Hela Toumi

Effects of deltamethrin (pyrethroid insecticide) on growth, reproduction, embryonic development and sex differentiation in two strains of Daphnia magna (Crustacea, Cladocera)

Acute and different chronic ecotoxic effects of deltamethrin have been investigated on two strains (coming from two different laboratories) of Daphnia magna. The effective concentrations immobilizing 50% of daphnids (EC50s) after 24 h and 48 h were 9.40 and 0.32 μg L(-1), 8.86 and 0.63 μg L(-1) for first strain (strain 1) and second strain (strain 2), respectively. Thus, there was an increase of deltamethrin ecotoxicity with time of exposure as confirmed by chronic studies. After 21 days of exposure to deltamethrin, daphnids have showed significant effects on survival at deltamethrin concentrations of 0.16 μg L(-1) and 0.31 μg L(-1) for strains 1 and 2, respectively. Eleven other endpoints were examined: body length, population growth rate and various reproductive parameters (days to first brood, number of broods, number of cumulative molts and number of neonates), embryotoxicity and appearance of males. IC10 values related to the number of juveniles per live adult were 11 and 46 ng L(-1) for strains 1 and 2, respectively. Furthermore, an increase in embryo deformities was observed at the highest concentrations tested for both strains. Following deltamethrin exposure, undeveloped second antennae, curved or unextended shell spines, and curved post abdomen spines were observed in live neonates. The production of male juveniles was only registered with strain 1 at 0.16 μg L(-1). Results suggest that deltamethrin could act as an endocrine disruptor in D. magna as it interferes with sex determination and development abnormality but there is a difference in sensitivity between the two tested strains.

Is acetylcholinesterase a biomarker of susceptibility in Daphnia magna (Crustacea, Cladocera) after deltamethrin exposure?

In the present study, we explored the possibility of using the acetylcholinesterase (AChE) as a biomarker after deltamethrin (pyrethroid insecticide) exposure with three strains of the cladoceran Daphnia magna. Four calculated time-weighted deltamethrin concentrations (20.1, 40.3, 80.6 and 161.3 ng L(-1)) were compared against control acetylcholinesterase activity. Our results showed that after 48 h of deltamethrin exposure, all treatments induced a significant decrease of AChE activities whatever the three considered strains. However, diverse responses were registered in terms of lowest observed effect concentrations (LOEC: 80.6 ng L(-1) for strain 1 and 20.1 ng L(-1) for strains 2 and 3) revealing differences in sensitivity among the three tested strains of D. magna. Our results suggest that after deltamethrin exposure, the AChE activity responses can be also used as a biomarker of susceptibility (i.e., variation of strain specific response). Moreover, our results show that strain 1 is the less sensitive in terms of IC50-48 h of AChE, whereas it became the most sensitive when considering the EC50-48 h estimated in the standard ecotoxicity test.

Investigation of differences in sensitivity between 3 strains of Daphnia magna (crustacean Cladocera) exposed to malathion (organophosphorous pesticide)

Acute and chronic ecotoxic effects of organophosphorous insecticide malathion (Fyfanon 50 EC 500 g L−1) were investigated on three strains of Daphnia magna. The nominal effective concentrations immobilizing 50% (EC50) of Daphnia after 24 and 48 h were 0.53 and 0.36 μg L−1, 0.70 and 0.44 μg L−1, and 0.75 and 0.46 μg L−1 for the strains 1, 2, and 3 respectively. There was an increase in malathion ecotoxicity with time of exposure as confirmed by chronic studies. In fact, after 21 days of exposure, significant effects on survival (lowest observed effect concentration or LOECs) were recorded at malathion concentrations of 22, 220 and 230 ng L−1 for strains 1, 2 and 3 respectively. Other endpoints were also examined, including reproduction (with different parameters), body length and embryo toxicity. ICs10 and ICs20 were calculated for these different parameters. ICs10 ranged from 4.7 to more than 220 ng L−1 for the three tested strains. The most sensitive parameter was the number of neonates per adult (ICs10 = 4.7 and 10.8 ng L−1 for strains 1 and 2 respectively) or the number of broods (IC10 = 10 ng L−1 for strain 3). Moreover, an increase in embryo development abnormalities was observed at the two highest tested malathion concentrations. Abnormalities comprised undeveloped second antennae, curved or unextended shell spines, and curved post-abdomen spines in live neonates. Results suggest that malathion could act as an endocrine disruptor in D. magna as it interferes with development. It also induces a significant decrease in acetylcholinesterase (AChE) activities for the three strains. Both strains 2 and 3 seemed more sensitive (LOECs = 60 ng L−1) than strain 1 (LOEC = 120 ng L−1). Our results suggest that the AChE activity response can also be used as a biomarker of inter-strain (or inter-clonal) susceptibility (i.e. strain (or clone)-specific response).

