The effects of different temperature and salinity levels on the acute toxicity of zinc in the Pink Shrimp (Farfantepenaeus paulensis)

The purpose of this study was to measure the acute toxicity of zinc (Zn) on Farfantepenaeus paulensis at different salinities and temperatures by monitoring oxygen consumption. This aspect of the effect of zinc has not been studied in this important commercial species before. First, we examined the acute toxicity of zinc in F. paulensis at 24, 48, 72, and 96?h medium lethal concentration (LC₅₀). One hundred and fifty shrimp were employed for the routine metabolism measurement utilizing sealed respirometers. Ten shrimp were subjected to oxygen consumption measurements in one of the four concentrations of zinc (control, 0.5, 1.0, 2.0, and 3.0 mg?L^?1) at three salinities (36, 20, and 5) and three temperatures (25°C, 20°C, and 15°C). Zinc was significantly more toxic at a salinity of 5 than at 20 or 36. The oxygen consumption was estimated through experiments performed on each of the 12 possible combinations of three temperatures (25°C, 20°C, and 15°C) and three salinities (36, 20, and 5). The shrimp showed a significant reduction in oxygen consumption at a salinity of 5. The results show that the oxygen consumption decreases with respect to the zinc concentration in all temperatures studied. At the highest zinc concentration employed (3.0?mg?L^?1), the salinity 5 and the temperature at 25°C, oxygen consumption decreases 60.92% in relation to the control. The results show that zinc is more toxic to F. paulensis at lower salinities. The significance of the findings for the biology of the species close to sources of zinc is discussed.     

Differential sensitivity of four Lemnaceae species to zinc sulphate

Lemnaceae are currently the only freshwater plants required for regulatory toxicity testing of pesticides and other chemicals. Toxicological protocols allow for the use of different Lemnaceae species in tests. However, few studies have compared the relative sensitivity of individual duckweed species. Zinc is an essential plant nutrient but is also a common pollutant in aquatic environments and elevated levels are phytotoxic. This study shows that four species of Lemnaceae differ in their relative sensitivities to zinc sulphate, a commonly used reference chemical. Comparative zinc sensitivity, in order, from most tolerant to most sensitive was: Landoltia punctata > Lemna minor > Wolffia brasiliensis > Lemna gibba. Zinc sensitivity was also endpoint dependant. EC₅₀ values typically increased in order of: specific biomass growth rate < specific frond number growth rate < chlorophyll absorbance. However, specific frond number growth rate was the most sensitive endpoint for L. punctata. Unlike the other species, L. punctata displayed no significant colony disintegration. Lemna species and L. punctata appear to be employing distinct response strategies when exposed to zinc. L. gibba and L. minor produce and release young, single fronds which are severely affected by zinc. In contrast, L. punctata produces fewer fronds, which are not released and form large colonies of high biomass that are relatively zinc tolerant.     

D1-Like Dopamine Receptor-Mediated Function in Congenic Mutants with D1 vs. D5 Receptor “Knockout”

Current understanding of the functional roles of individual dopamine D₁-like [D₁, D₅] and D₂-like [D_2L/S, D₃, D₄] receptor subtypes remains incomplete. In particular, the lack of pharmacological agonists and antagonists able to distinguish between D₁ and D₅ receptors means that any differential roles in the regulation of behavior are poorly understood. Mutant mice with targeted gene deletion (“knockout”) of individual dopamine receptor subtypes offer an important alternative approach to resolving these functional roles. In congenic D₁ mutants examined ethologically, progressive increases in specific topographies of behavior over wildtypes were considerably greater than those in D₁ mutants on a mixed genetic background; D₁ knockout appears to influence the neuronal substrate(s) of habituation to disrupt sculpture of the changing topography of behavior from initial exploration through to quiescence. Similarly, the D₁ receptor appears to regulate specific topographies of orofacial movement in the mouse as these are “sculpted” in a time-dependent manner. Although the well-recognized role of the D₁-like family in regulating several aspects of behavioral topography has been assumed to involve primarily D₁ receptors, this presumption may require modification to accommodate a subtle but not negligible role for their D₅ counterparts as evidenced in the phenotype of congenic D₅ mutants.     

