h LC(50) values. In addition, 24- and 48-h EC(50) values for D. magna and a 24-h EC(50) for B. calyciflorus were determined with the DAPHTOXKIT F(trade mark) magna (Creasel, Belgium) and the ROTOXKIT F(trade mark) (Creasel, Belgium), respectively. High-performance liquid chromatographic analysis revealed that APH, LVH, and PYM were stable in water, but BT was unstable, decreasing by 84% on average at 24 h. TRC rapidly decomposed, with only 0.7% of the initial concentration remaining after 96 h, forming dichlorvos. The toxicity of TRC to O. latipes was determined in two ways: exposure to the same medicated water for 96 h (static test) and exposure to medicated water replaced every 24 h (semistatic test). AMP, LVM, and PYM were tested in the static condition, and BT was tested in the semistatic condition. BT was most toxic to O. latipes, with a 96-h LC(50) of 0.24 mg L(-1), followed by PYM, with a 96-h LC(50) of 5.6 mg L(-1). The 24-, 48-, 72-, and 96-h LC(50) values of TRC in the static test were 92.0, 45.2, 29.5, and 17.6 mg L(-1), respectively, which tended to be lower than those in the semistatic test, especially late in the observation period. D. magna was the most susceptible to TRC, with a 48-h EC(50) as low as 0.00026 mg L(-1). The 48-h EC(50) values of BT, PYM, and LVH for D. magna were 0.3, 5.2, and 64.0 mg L(-1), respectively. B. calyciflorus was the most susceptible to BT, with an EC(50) of 0.063 mg L(-1), followed by PYM, with an EC(50) of 15.0 mg L(-1). Among the test compounds, APH was the least toxic to all the freshwater organisms tested, with a 96-h LC(50) of >600 mg L(-1) for O. latipes, a 48-h EC(50) of 227 mg L(-1) for D. magna, and an EC(50) of 403 mg L(-1) for B. calyciflorus.

Animals↗
PubMed2006

Toxicity reduction of metal pyrithiones by near ultraviolet irradiation.

Zinc pyrithione (ZnPT) or copper pyrithione (CuPT) have been effectively used as ship-antifouling agents, as an alternative to organotin compounds. Because of their instability in light and a lack of suitable analytical procedures, there is little data on their residue levels in environmental matrices. It is possible to investigate the fate of such compounds by toxicity alteration with certain treatments. The purpose of this study was to evaluate the degradation of pyrithiones through toxicity reduction by near ultraviolet (UV-A) irradiation. Metal pyrithiones dissolved in acetonitrile were irradiated with a UV-A lamp for 0, 0.5, 1, and 2 h, and were subjected to UV spectral measurement and toxicity evaluation using both sea urchin and freshwater rotifer bioassays. For the bioassays, photolyzed samples were dissolved in dimethyl sulfoxide after evaporation of the acetonitrile. The changes in UV spectra of photolyzed ZnPT or CuPT showed a time-dependent degradation, and the UV spectra at 2 h irradiation suggested substantial decomposition. Toxicities of ZnPT and CuPT were 12 and 5 microg/L as 24 h LC50 to the survival of rotifers and 10(-6) ng/L and 2.3 ng/L as 27 h EC50 to normal pluteus formation, respectively. By evaporation of the acetonitrile, the EC50 of ZnPT was 2.2 ng/L, which was the same as that of CuPT. The EC50s of ZnPT or CuPT for both species increased with longer irradiation times. Photolyzed ZnPT or CuPT demonstrated substantial degradation in the UV spectra, but possessed marked toxicity, which is probably due to toxic degradation products. One reason why photolyzed CuPT was toxic to rotifers was explained by the high toxicity of copper ions formed by UV-A irradiation.

Animals↗
PubMed2006

Application of leaching tests for toxicity evaluation of coal fly ash.