Effect of deltamethrin (pyrethroid insecticide) on two clones of Daphnia magna (Crustacea, Cladocera): a proteomic investigation.

Deltamethrin is a class II pyrethroid insecticide commonly used in agriculture. It is hazardous to freshwater ecosystems, especially for the cladoceran Daphnia magna (Straus 1820). The results of our previous studies based on acute and chronic ecotoxicity experiments revealed differences in the sensitivity between two different clones. In this work, to investigate deltamethrin toxicity mechanisms in two clones of D. magna, we used a proteomic approach in order to analyze changes in protein expression profiles after 48 h of exposure. We detected 1339 spots; then applying statistical criteria (ANOVA p<0.001 and minimum fold change 1.5), only 128 spots were significantly different in the normalized volume. Among the preselected proteins there were 88 up-regulated and 40 down-regulated proteins. Results showed differences in sensitivities after deltamethrin exposure between the clones. Moreover, using the 2-DIGE method, proteomic investigation for deltamethrin exposure proved to be a reliable and powerful approach to investigate effects of deltamethrin as part of research for new metabolic and cellular biomarkers. After identification by mass spectrometry, there were 39 proteins recognized and identified, in which 21 and 18 were up- and down-regulated, respectively, in deltamethrin-exposed clone A compared to three other conditions (controls of each clone and deltamethrin-exposed clone 2). Up- and down-regulated proteins belonged to 12 biological processes (i.e. metabolic processes, apoptosis and stimulus response) and 5 molecular functions (i.e. catalytic activity, binding, structural molecular activity, antioxidant and receptor activities). Identification of these deregulated proteins opens a new way in discovering new molecular targets and putative biomarkers in daphnids exposed to deltamethrin.

Sensitivity of different aquatic bioassays in the assessment of a new natural formicide

Agrochemicals have the potential to cause deleterious effects on living organisms and therefore they must be subjected to various (eco)toxicological studies and monitoring programs in order to protect human health and the environment. The aim of this study was to assess the ecotoxicity of a new natural formicide with a battery of three classical and three ecotox-kit tests. The former tests were performed with Aliivibrio fischeri bacteria (Lumistox test), the cladoceran Daphnia magna and Pseudokirchneriella subcapitata algae, and the latter with Thamnotoxkit FTM (Thamnocephalus platyurus), Ostracodtoxkit F® (Heterocypris incongruens) and LuminoTox (photosynthetic enzyme complexes). In the range of formicide concentrations tested (from 0.06 to 2.0 g L−1), the measurement endpoint values varied from 0.79 g L−1 for the algal test to > 2 g L−1 for the LuminoTox and Ostracodtoxkit F® tests. Hierarchical sensitivity ranking based on the no-observed effect concentration (NOEC) values established to assess the formicide ecotoxicity was as follows: algal growth inhibition test ≈ daphnid immobilization test ≈ bacterial luminescence inhibition test > Thamnotoxkit FTM > LuminoTox > Ostracodtoxkit F®. Overall, results from the battery of bioassays showed that this formicide preparation presents low ecotoxicity as compared to the aquatic ecotoxicity of presently commercialized formicides. In conclusion, classical aquatic bioassays are more sensitive than ecotox-kit tests in the assessment and monitoring of the new natural formicide.

Acute and chronic ecotoxicity of carbaryl with a battery of aquatic bioassays

ABSTRACT The ecotoxic effects of carbaryl (carbamate insecticide) were investigated with a battery of four aquatic bioassays. The nominal effective concentrations immobilizing 50% of Daphnia magna (EC50) after 24 and 48 h were 12.76 and 7.47 µg L−1, respectively. After 21 days of exposure of D. magna, LOECs (lowest observed effect concentrations) for cumulative molts and the number of neonates per surviving adult were observed at carbaryl concentration of 0.4 µg L−1. An increase of embryo deformities (curved or unextended shell spines) was observed at 1.8 and 3.7 µg L−1, revealing that carbaryl could act as an endocrine disruptor in D. magna. Other bioassays of the tested battery were less sensitive: the IC50-72h and IC10-72h of the algae Pseudokirchneriella subcapitata were 5.96 and 2.87 mg L−1, respectively. The LC50-6d of the ostracod Heterocypris incongruens was 4.84 mg L−1. A growth inhibition of H. incongruens was registered after carbaryl exposure and the IC20-6d was 1.29 mg L−1. Our results suggest that the daphnid test sensitivity was better than other used tests. Moreover, carbaryl has harmful and toxic effects on tested species because it acts at low concentrations on diverse life history traits of species and induce embryo deformities in crustaceans.