Na_2SeO_4对蛹虫草子实体生长的影响

蛹虫草是一种药食两用真菌,具有与冬虫夏草相似的功能,且富硒能力较强。本研究通过大量的人工栽培试验,旨在探究不同浓度Na_2SeO_4对新疆本地蛹虫草子实体生长的影响。试验表明,质量浓度为20 mg/L的Na_2SeO_4对蛹虫草的生长不产生显著影响,但蛹虫草各项生物学指标均随着培养基中外源Na_2SeO_4浓度的增加而呈下降趋势,说明随着外源Na_2SeO_4浓度的增加会对蛹虫草的生长产生抑制效应,当外源Na_2SeO_4质量浓度达到200 mg/L时,生产的蛹虫草已不具备商品价值。由此可见,20 mg/L的质量浓度是以Na_2SeO_4为硒源进行蛹虫草富硒研究的安全浓度。该研究为富硒产品开发寻找新的硒源开辟了新思路,为新疆地区进一步大规模栽培富硒蛹虫草提供一定的参考,但是对以Na_2SeO_4为硒源的最佳富硒浓度还有待于进一步研究。     

A novel fine tuning scheme of miR-200c in modulating lung cell redox homeostasis

Oxidative stress induces miR-200c, the predominant microRNA (miRNA) in lung tissues; however, the antioxidant role and biochemistry of such induction have not been clearly defined. Therefore, a lung adenocarcinoma cell line (A549) and a normal lung fibroblast (MRC-5) were used as models to determine the effects of miR-200c expression on lung antioxidant response. Hydrogen peroxide (H₂O₂) upregulated miR-200c, whose overexpression exacerbated the decrease in cell proliferation, retarded the progression of cells in the G2/M-phase, and increased oxidative stress upon H₂O₂ stimulation. The expression of three antioxidant proteins, superoxide dismutase (SOD)-2, haem oxygenase (HO)-1, and sirtuin (SIRT) 1, was reduced upon H₂O₂ stimulation in miR-200c-overexpressed A549 cells. This phenomenon of increased oxidative stress and antioxidant protein downregulation also occurs simultaneously in miR-200c overexpressed MRC-5 cells. Molecular analysis revealed that miR-200c inhibited the gene expression of HO-1 by directly targeting its 3′-untranslated region. The downregulation of SOD2 and SIRT1 by miR-200c was mediated through zinc finger E-box-binding homeobox 2 (ZEB2) and extracellular signal-regulated kinase 5 (ERK5) pathways, respectively, where knockdown of ZEB2 or ERK5 decreased the expression of SOD2 or SIRT1 in A549 cells. LNA anti-miR-200c transfection in A549 cells inhibited the endogenous miR-200c expression, resulting in increased expressions of antioxidant proteins, reduced oxidative stress and recovered cell proliferation upon H₂O₂ stimulation. These findings indicate that miR-200c fine-tuned the antioxidant response of the lung cells to oxidative stress through several pathways, and thus this study provides novel information concerning the role of miR-200c in modulating redox homeostasis of lung.     

Impact of bimetallic combinations of Cu,Ni and Fe on growth rate,uptake of nitrate and ammonium,14C02 fixation,nitrate reductase and urease activity ofChlorella vulgaris

Summary The toxicity of Cu, Ni and Fe individually, as well as in combination (Cu + Ni, Cu + Fe, Ni + Fe), on growth-rate depression, uptake of NO₃ ^– and NH₄ ⁺, photosynthesis, nitrate reductase and urease activity ofChlorella vulgaris has been studied. All the test metals when used individually showed pronounced toxicity on all the parameters studied. However, their interactive effect was mostly antagonistic except for Cu + Ni (synergism). Pre-addition of Fe offered more protection to the cells against copper and nickel toxicity. The data of statistical analysis reconfirmed that¹⁴C0₂ uptake is the most sensitive parameter (significant atP<0.005, both for time and treatment) than others in metal toxicity assessment. However, these results suggest further that exposure time and sequence of metal addition are very important in biomonitoring of heavy metal toxicity.     