The toxic properties of coal fly ash samples obtained from various coal combustion power plants were evaluated in this work using physicochemical analyses and bioassays. Physicochemical analyses showed that heavy metals present in solid samples included Cr, Cu, Mn, Ni, Pb, and Zn. The results of the chemical analysis of eluates deduced by the application of standard leaching tests according to EN 12457-2 and Toxicity Characteristic Leaching Procedure (TCLP) methods indicated that the compounds contained in fly ashes could potentially be transferred to the liquid phase depending upon the leaching method used. Heavy metal concentrations were higher in TCLP eluates, indicating that the initial pH value of the leaching medium significantly affected the transfer of these elements to the liquid phase. Tests conducted with the photobacterium Vibrio fischeri (Microtox test), the crustacean Daphnia magna, and the rotifer Brachionus calyciflorus were used to assess toxicity of eluates obtained by both leaching tests. Daphnia magna was the most sensitive test organism. The EN 12457-2 method proved to be more reliable for toxicity evaluation of eluates. In contrast, the TCLP method showed some interference owing to acetic acid toxicity, and precipitation occurred after pH adjustment of eluates from acid to neutral range. The toxicity of both fly ashes and the corresponding solid leaching residues of EN 12457-2 and TCLP leaching tests was also measured using the Microtox Basic Solid phase Test. The results generated with this bioassay indicated that toxicity was greatly influenced by the pH status of the solid samples.

Aliivibrio fischeri↗
PubMed2006

Ecotoxicological properties of wastewater treated using tertiary methods.

The objective of this work was the examination of the efficiency of coagulation and ozonation processes for the production of reclaimed wastewater with low toxicity. Municipal secondary effluents were treated by FeCl3, Al2(SO4)3 (alum), and a commercial substance at metal ion concentrations of 0.5 and 1 mmol/L. Alternatively, the effluents were treated by ozonation in a semibatch ozone reactor. The feed gas was introduced at a flowrate of 3 L/min containing ozone at various concentrations, ranging between 2.5 and 8 mg/L; ozone residence times were 2, 5, 15, and 30 min. The toxic effects of the advanced treated effluents were examined by a battery of tests using the marine bacteria Vibrio fischeri, the freshwater crustaceans Daphnia magna, Daphnia pulex, and Thamnocephalus platyurus, and the rotifers Brachionus calyciflorus. The addition of alum decreased the toxic effect of reclaimed wastewater on immobilization of D. pulex, from 90 to 60%. Ozonation was also effective for toxicity removal, which decreased to 25% effect on D. pulex after treatment by 2.5 mg O3/L for 2 min. However, acute toxic effects after ozonation, were observed on V. fischeri and were related to ozone gas concentration and contact time. At the highest ozone dosage, the toxicity reached almost 100% inhibition of bioluminescence after 15 min. The toxicity of the ozonated effluents to bacteria decreased with sample storage time and was almost negligible after 48 h, indicating that the potential adverse effect of reclaimed wastewaters on receiving waters might be reduced by storage for a certain time.

Aliivibrio fischeri↗
PubMed2006

Study of the effects of Pb and Hg toxicity using a chronic toxicity reproductive 5-day test with the freshwater rotifer Lecane quadridentata.

We have developed chronic toxicity reproductive 5-day tests to study the effects of Pb, as Pb(NO(3))(2), and Hg, as HgCl(2), exposure in the freshwater rotifer Lecane quadridentata. We used "r" (the instantaneous growth rate) as the endpoint. The test was performed using EPA medium at two food levels (10(5) and 10(6) cells/mL of Nannochloris oculata) at a controlled temperature of 25 degrees C and an L/D cycle of 16:8 h. We monitored the levels of both metals, using atomic absorption, at days 0, 2, and 5 of each experiment. Our results showed that rotifers fed at higher food concentrations were capable of withstanding higher levels of metal toxicity than those fed at lower food concentrations (EC50 = 0.704 versus 0.664 mg/L(-1) for lead, P < 0.05; EC50 = 0.057 versus 0.054 for mercury, P < 0.05). Our atomic absorption analysis showed that although 66% of lead nitrate can be taken up by algal cells efficiently and removed from the medium, rotifers also play an important role removing additional lead from the medium (up to 44% in some treatments). In the case of mercuric chloride, most of the mercury is bound by the salts contained in EPA medium or discarded by the organisms, and the remainder is removed by N. oculata in <48 h.