Effect of carbaryl (carbamate insecticide) on acetylcholinesterase activity of two strains of Daphnia magna (Crustacea, Cladocera)

ABSTRACT The present study was designed to investigate the effect of carbaryl (carbamate insecticide) on the acetylcholinesterase activity in two strains (same clone A) of the crustacean cladoceran Daphnia magna. Four carbaryl concentrations (0.4, 0.9, 1.8 and 3.7 µg L−1) were compared against control AChE activity. Our results showed that after 48 h of carbaryl exposure, all treatments induced a significant decrease of AChE activities whatever the two considered strains. However, different responses were registered in terms of lowest observed effect concentrations (LOEC: 0.4 µg L−1 for strain 1 and 0.9 µg L−1 for strains 2) revealing differences in sensitivity among the two tested strains of D. magna. These results suggest that after carbaryl exposure, the AChE activity responses can be also used as a biomarker of susceptibility. Moreover, our results show that strain1 is less sensitive than strain 2 in terms of IC50-48 h of AChE activity. Comparing the EC50-48 h of standard ecotoxicity test and IC50-48 h of AChE inhibition, there is the same order of sensitivity with both strains.

Use of phytoproductivity data in the choice of native plant species to restore a degraded coal mining site amended with a stabilized industrial organic sludge

Coal mining-related activities result in a degraded landscape and sites associated with large amounts of dumped waste material. The arid soil resulting from acid mine drainage affects terrestrial and aquatic ecosystems, and thus, site remediation programs must be implemented to mitigate this sequential deleterious processes. A low-cost alternative material to counterbalance the affected physico-chemical-microbiological aspects of the degraded soil is the amendment with low contaminated and stabilized industrial organic sludge. The content of nutrients P and N, together with stabilized organic matter, makes this material an excellent fertilizer and soil conditioner, fostering biota colonization and succession in the degraded site. However, choice of native plant species to restore a degraded site must be guided by some minimal criteria, such as plant survival/adaptation and plant biomass productivity. Thus, in this 3-month study under environmental conditions, phytoproductivity tests with five native plant species (Surinam cherry Eugenia uniflora L., C. myrianthum–Citharexylum myrianthum, Inga–Inga spp., Brazilian peppertree Schinus terebinthifolius, and Sour cherry Prunus cerasus) were performed to assess these criteria, and additional biochemical parameters were measured in plant tissues (i.e., protein content and peroxidase activity) exposed to different soil/sludge mixture proportions. The results show that three native plants were more adequate to restore vegetation on degraded sites: Surinam cherry, C. myrianthum, and Brazilian peppertree. Thus, this study demonstrates that phytoproductivity tests associated with biochemical endpoint measurements can help in the choice of native plant species, as well as aiding in the choice of the most appropriate soil/stabilized sludge proportion in order to optimize biomass production.

Cyclomorphosis in Daphnia magna and Ceriodaphnia reticulata (Cladocera) from northern Tunisian groundwater: influence of temperature and invertebrates?

In the present study, we investigated cyclomorphosis in two cladocerans, Daphnia magna and Ceriodaphnia reticulata , sampled from northern Tunisian groundwater (wells) during two seasons (spring and summer). Seasonal distribution of the two species was apparent, with dominance of D. magna only in spring and C. reticulata during the whole study period. Our results showed correlations between caudal spine length of D. magna and water temperature ( r = 0 . 95 , p = 0 . 002 ), and between caudal spine length and the density of coleopteran larvae ( Stictonectes escheri , Graptodytes sp., Gyrinus urinator , and Haliplus lineaticollis ) ( r = 0 . 98 , p = 0 . 0005 ). In C. reticulata , we registered a correlation ( r = 0 . 95 , p = 0 . 003 ) only between its size and the density of larvae of Ephemeroptera ( Cloeon cognatum ) but no correlation with water temperature was found.