DEBtox theory and matrix population models as helpful tools in understanding the interaction between toxic cyanobacteria and zooplankton

Bioassays were performed to find out how field samples of the toxic cyanobacteria Microcystis aeruginosa affect Moina micrura, a cladoceran found in the tropical Jacarepagua Lagoon (Rio de Janeiro, Brazil). The DEBtox (Dynamic Energy Budget theory applied to toxicity data) approach has been proposed for use in analysing chronic toxicity tests as an alternative to calculating the usual safety parameters (NOEC, ECx). DEBtox theory deals with the energy balance between physiological processes (assimilation, maintenance, growth and reproduction), and it can be used to investigate and compare various hypotheses concerning the mechanism of action of a toxicant. Even though the DEBtox framework was designed for standard toxicity bioassays carried out with standard species (fish, daphnids), we applied the growth and reproduction models to M. micrura, by adapting the data available using a weight-length allometric relationship. Our modelling approach appeared to be very relevant at the individual level, and confirmed previous conclusions about the toxic mechanism. In our study we also wanted to assess the toxic effects at the population level, which is a more relevant endpoint in risk assessment. We therefore incorporated both lethal and sublethal toxic effects in a matrix population model used to calculate the finite rate of population change as a continuous function of the exposure concentration. Alongside this calculation, we constructed a confidence band to predict the critical exposure concentration for population health. Finally, we discuss our findings with regard to the prospects for further refining the analysis of ecotoxicological data.     

Extrapolation from Individual-Level Responses to Population Growth Rate Using Population Modeling

Ecological risk assessments of chemicals are often based on simple measurements of toxicity in individuals. However, the protection goals are often set at the population and community levels. Population models may be a useful tool to extrapolate from individual-level measurements to population-level endpoints. In the present study, the population growth rate (λ) was calculated for three sets of full life-cycle data (Tetranychus urticae exposed to agrimek, and Daphnia pulex exposed to spinosad and diazinon). The results were compared to λ from population models, where survival and/or reproduction were adjusted according to 4 d of data from the same life-cycle data. This was done to determine whether truncated demographic data can give results similar to that obtained with full life-cycle data. The resulting correlations were strong when both effects on survival and reproduction were included in the model (p < .001, 0.93 < R₂ < 1.00). There were also strong correlations in several cases when only effects on survival or reproduction were considered, although the total risk to the population tended to be underestimated. The results of the present study show that population models can be useful to extrapolate truncated data on the individual level to more ecologically relevant population-level endpoints.     

Fumigant toxicity of essential oil of Mugwort (Artemisia vulgaris L.) against three major stored product beetles

Application of plants essential oil for the evaluation of their fumigant toxicity and insecticidal properties is the goal of many researches. In this study, aerial parts of Artemisia vulgaris L. were subjected to hydrodistillation using a Clevenger-type apparatus, and the chemical composition of the volatile oils was studied by gas chromatography–mass spectrometry. Alpha-Pinene (23.56) was the main component of the essential oil. Insecticidal activity of the oil was evaluated against Tribolium castaneum (Herbst), Callosobruchus maculatus (F.) and Rhizopertha dominica (F.) after 24, 48 and 72 h. After 24-h exposure time, C. maculatus was more susceptible (LC₅₀ = 52.47 μl/l air) and T. castaneum was more tolerant (LC₅₀ = 279.86 μl/l air) than other species. LT₅₀ values were indicated using highest concentration of LC₅₀ tests for three species. In general, mortality increased as the doses of essential oil and exposure time increased. These results proposed that A. vulgaris oil might have potential as a control agent against T. castaneum, R. dominica and especially C. maculates in storages.     