Animals↗
PubMed1996

Determination of vitamin E in aquatic organisms by high-performance liquid chromatography with fluorescence detection.

A liquid chromatographic (HPLC) method has been developed for the quantitative determination of different forms of vitamin E (alpha-, gamma-, and delta-tocopherol) in aquatic organisms. The assay consists of a simple extraction with methanol containing butylhydroxytoluene (BHT) as an antioxidant, followed by reversed-phase chromatography with fluorescence detection. The efficiency of the extraction method was equivalent or superior to that of more complex approaches for the isolation of tocopherols. Linearity has been achieved over the range of 0.02 to 3 micrograms/ml for alpha-tocopherol and within-run and between-run coefficients of variation at three levels were 0.7-2.9 and 1.2-3.7%, respectively. The recovery at three concentrations ranged from 73.8 to 96.6% and the minimal quantity that could be detected was 0.6 ng. Comparable figures were obtained for gamma- and delta-tocopherol. This method has been routinely applied to determine vitamin E in Artemia, rotifers, turbot and sea bass larvae, and shrimp postlarvae.

Animals↗
PubMed1993

Ecotoxicological studies with the freshwater rotifer Brachionus calyciflorus. III. The effects of chemicals on the feeding behavior.

The effect of short-term exposure to xenobiotics on the feeding behavior of the freshwater rotifer Brachionus calyciflorus was studied. The filtration and ingestion rates of this rotifer decreased after an exposure of 5 hr to sublethal concentrations of copper, pentachlorophenolate, 3,4-dichloroaniline, and lindane. The effective concentrations at which feeding rate was reduced to 50% of that in controls (EC50) for the respective chemicals are 0.032, 1.85, 41.2, and 8.5 mg/liter. The potential use of feeding behavior as test criterion for toxicity screening tests with aquatic invertebrates is discussed.

Aniline Compounds↗
PubMed1994

Ecotoxicological studies with the freshwater rotifer Brachionus calyciflorus. IV. Rotifer behavior as a sensitive and rapid sublethal test criterion.

The swimming behavior of the freshwater rotifer Brachionus calyciflorus exposed to copper (Cu), pentachlorophenol (PCP), 3,4-dichloroaniline (DCA), and lindane, for periods ranging from 5 min to 5 hr, was examined. A swimming behavior test is described which is based on the rotifers' movement rates as they swim over a grid. For all four toxicants a clear dose-response was observed, with the swimming activity decreasing with increasing toxicant concentrations. For Cu the EC50's, the concentration that reduced the swimming activity to 50% of that of the control value, sharply decreased from 0.22 mg/liter after an exposure of 5 min to 0.068, 0.038, and 0.014 mg/liter after exposures of 30, 60, and 300 min, respectively. PCP affected the rotifers' swimming behavior more gradually, with EC50's decreasing from 7.0 mg/liter after an exposure of 5 min to 5.9, 5.4, and 1.5 mg/liter after 30, 60, and 300 min, respectively. A similar pattern was found for DCA with EC50's ranging from 193 to 45.5 mg/liter for the 5-min and 3-hr exposures, respectively. Exposed to lindane however, B. calyciflorus swimming activity exhibited a different response, and the EC50's gradually increased from 13.7 mg/liter after an exposure of 5 min to significantly higher values of 16.4 and 18.5 mg/liter after periods of 1 and 5 hr, respectively. The results of the swimming activity assays were compared to those of acute and chronic toxicity tests performed with the same test species. The potential use and relevance of this behavioral test criterion were evaluated and discussed.

Aniline Compounds↗
PubMed1996

Chronic toxicity of fenitrothion to an algae (Nannochloris oculata), a rotifer (Brachionus calyciflorus), and the cladoceran (Daphnia magna).

