Search results for "Toxicant"
showing 10 items of 24 documents
Aquatic pollution may favor the success of the invasive species A. franciscana
2015
The genus Artemia consists of several bisexual and parthenogenetic sibling species. One of them, A. franciscana, originally restricted to the New World, becomes invasive when introduced into ecosystems out of its natural range of distribution. Invasiveness is anthropically favored by the use of cryptobiotic eggs in the aquaculture and pet trade. The mechanisms of out-competition of the autochthonous Artemia by the invader are still poorly understood. Ecological fitness may play a pivotal role, but other underlying biotic and abiotic factors may contribute. Since the presence of toxicants in hypersaline aquatic ecosystems has been documented, our aim here is to study the potential role of an…
Comparative toxicant sensitivity of sexual and asexual reproduction in the rotiferBrachionus calyciflorus
1995
Cyclically parthenogenetic zooplankters like rotifers are important tools for assessing toxicity in aquatic environments. Sexual reproduction is an essential component of rotifer life cycles, but current toxicity tests utilize only asexual reproduction. The authors compared the effects of four toxicants on asexual and sexual reproduction of the rotifer Brachionus calyciflorus. Toxicants had a differential effect on sexual and asexual reproduction, with sexual reproduction consistently the most sensitive. Concentrations of 0.2 {mu}g/ml PCP (sodium pentachlorophenate) had no effect on the asexual reproductive rate, but significantly reduced sexual reproduction. Likewise, chlorpyrifos concentr…
Physiological Perturbations in Several Generations of Daphnia magna Straus Exposed to Diazinon
2000
Abstract Daphnia magna was exposed to sublethal diazinon concentrations (0.05, 0.1, 0.5, 0.75, and 1.0 ng/L) for 21 days. The algae Nannochloris oculata (5×10 5 cells/mL) was used to feed the daphnids. Chronic toxicity tests were carried out using neonates of F 1 (first brood) and F 1 (third brood) offspring generations from parentals (F 0 ) preexposed to the organophosphate. The effect of diazinon on survival, reproduction, and growth was monitored for the selected daphnid generations. The parameters used to evaluate pesticide effect on reproduction were mean total young per female, mean brood size, time to first reproduction, mean number broods per female, and intrinsic rate of natural in…
Daphnia magna feeding behavior after exposure to tetradifon and recovery from intoxication.
1999
Abstract The feeding behavior of the cladocera Daphnia magna subjected to a short-term exposure to the acaricide tetradifon (4-chlorophenyl 2,4,5-trichlorophenyl sulfone) was studied. The experiments were performed using the unicellular algae Nannochloris oculata at a density of 5×10 5 cells/ml as food for the organisms. In a first experiment, three generations (F0, F1, and F3) of the daphnids were exposed to sublethal levels of tetradifon (0.1, 0.18, 0.22, and 0.44 mg/l) and the effect of the toxicant on filtration and ingestion rates was determined. Rates of filtration and ingestion of D. magna declined in the three generations studied with increasing toxicant concentrations; however, tox…
Pesticide toxicokinetics in fish: accumulation and elimination.
1998
Bioaccumulation of fenitrothion in the European eel (Anguilla anguilla) was studied using two sublethal concentrations of this pesticide in a flow-through test system. The pesticide concentrations used were one-tenth (0.002 ppm) and one-fifth (0.04 ppm) the 96-h LC50 of fenitrothion in this species. Steady state was reached early (2 h) when the animals were exposed to 0.02 ppm of toxicant, and after 48 h when the animals were exposed to 0.04 ppm. Toxicokinetic parameters for fenitrothion in eel muscle (K1, K2, and T1/2) were calculated for both experiments. The highest bioconcentration factor was calculated for animals exposed to 0.04 ppm of toxicant, indicating the relationship between the…
Prenatal exposure to mercury and neuropsychological development in young children: the role of fish consumption
2017
Background: Vulnerability of the central nervous system to mercury exposure is increased during early development. The aim of this study is to evaluate the association between prenatal exposure to mercury and child neuropsychological development in high-fish-intake areas in Spain. Methods: Study subjects were 1362 children, participants in the INMA (Environment and Childhood) birth cohort study. Cord blood total mercury (CB-Hg) and cord polyunsaturated fatty acids (PUFA) concentrations were analysed in samples collected between 2004 and 2008. Child neuropsychological development was assessed at age 4-5 years by the McCarthy Scales of Children's Abilities (MSCA). Socio-demographic, lifestyle…
Acute toxicity and bioaccumulation of endosulfan in rotifer (Brachionus calyciflorus).
1991
Abstract 1. 1. The acute toxicity of endosulfan was determined for the freshwater rotifer Brachionus calyciflorus . 2. 2. The mean 24 hr lc 50 value for endosulfan was 5.15 ppm with a coefficient of variation of 14.7%. 3. 3. Rotifers were exposed at two sublethal concentrations (1.5–2.0 ppm) of endosulfan for bioaccumulation experiments, for an exposure time of 24, 48, 72 and 96 hr. The rotifers were fed with Nannochloris oculata (5 × 10 5 cell/ml). 4. 4. The highest accumulation of endosulfan was found 24 hr after the start of the exposure to 1.5 ppm of the toxicant. A steady-state concentration in rotifer was reached between 24–48 hr, followed by a gradual decrease until 96 hr.
DNA methylation changes associated with prenatal mercury exposure:A meta-analysis of prospective cohort studies from PACE consortium
2022
Mercury (Hg) is a ubiquitous heavy metal that originates from both natural and anthropogenic sources and is transformed in the environment to its most toxicant form, methylmercury (MeHg). Recent studies suggest that MeHg exposure can alter epigenetic modifications during embryogenesis. In this study, we examined associations between prenatal MeHg exposure and levels of cord blood DNA methylation (DNAm) by meta-analysis in up to seven independent studies (n = 1462) as well as persistence of those relationships in blood from 7 to 8 year-old children (n = 794). In cord blood, we found limited evidence of differential DNAm at cg24184221 in MED31 (β = 2.28 × 10-4, p-value = 5.87 × 10-5) in relat…
Effect of sublethal exposure to mercury in the biochemical composition of hepatopancreas in Procambarus clarkii during the recovery after starvation
1993
Abstract Freshwater crayfish undergo seasonal periods of starvation. The hepatopancreas is the main energetic-storage organ in this animal. An adequate replenishment of energetic reserves after these periods of fasting is critical for the proper growth and reproduction in this species. Mercury compounds enter the biological environment from natural discharges and anthropogenic sources. Mercuric chloride is one of the most toxic metallic salts found in polluted waters. In these studies, we report the effect of mercuric chloride in the biochemical composition of crayfish hepatopancreas during the recovery period after prolonged starvation. Adult intermolt crayfish (P. clarkii) were kept starv…
Immediate biomarker responses to benzo[a]pyrene in polluted and unpolluted populations of the blue mussel (Mytilus edulis L.) at high-latitudes.
2008
Immediate biomarker responses of two high-latitude populations of the blue mussel Mytilus edulis to benzo[a]pyrene (B[a]P) were evaluated. Mussels collected from a clean and a polluted site in southwest Iceland were exposed to the nominal dose of 100 μg B[a]P L−l for 3 h, after 4 days of acclimatization in clean seawater. To test the sensitivity to the toxicant and immediate biological responses, the following biomarkers were used: DNA single strand breaks, heart rate and feeding rate.All the biomarkers revealed differences between the study sites. Irrespective of the origin of the organisms, the short time exposure to the high B[a]P concentration did not induce DNA single strand breaks or …