A new model for predicting time course toxicity of heavy metals based on Biotic Ligand Model (BLM)

A new model for predicting time course toxicity of heavy metals was developed by extending the effective ratio of biotic ligand binding with toxic heavy metals to the total biotic ligand for 50% of test organisms (f₅₀) derived by the Biotic Ligand Model (BLM). BLM has been well-known as a useful model for prediction of heavy metal toxicity. BLM can consider the effect of exposure conditions such as pH and Ca²⁺ on heavy metal toxicity. In addition to the exposure conditions, heavy metal toxicity is strongly dependent on exposure time. In this study, BLM is extended to predict time dependency of heavy metal toxicity by connecting with the concept of primary reaction. The model developed in this study also generates the estimation of the 50% effect concentration (EC₅₀) for toxicologically unknown organisms and heavy metals. Two toxicological and kinetic constants, f_50,0 and k, were derived from the initial value of f₅₀ (f_50,0) and a time constant (k) independent of time. The model developed in this study enables us to acquire information on the toxicity of heavy metals such as Cu, Cd and Co easily.     

Evaluating the use of pairwise dissimilarity metrics in paleoanthropology

Questions of alpha taxonomy are best addressed by comparing unknown specimens to samples of the taxa to which they might belong. However, analysis of the hominin fossil record is riddled with methods that claim to evaluate whether pairs of individual fossils belong to the same species. Two such methods, log se_m and the related STET method, have been introduced and used in studies of fossil hominins. Both methods attempt to quantify morphological dissimilarity for a pair of fossils and then evaluate a null hypothesis of conspecificity using the assumption that pairs of fossils that fall beneath a predefined dissimilarity threshold are likely to belong to the same species, whereas pairs of fossils above that threshold are likely to belong to different species. In this contribution, we address (1) whether these particular methods do what they claim to do, and (2) whether such approaches can ever reliably address the question of conspecificity. We show that log se_m and STET do not reliably measure deviations from shape similarity, and that values of these measures for any pair of fossils are highly dependent upon the number of variables compared. To address these issues we develop a measure of shape dissimilarity, the Standard Deviation of Logged Ratios (s_LR). We suggest that while pairwise dissimilarity metrics that accurately measure deviations from isometry (e.g., s_LR) may be useful for addressing some questions that relate to morphological variation, no pairwise method can reliably answer the question of whether two fossils are conspecific.     

Ca<Superscript>2+</Superscript> Signalling in Brain Synaptosomes Activated by Dinucleotides

Diadenosine polyphosphates are a family of dinucleotides formed by two adenosines joined by a variable number of phosphates. Diadenosine tetraphosphate, Ap₄A, diadenosine pentaphosphate Ap₅A, and diadenosine hexaphosphate, Ap₆A, are stored in synaptic vesicles and are released upon nerve terminal depolarization. At the extracellular level, diadenosine polyphosphates can stimulate presynaptic dinucleotide receptors. Responses to diadenosine polyphosphates have been described in isolated synaptic terminals (synaptosomes) from several brain areas in different animal species, including man. Dinucleotide receptors are ligand-operated ion channels that allow the influx of cations into the terminals. These cations reach a threshold for N- and P/Q-type voltage-dependent calcium channels, which become activated. The activation of the dinucleotide receptor together with the activation of these calcium channels triggers the release of neurotransmitters. The ability of Ap₅A to promote glutamate, GABA or acetylcholine release has been recently described by the present authors in rat midbrain synaptosomes.     