Chronic toxicity studies were conducted with an algae (Nannochloris oculata), a rotifer (Brachionus calyciflorus), and a cladoceran (Daphnia magna) to determine their relative sensitivities to the organophosphorus insecticide fenitrothion. The cladoceran D. magna was the most sensitive of the three species. The no observed effect concentrations (NOECs) for the study with the algae (1.0 mg/liter) and for the rotifer (1.0 mg/liter) were higher than the NOEC (0.009 microgram/liter) and the LC50 of 24 hr (0.067 microgram/liter) for D. magna. Most of the algal populations were not initially affected by exposure to fenitrothion. Pesticide concentrations higher than 1.0 mg/liter significantly reduced algal densities after 72 hr exposure. The effects of chronic exposure of the rotifer B. calyciflorus to fenitrothion were evaluated using some demographic parameters: intrinsic rate of natural increase (r), generation time, net reproductive rate, and life expectancy. All the parameters studied decreased with increasing toxicant concentrations. The parameters used to determine the effect of the pesticide on D. magna reproduction were mean total young per female, mean brood size, mean time to first reproduction, and r. The r and the rest of the studied parameters were affected at 0.011-microgram/liter and higher fenitrothion concentrations. Growth, as measured by body length, was only depressed significantly at 0.011 microgram/liter pesticide.

Animals↗
PubMed1999

In vitro populations of rotifer Brachionus plicatilis Müller demonstrate inhibition when fed with copper-preaccumulating microalgae.

Four marine microalgal species (Chlorella autotrophyca, Nannochloropsis gaditana, Tetraiselmis chuii, and Isochrysis aff. galbana) were exposed for 24 h to 1 mg L(-1) dissolved copper and then transferred to fresh medium. After that, a group of 10 neonate rotifers were fed with these four microalgal species. The levels of accumulated copper in cellular concentrations of the microalgae were checked, with the result of around 40% of original concentration, with the exception of I. aff. galbana (25% of original concentration). In all cases, cells with preaccumulated metal caused a delay of 1 or 2 days in populational development of rotifers (increase in "lag phase"). The microalgae that were not fed to rotifers (disposed in parallel series) did not significantly transfer metal to the medium after the first day.

Animals↗
PubMed2000

Comparison of four chronic toxicity tests using algae, bacteria, and invertebrates assessed with sixteen chemicals.

The performances of four chronic toxicity tests, comprising the Daphnia magna 21-day (d) (crustacean), Brachionus calyciflorus 2-d (rotifer), Pseudokirchneriella subcapitata 72-h (green algae), and the Microtox chronic 22-h (bacteria) tests, were compared. Sixteen chemicals with toxicity covering 6 orders of magnitude were studied. Very high correlations were found between the NOEC/EC(10) Pseudokirchneriella 72-h, NOEC/EC(10) Brachionus 2-d, and the NOEC Daphnia 21-d tests. The toxicological response of rotifers and microalgae were within the same order of magnitude as the response of Daphnia in 80% of cases (13/16 chemicals). The Microtox chronic test also anticipated the overall results of the Daphnia 21-d test, but the prediction was rather imprecise, compared with microalgae and rotifers. The test measuring the algal growth inhibition of P. subcapitata after 72h was the most sensitive bioassay. Toxicity on microalgae after 72h could be estimated after 5h by measuring either the direct fluorescence of either photosynthetic pigments or fluorescein diacetate in 56 and 43% of cases, respectively. The median value of the ratio between EC(10) and EC(50) was 3.75, 2, and 1.5 with the algae, the rotifers, and the bacteria, respectively.

Algorithms↗
PubMed2001

Effect of methyl parathion on the population growth of the rotifer Brachionus patulus (O. F. Müller) under different algal food (Chlorella vulgaris) densities.