Mechanism of the gas phase reactions of the C5H5Ni and C5H5Co ions with substituted pyridines. A combined experimental and theoretical study

Different products have been observed in the reactions of C₅H₅Co⁺ and C₅H₅Ni⁺ ions with halogen-substituted pyridines (XPy) that have been studied by ion trap mass spectrometry (ITMS) techniques. In particular, an addition product C₅H₅M(XPy)⁺ and a product ion C₅H₄M(Py)⁺ corresponding to a loss of a HX molecule (X = F, Cl, Br) have been detected. The relative yield of these products is determined by the nature of the metal and by the nature and position of the halogen on the pyridine ring. A computational study at the DFT level on model-systems formed by 2-fluoro and 2-bromopyridine reacting either with the C₅H₅Ni⁺ or the C₅H₅Co⁺ ion has been carried out. This study shows the existence of a general mechanistic pattern. The rate-determining step of this mechanism is the migration of the halogen from the pyridine ring to the metal. A final hydrogen abstraction step carried out by the halogen leads to the expulsion of a HX molecule. The existence of avoided crossings between surfaces of different multiplicities (ground and first excited state) allows the system to follow lower energy reaction pathways. The barrier determined for the reactions involving 2-bromopyridine is significantly lower than that found for 2-fluoropyridine. This is mainly due to the poor migrating/leaving character and low polarizability of fluorine compared to that of bromine.     

C<Subscript>4</Subscript> grasses in boreal fens: their occurrence in relation to microsite characteristics

C₄ plants are rare in cool climates, an ecological pattern attributable to their poor photosynthetic performance at low temperatures relative to C₃ species. However, some C₄ species are able to persist at high latitudes and high elevations, possibly due to the characteristics of the particular microsites they inhabit in these otherwise unfavourable environments. One such species is Muhlenbergia glomerata, which occurs above 60°N in Canada and is found in the atypical C₄ habitat of boreal fens. In this study, we evaluate how microsite features affect the success of M. glomerata in boreal fens. We surveyed 19 populations across northern Ontario during the summers of 1999 and 2000. The ground coverage by woody vegetation was the most important parameter affecting the presence or absence of M. glomerata. Woody plants covered over 50% of the ground area in plots where M. glomerata is absent, but less than 20% where it is present. The minimum light intensity threshold for the presence of the C₄ species was about 32% of full-sunlight at plant height. Surprisingly, in boreal fens M. glomerata was largely restricted to the wetter moss hollows, rather than occurring on the dry hummocks where its greater water use efficiency might have been advantageous. Woody species dominated the hummocks, but were uncommon in the hollows. In these cool northern climates M. glomerata apparently persists because sufficient periods of temperatures favourable to C₄ photosynthesis occur, but this persistence likely requires some factor that suppresses the woody vegetation.     

Biomarkers response to zinc exposure in the symbiont-bearing foraminifer Amphistegina lessonii (Amphisteginidae, Foraminifera)

The acute effects of zinc (Zn) were evaluated in the symbiont-bearing foraminifer Amphistegina lessonii from the Fernando de Noronha Archipelago (Northeastern Brazil). Foraminifers were acutely (48 h) exposed to dissolved Zn concentrations ranging from 9.5 to 93.4 μg Zn/l. Endpoints analyzed included mortality, visual alterations (white spots and dark-brown areas in the test), oxidative stress biomarkers (reactive oxygen species generation, lipid peroxidation and total superoxide dismutase activity), and concentration of metallothionein-like proteins in whole individuals after Zn exposure. No significant mortality was observed during the 48-h exposure period to waterborne Zn. However, a significant percentage of individuals showed visual alterations (white spots and/or dark-brown areas in the test) after 24 and 48 h of Zn exposure. In fact, a significant positive correlation between this endpoint and dissolved Zn concentrations was observed for both times of exposure. Based on this endpoint, the 24-h and 48-h EC₅₀ values and their corresponding 95% confidence intervals for total measured Zn concentrations were calculated as 112.2 (86.5 - 199.5) and 43.6 (34.9 - 57.3) μg Zn/l, respectively. Based on the dissolved Zn concentrations, they were 100.7 (75.3 - 175.9) and 38.2 (29.7 - 49.4) μg Zn/l, respectively. Therefore, a significant increase in Zn toxicity was observed with increasing time of exposure. After 48 h of Zn exposure, whole body antioxidant capacity was lower in normal-appearing individuals than in those at the initial stage of bleaching. Increases in lipid peroxidation, metallothionein-like protein concentration and total SOD activity was observed at a greater extent in pale/partly-bleached individuals associated with an increased Zn toxicity measured as visual alterations. These findings suggest that an activation of some components of the antioxidant system occurred in A. lessonii to counteract the oxidative stress induced by Zn exposure, and consequently avoid a possible complete loss of the symbiont.     

Light/dark modulation of phosphoenolpyruvate carboxylase in C3 and C4 species

In this report, the effects of light on the activity and allosteric properties of phosphoenolpyruvate (PEP) carboxylase were examined in newly matured leaves of several C₃ and C₄ species. Illumination of previously darkened leaves increased the enzyme activity 1.1 to 1.3 fold in C₃ species and 1.4 to 2.3 fold in C₄ species, when assayed under suboptimal conditions (pH 7) without allosteric effectors. The sensitivities of PEP carboxylase to the allosteric effectors malate and glucose-6-phosphate were markedly different between C₃ and C₄ species. In the presence of 5 mM malate, the activity of the enzyme extracted from illuminated leaves was 3 to 10 fold higher than that from darkened leaves in C₄ species due to reduced malate inhibition of the enzyme from illuminated leaves, whereas it increased only slightly in C₃ species. The Ki(malate) for the enzyme increased about 3 fold by illumination in C₄ species, but increased only slightly in C₃ species. Also, the addition of the positive effector glucose-6-phosphate provided much greater protection against malate inhibition of the enzyme from C₄ species than C₃ species. Feeding nitrate to excised leaves of nitrogen deficient plants enhanced the degree of light activation of PEP carboxylase in the C₄ species maize, but had little or no effect in the C₃ species wheat. These results suggest that post-translational modification by light affects the activity and allosteric properties of PEP carboxylase to a much greater extend in C₄ than in C₃ species.     

Germination response of Arabian desert species to gibberellic acid and potassium nitrate seed treatment

Abstract

Desert plant species commonly use seed dormancy to prevent germination during unfavorable environmental conditions and thus increase the probability of seedling survival. Seed dormancy presents a challenge for restoration ecology, particularly in desert species for which our knowledge of dormancy regulation is limited. In the present study the effect of gibberellic acid (GA₃) and potassium nitrate (KNO₃) on seed dormancy release was investigated on eight Arabian desert species. Both treatments significantly enhanced the germination of most species tested. GA₃ was more effective than KNO₃ in enhancing germination percentage, reducing mean germination time and synchronizing the germination in most of the studied species. Light requirement during germination was species-specific, but in general the presence of light promoted germination more effectively when combined with KNO₃ and GA₃. The wide variation in dormancy and germination requirements among the tested species is indicative of distinct germination niches, which might assist their co-existence in similar habitat/environmental conditions. Seed pre-treatments that optimize germination in this habitat must therefore be assessed for individual species to improve the outcomes of ecological restoration.     