The population growth of the rotifer Brachionus patulus was studied under a combination of different concentrations of Chlorella vulgaris and methyl parathion. To obtain sublethal concentrations of the pesticide a 24-h LC(50) bioassay was performed under two food densities (1.5 and 3.0x10(6) cells ml(-1)) using neonate rotifers. For the population growth experiments, seven toxicant concentrations were used ranging from 0.16 to 10.0 mg L(-1) and four food densities (0.75, 1.5, 3.0, and 6.0x10(6) cells ml(-1)), each with four replicates and thus in all, 128 test jars. A medium with Chlorella alone and without toxicant acted as control. The initial density of the rotifers in each replicate were 5 individual ml(-1). Experiments were conducted for 20 days. The LC(50) values of B. patulus were 8.8 and 10.7 mg L(-1) at low and high algal food density, respectively. Data on the population growth studies revealed a significant effect of both food density and toxicant concentration on the maximum abundance, day at which maximum abundance was reached, and rate of population increase per day. At any toxicant concentration, an increase in food density reduced the toxicity of methyl parathion to rotifers. In controls the maximum rotifer density under the highest food level (6x10(6) cells ml(-1)) was 795+/-46 individuals ml(-1). The rate of population increase per day (r) in controls varied from 0.22+/-0.01 to 0.34+/-0.01 depending on food density. Algal food density had a significant influence in reducing the toxicity of methyl parathion to B. patulus under both acute and chronic toxicity test conditions.

Animals↗
PubMed2001

Effects of methyl bromide fumigation on anhydrobiotic micrometazoans.

Anhydrobiotic organisms are well known for their resistance to extreme environmental conditions while in the inactive, ametabolic, state. This study confirms that this resistance also transfers to treatments with the fumigant methyl bromide. Live specimens of nematodes, rotifers, and tardigrades were found after 70 h of treatment with methyl bromide. Quantitative estimates of survival in the eutardigrade Richtersius coronifer revealed no difference between treated and untreated samples which had been kept dry for a short time. However, R. coronifer from samples collected 11 months before treatment had lower survival compared to samples collected shortly before the treatment. The fact that anhydrobiotic organisms escape treatments with biocides should be considered a serious problem, both for the food industry and from the perspective of human-mediated spread of organisms.

Animals↗
PubMed2000

Numerical methods and parameter estimation of a structured population model with discrete events in the life history.

We consider two numerical methods for the solution of a physiologically structured population (PSP) model with multiple life stages and discrete event reproduction. The model describes the dynamic behaviour of a predator-prey system consisting of rotifers predating on algae. The nitrate limited algal prey population is modelled unstructured and described by an ordinary differential equation (ODE). The formulation of the rotifer dynamics is based on a simple physiological model for their two life stages, the egg and the adult stage. An egg is produced when an energy buffer reaches a threshold value. The governing equations are coupled partial differential equations (PDE) with initial and boundary conditions. The population models together with the equation for the dynamics of the nutrient result in a chemostat model. Experimental data are used to estimate the model parameters. The results obtained with the explicit finite difference (FD) technique compare well with those of the Escalator Boxcar Train (EBT) method. This justifies the use of the fast FD method for the parameter estimation, a procedure which involves repeated solution of the model equations.

Animals↗
PubMed1999

Discrete event versus continuous approach to reproduction in structured population dynamics.

The governing equations are derived for the dynamics of a population consisting of organisms which reproduce by laying one egg at the time, on the basis of a simple physiological model for the uptake and use of energy. Two life stages are assumed, the egg and the adult stage where the adults do not grow. These assumptions hold true, for instance, for rotifers. From the model for the life history of the individuals, a physiologically structured population model for a rotifer population is derived. On the basis of this discrete event reproduction population model a continuous reproduction population model is proposed. The population model together with the equation for the food result in chemostat equations which are solved numerically. We show that for the calculation of the transient population dynamic behaviour after a step-wise change of the dilution rate, an age structure suffices, despite the size and energy structure used to describe the dynamics of the individuals. Aggregation of the continuous reproduction population model yields an approximate lumped parameter model in terms of delay differential equations. In order to assess the performance of the models, experimental data from the literature are fitted. The main purpose of this paper is to discuss the consequences of discrete event versus continuous reproduction. In both population models death by starvation is taken into account. Unlike the continuous reproduction model, the discrete model captures the experimentally observed lack of egg production shortly after the step change in the dilution rate of the chemostat.

Age Factors↗