The modeling and health risk assessment of PM2.5 from Tema Oil Refinery

Fine particulate matters (PM_2.5) are known to pose serious health problems compared to other air pollutants. The current study employed air dispersion modeling system (AERMOD) to simulate the concentration of PM_2.5 from Tema Oil Refinery (TOR) and to assess the non-cancer risk and mortalities of the exposed population. In addition, the effects of local climatic factors on the distribution and concentration of PM_2.5 within the three main seasons (Major Raining Season (MRS), Low Raining Season (LRS) and Dry Season (DS)) were investigated. The AERMOD results showed that both 24-h (38.8 µg m^?3) and annual (12.6 µg m^?3) PM_2.5 concentration levels were in exceedance of the international limits. However, a decreasing trend in seasonal PM_2.5 concentrations was observed. Health risk assessment (HRA), indicated by hazard index (HI), revealed that the amount of Al₂O₃ present in the PM_2.5 caused a significant non-carcinogenic health risk to the exposed population (both adults and children) within the Metropolis (HI = 2.4 for adults and HI = 1.5 for children). Additionally, cardiopulmonary disease related mortalities due to PM_2.5 exposure (181 deaths for adults and 24 deaths for children) were found high compared to deaths caused by lung cancer (137 deaths for adults and 16 deaths for children).     

Light- and seasonal-induced plasticity in leaf morphology, N partitioning and photosynthetic capacity of two temperate deciduous species

Processes involved in leaf photosynthetic acclimation to light and throughout the growing season were investigated in two hardwood species (Acer saccharum and Betula alleghaniensis), which differed in their level of shade-tolerance. For both species, variation in traits related to (i) leaf morphology (LMA, leaf mass:area ratio), (ii) leaf N content (N_A, leaf nitrogen content on an area basis and N_M, N concentration in leaf dry mass), (iii) leaf N partitioning among photosynthetic functions (P_r, N allocated to Rubisco, and P_b, N allocated to bioenergetics), and (iv) leaf photosynthetic capacity (V_cmax, maximal carboxylation rates, and J_max, maximal light-driven electron flow) were assessed at three different times during the growing season (early, mid- and late summer) and under four contrasting light regimes (40, 17, 6 and 2% of full sunlight). For both species, light-driven variation in most traits was greater than their seasonally driven variation. Furthermore, results showed for both species the pre-eminence of LMA changes in the light-driven acclimation of N_A. Importance of N_M to variation in N_A was restricted to seasonal acclimation, especially for the less shade-tolerant species, B. alleghaniensis. Similarly, for both species, light-driven acclimation of leaf photosynthetic capacities was tightly related to variation in N_A, which was related to LMA changes. However, variation in P_r and P_b better explained seasonally driven variation in V_cmax and J_max, specifically under lower light levels, where N_A was low. Thus, the great variability observed for leaf activity in response to contrasting light environments was related to efficient morphological adjustments, regardless of species level of shade-tolerance. Finally, physiological adjustments were mainly involved in fine-scale changes observed during seasonally driven acclimation of leaves, when LMA was constrained to a slight range of variation.     

Screening the Toxicity of Ni,Cd, Cu,Ivermectin, and Imidacloprid in a Short-Term Automated Behavioral Toxicity Test with Tubifex tubifex (Müller 1774) (Oligochaeta)

A new automated online toxicity test for screening of short-term effects of chemicals is presented using the freshwater oligochaete Tubifex tubifex in the Multispecies Freshwater Biomonitor? (MFB). Survival and locomotory behavior of the worms were observed during 24 h of exposure to metals (Cd, Cu, Ni), pesticides (Imidacloprid), and pharmaceuticals (Ivermectin). The LC₅₀ values revealed increasing toxicity in the following order: Ni (> 100 mg/l) < Cu (15.2 mg/l) < Cd (4.9 mg/l) < Ivermectin (1.8 mg/l) < Imidacloprid (0.3 mg/l). The EC₅₀ for locomotion showed a similar order of increasing toxicity: Ni (86 mg/l) < Cu (3.8 mg/l) < Ivermectin (2.0 mg/l) < Cd (1.1 mg/l) < Imidacloprid (0.09 mg/l). Toxicity was dependent on both concentration and exposure time. This could be demonstrated in 3d response models and proven in the statistical analysis showing a significant interaction term (C × T) for the experiments with Cu and Ni. T. tubifex proved to be very tolerant, but even then behavioral responses were more sensitive than mortality for Cu, Cd, and Imidacloprid.